5.1
Viral, mycoplasmal and rickettsial infections
Chapter Contents
Viral infections
155
Influenza 156
Parainfluenza 159
Respiratory syncytial virus 159
Metapneumovirus 160
Measles 160
Adenovirus 161
Severe acute respiratory syndrome 163
Herpes simplex 164
Cytomegalovirus 164
HIV and AIDS 165
Chickenpox (varicella) and herpes zoster 167
Smallpox (variola) 167
Hantavirus pulmonary syndrome 168
Mycoplasmal pneumonia 169
Rickettsial infection
170
Coxiella burnetti pneumonia (Q fever) 170
Bacillary angiomatosis 171
References
171
Viral infections
Many viruses infect the lower respiratory tract. They include the orthomyxoviruses
(influenza virus), paramyxoviruses (parainfluenza viruses, measles virus and respiratory
syncytial virus), adenoviruses, herpesviruses (cytomegalovirus, varicella-zoster virus
and herpes simplex virus) and formerly variola virus (smallpox). Many of these viruses
are of course also responsible for non-respiratory disease. The role of papillomavirus
in neoplasia of the respiratory tract is discussed on page 535 and parvovirus is mentioned
as a cause of hydrops fetalis on page 43. The role of herpes-like viruses in Kaposi's
sarcoma and body cavity-based lymphomas is discussed on pages 635 and 734 respectively.
Viral infection of the lower respiratory tract occurs in three general situations:
infections confined to the respiratory tract, systemic infections that involve the
lung and opportunistic infection of the lungs in the immunocompromised (Box 5.1.1
).
Box 5.1.1
Classification of viruses that infect the lower respiratory tract
Normal host
Primary respiratory infection
Respiratory syncytial virus
Parainfluenza
Influenza
Adenovirus
Secondary to systemic infection
Measles
Varicella-zoster virus
Adenovirus
Immunocompromised host
Cytomegalovirus
Herpes simplex virus
Varicella-zoster virus
Adenovirus
Respiratory viruses may strike any part or all the respiratory tract but on the whole
each tends to affect particular parts and thereby elicit characteristic clinical effects
(Fig. 5.1.1
). This pattern varies however if there is some predisposing cause. Thus, the rhinoviruses,
which usually cause nothing more serious than a cold, are the commonest viral trigger
of acute exacerbations of chronic bronchitis, while in the immunodeficient herpes
simplex virus and cytomegalovirus are serious pathogens in the lower respiratory tract.
Figure 5.1.1
Clinical features of the common respiratory virus infections.
The frequency of these various infections also differs in children and adults. In
children, respiratory syncytial virus is the most important viral cause of lower respiratory
tract disease, typically causing an obstructive bronchiolitis. Parainfluenza viruses
are the most frequent cause of viral pneumonia in children, and the influenza virus
in adults. These are followed by the measles and adenoviruses in children and varicella
virus in adults, whilst the immunocompromised are also susceptible to cytomegalovirus
and herpes simplex virus. A viral aetiology is responsible in 7–15% of adults admitted
to hospital with community-acquired pneumonia (see Table 5.2.2, p. 178).
The virus responsible can be cultured from sputum or nasopharyngeal washings and evidence
of infection by particular viruses may be provided by the demonstration of a rising
titre of specific antibodies in the patient's serum. The advent of monoclonal antibodies
has provided specific sensitive and reproducible probes that can be directly conjugated
to a fluorescent tag so that the examination of exfoliated cells for viral antigen
by immunofluorescent techniques is now the method of choice for the rapid identification
of most respiratory viruses. In tissue, the particular virus may be identified by
immunocytochemistry, electron microscopy or gene probes.1, 2, 3, 4, 5, 6, 7
Most respiratory viral infections end in recovery. In fatal cases, the pathological
changes in the lungs are often dominated by the effects of secondary bacterial infection,
which is a very frequent complication. Few bacterial species have developed mechanisms
for attachment to normal, intact human respiratory epithelium (notable exceptions
being Bordetella pertussis and Mycoplasma pneumoniae) but viral injury to the epithelium
permits bacterial attachment to take place and is associated with a greatly increased
incidence of bacterial pneumonia.
From the occasional postmortem studies that have been undertaken in uncomplicated
cases of viral pneumonia it is apparent that the inflammatory reaction in the lung
is mainly lymphocytic and interstitial. Neutrophils are numerous only when there is
a complicating bacterial infection. At the alveolar level viruses cause an atypical
pneumonia characterised by a chronic inflammatory interstitial infiltrate rather than
the acute inflammatory exudates that fill the air spaces in the bacterial pneumonias.
The pathology is modified to some extent by the type of virus responsible but infections
caused by different viruses have many features in common.
8
In the lungs, as in other organs, some viruses have a cytopathic effect and kill the
infected host cells, whilst others stimulate proliferative activity. Thus, influenza,
adenovirus, varicella and herpes simplex pneumonia are all characterised by epithelial
cell necrosis (Figure 5.1.2, Figure 5.1.3
), whilst respiratory syncytial virus and measles virus stimulate mitotic division
and cause characteristic proliferative changes in the bronchioles and alveoli respectively.
The distribution of the changes is often characteristic of a particular virus, but
not specific. Thus, within the alveoli, influenza tends to affect the epithelium diffusely.
The effects of adenovirus, on the other hand, are generally maximal in the region
of the terminal bronchioles, whilst varicella pneumonia is also focal but lacks any
particular relationship to the acinar architecture. Viral inclusions are evident in
certain viral pneumonias, notably measles, adenovirus, cytomegalovirus, varicella
and herpes simplex pneumonia, but not in others.
Figure 5.1.2
Necrotising viral bronchiolitis. The bronchiolar epithelium is partly destroyed and
the lumen is largely filled with pus due to secondary bacterial infection.
Figure 5.1.3
Viral pneumonia causing necrosis of the alveolar epithelium with the formation of
hyaline membranes. The virus responsible in this patient was that of measles but many
respiratory viruses have a similar effect, as do several other cytotoxic factors:
see diffuse alveolar damage, in Chapter 4.
(Courtesy of Dr V Chrystal, Durban, South Africa.)
Alveolar epithelial necrosis is a feature of severe viral pneumonia. It causes the
formation of hyaline membranes (Fig. 5.1.3) and the pathology of such viral pneumonia
is essentially that of diffuse alveolar damage (see Chapter 4). The regenerative changes
seen in diffuse alveolar damage may be evident, possibly involving epithelial metaplasia.
Much of the damage caused by respiratory viruses is due to a direct cytopathic effect
on the infected cells but there may also be indirect injury. The latter may be due
to normal immune mechanisms such as cytotoxic T lymphocytes attacking infected host
cells, depression of immunity by the virus (facilitating secondary infections) or
the development of autoimmunity initiated by the virus.
The possible threat of bioterrorism is a feature of life today and, because of the
ease with which they may be widely dispersed, respiratory pathogens figure large in
the thinking of defence forces. The US Centers for Disease Control have classified
six agents as category A threats. Several of these will be considered in this infectious
disease section. The six category A agents are Bacillus anthracis (anthrax), Variola
major (smallpox), Yersinia pestis (plague), Francisella tularensis (tularaemia), viral
haemorrhagic agents and Clostridium botulinum toxin. Category B and C agents, which
are seen as posing less of a threat, include the repiratory pathogens Coxiella burnetti
(Q fever), Hantavirus and multidrug-resistant Mycobacterium tuberculosis.
Influenza
Microbiology and epidemiology
Influenza is epidemic almost annually in the winter months in many parts of the world
and at long intervals the disease occurs in pandemic form, notably in 1889–92, 1918–19,
1957–58, 1968 and 2009. It is estimated that in the pandemic that followed the world
war of 1914–18, some 20–30 million people died from the disease in little more than
a year, more than were killed in the war itself. Until 1933 it was widely believed
that the disease was caused by the bacterium Haemophilus influenzae. The discovery
in 1933 that the disease could be transmitted to ferrets by intranasal inoculation
of filtered washings from the noses of patients established its viral nature.
9
There are several types of influenza virus. All are originally bird viruses, some
crossing from birds to species such as humans, pigs, horses and seals. Once established
in the new species they undergo constant changes in their antigenic makeup, a feature
that necessitates the constant manufacture of new vaccines. The strains involved in
most serious human infections belong to types A and B, with the former much the more
virulent. Outbreaks of infection with influenza A occur most years, with epidemics
every 5–15 years. Influenza B also causes epidemics, but less frequently. Influenza
C does not appear to cause epidemics. Successive epidemics appear to be decreasing
in severity, possibily due to natural selection involving evolutionary changes that
favour transmissibility over pathogenicity.
10
Antigenic lability involves changes in the principal surface antigens of the virus,
haemagglutinin and neuraminidase. Minor changes (‘antigenic drift’) are seen progressively
from season to season. Major changes (‘antigenic shift’) due to acquisition of a new
haemagglutinin occur periodically and are responsible for the emergence of new subtypes
to which populations have little immunity and which therefore cause epidemics or pandemics.
Influenza epidemics generally occur in the winter months and often start in countries
south of the equator or in the east, giving northern and western countries time to
prepare and distribute appropriate vaccines to those most at risk, notably the infirm.
Influenza A viruses are named after their haemagglutinins (H1, H2, etc.), their neuraminidases
(N1, N2, N3, etc.), and the place where and year when the strain was first identified.
Thus, the 1968 pandemic virus was H3N2 influenza A/Hong Kong/68.
The haemagglutinin molecule enables the virus to attach to host cells prior to infecting
them and neuraminidase permits new virus particles to bud from the cell membrane.
Although there are considerable differences between the influenza viruses that infect
different species, the haemagglutinin molecule's lability occasionally permits its
virus to switch from one host species to another, in which the disease is likely to
spread in epidemic form. It appears that all the devastating influenza pandemics of
the twentieth century, such as Spanish flu in 1918, Asian flu in 1957 and Hong Kong
flu in 1968, were caused by viruses that made such a switch from birds to humans.
11
Recent genomic studies of the H1N1 virus responsible for the 1918 pandemic suggest
that it was an avian virus that adapted to humans, rather than developing by a reassortment
of avian and human viruses, as in the 1957 and 1968 pandemics.
12
The switch from animals to humans in the ‘wet markets’ of the Far East is also relevant
to the severe acute respiratory syndrome (SARS), described on page 163.
In 2004, the H5N1 strain of the influenza A virus devastated flocks of poultry in
Asia and was responsible for the deaths of some humans from what was termed ‘Asian
bird flu’.13, 14 This strain was not very infective to humans, possibly because the
temperature of the human nose (32°C) is too cold for a virus whose natural host is
the avian intestine (temperature 40°C).15, 16 However, when the virus succeeded in
infecting humans it was particularly virulent for two reasons. First, it was resistant
to the antiviral effects of human interferons and tumour necrosis factor-α, a property
acquired by a simple mutation in the non-structural gene resulting in a change from
aspartate to glutamate at position 92.
17
Second, it preferentially targeted the alveolar rather than the tracheobronchial epithelium.
18
The year 2009 saw swine influenza A/H1N1 virus switch to humans and exhibit the ability
to spread from case to case, rapidly assuming pandemic proportions. Pigs are unusual
in that their respiratory epithelium has receptors for both avian and human influenza
viruses so that they can be infected with these viruses simultaneously, providing
the ideal environment for genetic reassortment. This appears to have taken place as
the 2009 swine influenza virus shows a novel reassortment of genes derived from swine,
avian and human influenza viruses, a feature that is probably responsible for this
virus being able to infect both pigs and humans. Unlike seasonal influenza, the disease
made its first appearance in the northern hemisphere, apparently originating in Mexico,
and its first impact was during the summer months. There was much mild disease but
again, in contrast to seasonal influenza, severe respiratory failure was seen in young,
previously healthy persons, as is often the case in influenza pandemics. This feature
is not well explained but it is possible that the healthy mount a more vigorous immune
response that is in some way detrimental to the host. Older people were less susceptible
but more likely to die when infected.
19
However, one year later it was apparent that the pandemic had not proved as severe
as first thought.
Clinical features
The severity of influenza varies from one epidemic to another and from case to case.
In its uncomplicated form it is relatively mild, with fever, coryza, headache and
body aches as its main features, and recovery after a few days. When the viral infection
is followed by invasion of the lungs by staphylococci, pneumococci, streptococci or
Haemophilus influenzae, the condition assumes a much graver form and the fatality
rate may rise alarmingly. Infection rates are highest among schoolchildren and decrease
with age but death is commonest in infants, the elderly and those with underlying
lung or heart disease, and is generally due to complications.
Primary influenzal pneumonia is generally rare but figured prominently in the 1918–19
pandemic. It carries a high case fatality rate and in the 1918–19 pandemic it was
notable that mortality was highest in adults aged 25–34, possibly because older people
had been exposed earlier to a similar strain of the virus.20, 21 Primary influenzal
pneumonia may be fulminant, leading to the death of a previously healthy person within
a few hours of the onset of symptoms.
22
Recent years have seen the development of effective antiviral agents such as the drugs
oseltamivir (Tamiflu) and zanamivir (Relenza) which inhibit viral neuraminidase (in
contrast to anti-influenza vaccines, which target viral haemagglutinin).
Pathology of uncomplicated influenza
The cytopathic effect of influenza virus is seen microscopically in characteristic
degenerative changes in the epithelial cells of the bronchial and bronchiolar mucosa.
These changes involve all cells of the surface epithelium and often the cells lining
the bronchial glands: swelling of the cells, vacuolation of their cytoplasm and degeneration
of the nucleus proceed to cell loss and frank necrosis (Fig. 5.1.4
). Viral inclusions are not evident but the virus can be identified in tissue sections
by immunocytochemistry and in situ hybridisation.23, 24 The deeper tissues show oedema,
hyperaemia and a moderate to marked accumulation of lymphocytes; neutrophils are present
but account for only a small proportion of the cellular infiltrate.
Figure 5.1.4
Influenza. This cytopathic virus has totally destroyed the bronchial epithelium, predisposing
to bacterial superinfection.
Alveolar involvement is unusual but cases of fulminating influenzal viral pneumonia
are occasionally encountered, particularly with the 1918 and more recent H5N1 and
H1N1 strains.14, 24, 25 Autopsy in such cases shows that the lungs are bulky and deeply
congested.14, 22, 24a Blood-stained, frothy fluid oozes freely from the cut surface.
Areas of haemorrhage are present and may be extensive. The mucosa of the bronchial
tree is very hyperaemic. Microscopically, the alveoli contain a fibrin-rich oedema
fluid, which is often frankly haemorrhagic. Macrophages may be numerous in the exudate
and hyaline membranes are often found lining the alveoli. T lymphocytes are often
prominent in the alveolar interstitium while focal necrosis of alveolar walls and
thrombosis of capillaries are conspicuous features in the parts most severely affected.
26
Postmortem examination of two victims of the H5N1 virus showed similar evidence of
diffuse alveolar damage but it was also found that viral replication in the respiratory
tract had resulted in particularly high levels of cytokines such as interferons and
tumour necrosis factor-α, which, with the resultant haemophagocytic syndrome, was
considered to be the chief cause of death.
27
Generally, however, H5N1 viral pneumonia shows no special features and it may be difficult
to distinguish the changes brought about by the H5N1 virus from those caused by viruses
such as that responsible for SARS or by factors such as acid aspiration or oxygen
toxicity. More specific tests such as viral isolation, in situ hybridisation and reverse
transcription-polymerase chain reaction (RT-PCR) are required to confirm H5N1 infection.
Fulminant uncomplicated influenzal pneumonia is often associated with changes in other
parts of the body that indicate the occurrence of influenzal viraemia
14
: among these are haemorrhagic encephalomyelitis, which is an acute infective condition
distinct from postinfluenzal encephalomyelopathy, rhabdomyolysis and placentitis.28,
29
In the healing phase of influenzal pneumonia there is conspicuous swelling of the
alveolar lining cells, which proliferate and in places may virtually fill the lumen.
The proliferation of alveolar lining cells may be so marked as to produce appearances
somewhat resembling a neoplastic state. The changes reach their peak on about the
third to fifth day of the disease and then regress, eventually subsiding completely.
Also during the phase of recovery, regeneration of the bronchial epithelium may involve
squamous metaplasia, but this soon gives place to normal ciliated pseudostratified
respiratory tract epithelium.
Bacterial superinfection in influenza
Although pneumonia is the usual cause of death in epidemics of influenza, it is often
a secondary bacterial pneumonia that is responsible. Neutrophilic exudates, organising
pneumonia and bronchiolitis obliterans are then added to or replace the changes seen
in uncomplicated cases.22, 24, 30, 31, 32, 33 The impact an influenza epidemic has
on respiratory death rates in general is shown in Figure 5.1.5
.
Figure 5.1.5
Weekly deaths from respiratory disease in England and Wales 1987–92, showing the impact
of an influenza epidemic in 1989/90 on deaths from other respiratory diseases.
(Data supplied by the Lung and Asthma Information Centre.)
Before the discovery of the influenza virus in 1933, the changes that are now known
to be due to the viral infection were often confused with those of complicating infections,
mainly caused by bacteria. Haemophilus influenzae was first isolated in the 1889–90
pandemic and so named because its discoverer, Pfeiffer, recovered it from a large
proportion of cases and mistook it for the cause of influenza. In the 1918–19 pandemic
H. influenzae was again found, along with Streptococcus pneumoniae and Staphylococcus
aureus.
32
With the advent of antibiotics, resistant strains of Staphylococcus aureus emerged
and in the 1957–58 pandemic staphylococcal superinfection of the lungs was the major
fatal complication of influenza. In the 1968 epidemic Streptococcus pneumoniae was
the principal bacterial pathogen in the elderly and Staphylococcus aureus in the young.
30
The relationship of the staphylococcus and the influenza virus has been much studied
and there is evidence that each promotes the growth of the other.
34
Thus, certain staphylococci have a protein in their cell wall that binds to the Fc
region of immunoglobulin G. In the presence of anti-influenzal serum this protein
enhances staphylococcal binding to cells infected by the influenza virus
35
and in this way the staphylococcus takes advantage of the host's immune reaction to
the influenza virus. In turn, the staphylococcus aids entry of the virus into the
host's cell. It does this by secreting a protease that activates a viral surface protein
necessary for penetration of the host's cells
36
: normally such proteases are in short supply, so limiting the rate at which influenza
virus can infect cells and reproduce. The relationship of influenza and Streptococcus
pneumoniae infection has been studied in less detail but there is evidence of similar
enhancement of bacterial adherence to tracheal epithelium following influenza infection.
37
Parainfluenza
Parainfluenza is caused by the parainfluenza viruses, not by Haemophilus parainfluenzae.
It is commoner in children and particularly affects the larynx, causing croup. There
may be necrosis of the mucosa as in influenza (Fig. 5.1.6A
), and quite frequently small polypoid growths of the bronchial and bronchiolar epithelium
develop, similar to those associated with infection by respiratory syncytial virus
(see below). In the lung there is hyperplasia of the alveolar epithelium and a serous
exudate containing increased numbers of macrophages is seen. In immunosuppressed individuals,
parainfluenza type III virus may result in a giant cell pneumonia that is indistinguishable
from that of measles except that the inclusion bodies typical of measles pneumonia
are not a feature (Fig. 5.1.6B).38, 39, 40, 41
Figure 5.1.6
Parainfluenza in an immunosuppressed patient. (A) The epithelium of the bronchiole
seen upper left has been destroyed and giant multinucleate epithelial cells are seen
in adjacent alveoli. (B) Higher magnification of the giant cell pneumonia.
Respiratory syncytial virus
Epidemiology
Respiratory syncytial virus was first isolated in 1956 from an outbreak of coryza
in a colony of chimpanzees and its infectivity for Man was shown when one of the investigators
of this epizootic illness contracted the disease. It has since been shown that the
virus frequently infects the lower respiratory passages of Man, particularly the young.
42
Specific neutralising antibodies indicative of an earlier infection are found in the
serum of almost all children over the age of 5 years in Britain. Most children merely
develop a cold but a few suffer from severe bronchiolitis, which in the developing
world is an important cause of death in the very young.42a, 42b Those that recover
are prone to develop recurrent wheeze later in childhood.
42c
The immunity infection conveys is incomplete and reinfections may occur throughout
life.
Respiratory syncytial virus infection shows a marked seasonal pattern, producing annual
epidemics each winter in temperate climates and in the hot rainy season in tropical
countries. During an incubation period of 3–6 days the virus replicates in the upper
respiratory tract, causing fever, cough and coryza. Spread from the upper to the lower
respiratory tract may occur, with consequent bronchiolitis and pneumonia.
Particularly important is the bronchiolitis that respiratory syncytial virus is prone
to cause in infants. The conductive airways of small infants are quite narrow and
easily blocked by relatively small amounts of inflammatory exudate: because of this,
fatal asphyxia is liable to follow respiratory syncytial virus infection. This is
particularly the case in those who have airflow obstruction as a consequence of prematurity
and its treatment. Several epidemics of acute bronchiolitis due to this virus have
been described among infants. These outbreaks are often remarkably focal in distribution,
affecting only a comparatively small area or community. Infants with bronchopulmonary
dysplasia and those who have congenital heart disease or are immunocompromised are
particularly at risk and units specialising in these underlying conditions have to
guard against nosocomial spread of infection.43, 44, 45 However, most children with
respiratory syncytial virus infection have no predisposing factors and even previously
healthy children may suffer fatal infection.42, 46
Pathogenesis
It is notable that infants under six months of age are particularly prone to respiratory
syncytial virus infection. Although this is a period when the infant benefits from
the presence of maternal antibodies, placental antibody transmission is selective,
being better for immunoglobulin G than A. Breast-feeding protects against respiratory
syncytial virus infection,
47
presumably by virtue of breast milk being rich in immunoglobulin A. It has been noted
that infants immunized against the virus and subsequently infected naturally, suffer
a more severe illness than those not so immunised,
48
suggesting that the damage is mediated immunologically.49, 50 This is supported by
the finding that the typical bronchiolitis is characterised by scanty virus whereas
in the rarer pneumonic form of the disease the virus is abundant. This is compatible
with the bronchiolitis representing an adverse immune reaction and the pneumonia being
the result of direct viral damage to the lungs.
51
The cytokine profile suggests that the reaction involved in the bronchiolitis involves
a predominantly type 2 response characterised by high interleukin-10/interleukin-12
and interleukin-4/γ-interferon ratios.
52
Suspicion has fallen upon the formaldehyde inactivation of the vaccine creating reactive
carbonyl groups on the antigen.
52a
Passive immunisation, conferred by monthly injection, is free of the hazards induced
by active immunisation and is recommended for high-risk babies.
53
Histopathology
The virus infects the bronchiolar epithelium and usually leads to its destruction.54,
55 Occasionally cytoplasmic inclusion bodies may be seen in degenerating bronchiolar
epithelial cells or the virus may be demonstrated by immunocytochemistry.1, 55 Regeneration
involves the proliferation of poorly differentiated cells which form a stratified
non-ciliated epithelium. Occasionally micropolypoid epithelial protrusions are evident
(Fig. 5.1.7
).
8
The bronchioles are occluded by plugs of mucus, fibrin and epithelial cell debris,
and cuffed by an infiltrate of lymphocytes, plasma cells and histiocytes. Except in
the immediate vicinity of the bronchioles, alveoli are generally not involved in the
inflammatory process. If, however, infection is on a major scale there may be pneumonia
with the general features of a viral pneumonia, as described above.
46
In severe immunodeficiency, respiratory syncytial virus may cause giant cell pneumonia,
56
a condition that is more often caused by measles virus.
Figure 5.1.7
Respiratory syncytial virus infection in which the patency of the bronchioles is compromised
by epithelial proliferation forming micropolypoid intrusions into the lumen. The bronchiolar
lumen is further narrowed by a neutrophil exudate in response to secondary bacterial
infection.
Metapneumovirus
Metapneumovirus was only discovered in 2001
57
but is now recognised to be ubiquitous; serological evidence of past infection is
universal by the age of 5 years. Much of this goes unrecognised but metapneumovirus
infection is nevertheless a leading cause of lower respiratory tract illness in young
children. In one investigation the virus or its DNA was found in 20% of nasal-wash
specimens previously declared virus-negative that had been collected from otherwise
healthy infants and children suffering from a lower respiratory tract illness: the
infection was associated with bronchiolitis in 59% of cases, pneumonia in 8%, croup
in 18% and exacerbation of asthma in 14%, a spectrum of disease similar to that found
with respiratory syncytial virus.
58
The pathological changes are not well described.
Measles
Clinical features and epidemiology
Measles (rubeola) is highly infectious and most children are infected soon after their
maternal antibodies have waned, the peak incidence being between 1 and 5 years of
age. After an incubation period of 1–2 weeks the patient develops coryza, cough and
fever. The subsequent development of small red spots with a white centre (Koplik's
spots) on the buccal mucosa followed by an erythematous maculopapular rash first involving
the face and then the rest of the body facilitates the diagnosis. The infection resolves
in about a week, following which the patient enjoys lifelong immunity.
In those parts of the world where measles has been prevalent for centuries the disease
is almost invariably mild and, unless complicated by bacterial pneumonia, it has a
very low mortality. In contrast, the mortality from measles may be appallingly high
in lands to which the virus is newly introduced. When the disease was carried to Fiji
from Australia in 1875, almost the whole population contracted it and a quarter of
them succumbed. Similar outbreaks have occurred in more recent times, when the infection
first reached Greenland for instance.
Measles has been regarded as one of the inevitable infections of childhood but with
an effective safe vaccine now available this is no longer necessary (Fig. 5.1.8
).
59
In the developed countries first and more recently in the developing world, immunisation
against measles has been promoted vigorously, with spectacular success. Between 2000
and 2007 mortality from measles fell by 74% worldwide and by 89% in Africa, where
it was formerly a major cause of death in childhood. The Americas were declared free
of endemic measles transmission in 2002 and cases there now occur only as a result
of its importation from other countries.60, 61 The disease has not yet been eradicated
in the UK, partly because unfounded claims that the vaccine is responsible for autism
led to declining vaccine uptake with consequent focal outbreaks of measles.
62
Other European countries still experiencing large outbreaks include the Ukraine, Switzerland
and Austria.
Figure 5.1.8
Annual measles notifications and vaccine coverage in England and Wales 1950–1999.
(Adapted by permission from BMJ Publishing Group Limited.
56
)
Where measles is prevalent, the incidence is usually highest in the early spring,
when droplet infections are particularly rife. The epidemics have a remarkably consistent
biennial character (see Fig. 5.1.8) and the explanation of this has been the subject
of several interesting hypotheses. The one most favoured envisages waning immunity
over the succeeding 2 years in those children who had only a subclinical illness in
the last epidemic. With the influx of two further entries into infant schools, a new
population of susceptible children is formed that is liable to contract overt disease
when the seasonal conditions are again favourable for the spread of the virus. In
this way a fresh epidemic develops. Overt clinical disease, on the other hand, confers
lifelong immunity.
If the lower respiratory tract is infected, the measles virus propagates in the epithelial
cells of the main respiratory passages, leading to the destruction of many of the
infected cells. In time there is recovery and multiplication of surviving cells, but
at the height of the disease the natural defences of the lower respiratory tract are
greatly compromised and secondary invading bacteria can successfully establish themselves
in the lungs, causing bronchiolitis and pneumonia.
Pneumonia is a rare complication of measles in the western world but is common in
malnourished African children, in whom it frequently proves fatal.
63
That pneumonic foci may develop in prosperous countries in the course of severe but
non-fatal attacks of measles is shown by the demonstration in some such cases of patchy
opacities on chest radiography; in almost all these cases the condition resolves rapidly.
The cause is usually one of the common bacterial pathogens but it can be another virus
taking advantage of the patient's debility and impaired cellular immunity. Measles
virus infection is characterised by both the development of a strong antiviral immune
response and abnormalities of immune regulation: there is often a poor skin response
to common antigens and helper/suppressor T-cell ratios may be low in both the blood
and bronchoalveolar lavage, suggesting that cellular immunity is impaired.
64
Thus, measles has predisposed to both adenovirus and herpesvirus pneumonia.65, 66
Secondary pulmonary infection is responsible for about half the mortality in measles.
67
Other causes of death include measles pneumonia and measles encephalitis.
Measles may also be very severe when it affects immunodeficient patients, whether
they are suffering from primary immunological defects, acquired diseases such as leukaemia
or conditions which require treatment with cytotoxic or immunosuppressant drugs.
68
Such patients may have unpredictable responses to measles virus. They may have a rash
but fail to produce antibodies, or they may fail to develop a rash although infected
with the virus. Fatal measles pneumonia in a previously healthy adult is very rare.
69
Pathology of measles pneumonia70, 71
Death from measles pneumonia occurs typically about 2 weeks after the appearance of
the rash. At necropsy, the lungs are heavy and of rubbery consistency, and their cut
surface is pale pink. Close examination may show that the small bronchi are cuffed
by a greyish zone. Extensive vascular thrombosis has been a feature of some cases.
Microscopically, there are degenerative changes in the epithelium of the bronchi and
bronchioles, often accompanied by hyperplasia, particularly in the small airways.
As in influenzal pneumonia, squamous metaplasia may occur and mitotic figures may
be numerous. Measles pneumonia may take the form of diffuse alveolar damage with hyaline
membrane formation (see Fig. 5.1.3), or, more characteristically, multinucleate giant
cells may line the alveolar ducts and alveoli (Fig. 5.1.9
). Electron microscopy shows that the giant cells are formed from type II alveolar
epithelial cells.71, 72 The giant cells contain prominent cytoplasmic and nuclear
viral inclusion bodies that are clearly evident in eosin-stained sections. Being epithelial,
the pulmonary giant cells are quite different from the Warthin–Finkeldey giant cells
that are found in lymphoid tissue throughout the body in measles, particularly in
the immediately pre-exanthematous stage.
Figure 5.1.9
Measles giant cell pneumonia. There is a syncytial proliferation of type II pneumocytes
containing eosinophilic cytoplasmic and nuclear viral inclusions. This response is
typical of measles pneumonia but is occasionally encountered with other forms of viral
pneumonia (see Fig. 5.1.6).
As well as the epithelial changes, there is a heavy accumulation of macrophages, lymphocytes
and plasma cells in the alveolar walls. This cellular infiltrate extends into the
connective tissue surrounding the bronchioles and small bronchi, accounting for the
pale cuff that is seen around them on naked-eye examination. Neutrophils are not numerous
unless there is a secondary bacterial infection. The appearances are closely comparable
to those found in the lungs of dogs that have died of distemper (Carre's disease),
which is also caused by a paramyxovirus.
Differential diagnosis
Measles is the commonest cause of giant cell pneumonia but occasionally other viruses
such as parainfluenza, respiratory syncytial and varicella-zoster viruses are responsible,
especially in the immunocompromised (see Fig. 5.1.6).38, 56, 73 The diagnosis is usually
evident clinically or is made serologically but immunohistochemistry can be performed
on tissue sections. Hard-metal disease is also characterised by the presence of alveolar
epithelial polykaryons but these are more focal than those of measles, lack viral
inclusion bodies and are not accompanied by such severe interstitial pneumonia (see
Fig.7.1.25, p. 354).
Adenovirus
Like measles, adenovirus causes a febrile rash and infects the upper respiratory tract
much more commonly than the lungs. However, adenovirus may infect the lower respiratory
tract at all levels and it is a relatively common cause of pneumonia in malnourished
children throughout the world.
Adenovirus pneumonia occurs sporadically and in epidemics, particularly in children
and young adults, and occasionally complicates measles.65, 66 Adenovirus pneumonia
is usually combined with bronchiolitis and the lesions are most severe at the centres
of the acini, being concentrated on the bronchioles. The virus causes necrosis of
the bronchioles, many of which are totally destroyed or are recognisable only by their
muscle coat: hyaline membranes replace the necrotic epithelium (Fig. 5.1.10A
). Surviving epithelial cells show nuclear inclusions of varying staining reaction:
some are diffusely basophilic or amphiphilic and fill the entire nucleus apart from
a rim of chromatin (Cowdry type B) while others are eosinophilic and surrounded by
a clear halo (Cowdry type A). The bronchioles are cuffed by a lymphoid infiltrate
and may show proliferative epithelial activity, variously interpreted as being the
result of viral stimulation or of regeneration.54, 74 The alveolar tissue shows a
mononuclear interstitial pneumonia.
Figure 5.1.10
Adenovirus pneumonia. (A) Bronchioles bear the brunt of the damage and here show necrosis
of their lining epithelium. (B) Viable alveolar lining cells contain basophilic nuclear
inclusions while others are necrotic, having been reduced to eosinophilic ‘smudge
cells’ by the viral inclusions disrupting the nucleus. (A and B from sections provided
by the late Dr N Rossouw, Tygerberg, South Africa and Dr V Chrystal, Durban, South
Africa.) (C) Electron microscopy shows that adenovirus particles measure 70–100 nm
and have a naked icosahedral structure.
(Courtesy of Miss A Dewar, Brompton, UK.)
The intranuclear viral inclusions measure up to 5 µm and eventually disrupt the nucleus,
leaving so-called smudge cells (Fig. 5.1.10B, C). Healing may be by complete resolution
or the pneumonia may be complicated by bronchiolitis obliterans or bronchiectasis.
75
Severe acute respiratory syndrome
SARS first appeared in southern China in 2002, from where it quickly traversed the
globe, facilitated by air travel and coming to international attention particularly
after an outbreak in Hong Kong in 2003.76, 77, 78, 79, 80, 81 Cases were subsequently
identified in many countries and about 10% of those affected died.82, 83, 84, 85 The
cause was a previously unknown coronavirus that had switched from civet cats encountered
in Asian food markets and adapted to human transmission.86, 87 Transmission is air-borne
but requires close person-to-person contact. There is no evidence of transmission
following casual contact. The virus has subsequently been identified in Chinese horseshoe
bats and it is likely that these animals represent the natural reservoir of the virus,
with the civets merely acting as carriers.88, 89
Clinical features
The incubation period ranges from 1 to 10 days, following which there is a prodromal
fever, cough and dyspnoea. Less common symptoms include headache, diarrhoea, dizziness,
myalgia, chills, nausea, vomiting and rigor.
90
There is no apparent sex predilection and the age distribution is wide. Common laboratory
features include lymphopenia involving both CD4 and CD8 lymphocytes, thrombocytopenia,
prolonged thromboplastin time, elevated alanine transminase, lactate dehydrogenase
and creatinine kinase. Positive viral recovery rates from urine, nasopharyngeal aspirate
and stool specimen have been reported to be 42%, 68% and 97% respectively on day 14
of illness, whereas serological confirmation may take 28 days to reach a detection
rate above 90%. However, quantitative measurement of blood SARS coronavirus RNA using
real-time RT-PCR techniques has a detection rate of 80% as early as day 1 of hospital
admission.
91
Radiographic abnormalities include focal, multifocal or diffuse opacities. Computed
tomography is more sensitive, sometimes showing extensive consolidation in patients
with normal chest radiographs. However, the radiological features are not specific
and need to be correlated with the clinical and histological findings.
92
Pathogenesis
Although pulmonary involvement is the dominant clinical manifestation, extrapulmonary
features are common and the virus can often be recovered from faeces and urine, indicating
that it is widely distributed in the body. The identification of a specific receptor
for the virus is relevant to its tissue distribution. The receptor, a metallopeptidase
known as angiotensin-converting enzyme 2, is expressed particularly strongly by pulmonary
alveolar and small intestinal epithelia and vascular endothelia.93, 94, 95
Pathology
The histology varies according to the duration of illness but the predominant pattern
is diffuse alveolar damage.96, 97, 98, 99, 100 Cases of less than 10 days’ duration
show air space oedema and hyaline membranes whereas those of longer duration exhibit
type II pneumocyte hyperplasia, squamous metaplasia, multinucleated giant cells and
acute bronchopneumonia succeeded by intra-alveolar organisation.26, 96 The alveolar
pneumocytes may also show striking cytomegaly with granular amphophilic cytoplasm
(Fig. 5.1.11
), that sometimes contains eosinophilic inclusions akin to the Mallory bodies of alcoholic
hepatitis.96, 97 Less common features include haemophagocytosis and thrombosis.97,
99 The virus can be identified by RT-PCR in fresh or formalin-fixed, paraffin-embedded
lung tissue. Electron microscopy may reveal the viral particles in the cytoplasm of
epithelial cells.97, 98, 99
Figure 5.1.11
Severe acute respiratory syndrome. (A) The features of early diffuse alveolar damage
are seen, consisting of extravasation of red blood cells, desquamation, an acute and
chronic interstitial inflammatory infiltrate and a few hyaline membranes. (B) Regenerating
epithelial cells show nuclear atypia.
Treatment and prognosis
Treatment with corticosteroids, broad-spectrum antibiotics and antiviral agents has
been beneficial.98, 102 Interferon-α may also have a role.
103
However, infection control is as important as pharmacological therapy in this disease.
In the acute phase, SARS is associated with considerable morbidity and mortality,
with a global case fatality rate ranging from 7 to 27% (average about 11%). Adverse
prognostic factors include advanced age, coexistent disease, high lactose dehydrogenase
levels and high initial neutrophil counts. CT data on the extent of the disease are
also useful in assessing prognosis.
104
Clinical follow-up of patients who recover has demonstrated residual abnormalities
of varying degree, including abnormal lung function and patchy fibrosis.105, 106 Many
survivors also experienced transient pituitary dysfunction.
107
Herpes simplex108, 109
Virology and predisposing causes
Herpes simplex virus typically causes mucocutaneous vesiculation, serotype 1 (HSV1)
generally affecting the oronasal area and serotype 2 (HSV2) the genital mucosae. As
with all herpesviruses, infection is lifelong; the virus remains dormant until immunity
weakens, which may be triggered by a variety of factors. In these circumstances either
serotype may involve the lower respiratory tract. Respiratory infection by HSV1 is
more commonly encountered in adults, the infection spreading from the oropharynx,
whereas neonatal respiratory infection is usually due to HSV2 as a component of generalised
haematogenous disease.110, 111 Infection of the lower respiratory tract takes the
form of tracheobronchitis or pneumonia. Herpes simplex tracheobronchitis is predisposed
to by damage to the respiratory epithelium, especially factors that lead to squamous
metaplasia, such as endotracheal intubation and burns.112, 113, 114, 115, 116 Risk
factors for herpes simplex pneumonia include transplantation,
117
cytotoxic chemotherapy and human immunodeficiency virus (HIV) infection
118
: herpes simplex pneumonia is rare in the immunocompetent.
119
Pathology
In herpes simplex tracheobronchitis there is extensive mucosal ulceration and pseudomembrane
formation. Viral inclusions are most prominent at the periphery of the ulcers and
may be identified in exfoliated cells (Fig. 5.1.12
). If they are not well developed an immunostain may establish the diagnosis. Long-standing
airway infection leads to luminal narrowing and obstructive features. In the lungs
the changes are very similar to those of adenovirus pneumonia, including the presence
of Cowdry type B ground-glass intranuclear viral inclusions, although these are more
eosinophilic than those of adenovirus. Both adenovirus and herpes simplex pneumonia
bear a superficial resemblance to bacterial bronchopneumonia but the similarity is
in the distribution of the lesions rather than their character: the bronchioles and
centriacinar alveoli are mainly affected but the lesions are characterised by necrosis
and the accumulation of nuclear debris rather than exudation of neutrophils. Occasionally
herpes simplex infection takes the form of a focal necrotising pneumonia more typical
of varicella infection (see below). Alternatively there may be arterial involvement
in herpes simplex pneumonia with a necrotising vasculitis affecting small and medium-sized
pulmonary arteries.
120
Sometimes the pneumonia is diffuse: it is suggested that focal disease represents
extension of oral mucocutaneous herpesvirus infection down the tracheobronchial tree
into the lung whereas diffuse pneumonia is the result of haematogenous spread.
108
Figure 5.1.12
Herpes simplex virus. Bronchial brushings from an ulcer in the lower trachea show
multinucleate epithelial cells with glassy nuclear features.
From a patient with oral herpes who had started steroid therapy for asthma.
Cytomegalovirus
Virology and epidemiology
Cytomegalovirus is the largest of the herpesviruses and is widespread in most communities,
persisting for life, like all herpesviruses. It is transmitted in saliva and blood
and by sexual contact and organ transplantation. Seropositivity, taken to indicate
carriage of the virus, steadily increases with age. The prevalence of seropositivity
in adults is generally over 50% and approaches 100% in homosexual men. However, carriage
of the virus does not necessarily equate with disease. The immunocompetent host is
unlikely to experience any recognisable clinical effects of cytomegalovirus infection.
Symptomatic cytomegalovirus infection is seen in newborn children infected before
birth by virus carried by their mother, and in adults who have undergone organ transplantation
or have been infected with HIV. In the newborn the disease presents as an acute fatal
infection with jaundice and leukoerythroblastic anaemia.
Cytomegalovirus is a serious pathogen in transplantation recipients,
121
possibly because the virus replicates best in cells that are activated, as in a transplanted
organ. The risk is greatest with bone marrow transplantation, intermediate with heart,
lung and liver transplantation and lowest with renal transplantation. However, donor
and recipient matching for cytomegalovirus status has reduced the incidence of transmission
from the donor. Before the introduction of this policy, fatal cytomegalovirus pneumonia
or systemic infection was common. Today reactivation of latent infection is a more
common problem but it is important to distinguish the mere presence of viral inclusions
from pneumonitis. When a lymphoid infiltrate accompanies the viral inclusions it is
also important to distinguish an infective pneumonitis from lung allograft rejection:
generally, the infiltrate of cytomegalovirus pneumonia lacks the perivascular lymphocyte
distribution seen in rejection. As well as causing a pneumonitis that has to be distinguished
from rejection, cytomegalovirus may be involved in chronic lung rejection.
122
It has been speculated that cytomegalovirus could promote allograft rejection by stimulating
the production of proinflammatory cytokines or increasing the expression of major
histocompatibility complex molecules.
The position of cytomegalovirus in regard to pulmonary disease in acquired immunodeficiency
syndrome (AIDS) can also be difficult to determine. Cytomegalovirus inclusions are
frequently encountered in AIDS but it is often difficult to determine whether pathological
changes are due to the virus or to accompanying bacterial or Pneumocystis infection.
Only occasionally is cytomegalovirus the only pathogen identified in severe pneumonia
in AIDS patients.
123
Some investigators claim that cytomegalovirus contributes to the high mortality from
pneumonia in AIDS patients
124
while others view it merely as a bystander rather than the primary pathogen in these
patients.
125
Sometimes, replication of the virus is unaccompanied by any significant degree of
pulmonary inflammation or damage,
126
indicating a poor host response, which, as in other viral infections, largely involves
T lymphocytes, cells that are particularly defective in AIDS. The differing roles
of cytomegalovirus in AIDS and transplant recipients have led to the view that the
pathological changes are not a direct effect of the virus but an immunopathological
condition attributable to the T-cell response to the virus.
127
Pathological features
The pneumonia may be unilateral or bilateral, and generally involves the lower lobes;
advanced lesions may appear as reddish purple nodular areas. Two patterns of pulmonary
involvement have been described in bone marrow transplant recipients: a fulminant
systemic infection characterised by a miliary pattern of disease and a more insidious
disease with a more diffuse distribution in the lungs.
121
Histologically, there is a chronic interstitial pneumonitis and some of the alveolar
epithelial cells are enlarged and contain characteristic inclusions. These measure
up to as much as 10 µm in diameter and are surrounded by a clear zone inside the nuclear
membrane (Fig. 5.1.13
). These Cowdry type A intranuclear inclusions have been likened to an owl's eyes.
The inclusions represent clumped chromatin and the clear zone the virus. Cytoplasmic
inclusions up to 2 µm in diameter are often also present. Severe cases may show a
necrotising pneumonia or tracheobronchitis without the inclusions being well developed,
in which case immunocytochemistry or in situ hybridisation may be used to advantage
as these techniques show that many more cells are infected than those containing the
characteristic inclusions (see Fig. 5.1.13D).6, 7, 128 Diffuse alveolar damage is
a further pattern of disease that is occasionally seen in cytomegalovirus pneumonia.
Figure 5.1.13
Cytomegalovirus pneumonia. (A) There is a prominent nuclear inclusion in the centre
of the field. (B) Electron micrograph of an alveolar epithelial cell infected by cytomegalovirus.
Numerous viral particles are evident in both nucleus (above) and cytoplasm (below).
As the viral particles leave the nucleus and enter the cytoplasm they acquire a coating
derived from the nuclear envelope and consequently enlarge. (C) Low-power electron
micrograph of the cell seen in (B), showing that it is greatly enlarged compared with
its neighbours. Coated viral particles are evident in the cytoplasm but uncoated particles
in the nucleus are too small to be recognised at this magnification. However, characteristic
central clumping of the chromatin is evident.
(B and C courtesy of Miss A Dewar, Brompton, UK.)
(D) Immunocytochemistry shows abundant virus in the cytoplasm as well as the nucleus
(immunoperoxidase stain).
HIV and AIDS
Virology and means of spread
The HIVs belong to the lentivirus subfamily of the retroviruses and are thought to
have originated from chimpanzees, which harbour the closely related simian immunodeficiency
virus. They are the cause of AIDS and are transmitted primarily through sexual contact,
by anal or vaginal intercourse with an HIV-positive person. Other routes of transmission
are by exposure to infected blood, generally through the use of contaminated needles
and syringes by drug addicts. Infected blood products and donor tissues are other
potential sources of infection. An infected woman can pass the virus to her child
in utero, at delivery or through breast-feeding. Occupational acquisition of HIV is
unusual but has occurred, chiefly through needlestick injuries. In histopathology
departments, particular care is required in handling unfixed tissues, as in preparing
frozen sections and conducting autopsies. Fixed tissues do not present a risk of infection.
Most national bodies have produced guidelines for safe laboratory practice in the
AIDS era.
129
HIV infection is not always recognisable and a practical approach is therefore to
treat every cadaver and all unfixed tissue as if it were infectious.
Pathogenesis of AIDS
Following entry into the body and the development of neutralising antibodies, HIV
is found in highest concentration within the germinal centres of lymphoid tissue where
it can be demonstrated by immunohistochemistry attached to a follicular dendritic
cell.
129a
The virus attacks both the follicular dendritic cells and the CD4+ helper T lymphocytes
and blood levels of these latter cells below 200/µL are associated with the development
of a variety of AIDS-defining conditions. The interferon-γ-secreting Th1 cells that
are central to immune defence against a variety of other infections are particularly
vulnerable to attack. Once HIV infection has occurred, antibody develops, generally
within a month, and after a period that is usually measured in years CD4 counts drop
and manifestations of AIDS develop. Concentrations of virus in the blood and body
fluids are particularly high around the time of seroconversion and when AIDS develops.
Epidemiology
AIDS was first recognised in 1981 in Haiti, since when it has spread widely and few
countries are now spared its ravages. A quarter of a century after its first recognition
AIDS had killed about 25 million people and about 65 million had been infected with
HIV. Many of those harbouring HIV do not know they are infected. The number of people
infected with HIV is rising, because of population growth and because drug treatment
is prolonging life. The epidemic is worst in sub-Saharan Africa and next the Caribbean
but it is growing fastest in eastern Europe and central Asia. Worldwide, women make
up about half of those infected with HIV, with the largest number in sub-Saharan Africa.
Since the introduction of highly active antiretroviral therapy (HAART) mortality rates
have declined and life expectancy improved amongst those so treated, but these benefits
have so far been largely confined to the industrialised countries.
Pathology
Few organs escape the ravages of fully developed AIDS but the lungs are those most
frequently involved in many series.130, 131 AIDS has many pulmonary manifestations,
all of which are described in detail under their relevant headings. Most are secondary
to the immunodeficiency but it is possible that certain lymphocytic infiltrates reflect
HIV infection of the lung. These are generally non-specific T-cell infiltrates, which
are largely CD8+ and milder than those that characterise lymphoid interstitial pneumonia132,
133, 134, 135, 136; HIV has been identified in the lung tissue by in situ hybridisation
in a minority of cases.
135
The heavier lymphoid infiltrates of lymphoid interstitial pneumonia seen in HIV-infected
children largely comprise CD8+ HIV-specific lymphocytes. Such children have fewer
opportunistic infections and survive longer than other HIV-positive children, suggesting
that in this setting lymphoid interstitial pneumonia reflects an effective immune
response.
137
Experiments in mice suggest that viral persistence and interferon-γ production are
involved.138, 139
The commonest pulmonary manifestations of AIDS are listed in Table 5.1.1
.140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150 Rarer pulmonary manifestations
include infection by herpes simplex118, 151 and varicella-zoster
152
viruses, Blastomyces dermatitidis,
153
Candida species,
152
cryptosporidia,
154
microsporidia
155
and Strongyloides stercoralis.
152
There is also an increased incidence of respiratory infection by common pyogenic organisms,143,
156, 157 especially Streptococcus pneumoniae and Haemophilus influenzae,
152
sometimes resulting in obliterative bronchiolitis
158
or unusual diseases such as bacterial tracheitis
159
where the trachea is narrowed by pus or necrotic material containing colonies of mixed
bacteria. Tuberculosis has also made an unwelcome resurgence since the advent of AIDS.160,
161, 162 Opportunistic mycobacterial infection,
163
malakoplakia,164, 165 bacillary angiomatosis,
166
secondary alveolar lipoproteinosis,
167
follicular bronchitis and bronchiolitis
149
are also encountered in AIDS patients. However, there are marked geographical differences
in the incidences of these manifestations of AIDS: tuberculosis is particularly common
in poor countries whereas Pneumocystis, non-tuberculous mycobacteriosis and lymphoma
are commoner in richer communities. Since the 1990s there has been a trend towards
multiple infections, more mycobacterial disease and less Pneumocystis infection and
Kaposi's sarcoma.130, 142, 168
Table 5.1.1
The varieties of pulmonary disease described in 131 patients with AIDS.137, 138 The
opportunistic invaders are often present in combination and the inflammatory reaction
to them is often atypical: for example, the reaction to mycobacterial infection (frequently
Mycobacterium avium-intracellulare) is often non-granulomatous, whilst Pneumocystis
jirovecii may provoke a granulomatous response or diffuse alveolar damage, rather
than the usual foamy alveolar exudate
Patients (%)
Opportunistic infection
Pneumocystis jirovecii pneumoniaa
63
Cytomegalovirus pneumonia
19
Mycobacterial pneumonia
13
Bacterial pneumoniaa
8
Invasive candidiasis
2
Toxoplasmosis
2
Cryptococcosis
1
Invasive aspergillosis
1
Histoplasmosis
1
Non-infectious diseases
Diffuse alveolar damage
15
Kaposi's sarcoma
9
Non-specific interstitial pneumonitisa
5
Pulmonary haemorrhage
3
Pulmonary lymphoid hyperplasiab
0
Lymphoid interstitial pneumonia
2
Lymphomaa
2
a
Since the introduction of highly active antiretroviral therapy (HAART), P. jirovecii
pneumonia has become less common while bacterial pneumonia and lymphoma have increased.139,
140, 141
b
Pulmonary lymphoid hyperplasia is seen particularly in children suffering from acquired
immunodeficiency syndrome (AIDS)142, 143, 144, 145 but is also recorded in occasional
adults.
146
Together with lymphoid interstitial pneumonia, pulmonary lymphoma and the sicca syndrome,
147
it forms a spectrum of pulmonary lymphoproliferative disease in AIDS and other conditions.
In most cases the secondary pulmonary infections can be diagnosed from material obtained
through the fibreoptic bronchoscope (brushings, washings, lavage or biopsy)
169
or from sputum
170
but occasionally a particular pulmonary manifestation of AIDS is not revealed until
open biopsy is undertaken or examination is made postmortem.
Rapidly progressive plexogenic pulmonary hypertension is also reported in persons
infected by HIV but generally not evincing AIDS.171, 172, 173, 174, 175, 176 The lungs
are often otherwise normal. The virus has not been identified in the pulmonary vessels
but tubuloreticular structures suggestive of cytokine accumulation have been identified
there by electron microscopy in HIV-positive individuals.
177
Less frequently, veno-occlusive disease or thrombotic arteriopathy is the basis of
HIV-associated pulmonary hypertension. Emboli of foreign particulate material may
also be found in the lungs of patients who have acquired their HIV infection through
the intravenous injection of drugs formulated for oral use, while a variety of vasculitides
affecting various organs including the lungs is described.
178
As well as the neoplastic manifestations of AIDS listed in Table 5.1.1 (Kaposi's sarcoma
and lymphoma), the incidence of carcinoma of the lung is increased in AIDS and the
affected patients are younger than those in the general population.179, 180, 181 All
these tumours may present as endobronchial lesions, as may tuberculosis and aspergillosis
in AIDS patients.
182
The lymphomas include diffuse large B-cell lymphomas that take the form of mass lesions
within the lungs and primary effusion lymphomas affecting the pleura.
Drug toxicity
HAART drug toxicity contributes up to 2% of deaths among HIV-infected patients so
treated. The toxicity is mainly hepatic but sarcoid-like nodules have been reported
in the lungs,
183
probably reflecting immune restoration.
184
Recovery of immune status may give rise to an active and often dramatic inflammatory
response to previously indolent infections, which has been termed the immune reconstitution
syndrome (IRIS).
185
It is also suggested that it is HAART rather than HIV that is responsible for the
pulmonary hypertension referred to above.
186
Chickenpox (varicella) and herpes zoster
The manifestations of chickenpox and herpes zoster are generally confined to the skin
but visceral involvement occurs on rare occasions.187, 188 Since chickenpox is so
common in childhood, most adults are immune. However when chickenpox affects adults,
especially pregnant women, it carries a risk of fulminating varicella pneumonia, which
can be rapidly fatal. The fetus is also at risk: in the first two trimesters of pregnancy
chickenpox may result in embryopathy and in the last trimester it may cause neonatal
pneumonia. The immunocompromised, including those receiving systemic corticosteroids,
are particularly prone to suffer severe infections, including pneumonia.
189
The severe forms of chickenpox sometimes encountered in otherwise healthy adults may
involve the lungs but recognition of this is often retrospective; the healed lesions
may produce characteristic radiographic changes, namely innumerable small foci of
calcification.190, 191 Such patients are generally cigarette smokers.
192
Pathological features
The pneumonias of varicella and herpes zoster pneumonia are identical.
193
They represent a focal necrotising condition that lacks any apparent relation to the
acinar architecture (Fig. 5.1.14A
). It starts as a fibrinous exudate, involving several adjacent alveoli, and goes
on to destroy the intervening alveolar walls. Eosinophilic intranuclear viral inclusions
may be evident in bronchiolar or alveolar epithelial cells. Giant cell pneumonia is
a rare manifestation of varicella-zoster infection.
73
Figure 5.1.14
Chickenpox pneumonia. (A) Lung showing a focus of necrosis similar to that more commonly
encountered in the skin. (B) Healed chickenpox pneumonia showing central dystrophic
calcification. (C) Healed chickenpox pneumonia evident macroscopically as numerous
hard, pale micronodules scattered through the lungs.
(Courtesy of Dr GA Russell, Tunbridge Wells, UK.)
Healing results in circumscribed fibrous nodules that measure up to 5 mm in diameter
and are prone to calcify (Fig. 5.1.14B, C).190, 191 Numerous calcified opacities scattered
throughout the lung fields present a radiographic appearance that, outside the USA
and other countries where histoplasmosis is endemic, is virtually diagnostic of previous
chickenpox pneumonia.
Smallpox (variola)
In 1980 the world was declared free of smallpox and it is to be hoped that this section
is only of historical interest. Severe smallpox was often accompanied by acute ulcerative
tracheobronchitis and pneumonia. The latter was ordinarily due to secondary bacterial
infection, but interstitial lesions of viral type were also found.
A condition described as ‘smallpox handler's lung’ was also observed. This affected
nursing and medical staff attending patients with smallpox. It was characterised by
high fever and prostration: radiological examination showed widespread mottling of
the lungs with shadows up to several millimetres across. Typically, there were no
catarrhal symptoms and recovery appeared to be the rule. These patients were well
immunised by previous vaccination against smallpox and did not develop a rash. The
pulmonary changes may have represented an allergic reaction to smallpox virus inhaled
in the dust of scales desquamated by their patients, but it was never possible to
study the pathological changes.
Hantavirus pulmonary syndrome
Hantaviruses are best known as the cause of haemorrhagic renal fever but they also
cause a (non-haemorrhagic) pulmonary syndrome. This was first recognised in 1993 when
an unusual respiratory illness was noted in rural communities in the south-west of
the USA and soon identified as a previously unrecognised hantavirus infection.194,
195, 196 As with the previously recognised hantaviruses, that responsible for the
pulmonary syndrome is maintained in the wild in a single species of rodent, in this
case the deer mouse, Peromyscus maniculatus, which is widely distributed across North
America. Like other mice they are inclined to impinge on humans in their hunt for
food and there had been a marked increase in the number of deer mice in the south-west
USA in 1993. Transmission of the virus is believed to be by inhalation of dried mouse
excreta. Further cases have subsequently been identified in other parts of the USA
and retrospective studies of archival material have shown that cases existed before
1993, the earliest in 1978.
197
The name Muerto Canyon virus was initially proposed for the hantavirus responsible
for the pulmonary syndrome but this has given way to Sin Nombre virus. It is now know
to be a member of the Bunyaviridae family of RNA viruses.
Cases of hantavirus pulmonary syndrome have subsequently been identified in several
South American countries, with one outbreak in southern Argentina being unusual in
that there appeared to be person-to-person transmission,
198
a feature that has so far not been observed in any other form of hantavirus infection.
Clinical features
The hantavirus pulmonary syndrome commences with a prodromal illness characterised
by fever and myalgia, and perhaps nausea, vomiting, abdominal pain, headache and dizziness.194,
195 After a few days, a cardiopulmonary phase is heralded by progressive cough and
shortness of breath. Common physical findings at this stage are tachypnoea, tachycardia,
hypotension and fever. Radiographic findings include the rapid development of pulmonary
oedema. Most of the original 17 patients with laboratory-confirmed disease required
intubation and mechanical ventilation and this led to large volumes of clear proteinaceous
fluid being obtained by endotracheal suction. In 13 cases (76%) intractable hypotension
terminated in cardiac dysrhythmia and death within 2–16 (median 7) days of the onset
of symptoms.
Pathological features
Autopsy shows heavy oedematous lungs and large, serous pleural effusions. Microscopy
confirms the oedema and shows interstitial lymphocytic infiltrates.195, 196, 199 Hyaline
membranes have been described in some studies.200, 201 Neutrophils are scarce and
viral inclusions are not found. Despite the profound circulatory failure the heart
is normal. Lymphocytosis is evident in the liver, spleen and lymph nodes. Immunocytochemistry
shows viral antigen in pulmonary endothelial cells and virus-like particles are evident
in these cells on electron microscopy. The target of infection appears to be the capillary
endothelium in all organs with particularly heavy involvement of those in the lung,
resulting in increased pulmonary vascular permeability.
The diagnosis is now made by serological tests that detect specific IgM antibodies
or a fourfold rise in IgG antibodies. Immunocytochemistry and PCR are used to detect
the virus in tissue. The danger to mortuary and laboratory staff is unknown but in
view of the high mortality rate, full precautionary measures are advocated.
202
Treatment is supportive. Prevention is based on methods that minimise contact with
the rodent vectors.
Mycoplasmal pneumonia
Epidemiology and microbiology
During the 1930s, cases of a mild form of pneumonia were reported that clinically
were unlike those attributable to bacterial infection. None of the bacteria known
to cause pneumonia could be recovered from the sputum, and as long as the condition
was uncomplicated by secondary bacterial infection the leukocyte count in the blood
showed little tendency to rise. Cases often occurred in small community epidemics
in schools, colleges and camps, although even under these conditions, which are usually
conducive to the spread of respiratory infections, the disease was not highly contagious.
It became known as primary atypical pneumonia.
The aetiology of primary atypical pneumonia attracted much interest and the first
advance came in 1944 with the isolation of an organism that became widely known as
the ‘Eaton agent’ after its discoverer. That this agent is specifically concerned
with the clinical disease is indicated by the rise in specific antibodies that occurs
during the course of the illness. The infection, mainly in subclinical form, has become
widely prevalent, as is shown by the frequency with which specific antibodies can
be detected in the serum of healthy people in the general population. The clinical
disease accounts for 18% of all community-acquired pneumonia requiring admission to
hospital, a frequency second only to that of pneumococcal pneumonia.
203
Because the disease could be transmitted to both experimental animals and human volunteers
by filtrates of sputum from cases of primary atypical pneumonia, the Eaton agent was
at first regarded as a virus. Later studies indicated instead that it belongs to the
group of ‘pleuropneumonia-like’ organisms (PPLO) – the mycoplasmas which can pass
through a coarse bacterial filter. The organism is now known as Mycoplasma pneumoniae:
it is one of the considerable number of mycoplasmas that have been recognised in humans,
animals, plants and soil. Because of their ubiquity in rats and mice, any experiments
involving the lungs of these animals are soon bedevilled by the development of bronchiectasis,
pneumonia, lung abscess and empyema, unless specific pathogen-free strains are used.
For a time, M. pneumoniae was regarded as the L form of Streptococcus MG, a non-haemolytic
streptococcus that is agglutinated by the serum of some 10% of patients with Mycoplasma
pneumonia and that was isolated originally from a case of the latter at necropsy:
comparative studies of the nucleic acids of the two organisms have shown that they
are in fact unrelated. The explanation of the presence of agglutinins against Streptococcus
MG is probably a matter of shared antigens. In about half the cases the patient's
serum agglutinates group O red blood cells at a temperature between 0 and 5°C (cold
haemagglutination test), but the diagnosis is best established by demonstrating antibodies
to M. pneumoniae in the patient's serum or more recently by PCR assay.204, 205
Clinical features
The organism generally follows a 4-yearly epidemic cycle and predominantly affects
younger patients. There is a wide spectrum of respiratory disease, including sore
throat, otitis media, sinusitis, laryngitis, bronchitis, bronchiolitis and pneumonia.
The chief clinical features are cough, fever, headache and malaise, sometimes associated
with rashes, arthritis and haemolytic anaemia. Pneumonia develops in about 10% of
cases and is characterised by a more gradual onset than acute bacterial pneumonia.
Chest radiography shows irregular, ill-defined opacities, usually in the hilar region
and sometimes bilateral. It is characteristic of the disease that the radiological
changes are much more extensive than the comparatively mild clinical manifestations
indicate. The case fatality rate is low, of the order of 1 in 1000 patients, and the
pulmonary opacities that are conspicuous during the 10 days or so that the illness
lasts gradually resolve during the ensuing days of convalescence.
Pathogenesis
The pathogenesis of M. pneumoniae infection has been studied in animal models and
organ cultures of human respiratory epithelium. The organisms adhere to the respiratory
epithelial cells and inhibit ciliary activity. Infected cells show cytoplasmic vacuolation
and nuclear swelling, with progression to complete loss of cilia.206, 207 The loss
of cilia predisposes the more distal lung to secondary bacterial superinfection but
the Mycoplasma may also affect the distal parenchyma directly.
Immunodeficient animals show reduced severity of mycoplasmal pneumonia and it is likely
that immune mechanisms are involved in the pathogenicity of the disease. Autoantibodies
are produced in response to Mycoplasma infection, probably as a result of mycoplasmal
antigens being shared by host cells; such antibodies could account for many of the
bronchopulmonary and extrapulmonary manifestations of the disease.
Histopathology
There have been few opportunities for histological study of the lesions in primary
atypical pneumonia but when undertaken it generally discloses widespread bronchiolitis
and chronic interstitial pneumonia similar to that caused by many respiratory viruses.208,
209 The bronchiolitis sometimes progresses to epithelial ulceration. Lymphocytic infiltration
of the walls of alveolar ducts and alveoli characterises the interstitial pneumonia
whilst oedema fluid, red blood cells and macrophages are found in many groups of alveoli,
and an occasional alveolus may contain hyaline membranes. Neutrophils are generally
less numerous, both in the bronchioles and the alveoli, than in the bacterial forms
of pneumonia, but bacterial superinfection is a common complication.
208
The more heavily involved parts may become fibrotic and pleural adhesions may develop.
There is nothing pathognomonic about any of these changes. Rarely, M. pneumoniae is
responsible for fatal respiratory disease, in which case the histological appearances
are those of diffuse alveolar damage.
210
Rickettsial infection
Rickettsia are rod-like or coccobacillary organisms that are similar to but smaller
than bacteria. However, rickettsial pneumonia is dealt with in this chapter rather
than with the bacterial pneumonias because its clinical and pathological features
more closely resemble those of mycoplasmal pneumonia. Of the tribe rickettsiae, three
genera contain organisms pathogenic to humans: Rickettsia, Bartonella (formerly Rochalimaea)
and Coxiella. Rickettsia species are responsible for typhus and certain spotted fevers,
and whilst pneumonia may occur in several of these,211, 212, 213 the most frequent
rickettsial pneumonia is that which occurs in Q fever, the causative organism of which
is Coxiella burnetti. Respiratory disease is rarely caused by Bartonella, but bacillary
angiomatosis is one example.
Coxiella burnetti pneumonia (Q fever)214, 215
Q fever (‘query fever’) was so named because of its ‘questionable’ nature prior to
the isolation of the causative organism, now recognised to be a Rickettsia known as
Coxiella burnetti. The disease was first recognised in a meat-packing plant in Queensland,
Australia, in 1937 and is now known to have a virtually global distribution. It is
essentially an infection of cattle, sheep and goats that is transmitted to humans,
probably more frequently than is apparent from the incidence of the disease, for many
people who have never had Q fever possess circulating antibodies against C. burnetti.
Among cattle, the disease is sometimes transmitted by ticks, but possibly more frequently
by the inhalation of contaminated dust from the floor of milking sheds. The organisms
are excreted in milk, urine and faeces, and particularly during calfing when amniotic
fluid and placentae are a rich source of infection. In humans, the disease may be
acquired by the inhalation of infected dust through close contact with cattle, as
in dairy farms, abattoirs and hide factories, or through drinking milk that has been
inadequately pasteurised. C. burnetti is resistant to drying and may survive exposure
to a temperature of 60°C, an important characteristic in regard to the pasteurisation
of milk.
Clinical features
Q fever is a disease of sudden onset marked by general malaise, severe frontal or
retro-orbital headache, high fever and muscle pain. Men are more often symptomatic
than women, despite equal seroprevalence, and there is evidence that sex hormones
such as 17β-oestradiol play a protective role.
216
Pneumonia develops in only a very small proportion of those infected. In these patients,
chest radiographs at the height of the disease disclose numerous relatively small,
but widely distributed, opacities. The symptoms generally subside after about a week
and most patients recover completely within a few months without treatment. Chronic
Q fever, characterised by infection that persists for more than 6 months, is uncommon
but more serious. This form of the disease may also represent a recrudescence of acute
Q fever years after apparent recovery. It generally takes the form of endocarditis,
usually developing in patients with pre-existent valvular heart disease, transplant
recipients or those with cancer. Q fever responds to treatment with doxycycline, quinolones
or macrolides.
The organism can generally be recovered during the height of the disease by inoculation
of the patient's blood or sputum into guinea pigs but few laboratories offer this
test because of the danger of laboratory infection. The detection of specific antibodies
is the laboratory test of choice.
Pathology
The case fatality rate in acute Q fever is very low, and few necropsies on cases uncomplicated
by bacterial superinfection have been recorded. In these, the lungs show nodular or
confluent areas of grey consolidation. The development of an inflammatory pseudotumour
is recorded but is a very rare complication.
217
Microscopically, the changes in the lungs resemble those seen in viral or mycoplasmal
pneumonias. There is a diffuse interstitial infiltrate of lymphocytes and plasma cells
and an alveolar exudate of fibrinous oedema fluid containing mainly macrophages and
only a few neutrophils. Lymphocytic cuffing is seen about the bronchioles and small
pulmonary arteries. The bronchioles contain an exudate similar to that in the alveoli
and often lose their epithelial lining. Organisation of the exudates may lead to obliterative
bronchiolitis and organizing pneumonia.
218
The causative organisms may be demonstrable: they usually measure about 0.25 × 0.45 µm
but bacillary forms measuring up to 1.5 µm in length also occur. The organisms form
microcolonies in infected cells, such as alveolar epithelium, and this facilitates
their recognition in Giemsa-stained preparations. C. burnetti may also be identified
in infected tissues by immunohistochemical staining and DNA detection. If the organisms
are not demonstrable the changes are non-specific and, therefore, in suspected cases,
coming to necropsy, blood should be taken for serology. It should be noted that there
is a real risk of pathologists and postmortem room staff contracting the disease if
precautions to avoid splashing and drying of body fluids are not taken. This infectivity
has raised its profile as a potential agent in bioterrorism.
219
Bacillary angiomatosis
Bacillary angiomatosis is a reactive vascular proliferation that was originally described
in the skin and regional lymph nodes of patients infected by HIV.220, 221 Mucosal
surfaces may also be involved, sometimes in the absence of cutaneous disease. In the
respiratory tract this results in polypoid endobronchial lesions.166, 222 Chest wall
involvement with intrathoracic spread is also recorded.
223
The disease has subsequently been described in other forms of immunodeficiency and
even in immunocompetent patients, implying that unrecognised cases preceded the AIDS
epidemic. The organisms involved have been identified as the rickettsial coccobacilli
Bartonella (formerly Rochalimaea) henselae and B. quintana,224, 225 These microbes
also cause trench foot and bacillary peliosis hepatis and are responsible for some
cases of cat scratch disease (which is also caused by the related bacillus Afipia
felis).
226
Histologically, the lesions are likely to be mistaken for granulation tissue or Kaposi's
sarcoma. Capillaries lined by plump endothelial cells are separated by neutrophils
and cell debris, often surrounding clumps of bacilli (Fig. 5.1.15
). The bacilli are easily overlooked in haematoxylin and eosin-stained sections and
do not stain well with conventional stains for bacteria. However, aggregates of them
are evident in sections stained by the Warthin–Starry or Dieterle silver techniques,
predominantly in the extracellular tissue surrounding blood vessels. It should be
remembered that these techniques stain many different types of microorganisms and
a positive result is only meaningful if conventional methods for bacteria fail to
stain the bacilli.
Figure 5.1.15
Bacillary angiomatosis. (A) There are many capillaries lined by plump endothelial
cells, neutrophils and prominent cell debris. (B) Warthin–Starry staining reveals
clumps of rickettsial coccibacilli.
(Courtesy of Dr I Abdalsamad, Creteil, France.)
The lesions lack the spindle cells of Kaposi's sarcoma and the endothelial cells are
more readily recognisable as such, carrying a wide variety of endothelial markers
(CD34, factor VIII-related antigen and Ulex europaeus lectin positivity) rather than
the more restricted CD34 positivity of Kaposi's sarcoma. Similarly, Weibel–Palade
bodies are readily identified on electron microscopy, which is not the case with Kaposi's
sarcoma.
227
Bacillary angiomatosis responds well to treatment with erythromycin and its distinction
from Kaposi's sarcoma is therefore important.
References
1
Wright
C
Oliver
KC
Fenwick
FI
A monoclonal antibody pool for routine immunohistochemical detection of human respiratory
syncytial virus antigens in formalin-fixed, paraffin-embedded tissue
J Pathol
182
1997
238
244
9274537
2
Eyzaguirre
E
Haque
AK
Application of immunohistochemistry to infections
Arch Pathol Lab Med
132
2008
424
431
18318584
3
Unger
ER
Budgeon
LR
Myerson
D
Viral diagnosis by in situ hybridization. Description of a rapid simplified colorimetric
method
Am J Surg Pathol
10
1986
1
8
4
Tomita
T
Chiga
M
Lenahan
M
Identification of herpes simplex virus infection by immunoperoxidase and in situ hybridization
methods
Virchows Arch A Pathol Anat Histopathol
419
1991
99
105
1651584
5
Hogg
JC
Irving
WL
Porter
H
In situ hybridization studies of adenoviral infections of the lung and their relationship
to follicular bronchiectasis
Am Rev Respir Dis
139
1989
1531
1535
2543250
6
Myerson
D
Lingenfelter
PA
Gleaves
CA
Diagnosis of cytomegalovirus pneumonia by the polymerase chain reaction with archived
frozen lung tissue and bronchoalveolar lavage fluid
Am J Clin Pathol
100
1993
407
413
8213636
7
Delvenne
P
Arrese
JE
Thiry
A
Detection of cytomegalovirus, Pneumocystis carinii, and Aspergillus species in bronchoalveolar
lavage fluid – a comparison of techniques
Am J Clin Pathol
100
1993
414
418
7692721
8
Zinserling
A
Peculiarities of lesions in viral and mycoplasma infections of the respiratory tract
Virchows Arch A Pathol Anat Histopathol
356
1972
259
273
Influenza
9
Oxford
JS
Schild
GC
The orthomyxoviridae and influenza
Parker
MT
Collier
LH
Topley and Wilson's Principles of Bacteriology, Virology and Immunity, Volume 4
8th ed
1990
Arnold
London
292
10
Morens
DM
Taubenberger
JK
Fauci
AS
The persistent legacy of the 1918 influenza virus
N Engl J Med
361
2009
225
229
19564629
11
Gamblin
SJ
Haire
LF
Russell
RJ
The structure and receptor-binding properties of the 1918 influenza hemagglutinin
Science
303
2004
1838
1842
14764886
12
Taubenberger
JK
Reid
AH
Lourens
RM
Characterization of the 1918 influenza virus polymerase genes
Nature
437
2005
889
893
16208372
13
Webster
RG
Govorkova
EA
H5N1 influenza – continuing evolution and spread
N Engl J Med
355
2006
2174
2177
17124014
14
Korteweg
C
J
Gu
Pathology, molecular biology, and pathogenesis of avian influenza A (H5N1) infection
in humans
Am J Pathol
172
2008
1155
1170
18403604
15
Wang
H
Feng
Z
Shu
Y
Probable limited person-to-person transmission of highly pathogenic avian influenza
A (H5N1) virus in China
Lancet
371
2008
1427
1434
18400288
16
Scull
MA
Gillim-Ross
L
Santos
C
Avian Influenza virus glycoproteins restrict virus replication and spread through
human airway epithelium at temperatures of the proximal airways
PLoS Pathog
5
2009
e1000424
19436701
17
Seo
SH
Hoffmann
E
Webster
RG
Lethal H5N1 influenza viruses escape host anti-viral cytokine responses
Nat Med
8
2002
950
954
12195436
18
van Riel
D
Munster
VJ
de Wit
E
Human and avian influenza viruses target different cells in the lower respiratory
tract of humans and other mammals
Am J Pathol
171
2007
1215
1223
17717141
19
Donaldson
LJ
Rutter
PD
Ellis
BM
Mortality from pandemic A/H1N1 2009 influenza in England: public health surveillance
study
BMJ
399
2009
b5213
20
Reid
AH
Taubenberger
JK
The 1918 flu and other influenza pandemics: ‘Over there’ and back again
Lab Invest
79
1999
95
101
10068198
21
Luk
J
Gross
P
Thompson
WW
Observations on mortality during the 1918 influenza pandemic
Clin Infect Dis
33
2001
1375
1378
11565078
22
Oseasohn
R
Adelson
L
Kaji
M
Clinicopathologic study of thirty-three fatal cases of Asian influenza
N Engl J Med
260
1959
509
518
13632920
23
Guarner
J
Shieh
WJ
Dawson
J
Immunohistochemical and in situ hybridization studies of influenza A virus infection
in human lungs
Am J Clin Pathol
114
2000
227
233
10941338
24
Gill
JR
Sheng
Z-M
Ely
SF
Pulmonary pathologic findings of fatal 2009 pandemic influenza A/H1N1 viral infections
Arch Pathol Lab Med
134
2010
235
243
20121613
Shieh
WJ
Blau
DM
Denison
AM
2009 Pandemic Influenza A (H1N1): Pathology and Pathogenesis of 100 Fatal Cases in
the United States
Am J Pathol
177
2010
166
175
20508031
25
Mauad
T
Hajjar
LA
Callegari
GD
Lung pathology in fatal novel human influenza A (H1N1) infection
Am J Respir Crit Care Med
181
2010
72
79
19875682
26
Ng
WF
To
KF
Lam
WWL
The comparative pathology of severe acute respiratory syndrome and avian influenza
A subtype H5N1 – a review
Human Pathology
37
2006
381
390
16564911
27
To
KF
Chan
PK
Chan
KF
Pathology of fatal human infection associated with avian influenza A H5N1 virus
J Med Virol
63
2001
242
246
11170064
28
Gerberding
JL
Morgan
JG
Shepard
JA
Case 9–2004 – An 18-year-old man with respiratory symptoms and shock
N Engl J Med
350
2004
1236
1247
15028828
29
Gu
J
Xie
Z
Gao
Z
H5N1 infection of the respiratory tract and beyond: a molecular pathology study
Lancet
370
2007
1137
1145
17905166
30
Parker
MT
Necropsy studies of the bacterial complications of influenza
J Infect
1
1979
9
16
31
Morens
D
Taubenberger
J
Fauci
A
Predominant role of bacterial pneumonia as a cause of death in pandemic influenza:
implications for pandemic influenza preparedness
The Journal of Infectious Diseases
198
2008
962
970
18710327
32
Brundage
JF
Shanks
GD
Deaths from bacterial pneumonia during 1918–19 influenza pandemic
Emerg Infect Dis
14
2008
1193
1199
18680641
33
Yeldandi
AV
Colby
TV
Pathologic features of lung biopsy specimens from influenza pneumonia cases
Hum Pathol
25
1994
47
53
8314260
34
Loosli
CG
Influenza and the interaction of viruses and bacteria in the respiratory tract
Medicine (Baltimore)
52
1973
369
384
4725960
35
Austin
RM
Daniels
CA
The role of protein A in the attachment of staphylococci to influenza-infected cells
Lab Invest
39
1978
128
132
682597
36
Tashiro
M
Ciborowski
P
Klenk
HD
Role of Staphylococcus protease in the development of influenza pneumonia
Nature
325
1987
536
537
3543690
37
Plotkowski
MC
Puchelle
E
Beck
G
Adherence of type I Streptococcus pneumoniae to tracheal epithelium of mice infected
with influenza A/PR8 virus
Am Rev Respir Dis
134
1986
1040
1044
3777666
38
Weintrub
PS
Sullender
WM
Lombard
C
Giant cell pneumonia caused by parainfluenza type 3 in a patient with acute myelomonocytic
leukemia
Arch Pathol Lab Med
111
1987
569
570
3034189
39
Akizuki
S
Nasu
N
Setoguchi
M
Parainfluenza virus pneumonitis in an adult
Arch Pathol Lab Med
115
1991
824
826
1650545
40
Mansell
AL
Bramson
RT
Shannon
DC
An 18-month-old immunosuppressed boy with bilateral pulmonary infiltrates – parainfluenza
virus type 3 pneumonia with giant cells (giant-cell pneumonia)
N Engl J Med
335
1996
1133
1140
8813045
41
Madden
JF
Burchette
J
Hale
LP
Pathology of parainfluenza virus infection in patients with congenital immunodeficiency
syndromes*1
Human Pathology
35
2004
594
603
15138935
Respiratory syncytial virus
42
Hall
CB
Weinberg
GA
Iwane
MK
The burden of respiratory syncytial virus infection in young children
N Engl J Med
360
2009
588
598
19196675
Nair
H
Nokes
DJ
Gessner
BD
Global burden of acute lower respiratory infections due to respiratory syncytial virus
in young children: a systematic review and meta-analysis
Lancet
375
2010
1545
1555
20399493
Hall
CB
Respiratory syncytial virus in young children
Lancet
375
2010
1500
1502
20399494
Smyth
RL
Openshaw
PJ
Bronchiolitis
Lancet
368
2006
312
322
16860701
43
Sinnot
JT
Cullison
JP
Sweery
MS
Respiratory syncytial virus pneumonia in a cardiac transplant recipient
J Infect Dis
158
1989
650
651
44
Harrington
SW
Hooton
TM
Hackman
RC
An outbreak of respiratory syncytial virus in a bone marrow transplant center
J Infect Dis
158
1989
987
993
45
Kramer
MR
Marshall
SE
Starnes
VA
Infectious complications in heart–lung transplantation
Arch Intern Med
153
1993
2010
2016
8357286
46
Kurlandsky
LE
French
G
Webb
PM
Fatal respiratory syncytial virus pneumonitis in a previously healthy child
Am Rev Respir Dis
138
1988
468
472
3195838
47
Downham
MAPS
Scott
R
Sims
DG
Breast-feeding protects against respiratory syncytial virus infections
BMJ
2
1976
274
276
953560
48
Zapikian
AZ
Mitchell
RH
Chanock
RM
An epidemiologic study of altered clinical reactivity to respiratory syncytial (RS)
virus infection in children previously vaccinated with an inactivated RS virus vaccine
Am J Epidemiol
89
1969
405
421
4305197
49
Openshaw
PJM
Immunity and immunopathology to respiratory syncytial virus: the mouse model
Am J Respir Crit Care Med
152
1995
S59
S62
7551415
50
Graham
BS
Pathogenesis of respiratory syncytial virus vaccine-augmented pathology
Am J Respir Crit Care Med
152
1995
S63
S66
7551416
51
Gardner
PS
McQuillen
J
Court
SDM
Speculation on pathogenesis in death from respiratory syncytial virus infection
BMJ
1
1970
327
330
4906701
52
Legg
JP
Hussain
IR
Warner
JA
Type 1 and type 2 cytokine imbalance in acute respiratory syncytial virus bronchiolitis
Amer J Respir Crit Care Med
168
2003
633
639
12773328
Moghaddam
A
Olszewska
W
Wang
B
A potential molecular mechanism for hypersensitivity caused by formalin-inactivated
vaccines
Nat Med
12
2006
905
907
16862151
53
The IMpact-RSV study group
Palivizumab, a humanized respiratory syncytial virus monoclonal antibody, reduces
hospitalization from respiratory syncytial virus infection in high-risk infants
Pediatrics
102
1998
531
537
54
Aherne
W
Bird
T
Court
SDM
Pathological changes in virus infections of the lower respiratory tract in children
J Clin Pathol
23
1970
7
18
4909103
55
Johnson
JE
Gonzales
RA
Olson
SJ
The histopathology of fatal untreated human respiratory syncytial virus infection
Mod Pathol
20
2007
108
119
17143259
56
Delage
G
Brochu
P
Robillard
L
Giant cell pneumonia due to respiratory syncytial virus. Occurrence in severe combined
immunodeficiency syndrome
Arch Pathol Lab Med
108
1984
623
625
6611144
Metapneumovirus
57
van den Hoogen
BG
de Jong
JC
Groen
J
A newly discovered human pneumovirus isolated from young children with respiratory
tract disease
Nat Med
7
2001
719
724
11385510
58
Williams
JV
Harris
PA
Tollefson
SJ
Human metapneumovirus and lower respiratory tract disease in otherwise healthy infants
and children
N Engl J Med
350
2004
443
450
14749452
Measles
59
Asaria
P
MacMahon
E
Measles in the United Kingdom: can we eradicate it by 2010?
BMJ
333
2006
890
895
17068034
60
de Quadros
CA
Izurieta
H
Carrasco
P
Progress toward measles eradication in the region of the Americas
J Infect Dis
187
2003
S102
S110
12721900
61
Vukshich
ON
Harpaz
R
Redd
SB
International importation of measles virus – United States, 1993–2001
J Infect Dis
189
2004
S48
S53
15106089
62
Jansen
VA
Stollenwerk
N
Jensen
HJ
Measles outbreaks in a population with declining vaccine uptake
Science
301
2003
804
12907792
63
Morley
D
Severe measles in the tropics
BMJ
l
1969
297
300
64
Myou
S
Fujimura
M
Yasui
M
Bronchoalveolar lavage cell analysis in measles viral pneumonia
Eur Respir J
6
1993
1437
1442
8112435
65
Kipps
A
Kaschula
ROC
Virus pneumonia following measles. A virological and histological study of autopsy
material
S Afr Med J
50
1976
1083
1088
183294
66
Warner
JO
Marshall
NC
Crippling lung disease after measles and adenovirus infection
Br J Dis Chest
70
1976
89
94
182195
67
Miller
DC
Frequency of complications of measles
BMJ
2
1964
75
78
14147791
68
Joliat
G
Abetel
G
Schindler
A-M
Measles giant cell pneumonia without rash in a case of lymphocytic lymphosarcoma
Virchows Arch A Pathol Anat Histopathol
358
1973
215
224
69
Sobonya
RE
Hiller
FC
Pingleton
W
Fatal measles (rubeola) pneumonia in adults
Arch Pathol Lab Med
102
1978
366
371
580870
70
Becroft
DMO
Osborne
DRS
The lungs in fatal measles infection in childhood: pathological, radiological and
immunological correlation
Histopathology
4
1980
401
412
7429429
71
Rahman
SM
Eto
H
Morshed
SA
Giant cell pneumonia: light microscopy, immunohistochemical, and ultrastructural study
of an autopsy case
Ultrastruct Pathol
20
1996
585
591
8940766
72
Archibald
RWR
Weller
RD
Meadow
SR
Measles pneumonia and the nature of inclusion-bearing giant cells: a light- and electron-microscope
study
J Pathol
103
1971
27
34
5566423
73
Saito
F
Yutani
C
Imakita
M
Giant cell pneumonia caused by varicella zoster virus in a neonate
Arch Pathol Lab Med
113
1989
201
203
2537070
Adenovirus
74
Becroft
DMO
Histopathology of fatal adenovirus infection of the respiratory tract in young children
J Clin Pathol
20
1967
561
569
4301496
75
Becroft
DMO
Bronchiolitis obliterans, bronchiectasis and other sequelae of adenovirus type 21
infection in young children
J Clin Pathol
24
1971
72
82
4324685
Severe acute respiratory syndrome (SARS)
76
Webster
RG
Wet markets – a continuing source of severe acute respiratory syndrome and influenza?
Lancet
363
2004
234
236
14738798
77
Guan
Y
Zheng
BJ
He
YQ
Isolation and characterization of viruses related to the SARS coronavirus from animals
in southern China
Science
302
2003
276
278
12958366
78
Parry
J
WHO confirms SARS in Chinese journalist
BMJ
328
2004
65
79
Chan-Yeung
M
Yu
WC
Outbreak of severe acute respiratory syndrome in Hong Kong Special Administrative
Region: case report
BMJ
326
2003
850
852
12702616
80
Tsang
KW
Ho
PL
Ooi
GC
A cluster of cases of severe acute respiratory syndrome in Hong Kong
N Engl J Med
348
2003
1977
1985
12671062
81
Lee
N
Hui
D
Wu
A
A major outbreak of severe acute respiratory syndrome in Hong Kong
N Engl J Med
348
2003
1986
1994
12682352
82
Poutanen
SM
Low
DE
Henry
B
Identification of severe acute respiratory syndrome in Canada
N Engl J Med
348
2003
1995
2005
12671061
83
Vu
HT
Leitmeyer
KC
Le
DH
Clinical description of a completed outbreak of SARS in Vietnam, February–May 2003
Emerg Infect Dis
10
2004
334
338
15030707
84
Schrag
SJ
Brooks
JT
Van Beneden
C
SARS surveillance during emergency public health response, United States, March–July
2003
Emerg Infect Dis
10
2004
185
194
15030681
85
Desenclos
JC
van der
WS
Bonmarin
I
Introduction of SARS in France, March–April, 2003
Emerg Infect Dis
10
2004
195
200
15030682
86
Ksiazek
TG
Erdman
D
Goldsmith
CS
A novel coronavirus associated with severe acute respiratory syndrome
N Engl J Med
348
2003
1953
1966
12690092
87
Drosten
C
Gunther
S
Preiser
W
Identification of a novel coronavirus in patients with severe acute respiratory syndrome
N Engl J Med
348
2003
1967
1976
12690091
88
Li
W
Shi
Z
Yu
M
Bats are natural reservoirs of SARS-like coronaviruses
Science
310
2005
676
679
16195424
89
Lau
SK
Woo
PC
Li
KS
Severe acute respiratory syndrome coronavirus-like virus in Chinese horseshoe bats
Proc Natl Acad Sci U S A
102
2005
14040
14045
16169905
90
Tiwari
A
Chan
S
Wong
A
Severe acute respiratory syndrome (SARS) in Hong Kong: patients’ experiences
Nurs Outlook
51
2003
212
219
14569227
91
Hui
DS
Wong
PC
Wang
C
SARS: clinical features and diagnosis
Respirology
8
2003
S20
S24
15018129
92
Paul
NS
Roberts
H
Butany
J
Radiologic pattern of disease in patients with severe acute respiratory syndrome:
the Toronto experience
Radiographics
24
2004
553
563
15026600
93
Ding
Y
He
L
Zhang
Q
Organ distribution of severe acute respiratory syndrome (SARS) associated coronavirus
(SARS-CoV) in SARS patients: implications for pathogenesis and virus transmission
pathways
J Pathol
203
2004
622
630
15141376
94
Hamming
I
Timens
W
Bulthuis
ML
Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus.
A first step in understanding SARS pathogenesis
J Pathol
203
2004
631
637
15141377
95
To
KF
Lo
AW
Exploring the pathogenesis of severe acute respiratory syndrome (SARS): the tissue
distribution of the coronavirus (SARS-CoV) and its putative receptor, angiotensin-converting
enzyme 2 (ACE2)
J Pathol
203
2004
740
743
15221932
96
Franks
TJ
Chong
PY
Chui
P
Lung pathology of severe acute respiratory syndrome (SARS): A study of 8 autopsy cases
from Singapore
Hum Pathol
34
2003
743
748
14506633
97
Nicholls
JM
Poon
LL
Lee
KC
Lung pathology of fatal severe acute respiratory syndrome
Lancet
361
2003
1773
1778
12781536
98
Tse
GMK
To
KF
Chan
PKS
Pulmonary pathological features in coronavirus associated severe acute respiratory
syndrome (SARS)
J Clin Pathol
57
2004
260
265
14990596
99
Chong
PY
Chui
P
Ling
AE
Analysis of deaths during the severe acute respiratory syndrome (SARS) epidemic in
Singapore – challenges in determining a SARS diagnosis
Arch Pathol Lab Med
128
2004
195
204
14736283
100
Cheung
OY
Chan
JWM
Ng
CK
The spectrum of pathological changes in severe acute respiratory syndrome (SARS)
Histopathology
45
2004
119
124
15279629
102
Chu
CM
Cheng
VC
Hung
IF
Role of lopinavir/ritonavir in the treatment of SARS: initial virological and clinical
findings
Thorax
59
2004
252
256
14985565
103
Stroher
U
DiCaro
A
Li
Y
Severe acute respiratory syndrome-related coronavirus is inhibited by interferon-alpha
J Infect Dis
189
2004
1164
1167
15031783
104
Paul
NS
Chung
T
Konen
E
Prognostic significance of the radiographic pattern of disease in patients with severe
acute respiratory syndrome
AJR Am J Roentgenol
182
2004
493
498
14736688
105
Hui
DS
Joynt
GM
Wong
KT
Impact of severe acute respiratory syndrome (SARS) on pulmonary function, functional
capacity and quality of life in a cohort of survivors
Thorax
60
2005
401
409
15860716
106
Ong
KC
Ng
AW
Lee
LS
1-year pulmonary function and health status in survivors of severe acute respiratory
syndrome
Chest
128
2005
1393
1400
16162734
107
Leow
MK
Kwek
DS
Ng
AW
Hypocortisolism in survivors of severe acute respiratory syndrome (SARS)
Clin Endocrinol (Oxf)
63
2005
197
202
16060914
Herpes simplex
108
Ramsey
PG
Fife
KH
Hackman
RC
Herpes simplex virus pneumonia – clinical, virologic and pathological features in
20 patients
Ann Intern Med
97
1982
813
820
6293356
109
Greenberg
SB
Respiratory herpesvirus infections: an overview
Chest
106
1994
S1
S2
110
Francis
DP
Herrman
KL
MacMahon
JR
Nosocomial and maternally acquired herpesvirus hominis infections: a report of four
fatal cases in neonates
Am J Dis Child
129
1975
889
893
169688
111
Greene
GR
King
D
Romansky
SG
Primary herpes simplex pneumonia in a neonate
Am J Dis Child
137
1983
464
465
6303110
112
Schuller
D
Lower respiratory tract reactivation of herpes simplex virus – comparison of immunocompromised
and immunocompetent hosts
Chest
106
1994
S3
S7
113
Klainer
AS
Oud
L
Randazzo
J
Herpes simplex virus involvement of the lower respiratory tract following surgery
Chest
106
1994
S8
14
114
Hayden
FG
Himel
HN
Heggers
JP
Herpesvirus infections in burn patients
Chest
106
1994
S15
S21
115
Byers
RJ
Hasleton
PS
Quigley
A
Pulmonary herpes simplex in burns patients
Eur Respir J
9
1996
2313
2317
8947077
116
Luyt
CE
Combes
A
Deback
C
Herpes simplex virus lung infection in patients undergoing prolonged mechanical ventilation
Am J Respir Crit Care Med
175
2007
935
942
17234903
117
Smyth
RL
Higenbottam
TW
Scott
JP
Herpes simplex virus infection in heart–lung transplant recipients
Transplantation
49
1990
735
739
2326868
118
Baras
L
Farber
CM
Vanvooren
JP
Herpes simplex virus tracheitis in a patient with the acquired immunodeficiency syndrome
Eur Respir J
7
1994
2091
2093
7875288
119
Martinez
E
Dediego
A
Paradis
A
Herpes simplex pneumonia in a young immunocompetent man
Eur Respir J
7
1994
1185
1188
7925891
120
Phinney
PR
Fligiel
S
Bryson
YJ
Necrotizing vasculitis in a case of disseminated neonatal herpes simplex infection
Arch Pathol Lab Med
106
1982
64
67
6895828
Cytomegalovirus
121
Beschorner
WE
Hutchins
GM
Burns
WH
Cytomegalovirus pneumonia in bone marrow transplant recipients: miliary and diffuse
patterns
Am Rev Respir Dis
122
1980
107
114
6250434
122
Ettinger
NA
Bailey
TC
Trulock
EP
Cytomegalovirus infection and pneumonitis – impact after isolated lung transplantation
Am Rev Respir Dis
147
1993
1017
1023
8385429
123
Wallace
JM
Hannah
J
Cytomegalovirus pneumonitis in patients with AIDS. Findings in an autopsy series
Chest
92
1987
198
203
3038474
124
Waxman
AB
Goldie
SJ
Brettsmith
H
Cytomegalovirus as a primary pulmonary pathogen in AIDS
Chest
111
1997
128
134
8996006
125
Millar
AB
Patou
G
Miller
RF
Cytomegalovirus in the lungs of patients with AIDS. Respiratory pathogen or passenger?
Am Rev Respir Dis
141
1990
1474
1479
2161629
126
Klatt
EC
Shibata
D
Cytomegalovirus infection in the acquired immunodeficiency syndrome. Clinical and
autopsy findings
Arch Pathol Lab Med
112
1988
540
544
2833874
127
Grundy
JE
Shanley
JD
Griffiths
PD
Is cytomegalovirus interstitial pneumonitis in transplant recipients an immunopathological
condition?
Lancet
2
1987
996
999
2889962
128
Weiss
LM
Movahed
LA
Berry
GJ
In situ hybridization studies for viral nucleic acids in heart and lung allograft
biopsies
Am J Clin Pathol
93
1990
675
679
2158226
Human immunodeficiency viruses
129
Royal College of Pathologists
HIV and the practice of pathology
1995
Royal College of Pathologists
London
Moonim
MT
Alarcon
L
Freeman
J
Mahadeva
U
van der Walt
JD
Lucas
SB
Identifying HIV infection in diagnostic histopathology tissue samples – the role of
HIV-1 p24 immunohistochemistry in identifying clinically unsuspected HIV infection:
a 3-year analysis
Histopathology
56
2010
530
541
20459560
130
Hofman
P
SaintPaul
MC
Battaglione
V
Autopsy findings in the acquired immunodeficiency syndrome (AIDS). A report of 395
cases from the South of France
Pathol Res Pract
195
1999
209
217
10337658
131
Cury
PM
Pulido
CF
Furtado
VMG
Autopsy findings in AIDS patients from a reference hospital in Brazil: Analysis of
92 cases
Pathol Res Pract
199
2003
811
814
14989493
132
Suffredini
AF
Ognibene
FP
Lack
EE
Non-specific interstitial penumonitis: a common cause of pulmonary disease in the
acquired immunodeficiency syndrome
Ann Intern Med
107
1987
7
13
3496030
133
Colclough
AB
Interstitial pneumonia in human immunodeficiency virus infection: a report of a fatal
case in childhood
Histopathology
12
1988
211
219
3366437
134
Ognibene
FP
Masur
H
Rogers
P
Nonspecific interstitial pneumonitis without evidence of Pneumocystis carinii in asymptomatic
patients infected with human immunodeficiency virus (HIV)
Ann Intern Med
109
1988
874
879
2973275
135
Travis
WD
Fox
CH
Devaney
KO
Lymphoid pneumonitis in 50 adult patients infected with the human immunodeficiency
virus – lymphocytic interstitial pneumonitis versus nonspecific interstitial pneumonitis
Hum Pathol
23
1992
529
541
1314778
136
Griffiths
MH
Miller
RF
Semple
SJG
Interstitial pneumonitis in patients infected with the human immunodeficiency virus
Thorax
50
1995
1141
1146
8553268
137
Mankowski
JL
Carter
DL
Spelman
JP
Pathogenesis of simian immunodeficiency virus pneumonia: An immunopathological response
to virus
Am J Pathol
153
1998
1123
1130
9777943
138
Fitzpatrick
EA
Avdiushko
M
Kaplan
AM
Role of virus replication in a murine model of AIDS-associated interstitial pneumonitis
Exp Lung Res
25
1999
647
661
10643562
139
Fitzpatrick
EA
Avdiushko
M
Kaplan
AM
Role of T cell subsets in the development of AIDS-associated interstitial pneumonitis
in mice
Exp Lung Res
25
1999
671
687
10643564
140
Marchevsky
A
Rosen
MJ
Chrystal
G
Pulmonary complications of the acquired immunodeficiency syndrome: a clinicopathologic
study of 70 cases
Hum Pathol
16
1985
659
670
3874142
141
Stover
DE
White
DA
Romano
PA
Spectrum of pulmonary diseases associated with the acquired immune deficiency syndrome
Am J Med
78
1985
429
437
2983548
142
Klatt
EC
Nichols
L
Noguchi
TT
Evolving trends revealed by autopsies of patients with the acquired immunodeficiency
syndrome – 565 autopsies in adults with the acquired immunodeficiency syndrome, Los
Angeles, Calif, 1992–1993
Arch Pathol Lab Med
118
1994
884
890
8080357
143
Afessa
B
Green
W
Chiao
J
Pulmonary complications of HIV infection: Autopsy findings
Chest
113
1998
1225
1229
9596298
144
Wolff
AJ
ODonnell
AE
Pulmonary manifestations of HIV infection in the era of highly active antiretroviral
therapy
Chest
120
2001
1888
1893
11742918
145
Joshi
VV
Oleske
JM
Minnefor
AB
Pathologic pulmonary findings in children with the acquired immunodeficiency syndrome:
a study of ten cases
Hum Pathol
16
1985
241
246
3972404
146
Joshi
VV
Oleske
JM
Pulmonary lesions in children with the acquired immunodeficiency syndrome. A reappraisal
based on data in additional cases and follow-up study of previously reported cases
Hum Pathol
17
1986
641
642
147
Joshi
VV
Pathology of AIDS in children
Pathol Annu
24
1989
355
381
2654843
148
Moran
CA
Suster
S
Pavlova
Z
The spectrum of pathological changes in the lung in children with the acquired immunodeficiency
syndrome: an autopsy study of 36 cases
Hum Pathol
25
1994
877
882
8088762
149
Yousem
SA
Colby
TV
Carrington
CB
Follicular bronchitis/bronchiolitis
Hum Pathol
16
1985
700
706
4007845
150
Itescu
S
Brancato
LJ
Winchester
R
A sicca syndrome in HIV infection: association with HLA-DR5 and CD8 lymphocytosis
Lancet
ii
1989
466
468
151
Carson
PJ
Goldsmith
JC
Atypical pulmonary diseases associated with AIDS
Chest
100
1991
675
677
1889255
152
Murray
JF
Mills
J
Pulmonary infectious complications of human immunodeficiency virus infection
Am Rev Respir Dis
1416
1990
1356
1372
153
Harding
CV
Blastomycosis and opportunistic infections in patients with acquired immunodeficiency
syndrome – an autopsy study
Arch Pathol Lab Med
115
1991
1133
1136
1747031
154
Moore
JA
Frenkel
JK
Respiratory and enteric cryptosporidiosis in humans
Arch Pathol Lab Med
115
1991
1160
1162
1747035
155
Scaglia
M
Sacchi
L
Croppo
GP
Pulmonary microsporidiosis due to Encephalitozoon hellem in a patient with AIDS
J Infect
34
1997
119
126
9138134
156
Nichols
L
Balogh
K
Silverman
M
Bacterial infections in the acquired immune deficiency syndrome. Clinicopathologic
correlations in a series of autopsy cases
Am J Clin Pathol
92
1989
787
790
2556018
157
Hirschtick
RE
Glassroth
J
Jordan
MC
Bacterial pneumonia in persons infected with the human immunodeficiency virus
N Engl J Med
333
1995
845
851
7651475
158
Diaz
F
Collazos
J
Martinez
E
Bronchiolitis obliterans in a patient with HIV infection
Respir Med
91
1997
171
173
9135857
159
Valor
RR
Polnitsky
CA
Tanis
DJ
Bacterial tracheitis with upper airway obstruction in a patient with the acquired
immunodeficiency syndrome
Am Rev Respir Dis
146
1992
1598
1599
1456581
160
Brudney
K
Dobkin
J
Resurgent tuberculosis in New York City – human immunodeficiency virus, homelessness,
and the decline of tuberculosis control programs
Am Rev Respir Dis
144
1991
745
749
1928942
161
Hill
AR
Premkumar
S
Brustein
S
Disseminated tuberculosis in the acquired immunodeficiency syndrome era
Am Rev Respir Dis
144
1991
1164
1170
1952449
162
Dolin
PJ
Raviglione
MC
Kochi
A
Global tuberculosis incidence and mortality during 1990–2000
Bulletin of the World Health Organization
72
1994
213
220
8205640
163
Rigsby
MO
Curtis
AM
Pulmonary disease from nontuberculous mycobacteria in patients with human immunodeficiency
virus
Chest
106
1994
913
919
8082377
164
Schwartz
DA
Ogden
PO
Blumberg
HM
Pulmonary malakoplakia in a patient with the acquired immunodeficiency syndrome –
differential diagnostic considerations
Arch Pathol Lab Med
114
1990
1267
1272
2252424
165
Bishopric
GA
d’Agay
MF
Schlemmer
B
Pulmonary pseudotumor due to Corynebacterium equi in a patient with the acquired immunodeficiency
syndrome
Thorax
43
1988
486
487
3420562
166
Foltzer
MA
Guiney
WB
Wager
GC
Bronchopulmonary bacillary angiomatosis
Chest
104
1993
973
975
8365330
167
Ruben
FL
Talamo
TS
Secondary pulmonary alveolar proteinosis occurring in two patients with acquired immune
deficiency syndrome
Am J Med
80
1986
1187
1190
3014876
168
Sehonanda
A
Choi
YJ
Blum
S
Changing patterns of autopsy findings among persons with acquired immunodeficiency
syndrome in an inner-city population: a 12-year retrospective study
Arch Pathol Lab Med
120
1996
459
464
8639049
169
Francis
ND
Goldin
RD
Forster
SM
Diagnosis of lung disease in acquired immune deficiency syndrome: biopsy or cytology
and implications for management
J Clin Pathol
40
1987
1269
1273
3500967
170
del Rio
C
Guarner
J
Honig
EG
Sputum examination in the diagnosis of Pneumocystis carinii pneumonia in the acquired
immunodeficiency syndrome
Arch Pathol Lab Med
112
1988
1229
1232
3142440
171
Coplan
NL
Shimony
RY
Ioachim
HL
Primary pulmonary hypertension associated with human immunodeficiency viral infection
Am J Med
89
1990
96
99
2368798
172
Speich
R
Jenni
R
Opravil
M
Primary pulmonary hypertension in HIV infection
Chest
100
1991
1268
1271
1935280
173
Jacques
C
Richmond
G
Tierney
L
Primary pulmonary hypertension and human immunodeficiency virus infection in a non-hemophiliac
man
Hum Pathol
23
1992
191
194
1740304
174
Mette
SA
Palevsky
HI
Pietra
GG
Primary pulmonary hypertension in association with human immunodeficiency virus infection
– a possible viral etiology for some forms of hypertensive pulmonary arteriopathy
Am Rev Respir Dis
145
1992
1196
1200
1586065
175
Cool
CD
Kennedy
D
Voelkel
NF
Pathogenesis and evolution of plexiform lesions in pulmonary hypertension associated
with scleroderma and human immunodeficiency virus infection
Hum Pathol
28
1997
434
442
9104943
176
Mehta
NJ
Khan
IA
Mehta
RN
HIV-Related pulmonary hypertension – analytic review of 131 cases
Chest
118
2000
1133
1141
11035689
177
Orenstein
JM
Preble
OT
Kind
P
The relationship of serum alpha-interferon and ultrastructural markers in HIV-seropositive
individuals
Ultrastruct Pathol
11
1987
673
679
3686706
178
Chetty
R
Vasculitides associated with HIV infection
J Clin Pathol
54
2001
275
278
11304843
179
Aaron
SD
Warner
E
Edelson
JD
Bronchogenic carcinoma in patients seropositive for human immunodeficiency virus
Chest
106
1994
640
642
7774362
180
Cadranel
J
Naccache
JM
Wislez
M
Pulmonary malignancies in the immunocompromised patient
Respiration
66
1999
289
309
10461078
181
Cadranel
J
Garfield
D
Lavole
A
Lung cancer in HIV infected patients: facts, questions and challenges
Thorax
61
2006
1000
1008
17071836
182
Judson
MA
Sahn
SA
Endobronchial lesions in HIV-infected individuals
Chest
105
1994
1314
1323
8181313
183
Naccache
JM
Antoine
M
Wislez
M
Sarcoid-like pulmonary disorder in human immunodeficiency virus- infected patients
receiving antiretroviral therapy
Am J Respir Crit Care Med
159
1999
2009
2013
10351953
184
Lassalle
S
Selva
E
Hofman
V
Sarcoid-like lesions associated with the immune restoration inflammatory syndrome
in AIDS: absence of polymerase chain reaction detection of Mycobacterium tuberculosis
in granulomas isolated by laser capture microdissection
Virchows Arch
449
2006
689
696
17043810
185
Shelburne
SA
III
Hamill
RJ
The immune reconstitution inflammatory syndrome
AIDS Rev
5
2003
67
79
12876896
186
Wang
X
Chai
H
Lin
PH
Roles and mechanisms of human immunodeficiency virus protease inhibitor ritonavir
and other anti-human immunodeficiency virus drugs in endothelial dysfunction of porcine
pulmonary arteries and human pulmonary artery endothelial cells
Am J Pathol
174
2009
771
781
19218343
Chickenpox (varicella) and herpes zoster
187
Feldman
S
Varicella-zoster virus pneumonitis
Chest
106
1994
S22
S27
188
Mohsen
AH
McKendrick
M
Varicella pneumonia in adults
Eur Resp J
21
2003
886
891
189
Rice
P
Banatvala
J
Simmons
K
Near fatal chickenpox during prednisolone treatment
BMJ
309
1994
1069
1070
7950743
190
Raider
L
Calcification in chickenpox pneumonia
Chest
60
1971
504
507
5119892
191
Sargent
EN
Carson
MJ
Reilly
ED
Roentgenographic manifestations of varicella pneumonia with postmortem correlation
Am J Roentgenol
98
1966
305
317
192
Ellis
ME
Neal
KR
Webb
AK
Is smoking a risk factor for pneumonia in adults with chickenpox?
BMJ
294
1987
1002
3119001
193
Pek
S
Gikas
PW
Pneumonia due to herpes zoster. Report of a case and review of the literature
Ann Intern Med
62
1965
350
358
14259218
Hantavirus pulmonary syndrome
194
Duchin
JS
Koster
FT
Peters
CJ
Hantavirus pulmonary syndrome – a clinical description of 17 patients with a newly
recognized disease
N Engl J Med
330
1994
949
955
8121458
195
Butler
JC
Peters
CJ
Hantaviruses and hantavirus pulmonary syndrome
Clin Infect Dis
19
1994
387
395
7811854
196
Foucar
K
Nolte
KB
Feddersen
RM
Outbreak of Hantavirus pulmonary syndrome in the southwestern United States. Response
of pathologists and other laboratorians
Am J Clin Pathol
101
1994
S1
S5
8154449
197
Zaki
SR
Khan
AS
Goodman
RA
Retrospective diagnosis of Hantavirus pulmonary syndrome, 1978–1993: implications
for emerging infectious diseases
Arch Pathol Lab Med
120
1996
134
139
8712893
198
Wells
RM
Sosa Estani
S
Yadon
ZE
An unusual hantavirus outbreak in southern Argentina: person-to-person transmission?
Hantavirus Pulmonary Syndrome Study Group for Patagonia
Emerg Infect Dis
3
1997
171
174
9204298
199
Nolte
KB
Feddersen
RM
Foucar
K
Hantavirus pulmonary syndrome in the United States: a pathological description of
a disease caused by a new agent
Hum Pathol
26
1995
110
120
7821907
200
Zaki
SR
Greer
PW
Coffield
LM
Hantavirus pulmonary syndrome: pathogenesis of an emerging infectious disease
Am J Pathol
146
1995
552
579
7887439
201
Colby
TV
Zaki
SR
Feddersen
RM
Hantavirus pulmonary syndrome is distinguishable from acute interstitial pneumonia
Arch Pathol Lab Med
124
2000
1463
1466
11035576
202
Nolte
KB
Foucar
K
Richmond
JY
Hantaviral biosafety issues in the autopsy room and laboratory: concerns and recommendation
Hum Pathol
27
1996
1253
1254
8958293
Mycoplasmal pneumonia
203
British Thoracic Society Research Committee
Community acquired pneumonia in adults in British hospitals in 1982–83: a survey of
aetiology, mortality, prognostic factors and outcome
Q J Med
62
1987
195
220
3116595
204
Abele-Horn
M
Busch
U
Nitschko
H
Molecular approaches to diagnosis of pulmonary diseases due to Mycoplasma pneumoniae
J Clin Microbiol
36
1998
548
551
9466774
205
Templeton
KE
Scheltinga
SA
Graffelman
AW
Comparison and evaluation of real-time PCR, real-time nucleic acid sequence-based
amplification, conventional PCR, and serology for diagnosis of Mycoplasma pneumoniae
J Clin Microbiol
41
2003
4366
4371
12958270
206
Collier
AM
Clyde
WA
Relationships between Mycoplasma pneumoniae and human respiratory epithelium
Diag Radiology
3
1971
694
701
207
Rosendal
S
Vinther
O
Experimental mycoplasmal pneumonia in dogs: electron microscopy of infected tissue
Acta Path Microbiol Scand Sect B
85
1977
462
465
208
Rollins
S
Colby
T
Clayton
F
Open lung biopsy in Mycoplasma pneumoniae pneumonia
Arch Pathol Lab Med
110
1986
34
41
3753567
209
Ebnother
M
Schoenenberger
RA
Perruchoud
AP
Severe bronchiolitis in acute Mycoplasma pneumoniae infection
Virchows Archiv
439
2001
818
822
11787856
210
Donat
WE
Shepard
JAO
Mark
EJ
A 20-year-old man with diffuse pulmonary infiltrates and disseminated intravascular
coagulation – mycoplasma pneumonia, with diffuse alveolar damage and disseminated
intravascular coagulation
N Engl J Med
326
1992
324
336
1728737
Rickettsial infection
211
Chayakul
P
Panich
V
Silpapojakul
K
Scrub typhus pneumonitis: an entity which is frequently missed
Q J Med
68
1988
595
602
3076676
212
Walker
DH
Crawford
CG
Cain
BG
Rickettsial infection of the pulmonary microcirculation: the basis for interstitial
pneumonitis in Rocky Mountain spotted fever
Human Pathology
11
1980
263
272
6772542
213
Samuels
MA
Newell
KL
Trotman Dickenson
B
A 43-year-old woman with rapidly changing pulmonary infiltrates and markedly increased
intracranial pressure – Rocky Mountain spotted fever with meningoencephalomyelitis,
vasculitis, and focal myocarditis
N Engl J Med
337
1997
1149
1156
9329937
Coxiella burnetti pneumonia (Q fever)
214
Spelman
DW
Q fever. A study of 111 consecutive cases
Med J Aust
1
1959
547
553
215
Marrie
TJ
Coxiella burnetii pneumonia
Eur Resp J
21
2003
713
719
216
Leone
M
Honstettre
A
Lepidi
H
Effect of sex on Coxiella burnetii infection: protective role of 17beta-estradiol
J Infect Dis
189
2004
339
345
14722900
217
Janigan
DJ
Marrie
TJ
An inflammatory pseudotumor of the lung in Q fever pneumonia
N Engl J Med
308
1983
86
87
6847938
218
deLlano
LAP
Racamonde
AV
Bande
MJR
Bronchiolitis obliterans with organizing pneumonia associated with acute Coxiella
burnetii infection
Respiration
68
2001
425
427
11464095
219
Kagawa
FT
Wehner
JH
Mohindra
V
Q fever as a biological weapon
Semin Respir Infect
18
2003
183
195
14505280
Bacillary angiomatosis
220
Walford
N
Van der Wouw
PA
Das
PK
Epithelioid angiomatosis in the acquired immunodeficiency syndrome: morphology and
differential diagnosis
Histopathology
16
1990
83
88
2307419
221
Stoler
M
Bonfiglio
T
Steigbigel
R
An atypical subcutaneous infection associated with acquired immune deficiency virus
Am J Clin Pathol
80
1993
714
718
222
Slater
LN
Min
KW
Polypoid endobronchial lesions – a manifestation of bacillary angiomatosis
Chest
102
1992
972
974
1516441
223
Finet
JF
Abdalsamad
I
Bakdach
H
Intrathoracic localization of bacillary angiomatosis
Histopathology
28
1996
183
185
8834530
224
Koehler
JE
Quinn
FD
Berger
TG
Isolation of Rochalimaea species from cutaneous and osseous lesions of bacillary angiomatosis
N Engl J Med
327
1992
1625
1631
1435899
225
Leboit
PE
In consultation – bacillary angiomatosis
Mod Pathol
8
1995
218
222
7539912
226
Adal
KA
Cockerell
CJ
Petri
WA
Cat scratch disease, bacillary angiomatosis, and other infections due to rochalimaea
N Engl J Med
330
1994
1509
1515
8164704
227
Kostianovsky
M
Lamy
Y
Greco
MA
Immunohistochemical and electron microscopic profiles of cutaneous Kaposi's sarcoma
and bacillary angiomatosis
Ultrastruct Pathol
16
1992
629
640
1448882
5.2
Acute bacterial pneumonia
Chapter Contents
Bronchopneumonia
179
Pneumococcal pneumonia
180
Staphylococcal pneumonia
182
Streptococcal pneumonia
183
Haemophilus pneumonia
184
Moraxella pneumonia
184
Legionella pneumonia (legionnaire's disease)
184
Klebsiella pneumonia
185
Pseudomonas pneumonia
185
Burkholderia infection
186
Acute melioidosis 186
Burkholderia cepacia pneumonia 186
Pneumonic plague
187
Tularaemic pneumonia
187
Anthrax pneumonia (woolsorter's disease)
187
Leptospiral pneumonia
188
Chlamydophila pneumonia (psittacosis, ornithosis)
188
C. pneumoniae pneumonia 189
Aspiration pneumonia
189
Lung abscess
191
Secondary lung abscess 191
Primary lung abscess: an aspiration lesion 191
Botrymycosis
191
References
192
Acute bacterial infection of the lungs is still one of the commonest causes of death,
especially in the young and the aged, but very often it is merely a terminal event
secondary to some other debilitating process. Primary pneumonia is one that develops
in a previously healthy individual. Whilst it is still possible to classify pneumonia
on the classic basis of its lobar, bronchial (lobular) or interstitial distribution,
an aetiological classification facilitates the choice of an appropriate antibiotic,
and will be followed here as far as possible. Consideration of the clinical situation
provides important clues to the likely bacterium responsible (Table 5.2.1
), and so aids the initial treatment. Most bacterial pneumonia is endogenous, caused
by microorganisms that make up the flora of the pharynx. Cultures taken at autopsy
have identified similar bacterial species in lung and pharynx.1, 2, 3
Table 5.2.1
Acute pneumonia: inference of the bacterium responsible from the clinical situation
Clinical situation
Likely bacterium
Previously healthy individual
Streptococcus pneumoniae
Complication of viral infection
Staphylococcus aureus
Streptococcus pneumoniae
Chronic bronchitis
Streptococcus pneumoniae
Haemophilus influenzae
Cystic fibrosis
Staphylococcus aureus
Haemophilus influenzae
Pseudomonas aeruginosa
Burkholderia cepacia
Immunosuppression
Streptococcus pneumoniae
Staphylococcus aureus
Pseudomonas aeruginosa
Klebsiella pneumoniae
Anaerobes
Hospital inpatient
Pseudomonas aeruginosa
Enterobacteriaceae spp.
Staphylococcus aureus (often methicillin-resistant)
Bronchial tumour
Streptococcus pneumoniae
Staphylococcus aureus
Anaerobes
Aspiration
Anaerobes
Alcoholism
Streptococcus milleri
Haemophilus influenzae
Anaerobes
Klebsiella pneumoniae
Of outstanding importance is the Gram-positive diplococcus Streptococcus pneumoniae,
which is generally known as the pneumococcus. This bacterium is responsible for almost
all cases of lobar pneumonia and for most cases of bronchopneumonia. Other varieties
of bacteria that may produce pneumonia, almost always in its bronchopneumonic form,
include Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae (Pfeiffer's
bacillus), Klebsiella pneumoniae (Friedlander's bacillus), and Legionella pneumophila.
Streptococcus pneumoniae is much the commonest cause of adult cases of community-acquired
pneumonia requiring admission to hospital (Table 5.2.2
).4, 5, 6, 7, 8, 9, 10 However, the situation is very different in patients who develop
pneumonia after admission to hospital (nosocomial pneumonia), in whom Gram-negative
enteric bacilli such as Pseudomonas aeruginosa and members of the Enterobacteriaceae
family (Escherichia coli, Proteus and Klebsiella species) are most commonly responsible.11,
12, 13, 14, 15 This is largely due to the administration of wide-spectrum antibiotics.
Soon after such antibacterial drugs are administered, the oral flora changes and the
upper respiratory tract commonly becomes colonised by bowel organisms.16, 17 Acid
suppressants also increase the risk of nosocomial pneumonia.
18
They act by countering an important natural defence mechanism against bacterial growth
in the stomach and upper small intestine. The problem has been particularly seen in
intensive care units where acid suppressants may be administered to minimise the risk
of gastric stress ulceration.
12
Sometimes the lungs are infected by way of the blood stream and on rare occasions
an exogenous source such as a contaminated ventilator or nebuliser has been identified.19,
20 The mechanisms involved in nosocomial pneumonia are summarised in Figure 5.2.1
.
Table 5.2.2
Microbial diagnoses (%) in adults admitted to hospital with community-acquired pneumonia
UK
4
New Zealand
5
Spain
6
Netherlands
7
North Americaa
,
8
Chile
9
Australia
10
Streptococcus pneumoniae
34
27
39
20–60
11
24
5
Mycoplasma pneumoniae
18
6
16
1–6
4
2
9
Viruses
7
8
–
2–15
14
12
15
Haemophilus influenzae
6
8
11
3–10
0.4
3
5
Chlamydia
3
3
–
4–6
9
2
2
Legionella pneumophila
2
2
11
2–8
2
2
3
Staphylococcus aureus
1
–
–
3–5
–
1
1
Microbiologically negative
33
45
27
–
57
54
45
a
Based on 15 separate reports.
Figure 5.2.1
Mechanisms involved in the development of nosocomial pneumonia. Other risk factors
include older age, underlying diseases such as cancer and diabetes mellitus, obesity
and cigarette smoking.
Bacteriological diagnosis is usually made from the direct examination or culture of
expectorated sputum. Sputum is prone to be contaminated by upper respiratory tract
commensals and bronchoscopic or transcutaneous tracheal aspirates free of this problem
have much to commend them. At autopsy, bacterial contamination is unavoidable and
microbiological sampling of a consolidated area of lung should be through a surface
sterilised by searing with a hot iron rod. A more elegant method entails the in situ
culture of bacteria in the whole frozen organ using large Petri dishes.
21
By this method bacteria can be matched topographically to foci of consolidation, and
contaminants recognised as being on the pleural surface of the lung.
Bronchopneumonia
Although it has been resolved to follow an aetiological classification as far as possible,
many bacteria cause a common morphological pattern of disease and this will be described
before proceeding to specific aetiological agents. This pattern of pneumonia results
from the successive infection of conductive airways and is therefore called bronchopneumonia.
Predisposing causes
Bronchopneumonia occurs most frequently in infants, debilitated young children and
elderly people, and in such patients often proves fatal. The disease is particularly
likely to complicate a condition that predisposes to infection by weakening either
the local or general defence mechanisms. Local predisposing conditions include other
acute infections of the respiratory tract, such as influenza, measles, pertussis and
Mycoplasma infection, and chronic infective conditions such as chronic bronchitis
and cystic fibrosis. Bronchopneumonia may also follow inhalation of irritant gases,
aspiration of food or vomit, and obstruction of a bronchus by a foreign body or tumour.
Bronchopneumonia is also common after surgical operations. The pathogenesis of postoperative
bronchopneumonia is complex. Tracheal intubation bypasses the nose, which normally
warms and moistens the inspired air, whilst ether or other irritant vapours may further
impair the ciliary defence mechanism of the bronchial tree. The unconscious patient
may inhale infected material from the mouth or nose, and the temporary depression
of the cough reflex may allow microorganisms to establish themselves in the lungs.
Once the effect of the anaesthetic has worn off, the pain associated with movement,
particularly of the abdominal wall, may restrict the normal aeration of the lower
parts of the lungs. The haemorrhage and shock that may accompany any major surgical
operation also result in some general depression of resistance to infection.
Other factors predisposing to bronchopneumonia include generalised metabolic disorders
such as diabetes mellitus. Finally, bronchopneumonia is a very common terminal event
in patients debilitated by cancer.
Clinical features
The onset of bronchopneumonia is insidious but once established it may have serious
effects on respiratory function. The filling of many air spaces with exudate excludes
air from much of the lungs and may lead to serious peripheral hypoxia. Healing is
slow and the patient's temperature, which is seldom as high as in lobar pneumonia,
subsides only gradually: resolution is said to be ‘by lysis’ rather than ‘by crisis’.
Pathological features
Bronchopneumonia is characterised by widespread patchy areas of inflammation that
begin as a widely dispersed bronchitis and bronchiolitis: focal areas of pneumonia
then develop in the centres of the acini. The consolidated areas are generally larger
and more numerous in the lower lobes, where they may be several millimetres across.
In the freshly cut lung they are commonly seen as pale, solid, centriacinar foci,
often somewhat raised above the surface of the surrounding lung substance (Fig. 5.2.2
). These consolidated areas can be felt as well as seen. Small beads of yellow mucopus
can often be expressed from the bronchioles on the cut surface of the lung. In severe
cases, the patches of consolidation may become confluent but even when this happens
the affected area seldom presents the uniformity of texture and colour that is characteristic
of lobar pneumonia, in which all parts of the lobe are involved almost simultaneously.
Figure 5.2.2
Bronchopneumonia. There are focal areas of pale consolidation surrounding small airways.
Once the organisms are established in the small bronchioles, they spread partly by
the aspiration of pus and partly by penetrating the inflamed bronchiolar walls. When
the bacteria reach the alveoli they excite an acute inflammation, with copious exudation
of fluid and migration of neutrophils into the alveoli (Fig. 5.2.3
). The air spaces nearest to the bronchioles show the most advanced degree of inflammation;
those at a greater distance may be filled merely with fluid exudate.
Figure 5.2.3
Bronchopneumonia. Pus fills a bronchiole (centre) and some of the adjacent alveoli.
The point at which neutrophils interact with the pulmonary vasculature is unusual.
In contrast to other tissues where neutrophil migration takes place in postcapillary
venules, in the lungs neutrophils leave the circulation through the thin walls of
the alveolar capillaries, a difference that may serve to localise the inflammation
to the alveoli.
22
When recovery from bronchopneumonia takes place the exudate liquefies and is expectorated
or absorbed and respiratory function is restored. However, healing by fibrosis rather
than resolution is commoner in bronchopneumonia than in lobar pneumonia. Bronchopneumonia
healing by fibrosis is the commonest cause of organising pneumonia. It takes the form
of granulation tissue polyps, which are often known as ‘Masson bodies’, protruding
into the alveoli and bronchioles (Fig. 5.2.4
).
Figure 5.2.4
Organising pneumonia. Micropolypoid buds of pale, myxoid, granulation tissue (Masson
bodies) are seen in three alveoli.
Pneumococcal pneumonia
In 1880 Sternberg and Pasteur independently recovered pneumococci from saliva of ill
patients23, 24 and it was soon recognised that this bacterium was an important cause
of lobar pneumonia. At least 90 types of pneumococcus are distinguished serologically
on the basis of antigenic differences between their capsular polysaccharides.
25
Any serological type may be found from time to time in sputum from normal people and
most, if not all, are capable of causing serious disease in humans. However, some
types are more pathogenic than others. Type 3 is particularly pathogenic and is commonly
isolated from patients with acute respiratory illness
26
and pneumococcal bacteraemia.
27
The distribution of the various serotypes differs from country to country and between
different age groups but overall type 14 is the commonest, particularly in young children,
followed by types 4, 1, 6 and 3.
25
Host resistance is very dependent upon the development of opsonic anticapsular antibodies
because the polysaccharide capsule of the pneumococcus impairs phagocytosis. The identification
of the serological type of the pneumococcus responsible for each case of pneumonia
was of great importance when effective treatment depended on the prompt administration
of the appropriate type-specific antiserum but the introduction of sulphonamides and
then antibiotics made serum therapy obsolete. Unfortunately, penicillin-resistant
strains have now emerged. Serological typing is based on the Quellung reaction, an
easily recognisable swelling of the bacterial capsule when the specific antiserum
is applied.
Pathogenesis
The widespread distribution of all types of pneumococcus in the throats of healthy
people is relevant to the pathogenesis of pneumococcal pneumonia, the development
of which must be regarded as attributable to circumstances that sharply lower resistance
to a potentially pathogenic strain of pneumococcus that has been carried in the nose
or throat, perhaps over a long period. Pneumococcal pneumonia is, essentially, an
endogenous infection, due to failure of the natural defences of the respiratory tract
to prevent the spread of a potentially pathogenic strain of pneumococcus from the
nasopharynx to the lungs, where it causes acute inflammation. Pneumococci may also
cause bacteraemia and meningitis.
Although most cases of pneumococcal pneumonia occur sporadically, minor epidemics
sometimes occur as a result of the spread of newly introduced pathogenic strains into
a community, such as a school or military camp, where personal contacts are especially
close.
28
Under these circumstances, a rise in the carrier rate for the responsible type generally
precedes the outbreak.
In temperate climates, pneumococcal infections of the lungs, especially in infants
and the elderly, are much commoner in winter than in summer. Low external temperature
probably has the greatest bearing on the seasonal occurrence of pneumonia, partly
by impairing the natural defences of the respiratory tract through cold air chilling
its mucosa and partly indirectly, by aggravating the overcrowding that occurs in inclement
weather. Both these mechanisms also promote viral infections of the respiratory tract
that predispose to subsequent pneumococcal infection. The carrier rate for pneumococci
in the general population also tends to rise considerably during the winter and thus
to increase dispersal of the more pathogenic strains by droplet spread.
An absent or non-functioning spleen (perhaps removed because of trauma or destroyed
by sickle cell disease) also predisposes to pneumococcal infection. Other contributory
conditions include alcoholic binge-drinking, chronic chest disease, respiratory-depressant
drugs, debilitating metabolic diseases such as diabetes mellitus, cirrhosis, the nephrotic
syndrome, carcinomatosis, immunodeficiency or immunosuppression due to treatment or
disease, including human immunodeficiency virus infection, and any condition, such
as coma, that depresses the cough reflex and so impairs clearance of the respiratory
tract.27, 29 Chronically high-risk individuals and elderly people in residential nursing
homes benefit from a polyvalent vaccine containing purified capsular polysaccharide
that is now available.
30
Pneumococcal infection of the lungs may result in either lobar pneumonia or bronchopneumonia.
These two forms of pneumonia differ greatly in their clinical and pathological features
but the contributory conditions outlined above underlie both.
31
Whether the pneumonia has a lobar or bronchial distribution appears to depend more
on the virulence of the particular serotype than on host defence. However, host factors
involving hypersensitivity have been implicated in the development of lobar pneumonia,
largely because of the rapidity with which the disease spreads to involve a whole
lobe. Bronchopneumonia is dealt with above and only lobar pneumonia will be considered
here.
Clinical features
The onset of lobar pneumonia is typically abrupt. The patient feels ill, complains
of a sharp pain in the side of the chest that is made worse by deep breathing, coughs
up ‘rusty’ sputum, and quickly develops a fever of about 40°C. The respiration is
shallow and its rate becomes fast, sometimes reaching 50 breaths/min or more: the
ratio of pulse to respiration may fall from its usual 4 : 1 to 2 : 1. Cyanosis usually
appears as the disease advances. A leukocytosis of 15–20 × 109/l, mainly neutrophils,
is frequently found. In many cases, pneumococci can be cultured from the blood during
the height of the fever. The patient is delirious and before effective treatment became
available the death rate was high. Before the days of chemotherapy, resolution generally
began on about the eighth or ninth day of the illness, if the patient survived that
long. Quite frequently, the fever fell suddenly, sweating was profuse, respiration
became deeper and less rapid, the delirium abated and the temperature quickly returned
to normal (Fig. 5.2.5
). The healing was said to be ‘by crisis’, as opposed to the gradual abatement of
symptoms seen in bronchopneumonia, which was described as healing ‘by lysis’. This
rapid recovery followed the appearance of specific antibodies against the pneumococcus
responsible.
Figure 5.2.5
Temperature chart (Fahrenheit) of a patient spontaneously recovering from pneumococcal
lobar pneumonia.
Structural changes in the lungs
As the name lobar pneumonia implies, it is usual for the typical changes to be uniform
throughout the affected lobe. Sometimes two or even three lobes may be involved simultaneously
or after brief intervals, in which case 2 or 3 days may separate the onset of involvement
of the different lobes. The lower lobes are most commonly affected; there is no significant
difference in the frequency of involvement of the two lungs. Before the introduction
of effective treatment, the morphological alterations in the lungs generally followed
a classic sequence which, following Laennec's original description, comprised four
stages:
1
congestion
2
red hepatisation
3
grey hepatisation
4
resolution.
It should be realised that these terms apply to typical appearances, and that each
stage shades into the next. Antibiotic treatment has curtailed and modified the natural
course of lobar pneumonia, and reduced both its incidence and its mortality so that
the classic morbid anatomical appearances are now rare.
Congestion
The stage of congestion generally lasts less than 24 hours. It is exceptional for
patients to die so early in the disease, but when such cases are seen at necropsy,
the affected lobe is more or less uniformly involved and appears disproportionately
large in comparison with the other lobes, which collapse in the usual way when the
pleural sacs are opened. The pneumonic lobe is heavy and congested with blood. A blood-stained,
frothy fluid oozes freely from the cut surface.
Histological examination shows that alveolar capillaries are much dilated, and the
air spaces are filled with pale eosinophilic fluid in which there are a few red cells
and neutrophils. The uniformity of the appearances throughout the lobe is taken to
indicate widespread, rapid dissemination of the bacteria through the pores of Kohn
by a flood of oedema fluid. In Gram-stained sections, the paired, lanceolate pneumococci
can often be seen, mainly free, in the alveolar fluid. At this stage, little fibrin
has formed, and the affected lobe has not yet acquired the firm consistency typical
of hepatisation.
Red hepatisation
The feature that led Laennec to popularise Morgagni's term ‘hepatisation’ is the consistency
of the affected lobe, which resembles that of the liver. The cut surface of the lung
is dry and there is a serofibrinous pleurisy. Small rough tags of fibrin cover much
of the visceral pleura of the affected lobe. Congestion persists and the lung remains
red.
The changes in the gross features of the affected lobe are readily explained by the
histological changes that have taken place during the preceding few hours. The copious
fluid exudate, which at the time of its formation contained abundant fibrinogen, has
clotted in the alveolar spaces and interlacing strands of fibrin now occupy each air
space and can often be seen connecting with those in neighbouring alveoli through
the pores of Kohn. At the same time, more and more neutrophils have migrated from
the congested capillaries into the fibrin meshwork. Usually, at this stage, the pneumococci
are numerous, and many of them have been ingested by neutrophils.
Grey hepatisation
After 2–3 days, the affected lobe gradually loses its red colour and assumes the grey
appearance that it retains for the next few days (Fig. 5.2.6
). This change in colour, which starts at the hilum and spreads towards the periphery,
is brought about by a lessening of the capillary congestion and by the migration of
very large numbers of leukocytes, at first mainly neutrophils but later macrophages,
into the fibrin in the alveoli. An almost complete shutdown of the vasculature of
the affected lobe can be demonstrated in radiographs of the lungs after their injection
at necropsy with radiopaque material. The temporary virtual cessation of blood flow
through the unventilated lobe lessens the liability to systemic hypoxia that might
otherwise develop, a good example of ventilation/perfusion matching (see p. 22).
Figure 5.2.6
Lobar pneumonia in the stage of grey hepatisation. The lower lobe is uniformly consolidated.
The cut surface of the lung is now moist as the fibrin has contracted, expelling serum.
Toward the end of the stage of grey hepatisation, pneumococci are less numerous and
appear in degenerate forms, varying much in size, and often no longer Gram-positive.
Resolution
Resolution proceeds in a patchy yet progressive manner by liquefaction of the previously
solid, fibrinous constituent of the exudate in the air spaces. Soon the affected lobe
becomes more crepitant as the air spaces reopen. Liquefaction of the fibrin is thought
to be due to a fibrinolytic enzyme liberated from senescent neutrophils. However,
excessive neutrophil breakdown would probably damage the lung and an alternative form
of cell death is also utilised, namely apoptosis: apoptotic neutrophils are ingested
by macrophages and excessive lysosomal enzyme release is thereby avoided.
32
The now fluid contents of the alveoli are removed, partly by expectoration but mainly
through the lymphatics, resulting in the hilar lymph nodes being soft, moist and swollen.
By the end of the stage of resolution, completion of which is shown by chest radiographs
to require several weeks, the lung has recovered its normal structure.
Complications
Lobar pneumonia may be complicated by dissemination of the pneumococci throughout
the lungs and to other organs. In some patients acute pneumococcal bronchitis and
foci of bronchopneumonia may be present in lobes other than that mainly involved.
These accessory lesions, if severe, may exacerbate the disease by further impairing
the respiratory exchange in the lungs. In many cases of lobar pneumonia there is a
bacteraemia at the height of the infection. Acute endocarditis may then develop, and
this is sometimes followed by the formation of an abscess in the brain after lodgement
of an infected embolus. Pneumococcal meningitis, peritonitis and arthritis are rarer
manifestations of the dissemination of the organisms by the blood but septicaemia
with consequent septic shock are important complications in patients requiring hospital
admission.
33
Pneumonia is the commonest cause of septic shock (Table 5.2.3
).34, 35
Table 5.2.3
Pneumonia as a cause of septic shock
Number of patients
Source of infection (%)
Lung
Abdomen
Urinary tract
Other
Warren et al. 2001
34
2314
34
27
7
31
Abraham et al. 2003
35
1754
51
28
13
8
Although, in patients who recover, the area of lobar consolidation usually resolves
completely, several complications may interfere with the healing process. Resolution
may be delayed through incomplete digestion of the fibrin in the exudate within the
alveoli, and organisation, followed by fibrosis (‘carnification’), may develop. The
fibrosis is essentially intraluminal, taking the form of micropolypoid buds of granulation
tissue (Masson bodies) that largely fill alveoli and extend into alveolar ducts and
respiratory bronchioles (organising pneumonia), as described above under bronchopneumonia
(see Fig. 5.2.4). The contracting fibrous tissue may exert traction on the airways,
leading to bronchiectasis, which may affect the whole or part of the lobe. Alternatively,
part of the affected tissue may break down, especially in cases of infection by pneumococci
of serotype 3, and a lung abscess may form.
36
On the pleural surface, the serofibrinous exudate may develop into empyema (see Fig.
13.6, p. 713) or be complicated by suppurative pericarditis.
Staphylococcal pneumonia
Staphylococcus aureus pneumonia is a serious but relatively uncommon disease with
a high case fatality rate. It often complicates influenza. The special relationship
of staphylococci and influenza virus has been dealt with on page 158. In children,
staphylococcal pneumonia may follow measles or whooping cough. In infants a primary
staphylococcal bronchopneumonia is known, with a case fatality rate as high as 80%
in the pre-antibiotic era. The infection is generally endogenous, the bacteria frequently
being derived from the patient's skin or nose and the infection air-borne. However,
staphylococcal pneumonia or lung abscess sometimes follows bacteraemia or septicaemia,
37
particularly in drug addicts with right-sided bacterial endocarditis.
Although the mortality from most forms of pneumonia has been reduced by modern drugs,
many strains of Staphylococcus now widely distributed in the population are resistant
to the generally used antibiotics. Even relatively new antibiotics such as meticillin
are inactive against some of these staphylococci, which have become known as meticillin-resistant
S. aureus or MRSA. Such strains periodically become prevalent in hospitals,
15
carried in the nose by staff and patient, and fatalities from staphylococcal infection,
often with pneumonia, have occurred among surgical patients who otherwise should have
recovered from their operation. In addition, although MRSA is primarily viewed as
the prototype of multiresistant nosocomial (hospital-acquired) infections, new lineages
have emerged that cause community-acquired infections in individuals without risk
factors, including rare cases of necrotising pneumonia.38, 39, 40
S. aureus owes its pathogenicity to a series of necrotising exotoxins that induce
a marked neutrophil response resulting in suppurative tissue necrosis.
41
Particularly potent is a strain of meticillin-resistant S. aureus that secretes an
exotoxin known as Panton–Valentine leukocidin. As well as complicating influenza,42,
43, 44 this strain has resulted in fatal septic shock in previously healthy persons.
38
At necropsy, the bronchi are acutely inflamed and the lungs contain many bright yellow
centrilobular foci of suppuration (Fig. 5.2.7
), which in the more advanced cases may have enlarged and coalesced to form abscesses
1 cm or more in diameter. Adjacent air spaces contain a purulent exudate. A superficial
abscess may rupture into the pleura and cause empyema, which is a common complication
of staphylococcal pneumonia. If the patient survives, there may be permanent damage
to the lungs in the form of pulmonary fibrosis, bronchiectasis or large air-filled
cysts known as pneumatoceles (Fig. 5.2.8
).
Figure 5.2.7
Staphylococcal bronchopneumonia. The pneumonic foci show early suppuration.
Figure 5.2.8
Pneumatoceles in a child's lung, the consequence of staphylococcal pneumonia.
Streptococcal pneumonia
In the pre-antibiotic era, up to 5% of all acute pneumonias were caused by group A
β-haemolytic streptococci but Streptococcus pyogenes is now a rare cause of serious
pulmonary infection; nevertheless, occasional cases of streptococcal pneumonia are
still encountered,
45
and infective pulmonary embolism is recorded in streptococcal toxic shock.
46
Streptococcal pneumonia typically follows viral infections of the respiratory tract
and is thought to have been a prominent bacterial superinfection during the 1919 influenza
pandemic. Patients present with abrupt fever, dyspnoea and pleuritic chest pain. They
often develop haemoptysis and cynosis. Death may take place within 2–3 days of the
onset, in which case the lungs show haemorrhagic oedema and pneumonic consolidation
is not well developed. In subacute cases there is bronchopneumonic consolidation,
which is characteristically accompanied by early pleural involvement and effusion.
The anaerobic Streptococus milleri is now recognised to be an important cause of necrotising
lung disease, causing lung abscess and empyema. Patients are often elderly men with
periodontal disease, excessive alcohol consumption, malignant disease or recent thoracic
surgery.
47
Haemophilus pneumonia
The Gram-negative bacillus Haemophilus influenzae is a frequent isolate from the upper
respiratory tract of healthy individuals and can often be cultured from the sputum
of patients with pneumonia due to other organisms, the true pathogen being identified
by lung aspiration or blood culture. It was first isolated in the 1889–90 influenza
pandemic and so named because its discoverer, Pfeiffer, recovered it from a large
proportion of cases and mistook it for the cause of influenza. Occasionally however
H. influenzae is itself the cause of pneumonia.
48
Patients are often elderly or predisposed to pneumonia by alcoholism or chronic bronchitis.
The consolidation may take the form of either lobar pneumonia or bronchopneumonia.
The changes in the lung are similar to those in pneumococcal pneumonia (see above).
Pleural effusion is a common feature.
Moraxella pneumonia
The Gram-negative diplococcus Moraxella catarrhalis, previously known as Branhamella
catarrhalis or Neisseria catarrhalis, is usually a harmless pharyngeal commensal but
in the immunodeficient it can cause many serious infections, including pneumonia.49,
50, 51
M. catarrhalis is one of the bacteria that colonise the bronchi in chronic bronchitis
and are responsible for acute exacerbations of this disease.
52
Chronic bronchitis and lung cancer both predispose to M. catarrhalis pneumonia.53,
54, 55 Other conditions predisposing to M. catarrhalis infection include old age,
heart failure, diabetes mellitus and corticosteroid treatment. The incidence of M.
catarrhalis colonisation and infection is highest in winter. The pathological appearances
are those of acute bronchitis and bronchopneumonia.
Acinetobacter is another genus belonging to the family Moraxellaceae, one species
of which (A. baumannii) has emerged as a potential cause of pneumonia in intensive
care units. Acinetobacter are generally regarded as harmless soil-living commensals
but they may colonise hospitals and cause serious respiratory illness in severely
immunocompromised patients. Acinetobacter species are innately resistant to many classes
of antibiotics.
Legionella pneumonia (legionnaire's disease)56, 57, 58
Aetiology and epidemiology
The legionellae were only discovered after prolonged investigations into the deaths
of 34 of some 4500 members of the American Legion attending a convention in a Philadelphia
hotel in 1976.59, 60 The investigations took so long because the responsible bacterium,
subsequently named Legionella pneumophila, is resistant to conventional stains and
fastidious in its culture requirements. Once identified, it was possible to recognise
retrospectively from stored sera that Legionella had been responsible for pneumonia
in the past. Sporadic cases were subsequently recognised.61, 62 These are commoner
than those encountered in epidemic outbreaks but nevertheless only form a small proportion
of community-acquired pneumonia (see Table 5.2.2). In addition to causing pneumonia
(legionnaire's disease), Legionella is responsible for a less severe, non-pneumonic,
acute febrile illness known as Pontiac fever. The term ‘legionellosis’ embraces both
diseases.
Although Legionella pneumonia occurs in epidemics, the bacterium is seldom transmitted
from person to person. Spread is usually due to atmospheric contamination. It is ironic
that a bacterium so hard to grow in the laboratory can succeed so well in air-conditioning
plants. These provide the necessary warm, moist conditions that the bacterium requires,
drawing it in from the outside, fostering its growth and dispersing it around a building.
The contaminated buildings are therefore generally modern, but with neglected engineering
plants. Colonisation of the plant by certain free-living amoebae may also promote
the growth and survival of legionellae for these bacteria are resistant to amoebic
digestion and may survive exposure to disinfectants when the amoeba encysts.
63
Passers-by as well as those within the building may be infected. In 1985, the 2-year-old
Stafford General Hospital in the UK was the setting of one of the biggest outbreaks:
46 people died there of legionnaire's disease, mostly patients rather than staff.
It is no coincidence that outbreaks affect hospitals or conventions of ex-servicemen,
for the old, the infirm, heavy smokers and those who drink to excess are at particular
risk. Hospital-acquired infection is particularly likely to affect immunocompromised
patients, such as transplant recipients.
62
Also, mixed infections involving legionellae may be commoner than previously thought.
64
Bacteriology
Legionellae are aerobic, 1–2-µm, Gram-negative bacilli that differ from other such
bacilli in the fatty acid profile of their cell wall. They fail to grow on standard
media and require buffered charcoal yeast extract, which is also useful for isolating
Nocardia. The number of species has been continually increasing since the original
isolation of L. pneumophila and now exceeds 50, of which about half are pathogenic
to humans. In the USA L. pneumophila accounts for about 85% of Legionella infections,
L. micadadei for about 8% and L. longbeachae for 1–3%. The legionellae are facultative
intracellular organisms that are able to proliferate within phagocytic cells. They
are also able to invade and proliferate within alveolar epithelial cells.
65
Host defence
Humoral mechanisms of defence appear to be limited to opsonic enhancement of phagocytosis.
The role of neutrophils is unclear: neutropenic patients are not particularly susceptible
to legionnaire's disease. Macrophages activated by T-cell lymphokines appear to be
more important.
66
Clinical features
Legionnaire's disease is heralded by a vague prodromal illness that lasts about 5
days. Malaise and muscle pain are followed by rapidly rising fever, rigors, cough,
chest pain and dyspnoea. There may also be confusion, diarrhoea and proteinuria. There
is usually a moderate leukocytosis. Thus, the clinical features of legionnaire's disease
are similar to those encountered in other bacterial pneumonias. The radiographic findings
are similarly non-specific but detection of Legionella antigen in urine provides a
reliable diagnostic test.
67
Macrolides, fluoroquinolones and rifampin (rifampicin) are the most widely used drugs
in treatment.
Pathology56, 57, 61, 68, 69, 70, 71, 72
The gross appearances of the lungs are those of a confluent or multifocal lobular
pneumonia with a fibrinous pleurisy and a serosanguineous pleural effusion. If confluent,
the boundaries of the consolidation generally fail to match the interlobar fissures
(Fig. 5.2.9
). There may be abscess formation
73
but this is not typical. A miliary distribution is another atypical manifestation.
74
Figure 5.2.9
Legionnaire's disease, represented by a confluent lobular pneumonia that does not
show the uniform involvement of the affected lobe seen in lobar pneumonia.
Microscopically, airways do not appear to be particularly involved in the inflammatory
process, so the disease is not a bronchopneumonia. An acute, leukocytoclastic, fibrinopurulent
pneumonia is characteristic (Fig. 5.2.10
) but sometimes macrophages are more prominent than neutrophils. The legionellae resist
digestion and multiply within the phagocytes, which they eventually destroy so that
intense necrosis of the inflammatory cells is often observed. At low magnifications,
alveolar walls may be difficult to recognise but even when there is extensive necrosis
of the exudate, close inspection, perhaps aided by reticulin stains, shows that the
alveolar architecture is generally intact. Occasionally however there are breaks in
the alveolar walls or more widespread destruction may be seen. This may be due to
vasculitis and thrombosis, which is sometimes evident in small blood vessels.
Figure 5.2.10
Legionnaire's disease, showing widespread alveolar filling by fibrin and necrotic
neutrophils.
Demonstration of the organisms is difficult; the fickle and non-specific Dieterle
silver impregnation method is the best of the non-immunological techniques used to
stain the small coccobacilli. Fortunately the bacterial antigens withstand formalin
fixation and routine processing, permitting immunostaining to be applied to paraffin
sections.
75
Electron microscopy of the bacteria shows features that are indistinguishable from
those of Gram-negative bacilli.
76
In practice, most cases are diagnosed without recourse to pathology.
The hilar lymph nodes are often infected and there is haematogenous dissemination
to sites such as the spleen and bone marrow in 27% of cases.
61
The process generally resolves completely but healing by organisation may be recognised
in fatal cases as buds of connective tissue (Masson bodies) in the lumen of alveoli,
alveolar ducts and respiratory bronchioles. Such postpneumonic fibrosis presumably
accounts for the permanent impairment of lung function that has been noted in some
patients.
Klebsiella pneumonia
Klebsiella pneumoniae (Friedlander's bacillus) is a rare cause of community-acquired
pneumonia but accounts for a higher proportion of pneumonia acquired in hospital,
where patients are more likely to be treated with antibiotics that permit this bacterium
to dominate the pharyngeal flora.
77
K. pneumoniae is also a particularly common inhabitant of the oral cavity in those
with poor dental hygiene and such persons are accordingly at increased risk of Klebsiella
pneumonia. Alcoholics are also particularly susceptible to Klebsiella pneumonia, constituting
about half the patients dying of Klebsiella infection.
78
Others at particular risk are the elderly and diabetics. The mortality of Klebsiella
pneumonia is much higher than that of pneumococcal pneumonia: 21% in the general population
and 64% in alcoholics.78, 79 Bacteraemia is a particularly adverse prognostic factor.
78
Klebsiella pneumonia has a predilection for the upper lobes. There is often uniform
diffuse consolidation but, with only part of the lobe involved, a sharply demarcated
edge abutting interlobular septa rather than interlobar fissures: the part of the
lobe affected by such consolidation enlarges by the progressive involvement of adjacent
lobules (Fig. 5.2.11
). The abundant mucoid coat of the klebsiellae gives the pneumonic lesions a distinctively
slimy appearance and feel. This material is mucicarminophilic, a characteristic that
is often helpful in identifying the infection in histological sections. Klebsiella
pneumonia is particularly liable to suppurate and form lung abscesses (Fig. 5.2.12
). These may progress to massive pulmonary gangrene.
80
Chronic Klebsiella pneumonia may mimic tuberculosis by presenting with cavitating
upper-lobe disease.
Figure 5.2.11
Friedlander's (Klebsiella) pneumonia showing diffuse consolidation of the upper part
of the upper lobe. The unaffected lower portion has collapsed on slicing but the consolidated,
airless upper portion has retained its shape.
Figure 5.2.12
Abscess formation complicating Friedlander's (Klebsiella) pneumonia.
Pseudomonas pneumonia
The species of Pseudomonas involved in lung infections is usually Pseudomonas aeruginosa,
which is the commonest bacterium isolated in hospital-acquired pneumonia.
15
Infection may be inhalational or blood-borne. Infection via the airways generally
follows colonisation of the pharynx, especially in patients on antibiotics that destroy
the normal flora of the upper respiratory tract. As with many bacterial infections,
prior viral injury promotes adhesion to the bronchial mucosa,81, 82 for it is difficult
for P. aeruginosa to adhere to normal epithelial cells. Adhesion of the bacteria is
dependent upon the transient expression of a sialoganglioside at the apex of the regenerating
epithelial cells.
83
Inhalational Pseudomonas pneumonia has also developed in patients treated by tracheostomy
and mechanical ventilation due to contamination and inadequate disinfection of the
ventilators.
19
Several outbreaks in the USA were attributable to faulty bronchoscopes.84, 85
Pseudomonas pneumonia is often characterised by well-demarcated pale areas of necrosis,
which histologically are composed of an amorphous coagulum containing many bacteria,
the nuclear debris of necrotic neutrophils and small numbers of lymphocytes and macrophages.86,
87
Pseudomonas appears to be able not only to resist, but also to destroy neutrophils.
88
It is debatable whether the tissue necrosis is due to bacterial toxins or an immunological
response.
Pseudomonas septicaemia may complicate Pseudomonas pneumonia
87
or abdominal infection. It results in further changes, notably prominent colonisation
of blood vessels. So pronounced is this feature that the vessels exhibit a distinctive
blue haze with haematoxylin, or a red one with a Gram stain.
89
The rod-like form of the bacteria is usually readily apparent at high magnification
but the Sandiford modification of the Gram stain is especially useful for demonstrating
Gram-negative bacteria in tissue sections (Fig. 5.2.13A
).
90
The bacterial colonisation causes a vasculitis with resultant thrombosis and ischaemic
necrosis (Fig. 5.2.13B). Such necrotising arteritis is not found in non-bacteraemic
Pseudomonas pneumonia.
91
Meningitis, arthritis and jaundice are further manifestations of Pseudomonas septicaemia.
There may also be striking skin lesions, including vesicles and sharply demarcated
foci of cellulitis that enlarge rapidly and become haemorrhagic and necrotic.
Figure 5.2.13
Blood-borne Pseudomonas aeruginosa pneumonia. (A) A Gram–Sandiford stain shows heavy
colonisation of arterial walls by Gram-negative bacilli. (B) The consequent vasculitis
has led to extensive infarction of the lower part of the lung.
Burkholderia infection
Acute melioidosis
Melioidosis is a generalised infection caused by Burkholderia (formerly Pseudomonas)
pseudomallei, a Gram-negative bacillus found in watery environments in certain tropical
areas, notably south-eastern Asia and northern Australia.
92
However, isolated cases have been described in many other countries.93, 94 The route
of infection is most often through the skin but may be through the respiratory tract,
where cystic fibrosis appears to be a predisposing factor.
95
Early studies were made during the British occupation of Burma, whilst French and
American servicemen were infected in Vietnam.
96
The prognosis was initially thought to be very poor but improved serological testing
indicated that subclinical and mild forms of the disease are common in certain tropical
areas.
96
The bacterium may lie dormant in an infected person for many years before causing
disease and it is estimated on the basis of high antibody titres that many thousands
of American veterans of the Vietnam war are at risk. Acute and chronic forms are recognised,
and, in both, lesions are commonest in the lungs. Melioidosis is very similar clinically
(but not epidemiologically) to the equine disease, glanders, which is caused by infection
with Malleomyces mallei, with which B. pseudomallei shares certain antigenic determinants.
Chronic melioidosis is described on page 213.
Acute melioidosis is characterised by the sudden onset of severe diarrhoea, overwhelming
pneumonia and septicaemia, and if untreated is rapidly fatal. Numerous abscesses are
found throughout the body. In chest radiographs these are seen as disseminated nodules.
97
The early lesions take the form of small foci of neutrophils surrounded by haemorrhagic
zones. As the abscess enlarges, fibrin becomes more prominent and necrosis ensues.
Cases with prominent pulmonary features are characterised by a confluent necrotising
pneumonia which has a bronchitis element that is not evident when there are only discrete
abscesses. Vasculitis, a feature of P. aeruginosa pneumonia, is not seen in melioidosis.
Bacilli are generally quite numerous and often form distinct collections within multinucleate
macrophages that are scattered amongst the numerous neutrophils.
98
They have been shown to survive and multiply within cells, including neutrophils.
99
The bacteria are most easily identified by the Giemsa stain, which can then be supplemented
by a Gram preparation. Staining is strongest at the ends of the bacilli, which therefore
have a bipolar appearance that has been likened to that of a closed safety pin.
Burkholderia cepacia pneumonia
Burkholderia cepacia (formerly Pseudomonas cepacia) is an important pathogen in cystic
fibrosis
100
but is seldom isolated in the immunocompetent. The few pathological studies of B.
cepacia pneumonia have shown necrotising granulomatous inflammation merging with areas
of more conventional necrotising bronchopneumonia, occasionally with necrotising granulomas
in the mediastinal lymph nodes.
101
Pneumonic plague
In humans, infection with the Gram-negative bacillus Yersinia pestis takes two main
forms: bubonic plague, in which the bacillus is transmitted to humans by the bite
of infected rat fleas, and pneumonic plague, in which the organism is usually spread
from person to person by infected sputum droplets. Before the era of effective antibiotics
both forms had a high case fatality rate: indeed, the plague bacillus has been the
cause of some of the most widespread and devastating epidemics in human history.
In the pneumonic form the lungs show many areas of bronchopneumonia: these are sometimes
confluent but the course of the untreated disease is generally too short for massive
consolidation to develop. The pulmonary lesions are often haemorrhagic and they are
usually accompanied by serofibrinous pleurisy and great enlargement of the hilar lymph
nodes. Histologically the alveolar capillaries are engorged and the air spaces are
full of fluid exudate containing few leukocytes but many bacilli. In successfully
treated cases, progression to consolidation and rarely cavitation has been noted radiologically.
102
Tularaemic pneumonia
Tularaemia is caused by Francisella (formerly Pasteurella) tularensis, a Gram-negative
coccobacillus that infects many wild animals in North America and, to a lesser extent,
Scandinavia, Japan and elsewhere, including the UK.
103
The bacterium was named after Tulare county in California where human infection was
first identified. The infected animals include rabbits, hares, muskrats and ground
squirrels. Humans are infected when handling these animals or when bitten by ticks
that act as vectors of the disease. Direct infection takes place through skin abrasions,
mucous membranes, the conjunctivae, and, less commonly, the lungs. The bacterium is
highly virulent and its handling poses an extreme hazard to microbiology staff. It
is a facultative intracellular pathogen with its primary target being the macrophage.
Pulmonary involvement is usually by septicaemic spread from a lesion in the skin or
eyes, via the local lymph nodes, but may be primary. Many patients show neither septicaemia
nor pulmonary involvement but in fatal cases the incidence of pneumonia rises to 70%.
At necropsy, the lungs show necrotising bronchiolitis, bronchopneumonia, pleurisy
and pleural effusions. The consolidation tends to become confluent and undergo necrosis.
104
The alveoli then contain abundant fibrin and necrotic macrophages, resembling the
changes seen in Legionella pneumonia. Vasculitis and thrombosis may lead to necrosis
of the alveolar walls. The bacteria are difficult to demonstrate in sections with
conventional stains but can be identified by immunocytochemistry. Culture is important
and the demonstration of a rising titre of antibodies is also helpful in establishing
the diagnosis.
Anthrax pneumonia (woolsorter's disease)
Anthrax occurs in many species of domestic animals, especially herbivores. Spores
of the causative organism, Bacillus anthracis, occasionally infect humans, most commonly
by skin inoculation, where they cause a ‘malignant pustule’, least commonly by ingestion,
or with devastating effect by inhalation, resulting in ‘woolsorter's disease’.
Woolsorter's disease was formerly seen in the Yorkshire textile towns, where it was
acquired by inhalation of dust from imported wool contaminated with anthrax spores.
Others at risk include those exposed to infected hides, hair, bristle, bonemeal and
animal carcasses. The spores are very resistant to drying but effective measures are
now directed to their destruction by exposure of imported materials to antiseptics
before they are handled; as a result anthrax is now very rare in Great Britain. In
1979 there was a major epidemic of anthrax resulting in over 60 deaths in a narrow
corridor of land downwind of a military establishment near Sverdlovsk, Russia, which
was suspected of conducting microbiological warfare research.105, 106 Anthrax spores
were also used as a bioweapon by terrorists operating in the USA in 2001: of 11 people
who were infected, 5 died. Screening procedures and plans to deal with the possibility
of similar attacks have subsequently been put in place.107, 108, 109
If inhaled, the spores are rapidly transmitted to the mediastinal lymph nodes. It
is here that the bacilli form and the disease starts. From the lymph nodes the bacilli
reach the blood stream and are distributed in large numbers throughout the body. The
septicaemia is often so severe that the organisms are recognisable in films of the
circulating blood. Although the lungs may have provided the portal of entry, they
are affected secondarily as part of a systemic blood-borne disease.110, 111
The course of inhalational anthrax is dramatic. Non-specific influenza-like symptoms
rapidly progress to cardiopulmonary failure and death within a few days.
112
Necropsy shows haemorrhagic necrosis of the infected tissues. The process is most
advanced in the lymph nodes draining the site of primary infection.
106
Thus, in woolsorter's disease a haemorrhagic mediastinal mass is one of the principal
findings at necropsy. Other changes commonly encountered at necropsy include a large,
dark, soft spleen, haemorrhagic effusions, haemorrhagic intestinal ulceration, haemorrhagic
meningitis (which is often limited to the top of the cerebral hemispheres in a so-called
‘cardinal's cap’), haemorrhagic bronchitis and widespread, often confluent, areas
of haemorrhagic pneumonia. As in other organs, the haemorrhagic inflammatory oedema
that constitutes the exudate in the alveoli contains large numbers of the characteristic
large Gram-positive bacilli, which are readily seen in haematoxylin and eosin preparations.105,
111, 113 However, immunohistochemistry is proving more reliable than Gram staining
in identifying the bacteria.108, 109
Leptospiral pneumonia
Leptospirosis is a zoonosis of worldwide distribution with many wild and domestic
animal reservoirs. Human infection occurs through direct contact with infected animals
or, more commonly, through contact with water or soil contaminated with the urine
of infected animals. Sewage workers, farmers, animal handlers and veterinarians are
at particular risk. Pulmonary disease may be seen in cases of infection by leptospires
of various serogroups: they are severest in cases of infection by Leptospira icterohaemorrhagiae,
which is acquired from rats, but have been a conspicuous feature in a small proportion
of cases of canicola fever (infection by L. canicola, acquired from dogs) and of infection
by L. bataviae, which occurs in parts of south-eastern Asia. The spirochaetal leptospires
can be demonstrated in the lesions by Levaditi's silver impregnation method, immunocytochemistry
or in situ hybridisation.
Pulmonary involvement is manifest as cough and haemoptysis in association with patchy
consolidation of the lungs.114, 115 Occasionally, severe pulmonary haemorrhage is
the predominant or only manifestation of the infection.116, 117 but provided the disease
is recognised, and treated early and efficiently, the case fatality rate is low.
The pulmonary lesions are foci of haemorrhagic pneumonia or, in some cases, of simple
haemorrhage.
116
In the pneumonic foci there is a haemorrhagic fibrinous exudate that contains a few
neutrophils and occasional macrophages; the exudate is most conspicuous within the
alveoli but is seen also in the interalveolar septa, which are correspondingly thickened.
Diffuse alveolar damage is occasionally observed. In cases of simple pulmonary haemorrhage,
the bleeding is often associated with the profound thrombocytopenia that is an occasional
accompaniment of leptospirosis but electron microscopy reveals that there is also
profound capillary damage, culminating in endothelial necrosis
118
: a paucity of bacteria near the lesions supports the suggestion that they are due
to toxins released elsewhere.
119
Chlamydophila pneumonia (psittacosis, ornithosis)
The chlamydophilae, formerly known as the chlamydiae or bedsoniae and once considered
to be viruses, are obligate, intracellular organisms, 0.25–0.50 µm in diameter, that
are now classed as bacteria. The genus includes three species pathogenic for humans:
Chlamydophila psittaci, C. trachomatis and C. pneumoniae.
C. psittaci pneumonia is contracted from infected birds, particularly parrots imported
from South America, where the disease is enzootic. In contrast, C. trachomatis is
almost exclusively confined to humans, causing trachoma, lymphogranuloma venereum
and other genital diseases, and, in infants, pneumonia, which is usually accompanied
by ocular infection.120, 121
C. pneumoniae was described as a separate pathogen in 1986 and in some communities
is responsible for as many as 10% of pneumonia admissions to hospital,122, 123, 124,
125 although generally causing milder disease than C. psittaci.
Organisms similar to C. psittaci are found in many species of wild and domesticated
birds in various parts of the world and at least some of these are pathogenic for
humans. For this reason, the more generally applicable name, ornithosis, is more appropriate
to this group of diseases rather than psittacosis (parrot's disease). Budgerigars
are now the commonest source of ornithosis in the UK.
126
Outbreaks have also been associated with ducks, chickens and turkeys.127, 128
Infected birds, which may show no signs of disease, excrete the organisms in droppings
that eventually form a highly infected dust. It is usually through the inhalation
of such dust while attending to the birds that individuals become infected, but the
disease may also be contracted in poultry-processing plants or pillow-filling factories.
127
The infectivity of ornithosis is high and numerous instances have been recorded of
nurses and relatives contracting the disease while caring for patients. The disease
has also been acquired through exposure to the organism in the laboratory and in the
performance of necropsies.
Clinical features
The clinical presentation of ornithosis varies from a mild influenza-like illness
to fulminating pneumonia complicated by lesions in other systems. Fulminating cases
carry a high mortality. Symptoms usually start within 1–2 weeks of exposure. The organism
may be cultured from the patient's blood, but more usually the diagnosis is established
by demonstrating a rising titre of complement-fixing antibodies. Cross-reactions with
other organisms of the psittacosis–lymphogranuloma–trachoma group occur but should
not be confusing in practice. Many patients with ornithosis give a positive skin reaction
to Frei (lymphogranuloma venereum) antigen.
Pathology
At necropsy, the lungs are bulky and patchily consolidated. The consolidated areas,
which are usually haemorrhagic, are more numerous in the lower lobes than elsewhere.
Where they abut the pleura there is local fibrinous pleurisy but pleural effusion
is uncommon.
Microscopically, the changes are appropriate to a bacterial rather than to a viral
pneumonia, for exudation within the alveoli is more marked than interstitial changes.
However, the inflammatory cells are a mixture of those found in bacterial and viral
pneumonia, macrophages predominating in the air spaces and a mixed lymphocytic and
neutrophil infiltrate being seen in the interstitium. The changes are concentrated
on the terminal bronchioles, from which they spread to involve adjacent alveoli and
then the whole lobule, by which time there is often necrosis of the bronchiolar and
bronchial epithelium.
129
There is engorgement and often thrombosis of capillaries that can result in foci of
alveolar necrosis. Later, the alveoli develop a conspicuous lining of swollen epithelial
cells. The chlamydophilae are just visible with the light microscope as cytoplasmic
inclusion bodies (known as Levinthal–Coles–Lillie bodies, LCL bodies, or Levinthal
bodies) that range from about 0.25 to 0.50 µm in diameter. They are to be seen in
the cytoplasm of a variable proportion of the alveolar lining cells. They are basophilic
and may most easily be found in preparations stained by the prolonged Giemsa method.
As with many bacterial pneumonias, healing may be by repair rather than resolution,
resulting in bronchiolitis obliterans organising pneumonia.
130
C. pneumoniae pneumonia
C. pneumoniae is spread from person to person rather than from birds, infecting both
upper and lower respiratory tracts and causing prolonged bronchitis and mild pneumonia
of rather non-specific character, somewhat similar to that caused by Mycoplasma pneumoniae.
125
Retrospective studies of stored sera have shown that many patients diagnosed as having
psittacosis on the basis of a positive serological test were actually infected with
C. pneumoniae. Antibodies to C. pneumoniae have also been identified in many persons
who give no history of respiratory disease.
131
C. pneumoniae infection has a bimodal age distribution, affecting schoolchildren and
the elderly. C. pneumoniae pneumonia is not fatal and there have consequently been
few histopathological studies in humans. Experimental studies suggest that the bacterium
causes a non-specific acute pneumonia.
125
C. pneumoniae has been linked to chronic obstructive lung disease125, 132, 133 and
an intriguing relationship between C. pneumoniae and atheroma has been identified.124,
134, 135
Aspiration pneumonia
136
Causes of aspiration pneumonia
Aspiration lesions include infective processes such as pneumonia and lung abscess,
which are dealt with here, and non-infective processes such as exogenous lipid pneumonia
and the chemical pneumonias or pulmonary fibrosis that result from the aspiration
of gastric acid and other irritants. Aspiration is promoted by loss of consciousness
and suppression of the cough reflex, particularly the latter.
137
It is therefore likely to complicate drunkenness, general anaesthesia, cerebrovascular
accidents, drug overdosage or other causes of coma. Aspiration is also promoted by
dysphagia, whether it be neurological or due to oesophageal diseases such as achalasia,
stricture, diverticulum or involvement in systemic sclerosis.
138
Aspiration pneumonia and lung abscess are also promoted by poor oropharyngeal hygiene:
they are rare in the edentulous.
Anatomical location
Aspiration lesions affect the dependent parts of the lungs so that their anatomical
location is dictated by the position of the individual when aspiration occurs. Common
sites of aspiration pneumonia include the apical segment of the lower lobe and the
lateral parts of the basal segments of the upper lobe because gravity carries the
aspirated material into these lung segments when the patient is in the prone and lateral
positions respectively (Figure 5.2.14, Figure 5.2.15
).
139
Conversely, the right middle lobe is affected when gasoline is accidentally aspirated
while it is being syphoned from a motor vehicle, a procedure that necessitates the
person bending forward so that the right middle lobe and the lingula become the most
dependent parts of the lungs.
140
Figure 5.2.14
The effect of posture on the distribution of aspirated material. When the patient
is fully supine (left) aspirated material is preferentially distributed by gravity
to the apical segment of the lower lobe, whereas when tilted to one side (right) the
lateral portions of the anterior and posterior basal segments of the upper lobe are
affected.
(Reproduced from Brock et al. (1942)
139
courtesy of the Editor of The Guy's Hospital Reports.)
Figure 5.2.15
Aspiration pneumonia showing necrotizing foci of consolidation in the apical segment
of the lower lobe.
Pathological findings
Aspiration pneumonia is a bronchopneumonia in that the conductive air passages as
well as the alveoli are filled with pus and the consolidation is peribronchiolar.
The consolidation is particularly florid; individual foci are often much larger than
those encountered in the more usual type of bronchopneumonia. The lesions also tend
to undergo necrosis (see Fig. 5.2.15). Microscopically, particles of undigested food
may sometimes be observed in the pus. These are generally attended by foreign-body
giant cells (Fig. 5.2.16
) and a florid granulomatous reaction may be provoked, sometimes termed ‘pulse granuloma’
(Fig. 5.2.17
).141, 142, 143 In such cases, the surgeon palpitating the lung at thoracotomy may
suspect metastatic carcinoma but the pathologist is more likely to mistake the microscopic
changes for a specific infective granulomatous disease, such as miliary tuberculosis,
if the aspirated debris goes unrecognised. Less frequently, the granulomas may contain
components of pharmaceutical tablets such as starch, talc, microcrystalline cellulose
and crospovidone used as fillers, or kayexalate, which is a polystyrene sulphonate
used in the treatment of hyperkalaemia.
143
The fillers may also gain access to the lungs via the blood stream in intravenous
drug abusers and are described in the section on foreign-body emboli on page 411.
Figure 5.2.16
Aspiration pneumonia showing a bronchiole filled with pus in which there is a spicule
of foreign material with attendant foreign-body giant cells.
Figure 5.2.17
Aspiration pneumonia characterised by florid foreign-body granulomas.
Clinical features
Fever, consolidation of the lung and leukocytosis may develop soon after the aspiration.
Alternatively, the precipitating episode may not be recognised and the onset of the
pneumonia may be insidious. Cavitation and the production of foul purulent sputum
are common late manifestations of aspiration pneumonia.
Bacteriology
The bacteria responsible for aspiration pneumonia are the dominant components of the
indigenous flora of the upper respiratory tract and mouth. Because of this, specimen
contamination bedevils the interpretation of sputum samples. Cultures of blood, pleural
fluid or transcutaneous tracheal aspirates are more informative. Facilities for anaerobic
culture are essential as anaerobes outnumber aerobes by 10 to 1, as they do in the
mouth and pharynx. Mixed infections are the rule, comprising either a variety of different
anaerobes or mixed anaerobes and aerobes. The commonest isolates are Bacteroides melaninogenicus,
Fusobacterium necrophorum, anaerobic or microaerophilic cocci and Bacteroides fragilis.
144
It is fortunate that all except the last of these are sensitive to penicillin. B.
fragilis is sensitive to the cephamycin, cefoxitin. A predilection for opportunistic
mycobacteria to infect lungs containing aspirated lipids, such as those in milk, is
referred to on page 212.
Lung abscess
An abscess is a focus of suppuration consisting of a collection of pus that is walled
off by chronic inflammatory granulation tissue and fibrous tissue. Although abscesses
are very familiar lesions, in the lung they are often confused with other pus-filled
cavities, particularly those of bronchiectasis. Similarly, when a lung abscess discharges
into the air passages, as it is prone to do, the air-filled space that results is
often confused with an empty bronchiectatic cavity. Lung abscess and bronchiectasis
are fundamentally different diseases. The essential structural difference between
them is that several airways communicate with an abscess cavity, whereas if multiple
airways are ectatic, they only communicate at their normal branching points (see Fig.
3.34, page 119). This is because the formation of an abscess entails ‘cross-country’
destruction of lung tissue, something that is unique to an abscess, regardless of
its aetiology.
Spontaneous rupture of an abscess into a bronchus is a likely event and if the patient
survives this by coughing up the pus instead of disseminating it throughout the bronchial
tree, a marked improvement in the patient's general condition can be expected. With
time, the granulation tissue bordering the now empty cavity may become epithelialised.
Also, the many airways cut across when the abscess formed may be sealed off by scar
tissue. The cavity may then resemble a congenital cyst. A congenital bronchogenic
cyst is distinguished by the presence of cartilage and glands in its wall, but a simple
congenital cyst may be indistinguishable morphologically from a cavity that started
as an abscess. Other congenital cysts (dealt with in Chapter 2) have their own special
features (see Table 2.2, p. 56).
Sometimes the airways leading into a postinfective cavity only open in inspiration
so that they act as check valves. The fibrous wall is then stretched progressively,
resulting in a very thin-walled air sac that is often termed a pneumatocele. This
process is seen particularly after staphylococcal infection (see Fig. 5.2.8). Pneumatoceles
resemble emphysematous bullae but, although they are often multiple, the remainder
of the lung tissue is generally free of emphysema, something that is unlikely with
bullae.
Secondary lung abscess
Abscesses develop in the lungs as a complication of several conditions. Pneumococcal
pneumonia was formerly a common cause but pneumonia due to staphylococci, klebsiellae
(see Fig. 5.2.12) and anaerobic bacteria is now more important in this respect.
145
Local predisposing conditions include bronchial cancer and the presence of a foreign
body. Septic embolism and multiple pyaemic abscesses of the lung were formerly common
complications of such staphylococcal infections as osteomyelitis and carbuncle but
antibiotics have rendered these rare. Still seen on occasion is necrobacillosis (Lemierre's
disease), a severe septicaemic illness in which pharyngitis caused by the anaerobe
Fusobacterium necrophorum is complicated by thrombophlebitis of the internal jugular
vein and multiple metastatic abscesses, particularly in the lungs.146, 147, 148, 149
Primary lung abscess: an aspiration lesion
The development of a secondary lung abscess is easily understood and clearly dependent
upon some other underlying disease. On occasion, however, a lung abscess has no apparent
cause and is therefore termed primary. The available evidence indicates that primary
lung abscesses are nearly always a consequence of the aspiration of infected oropharyngeal
secretions. First, there is usually some condition predisposing to aspiration or impairing
the cough reflex, for example, alcoholic stupor, general anaesthesia, head injury
or neurological disease causing loss of consciousness, dysphagia or primary oesophageal
dysfunction. Second, dental hygiene is usually poor, and there is often periodontitis
or gingivitis. Third, primary lung abscesses are usually found in the dependent parts
of the lungs. They are commoner on the right, probably because the right main bronchus
is a more direct continuation of the trachea than the left, and in the apical segment
of the lower lobe and the lateral parts of the basal segments of the upper lobe, these
being the most dependent parts in the prone and lateral positions respectively (Figure
5.2.14, Figure 5.2.18, Figure 5.2.19
).
139
Fourth, the bacteria responsible are usually the mixed anaerobes that predominate
in the oropharynx, particularly in people with bad teeth (Fusobacterium, Bacteroides
and Peptostreptococcus species), and aerobes such as Streptococcus milleri.47, 150,
151 Thus, primary lung abscess has much in common with aspiration pneumonia and it
is for this reason that it is dealt with here, rather than in Chapter 5.3, the chapter
on chronic bacterial infection, which its indolent nature would justify. The bacteriology
of empyema is similar to that of aspiration pneumonia and primary lung abscess but
this condition is dealt with in Chapter 13, the chapter on pleural disease.
Figure 5.2.18
Bilateral aspiration abscesses. High-resolution computed tomography scan shows bilateral
consolidation and cavitation. Culture grew anaerobic bacteria.
Figure 5.2.19
Primary lung abscess straddling the fissure and involving the lateral parts of the
basal segments of the upper lobe and the apical segment of the lower lobe.
Botryomycosis
The term ‘botryomycosis’ is used to describe colonies of pyogenic bacteria growing
within tissues such as the skin, muscle, bone and various viscera, including the lungs.152,
153, 154 The colonies generally exist within pus-filled cavities and are often enclosed
within sheaths of eosinophilic hyaline material (Splendore–Hoeppli reaction – see
p. 214) (Fig. 5.2.20
). They are indistinguishable from the granules of actinomycosis in sections stained
by haematoxylin and eosin but Gram stains show cocci or bacilli rather than filamentous
bacteria. The bacteria are viable but the growth of the colonies is slow and there
is no invasion of the adjacent tissues: something approaching a state of balance exists
between the body defences and the bacteria.
Figure 5.2.20
Botryomycosis. A colony of mixed bacteria is seen within a purulent exudate.
The size of the bacterial colonies varies. They may only be identifiable with the
aid of a microscope or they may form visible flecks within the pus, similar to the
sulphur granules of actinomycosis. Rarely the colonies are considerably larger; sometimes
a single mass of bacteria may attain a size of 5 cm in diameter. One such colony simulated
an aspergilloma and was called a ‘botryomycoma’.
155
The bacteria involved are often of mixed species but generally include anaerobes such
as Bacteroides or peptostreptococci.
155
These are normal inhabitants of the pharynx and are generally found in aspiration
pneumonia and primary lung abscess, thus relating botryomycosis to these aspiration
lesions. Botryomycosis is also a complication of cystic fibrosis,
156
acquired immunodeficiency syndrome (AIDS)
157
and tracheopathia osteochondroplastica.
158
References
1
Smillie
WG
Duerschner
DR
The epidemiology of terminal bronchopneumonia II. The selectivity of nasopharyngeal
bacteria in invasion of the lungs
Am J Hyg
45
1947
13
18
20279321
2
Kneeland
Y
Jr
Price
KM
Antibiotics and terminal pneumonia: a postmortem microbiological study
Am J Med
29
1960
967
979
13757080
3
Knapp
BE
Kent
TH
Post-mortem lung cultures
Arch Pathol Lab Med
85
1968
200
203
4
British Thoracic Society Research Committee
Community acquired pneumonia in adults in British hospitals in 1982–83: a survey of
aetiology, mortality, prognostic factors and outcome
Q J Med
62
1987
195
220
3116595
5
Neill
AM
Martin
IR
Weir
R
Community acquired pneumonia: aetiology and usefulness of severity criteria on admission
Thorax
51
1996
1010
1016
8977602
6
Almirall
J
Bolibar
I
Vidal
J
Epidemiology of community-acquired pneumonia in adults: a population-based study
Eur Resp J
15
2000
757
763
7
Bohte
R
Vanfurth
R
Vandenbroek
PJ
Aetiology of community-acquired pneumonia: a prospective study among adults requiring
admission to hospital
Thorax
50
1995
543
547
7597669
8
Bartlett
JG
Mundy
LM
Current concepts: community-acquired pneumonia
N Engl J Med
333
1995
1618
1624
7477199
9
Diaz
A
Barria
P
Niederman
M
Etiology of community-acquired pneumonia in hospitalized patients in Chile: the increasing
prevalence of respiratory viruses among classic pathogens
Chest
131
2007
779
787
17356093
10
Charles
PG
Whitby
M
Fuller
AJ
The etiology of community-acquired pneumonia in Australia: why penicillin plus doxycycline
or a macrolide is the most appropriate therapy
Clin Infect Dis
46
2008
1513
1521
18419484
11
Heyland
D
Mandell
LA
Gastric colonization by Gram-negative bacilli and nosocomial pneumonia in the Intensive
Care Unit patient – evidence for causation
Chest
101
1992
187
193
1729067
12
Acourt
C
Garrard
CS
Nosocomial pneumonia in the Intensive Care Unit – mechanisms and significance .1
Thorax
47
1992
465
473
1496508
13
Vincent
JL
Bihari
DJ
Suter
PM
The prevalence of nosocomial infection in intensive care units in Europe. Results
of the European Prevalence of Infection in Intensive Care (EPIC) Study. EPIC International
Advisory Committee
JAMA
274
1995
639
644
7637145
14
Lynch
JP
Hospital-acquired pneumonia – risk factors, microbiology, and treatment
Chest
119
2001
373S
384S
11171773
15
Leroy
O
Giradie
P
Yazdanpanah
Y
Hospital-acquired pneumonia: microbiological data and potential adequacy of antimicrobial
regimens
Eur Resp J
20
2002
432
439
16
Johanson
WG
Pierce
AK
Sanford
JP
Changing pharyngeal bacterial flora of hospitalized patients
N Engl J Med
281
1969
1137
1140
4899868
17
Craven
DE
Steger
KA
Epidemiology of nosocomial pneumonia: new perspectives on an old disease
Chest
108
1995
S1
S6
18
Herzig
SJ
Howell
MD
Ngo
LH
Acid-suppressive medication use and the risk for hospital-acquired pneumonia
JAMA
301
2009
2120
2128
19470989
19
Phillips
I
Pseudomonas aeruginosa respiratory tract infections in patients receiving mechanical
ventilation
J Hyg
65
1967
229
235
20475882
20
Estivariz
CF
Bhatti
LI
Pati
R
An outbreak of Burkholderia cepacia associated with contamination of albuterol and
nasal spray
Chest
130
2006
1346
1353
17099009
21
Zanen-Lim
OG
Zanen
HC
Postmortem bacteriology of the lung by print culture of frozen tissue. A technique
for in situ culture of microorganisms in whole frozen organs
J Clin Pathol
33
1980
474
480
6995493
22
Lien
DC
Henson
PM
Capen
RL
Neutrophil kinetics in the pulmonary microcirculation during acute inflammation
Lab Invest
65
1991
145
159
1908922
Pneumococcal pneumonia
23
Sternberg
GM
A fatal form of septicemia, produced by the injection of human saliva. An experimental
research
Bull Nat Board Health USA
2
1881
781
783
24
Pasteur
L
Sur une maladie nouvelle, provoquée par la salive d’une enfant mort de la rage
Comptes rendus de l’Academie des Sciences
92
1881
159
165
25
Kalin
M
Pneumococcal serotypes and their clinical relevance
Thorax
53
1998
159
162
9659348
26
Gould
GA
Rhind
GB
Morgan
AD
Pneumococcal serotypes in sputum isolates during acute respiratory illness in Edinburgh
Thorax
42
1987
589
592
3660311
27
Gransden
WR
Eykyn
SJ
Phillips
I
Pneumococcal bacteraemia: 325 episodes diagnosed at St Thomas's Hospital
BMJ
290
1985
505
508
3918650
28
Gupta
A
Khaw
FM
Stokle
EL
Outbreak of Streptococcus pneumoniae serotype 1 pneumonia in a United Kingdom school
BMJ
337
2008
a2964
19118084
29
de Roux
A
Cavalcanti
M
Marcos
MA
Impact of alcohol abuse in the etiology and severity of community-acquired pneumonia
Chest
129
2006
1219
1225
16685012
30
Whitney
CG
Farley
MM
Hadler
J
Decline in invasive pneumococcal disease after the introduction of protein-polysaccharide
conjugate vaccine
N Engl J Med
348
2003
1737
1746
12724479
31
Ort
S
Ryan
JL
Barden
G
Pneumococcal pneumonia in hospitalized patients. Clinical and radiological presentations
JAMA
249
1983
214
218
6848806
32
Haslett
C
Resolution of acute inflammation and the role of apoptosis in the tissue fate of granulocytes
Clin Sci
83
1992
639
648
1336433
33
Garcia-Vidal
C
Ardanuy
C
Tubau
F
Pneumococcal pneumonia presenting with septic shock: host- and pathogen-related factors
and outcomes
Thorax
65
2010
77
81
19996337
34
Warren
BL
Eid
A
Singer
P
Caring for the critically ill patient. High-dose antithrombin III in severe sepsis:
a randomized controlled trial
JAMA
286
2001
1869
1878
11597289
35
Abraham
E
Reinhart
K
Opal
S
Efficacy and safety of tifacogin (recombinant tissue factor pathway inhibitor) in
severe sepsis: a randomized controlled trial
JAMA
290
2003
238
247
12851279
36
Sawicki
GS
Lu
FL
Valim
C
Necrotising pneumonia is an increasingly detected complication of pneumonia in children
Eur Respir J
31
2008
1285
1291
18216055
Staphylococcal pneumonia
37
Naraqi
S
McDonnell
G
Hematogenous staphylococcal pneumonia secondary to soft tissue infection
Chest
79
1981
173
175
7460648
38
Vardakas
KZ
Matthaiou
DK
Falagas
ME
Incidence, characteristics and outcomes of patients with severe community acquired-MRSA
pneumonia
Eur Respir J
34
2009
1148
1158
19541719
39
Pantosti
A
Venditti
M
What is MRSA?
Eur Respir J
34
2009
1190
1196
19880619
40
Defres
S
Marwick
C
Nathwani
D
MRSA as a cause of lung infection including airway infection, community-acquired pneumonia
and hospital-acquired pneumonia
Eur Respir J
34
2009
1470
1476
19948913
41
Hayashida
A
Bartlett
AH
Foster
TJ
Staphylococcus aureus beta-toxin induces lung injury through syndecan-1
Am J Pathol
174
2009
509
518
19147831
42
Gillet
Y
Issartel
B
Vanhems
P
Association between Staphylococcus aureus strains carrying gene for Panton–Valentine
leukocidin and highly lethal necrotising pneumonia in young immunocompetent patients
Lancet
359
2002
753
759
11888586
43
Morgan
M
Staphylococcus aureus, Panton–Valentine leukocidin, and necrotising pneumonia
BMJ
331
2005
793
794
16210260
44
Micek
ST
Dunne
M
Kollef
MH
Pleuropulmonary complications of Panton–Valentine leukocidin-positive community-acquired
methicillin-resistant Staphylococcus aureus: importance of treatment with antimicrobials
inhibiting exotoxin production
Chest
128
2005
2732
2738
16236949
Streptococcal pneumonia
45
McMurray
JJ
Fraser
DM
Brogan
O
Fatal Streptococcus pyogenes pneumonia
J R Soc Med
80
1987
525
526
3309306
46
Cramer
SF
Tomkiewicz
ZM
Septic pulmonary thrombosis in streptococcal toxic shock syndrome
Hum Pathol
26
1995
1157
1160
7557952
47
Wong
CA
Donald
F
Macfarlane
JT
Streptococcus milleri pulmonary disease: a review and clinical description of 25 patients
Thorax
50
1995
1093
1096
7491559
Haemophilus pneumonia
48
Barnes
DJ
Naraqi
S
Igo
JD
Haemophilus influenzae pneumonia in Melanesian adults: report of 15 cases
Thorax
42
1987
889
891
3321545
Moraxella pneumonia
49
Diamond
LA
Lorber
B
Branhamella catarrhalis pneumonia and immunoglobulin abnormalities: A new association
Am Rev Respir Dis
129
1984
876
878
6721286
50
Verghese
A
Berk
SL
Branhamella catarrhalis. A microbiologic and clinical update
Am J Med
88
1990
S1
56
51
Murphy
TF
Branhamella catarrhalis: epidemiological and clinical aspects of a human respiratory
tract pathogen
Thorax
53
1998
124
128
9624298
52
Mannion
PT
Sputum microbiology in a district general hospital. The role of Branhamella catarrhalis
Br J Dis Chest
81
1987
391
396
3130089
53
McLeod
DT
Ahmad
F
Capewell
S
Increase in bronchopulmonary infection due to Branhamella catarrhalis
BMJ
292
1986
1103
1105
3084017
54
Black
AJ
Wilson
TS
Immunoglobulin G (IgG) serological response to Branhamella catarrhalis in patients
with acute bronchopulmonary infections
J Clin Pathol
41
1988
329
333
3129454
55
Capewell
S
McLeod
DT
Croughan
MJ
Pneumonia due to Branhamella catarrhalis
Thorax
43
1988
929
930
3146819
Legionella pneumonia
56
Winn
WC
Myerowitz
RL
The pathology of the legionella pneumonias. A review of 74 cases and the literature
Hum Pathol
12
1981
401
422
6166529
57
Roig
J
Domingo
C
Morera
J
Legionnaires’ disease
Chest
105
1994
1817
1825
8205883
58
Stout
JE
Yu
VL
Current concepts: legionellosis
N Engl J Med
337
1997
682
687
9278466
59
Fraser
DW
Tsai
TR
Orenstein
W
Legionnaires’ disease. Description of an epidemic of pneumonia
N Engl J Med
297
1977
1189
1197
335244
60
McDade
JE
Shepard
CC
Fraser
DW
Legionnaires’ disease. Isolation of a bacterium and demonstration of its role in other
respiratory disease
N Engl J Med
297
1977
1197
1203
335245
61
Weisenberger
DD
Helms
CM
Renner
ED
Sporadic legionnaires’ disease. A pathologic study of 23 fatal cases
Arch Pathol Lab Med
105
1981
130
137
6894076
62
England
AC
Fraser
DW
Plikaytis
BD
Sporadic legionellosis in the United States: the first thousand cases
Ann Intern Med
94
1981
164
170
7469207
63
Barker
J
Brown
MR
Collier
PJ
Relationship between Legionella pneumophila and Acanthamoeba polyphaga: physiological
status and susceptibility to chemical inactivation
Appl Environ Microbiol
58
1992
2420
2425
1514790
64
Roig
J
Sabria
M
Pedro-Botet
ML
Legionella spp.: community acquired and nosocomial infections
Curr Opin Infect Dis
16
2003
145
151
12734447
65
Maruta
K
Miyamoto
H
Hamada
T
Entry and intracellular growth of Legionella dumoffii in alveolar epithelial cells
Am J Respir Crit Care Med
157
1998
1967
1974
9620934
66
Skerrett
SJ
Martin
TR
Alveolar macrophage activation in experimental legionellosis
J Immunol
147
1991
337
345
1646846
67
Sabria
M
Campins
M
Legionnaires’ disease: update on epidemiology and management options
Am J Respir Med
2
2003
235
243
14720005
68
Blackmon
JA
Chandler
FW
Cherry
WB
Legionellosis
Am J Pathol
103
1981
429
465
7015873
69
Winn
WC
Glavin
FL
Perl
DP
The pathology of legionnaires’ disease. Fourteen fatal cases from the 1977 outbreak
in Vermont
Arch Pathol Lab Med
102
1978
344
350
580866
70
Blackmon
JA
Hicklin
MD
Chandler
FW
Legionnaires’ disease. Pathological and historical aspects of a ‘new’ disease
Arch Pathol Lab Med
102
1978
337
343
580865
71
Lattimer
GL
Rachman
RA
Scarlato
M
Legionnaires’ disease pneumonia: histopathologic features and comparison with microbial
and chemical pneumonias
Ann Clin Lab Sci
9
1979
353
361
533230
72
Hernandez
FJ
Kirby
BD
Stanley
TM
Legionnaires’ disease. Postmortem pathologic findings of 20 cases
Am J Clin Pathol
73
1980
488
495
7369172
73
Edwards
D
Finlayson
DM
Legionnaires’ disease causing severe lung abscesses
CMA Journal
123
1980
524
526
74
Cluroe
AD
Legionnaire's disease mimicking pulmonary miliary tuberculosis in the immunocompromised
Histopathology
22
1993
73
75
8436344
75
Theaker
JM
Tobin
OJ
Jones
SEC
Immunohistological detection of Legionella pneumophila in lung sections
J Clin Pathol
40
1987
143
146
3546392
76
Chandler
FW
Cole
RM
Hicklin
MD
Ultrastructure of the legionnaires’ disease bacterium. A study using transmission
electron microscopy
Ann Intern Med
90
1979
642
647
86315
Klebsiella pneumonia
77
Garb
JL
Brown
RB
Garb
JR
Differences in etiology of pneumonia in nursing home and community patients
JAMA
240
1978
2169
2172
359845
78
Jong
GM
Hsiue
TR
Chen
CR
Rapidly fatal outcome of bacteremic Klebsiella pneumoniae pneumonia in alcoholics
Chest
107
1995
214
217
7813281
79
Dorff
GJ
Rytel
MW
Farmer
SG
Etiologies and characteristic features of pneumonias in a municipal hospital
Am J Med Sci
266
1973
349
358
4148638
80
Schamaun
M
von Buren
U
Pirozynski
W
Ausgedehnte Lungennekrose bei Klebsiellen-Pneumonie (sogenannte massive Gangran der
Lunge)
Schweiz Med Wochenschr
110
1980
223
225
6990484
Pseudomonas pneumonia
81
Philippon
S
Streckert
HJ
Morgenroth
K
Invitro study of the bronchial mucosa during Pseudomonas aeruginosa infection
Virchows Arch A Pathol Anat Histopathol
423
1993
39
43
8212532
82
Tsang
KWT
Rutman
A
Kanthakumar
K
Interaction of Pseudomonas aeruginosa with human respiratory mucosa in vitro
Eur Respir J
7
1994
1746
1753
7828679
83
Debentzmann
S
Roger
P
Puchelle
E
Pseudomonas aeruginosa adherence to remodelling respiratory epithelium
Eur Respir J
9
1996
2145
2150
8902481
84
Kirschke
DL
Jones
TF
Craig
AS
Pseudomonas aeruginosa and Serratia marcescens contamination associated with a manufacturing
defect in bronchoscopes
N Engl J Med
348
2003
214
220
12529461
85
Srinivasan
A
Wolfenden
LL
Song
XY
An outbreak of Pseudomonas aeruginosa infections associated with flexible bronchoscopes
N Engl J Med
348
2003
221
227
12529462
86
Fetzer
AE
Werner
AS
Hagstrom
JWC
Pathologic features of pseudomonal pneumonia
Am Rev Respir Dis
96
1967
1121
1130
6057615
87
Bonifacio
SL
Kitterman
JA
Ursell
PC
Pseudomonas pneumonia in infants: An autopsy study
Hum Pathol
34
2003
929
938
14562290
88
Teplitz
C
Pathogenesis of Pseudomonas vasculitis and septic lesions
Arch Pathol
80
1965
297
307
14322952
89
Barson
AJ
Fatal Pseudomonas aeruginosa bronchopneumonia in a children's hospital
Arch Dis Child
46
1971
55
60
5555490
90
Leaver
RE
Evans
BJ
Corrin
B
Identification of Gram-negative bacteria in histological sections using Sandiford's
counterstain
J Clin Pathol
30
1977
290
291
66239
91
Tillotson
JR
Lerner
AM
Characteristics of non-bacteremic Pseudomonas pneumonia
Ann Intern Med
68
1968
295
307
4306124
Acute melioidosis
92
Currie
BJ
Melioidosis: an important cause of pneumonia in residents of and travellers returned
from endemic regions
Eur Resp J
22
2003
542
550
93
Barnes
PF
Appleman
MD
Cosgrove
MM
A case of melioidosis originating in North America
Am Rev Respir Dis
134
1986
170
171
3729152
94
Ip
M
Osterberg
LG
Chau
PY
Pulmonary melioidosis
Chest
108
1995
1420
1424
7587451
95
OCarroll
MR
Kidd
TJ
Coulter
C
Burkholderia pseudomallei: another emerging pathogen in cystic fibrosis
Thorax
58
2003
1087
1091
14645982
96
Piggott
JA
Hochholzer
L
Human melioidosis. A histopathologic study of acute and chronic melioidosis
Arch Pathol
90
1970
101
111
5433595
97
Dhiensiri
T
Puapairoj
S
Susaengrat
W
Pulmonary melioidosis: clinical-radiologic correlation in 183 cases in northeastern
Thailand
Radiology
166
1988
711
715
3340766
98
Wong
KT
Puthucheary
SD
Vadivelu
J
The histopathology of human melioidosis
Histopathology
26
1995
51
55
7713483
99
Jones
AL
Beveridge
TJ
Woods
DE
Intracellular survival of Burkholderia pseudomallei
Infect Immun
64
1996
782
790
8641782
Burkholderia cepacia pneumonia
100
Stableforth
DE
Smith
DL
Pseudomonas cepacia in cystic fibrosis
Thorax
49
1994
629
630
7520606
101
Belchis
DA
Simpson
E
Colby
T
Histopathologic features of Burkholderia cepacia pneumonia in patients without cystic
fibrosis
Modern Pathol
13
2000
369
372
Pneumonic plague
102
Florman
AL
Spencer
RR
Sheward
S
Multiple lung cavities in a 12-year-old girl with bubonic plague, sepsis, and secondary
pneumonia
Am J Med
80
1986
1191
1193
3728514
Tularaemic pneumonia
103
Tarnvik
A
Berglund
L
Tularaemia
Eur Resp J
21
2003
361
373
104
Shapiro
DS
Mark
EJ
Sabloff
B
A 60-year-old farm worker with bilateral pneumonia. Tularemic pneumonia
N Engl J Med
342
2000
1430
1438
10805829
Anthrax pneumonia (woolsorters’ disease)
105
Abramova
FA
Grinberg
LM
Yampolskaya
OV
Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979
Proc Natl Acad Sci USA
90
1993
2291
2294
8460135
106
Grinberg
LM
Abramova
FA
Yampolskaya
OV
Quantitative pathology of inhalational anthrax I: Quantitative microscopic findings
Modern Pathol
14
2001
482
495
107
Bush
LM
Abrams
BH
Beall
A
Index case of fatal inhalational anthrax due to bioterrorism in the United States
N Engl J Med
345
2001
1607
1610
11704685
108
Guarner
J
Jernigan
JA
Shieh
WJ
Pathology and pathogenesis of bioterrorism-related inhalational anthrax
Am J Pathol
163
2003
701
709
12875989
109
Hupert
N
Bearman
GM
Mushlin
AI
Accuracy of screening for inhalational anthrax after a bioterrorist attack
Ann Intern Med
139
2003
337
345
12965942
110
Ross
JM
The pathogenesis of anthrax following the administration of spores by the respiratory
route
J Path Bact
73
1957
485
494
111
Zaucha
GM
Pitt
MLM
Estep
J
The pathology of experimental anthrax in rabbits exposed by inhalation and subcutaneous
inoculation
Arch Pathol Lab Med
122
1998
982
992
9822127
112
Shafazand
S
Doyle
R
Ruoss
S
Inhalational anthrax – Epidemiology, diagnosis, and management
Chest
116
1999
1369
1376
10559102
113
Severn
M
A fatal case of pulmonary anthrax
BMJ
1
1976
748
Leptospiral pneumonia
114
Teglia
OF
Battagliotti
C
Villavicencio
RL
Leptospiral pneumonia
Chest
108
1995
874
875
7656649
115
Tattevin
P
Leveiller
G
Flicoteaux
R
Respiratory manifestations of leptospirosis: a retrospective study
Lung
183
2005
283
289
16211464
116
Zaki
SR
Shieh
WJ
Leptospirosis associated with outbreak of acute febrile illness and pulmonary haemorrhage,
Nicaragua, 1995. The Epidemic Working Group at Ministry of Health in Nicaragua [letter]
[see comments]
Lancet
347
1996
535
536
8596276
117
Silva
JJ
Dalston
MO
Carvalho
JE
Clinicopathological and immunohistochemical features of the severe pulmonary form
of leptospirosis
Rev Soc Bras Med Trop
35
2002
395
399
12170336
118
Nicodemo
AC
Duarte
MI
Alves
VA
Lung lesions in human leptospirosis: microscopic, immunohistochemical, and ultrastructural
features related to thrombocytopenia
Am J Trop Med Hyg
56
1997
181
187
9080878
119
de Brito
T
Bohm
GM
Yasuda
PH
Vascular damage in acute experimental leptospirosis of the guinea pig
J Pathol
128
1979
177
182
521862
Chlamydophila pneumonia
120
Beem
MO
Saxon
EM
Respiratory tract colonization and a distinctive pneumonia syndrome in infants infected
with Chlamydia trachomatis
N Engl J Med
296
1977
306
310
831128
121
Harrison
HR
Enlish
MG
Lee
CK
Chlamydia trachomatis infant pneumonitis. Comparison with matched controls and other
infant pneumonitis
N Engl J Med
298
1978
702
708
628397
122
Grayston
JT
Wang
SP
Kuo
CC
Current knowledge on Chlamydia pneumoniae, strain TWAR: an important cause of pneumonia
and other acute respiratory diseases
Eur J Clin Microbiol Infect Dis
8
1989
191
202
2496986
123
Grayston
IT
Campbell
LA
Kuo
C-C
A new respiratory tract pathogen: Chlamydia pneumoniae strain TWAR
J Infect Dis
161
1990
618
625
2181028
124
Marrie
TJ
Chlamydia pneumoniae
Thorax
48
1993
1
4
8434345
125
Hammerschlag
MR
Chlamydia pneumoniae and the lung
Eur Resp J
16
2000
1001
1007
126
Grist
NR
McLean
C
Infections by organisms of psittacosis/lymphogranuloma venereum group in the west
of Scotland
BMJ
2
1964
21
25
14147769
127
Andrews
BE
Major
R
Palmer
SR
Ornithosis in poultry workers
Lancet
i
1981
632
634
128
Irons
JV
Sullivan
TD
Rowan
J
Outbreak of psittacosis [ornithosis] from working with turkeys or chickens
Am J Public Health
41
1951
931
937
129
Sax
PE
TrotmanDickenson
B
Klein
RS
Pneumonia and the acute respiratory distress syndrome in a 24-year-old man – psittacosis,
causing the acute respiratory distress syndrome
N Engl J Med
338
1998
1527
1535
9599105
130
Diehl
JL
Gisselbrecht
M
Meyer
G
Bronchiolitis obliterans organizing pneumonia associated with chlamydial infection
Eur Respir J
9
1996
1320
1322
8804955
131
BenYaakov
M
Eshel
G
Zaksonski
L
Prevalence of antibodies to Chlamydia pneumoniae in an Israeli population without
clinical evidence of respiratory infection
J Clin Pathol
55
2002
355
358
11986341
132
Wu
L
Skinner
SJM
Lambie
N
Immunohistochemical staining for Chlamydia pneumoniae is increased in lung tissue
from subjects with chronic obstructive pulmonary disease
Am J Respir Crit Care Med
162
2000
1148
1151
10988144
133
Webley
WC
Tilahun
Y
Lay
K
Occurrence of Chlamydia trachomatis and Chlamydia pneumoniae in paediatric respiratory
infections
Eur Respir J
33
2009
360
367
19010996
134
Jackson
LA
Campbell
LA
Schmidt
RA
Specificity of detection of Chlamydia pneumoniae in cardiovascular atheroma: Evaluation
of the innocent bystander hypothesis
Am J Pathol
150
1997
1785
1790
9137101
135
Shor
A
Phillips
JI
Ong
G
Chlamydia pneumoniae in atheroma: consideration of criteria for causality
J Clin Pathol
51
1998
812
817
10193321
Aspiration pneumonia and lung abscess
136
Marik
PE
Primary care: Aspiration pneumonitis and aspiration pneumonia
N Engl J Med
344
2001
665
671
11228282
137
Huxley
EJ
Viroslav
J
Gray
WR
Pharyngeal aspiration in normal adults and patients with depressed consciousness
Am J Med
64
1978
564
568
645722
138
Kennedy
JH
‘Silent’ gastroeosophageal reflux: an important but little known cause of pulmonary
complications
Dis Chest
42
1962
42
45
139
Brock
RC
Hodgkiss
F
Jones
HO
Bronchial embolism and posture in relation to lung disease
Guy Hosp Rep
91
1942
131
139
140
Carlson
DH
Right middle lobe aspiration pneumonia following gasoline siphonage
Chest
80
1981
246
247
141
Crome
L
Valentine
JC
Lentil soup inhalation?
J Clin Pathol
15
1962
21
25
13882315
142
Matsuse
T
Oka
T
Kida
K
Importance of diffuse aspiration bronchiolitis caused by chronic occult aspiration
in the elderly
Chest
110
1996
1289
1293
8915236
143
Mukhopadhyay
S
Katzenstein
A-LA
Pulmonary disease due to aspiration of food and other particulate matter: a clinicopathologic
study of 59 cases diagnosed on biopsy or resection specimens
Am J Surg Pathol
31
2007
752
759
17460460
144
Bartlett
JG
Gorbach
SL
Finegold
SM
The bacteriology of aspiration pneumonia
Am J Med
56
1974
202
207
4812076
145
Penner
C
Maycher
B
Long
R
Pulmonary gangrene – a complication of bacterial pneumonia
Chest
105
1994
567
573
8306765
146
Lemierre
A
On certain septicaemias due to anaerobic organisms
Lancet
i
1936
701
703
147
Moore-Gillon
J
Lee
TH
Eykyn
SJ
Necrobacillosis: a forgotten disease
BMJ
288
1984
1526
1527
6426626
148
Dykhuizen
RS
Olson
ES
Clive
S
Necrobacillosis (Lemierre's syndrome): a rare cause of necrotizing pneumonia
Eur Respir J
7
1994
2246
2248
7713211
149
Riordan
T
Wilson
M
Lemierre's syndrome: more than a historical curiosa
Postgrad Med J
80
2004
328
334
15192164
150
Bartlett
JG
Gorbach
SL
Tally
FP
Bacteriology and treatment of primary lung abscess
Am Rev Respir Dis
109
1974
510
518
4595941
151
Neild
JE
Eykyn
SJ
Phillips
I
Lung abscess and empyema
Q J Med
57
1985
875
882
4095257
Botrymycosis
152
Multz
AS
Cohen
R
Azeuta
V
Bacterial pseudomycosis: a rare cause of haemoptysis
Eur Respir J
7
1994
1712
1713
7995403
153
Tuggey
JM
Hosker
HSR
DaCosta
P
Primary pulmonary botryomycosis: a late complication of foreign body aspiration
Thorax
55
2000
1068
1069
11083895
154
Kathir
K
Dennis
C
Primary pulmonary botryomycosis: an important differential diagnosis for lung cancer
Respirology
6
2001
347
350
11844127
155
Naidech
H
Ruttenberg
N
Axelrod
R
Pulmonary botryomycoma
Chest
70
1976
385
387
954467
156
Katznelsen
D
Vawter
GF
Foley
GE
Botryomycosis: a complication in cystic fibrosis. Report of 7 cases
J Pediatr
65
1964
525
539
14216641
157
Katapadi
K
Pujol
F
Vuletin
JC
Pulmonary botryomycosis in a patient with AIDS
Chest
109
1996
276
278
8549198
158
Shih
JY
Hsueh
PR
Chang
YL
Tracheal botryomycosis in a patient with tracheopathia osteochondroplastica
Thorax
53
1998
73
75
9577526
5.3
Chronic bacterial infections
Chapter Contents
Tuberculosis
197
Primary and postprimary types of tuberculosis 199
Primary tuberculosis 199
The immunity and hypersensitivity that result from tuberculous infection 205
Postprimary tuberculosis 207
Infection by opportunistic mycobacteria
211
Brucellosis
212
Chronic melioidosis
213
Actinomycosis
213
Nocardiosis
215
Rhodococcus pneumonia
215
Malakoplakia 216
Syphilis
216
Congenital pulmonary syphilis 217
Acquired pulmonary syphilis 217
References
217
Tuberculosis
Bacteriology
Tuberculosis is caused by certain mycobacteria. In the laboratory these microbes are
difficult to stain and in the body they are difficult to kill. Their comparative resistance
to the normal body defences is due to an ability to inhibit phagosome–lysosome fusion,
permitting them to survive within the host's phagocytes.1, 2 Their resistance to ordinary
stains is attributed to their cell walls being rich in mycolic acid waxes. This necessitates
the use of hot concentrated carbol fuchsin for their demonstration, as in the Ziehl–Neelsen
stain. Once stained in this way, they are difficult to decolorise, even with strong
acids and alcohol, hence references to the acid- and alcohol-fast bacilli. Mycobacteria
also show some resistance to formalin: of 138 tissue specimens from autopsy lungs
fixed in formalin and showing histological evidence of acid-fast bacilli, 12 grew
mycobacteria, including three Mycobacterium tuberculosis isolates.
3
The bacilli are normally scanty in tuberculous tissue and their identification with
the Ziehl–Neelsen stain may require tedious examination of many sections.
4
They are easier to identify in rhodamine-auramine-stained sections examined by fluorescence
microscopy.5, 6, 7 Tissue containing necrotising granulomas is most likely to give
positive results whereas specimens showing only non-necrotising granulomas, poorly
formed granulomas or acute inflammation are less likely to reveal acid-fast bacilli.8,
9 Culture is no more likely to identify the mycobacteria than the examination of tissue
sections.9, 10 Failure to demonstrate them does not exclude a diagnosis of tuberculosis.
The future lies in immunohistochemistry
11
or molecular techniques such as the polymerase chain reaction, which can be adapted
for application to paraffin sections.12, 13, 14, 15, 15a The detection of mycobacterial
RNA indicates that the bacilli are viable and is therefore preferable to tests for
mycobacterial DNA. Molecular techniques are also useful in identifying drug resistance,
distinguishing mycobacterial species and identifying specific strains of M. tuberculosis.16,
17, 18
The mycobacteria that cause tuberculosis in humans are sometimes listed as M. tuberculosis,
M. bovis, M. africanum and M. microti, the so-called tuberculosis complex, although
these four organisms are probably just variants of a single species. The first two
correspond to the human and bovine tubercle bacilli while M. africanum includes a
heterogeneous group of strains, with properties intermediate between the former two,
isolated from humans in equatorial Africa and from African immigrants in Europe. The
features and management of tuberculosis in humans caused by these three variants are
very similar. M. microti, the vole tubercle bacillus, is of attenuated pathogenicity
for humans and has been used as a vaccine.
M. tuberculosis is largely responsible for the disease and the infection is predominantly
pulmonary, acquired through inhalation of this organism into the lungs. Formerly,
intestinal tuberculosis, acquired by drinking milk infected with M. bovis, was much
commoner, but the eradication of mycobacteriosis from cattle and the widespread pasteurisation
of milk brought about a virtual disappearance of this form of disease in developed
countries.
In addition to the human, bovine and vole types, the term ‘tubercle bacillus’ includes
the avian and the ‘cold-blooded’ types. The avian tubercle bacillus is a distinct
species, M. avium, while the ‘cold-blooded’ group includes the fish, turtle and frog
tubercle bacilli, which are known as M. marinum, M. chelonei and M. fortuitum respectively.
All these other ‘tubercle bacilli’ can cause opportunistic infections in humans and,
together with a number of other opportunistic species, are often referred to as the
atypical, anonymous or opportunistic mycobacteria. M. intracellulare is no longer
distinguished from M. avium, and the collective M. avium-intracellulare is often used.
Similarly, reference is sometimes made to M. fortuitum-chelonei. The opportunistic
mycobacteria are dealt with separately later in this chapter (see p. 211).
Route of infection in pulmonary tuberculosis
In the past, there was much speculation about the possible routes of infection in
tuberculosis. Today, there is little doubt that when the lesions are present in the
lungs the infection has taken place as a result of inhalation of tubercle bacilli.
That the respiratory tract should be the chief portal of entry is scarcely surprising
in view of the great preponderance of the pulmonary form of chronic tuberculosis in
humans and of the enormous numbers of tubercle bacilli that are eliminated daily in
the sputum of most untreated active cases. Those in close contact with such patients
are liable to inhale the bacilli and acquire the infection in their lungs. Although
the smaller droplets of expectorated sputum, which may remain for many minutes suspended
in the air after a cough, are probably the chief vehicle for the transmission of tubercle
bacilli, it should be realised that the organisms are resistant to desiccation, and
that in consequence, dried ‘droplet nuclei’, or the dust that they ultimately contaminate,
may long remain as potential carriers of the infection. Tuberculosis transmission
can be reduced however by hospitalising patients with positive sputa in isolation
rooms equipped with ultraviolet light and exhaust ventilation.
19
Other routes of infection which may have operated in pulmonary mycobacteriosis in
the past include haematogenous dissemination from a primary focus of M. bovis infection
in the intestine, acquired by drinking infected milk, and similar spread from a primary
focus in the skin acquired by traumatic inoculation (a rare occupational hazard of
pathologists and butchers, hence the old term ‘butcher's wart’), but these have never
been as important as droplet spread.
Epidemiology
In most developed countries there has been a considerable fall in the incidence of
tuberculosis and its mortality over the last century (Fig. 5.3.1
). This is attributable to a variety of factors that began to operate among the prosperous
classes and subsequently extended to all strata of society. During almost the whole
of this period an amelioration in social conditions took place in an almost uninterrupted,
unspectacular manner and it is to these unspecific factors that for many years the
progressive fall in mortality was essentially due, although it was aided by public
health measures such as the eradication of tuberculous cattle and mass radiography
screening. After 1950, the decline in mortality from tuberculosis was hastened by
the introduction of effective antituberculosis drugs. By bringing about a great fall
in the number – often even the complete disappearance – of bacilli in the sputum in
cases of active respiratory tuberculosis, these drugs have much reduced the hazard
of infection that was formerly incurred by those who inadvertently or by obligatory
associations were brought into contact, at work or at home, with an infectious case
of the disease.
Figure 5.3.1
Deaths from tuberculosis in England and Wales in the twentieth century. The decline
in mortality, temporarily checked by two world wars, was established well before specific
chemotherapy became available, and is largely attributable to improved living standards.
The reduced incidence of the disease in developed countries led to changes in the
ages of the affected patients. Whereas it was formerly a disease of the young, tuberculosis
came to be largely limited to the elderly in these countries, the disease representing
recrudescence of quiescent infection acquired in youth. Many of these elderly patients
suffered from an insidiously progressive form of the disease and this is still the
case today (see p. 210).
The situation remained very different elsewhere. Much of the world has still not shared
the economic and health benefits enjoyed in the west and in many countries tuberculosis
remains one of the most important specific communicable diseases. Furthermore, the
considerable gains that have slowly been achieved are now in peril because of the
acquired immunodeficiency syndrome (AIDS) and other factors. There has been a resurgence
of tuberculosis recently, even in groups where AIDS has yet to make a major impact,
possibly due to new levels of urban deprivation and the influx of immigrants and refugees
from countries with a high incidence of the disease.
20
In the UK, for example, immigrants from the Indian subcontinent have rates of tuberculosis
about 25 times as high as that of the white population.
21
The decline in the incidence of tuberculosis in the UK slowed towards 1987 and has
subsequently reversed: since that date case numbers have risen, particularly in inner
London. The situation is similar in many other developed countries. Tuberculosis can
therefore be regarded once more as a worldwide problem. It is estimated that about
one-third of the world's population (approximately 2000 million people) have latent
tuberculosis while the prevalence of active disease is put at more than 20 million
worldwide. In 2006 there were 9.2 million new cases and 1.7 million deaths, which
makes tuberculosis the largest cause of death from a single pathogen in the world.
Despite the prevalence of tuberculosis, the human response to infection is good. In
the absence of immunosuppressive disorders such as human immunodeficiency virus (HIV)
infection, only about 10% of those infected develop clinically evident disease. The
basis of these patients’ susceptibility is not well understood but tobacco smoking
is a predisposing cause
22
and genetic factors appear to be involved.
23
The impact of HIV infection
Following the advent of AIDS the downward trend in tuberculosis stabilised or was
reversed.24, 25 An alarming resurgence of the disease is being witnessed, particularly
in the poorer communities where drug abuse is prevalent (Table 5.3.1
).26, 27, 28 Furthermore, multidrug-resistant strains have emerged and now represent
a global problem.29, 30, 31, 32, 33 The mortality is high with such strains, even
in patients who are not immunodeficient, but it is particularly high in AIDS.
Table 5.3.1
The effect of human immunodeficiency virus (HIV) infection on the global toll of tuberculosis27,
28
Region
People infected (millions)
New cases
Deaths
HIV-attributed
Western Pacifica
574
2 560 000
890 000
19 000
South-East Asia
426
2 480 000
940 000
66 000
Africa
171
1 400 000
660 000
194 000
Eastern Mediterranean
52
594 000
160 000
9000
The Americasb
117
560 000
220 000
20 000
The industrialized countriesc
382
410 000
40 000
6000
Total
1722
8 004 000
2 910 000
315 000
a
Excluding Japan, Australia and New Zealand.
b
Excluding USA and Canada.
c
Western Europe, USA, Canada, Japan, Australia and New Zealand.
It is estimated that worldwide more than 6 million people are dually infected with
the tubercle bacillus and HIV, the majority in 10 sub-Saharan African countries. In
2007, there were an estimated 1.37 million new cases of tuberculosis among HIV-infected
people and 456 000 deaths, one in four deaths from tuberculosis being HIV-related.
34
In sub-Saharan Africa, the AIDS epidemic is having a devastating effect on tuberculosis
control programmes, with up to 100% increases in reported tuberculosis cases. The
annual risk of active tuberculosis in those who are doubly infected is 10%, compared
with a 10% lifetime risk in those who harbour the tubercle bacillus but are HIV-negative.
35
The situation in richer countries may not be so bad because HIV-infected persons tend
to be young and those harbouring tuberculosis old, rendering recrudescence unlikely.
35
However, within HIV units, cross-infection is being reported.
31
Such nosocomial transmission has involved patients and hospital staff who are immunocompetent
as well as other HIV-positive patients.
36
The mechanism whereby HIV infection promotes tuberculosis is probably related to the
pattern of cytokines produced by T-lymphocyte subsets. T-helper-1 lymphocytes produce
interferon-γ and are central to antimycobacterial immune defence. However, when peripheral
blood lymphocytes from HIV-infected patients with tuberculosis are exposed to tubercle
bacilli in vitro they produce less interferon-γ than lymphocytes from HIV-negative
patients with tuberculosis, suggesting that a reduced T-helper-1 response contributes
to HIV-infected patients’ susceptibility to tuberculosis.
37
It is also noteworthy that there is a reciprocal relationship between tuberculosis
and HIV infection: tuberculosis appears to promote the course of HIV infection, probably
by inducing macrophages to secrete cytokines that increase HIV replication.38, 39,
40
Not surprisingly in view of the interrelationship of HIV and the tubercle bacillus,
the tuberculosis associated with HIV infection is particularly aggressive, being characterised
by widespread dissemination throughout the body and a poor host response.
41
This non-reactive form of tuberculosis is similar to the insidious disease of elderly
patients referred to above and described on page 210.
Primary and postprimary types of tuberculosis
Although the morbid anatomical changes that develop in tuberculosis assume a variety
of forms, the great majority of cases fall into one or other of two distinctive types.
The first type was formerly found mainly in children and became known as the ‘childhood
type’ of tuberculosis. Further experience has shown that it is not so much the youth
of these patients as the fact that they are infected for the first time that accounts
for the distinctive structural features of their lesions. In consequence, this form
of tuberculosis is now known as the ‘primary type’, and as the incidence of the disease
in the general population has declined and the age of first infection has correspondingly
risen, it is now met with increasing frequency in adults. The second morphological
form – previously known as the ‘adult type’ of the disease – occurs in those patients
who have been sensitised by an earlier exposure to tuberculosis: this type of disease
is now generally termed ‘postprimary tuberculosis’. Postprimary tuberculosis is due
to either fresh infection or reactivation of a dormant primary lesion (Fig. 5.3.2
). Reinfection is common in countries in which tuberculosis is prevalent but in the
developed countries reactivation of infection acquired decades earlier is commoner.
The various patterns of tuberculous infection are summarised in Box 5.3.1
.
Figure 5.3.2
Possible events following infection by tubercle bacilli.
Box 5.3.1
Summary of patterns of tuberculous infection of the lungs
Primary tuberculosisa
Ghon focus + regional lymph node = primary complex
Reparative
Quiescent
Progressive
Pleural involvement
Airway dissemination (tuberculous bronchopneumonia, laryngeal lesions)
Epituberculosis (segmental tuberculosis)
Haematogenous (miliary tuberculosis, meningitis, solitary lesions in organs with a
rich systemic blood supply and therefore a high oxygen tension, e.g. kidney. Also
the lung apices because of their high ventilation/perfusion ratio)
Postprimary tuberculosisa (reactivation or reinfection)
Fibrocaseous apical cavitation (high oxygen tension)
Reparative
Quiescent
Progressive
Local extension
Pleural involvement
Airway dissemination (tuberculous bronchopneumonia)
Haematogenous (miliary tuberculosis)
Non-reactive tuberculosis (immunocompromised or elderly)
Primary tuberculosis
The very early stages of a tuberculous lesion in the human lung have seldom been seen,
and our ideas on its pathogenesis have been derived almost wholly from study of lesions
in experimental animals.
42
Initially, the presence of tubercle bacilli in an alveolus excites little immediate
reaction, and for the first day or two the only change may be a small amount of exudate
and a few neutrophils round the organisms. Within the next few days, macrophages collect
in increasing numbers, and ingest most of the bacilli.
Gradually, the macrophages, with living bacilli in their cytoplasm, aggregate to form
microscopical nodules. The macrophages also develop an abundant eosinophilic cytoplasm
and are described as ‘epithelioid’. This represents a switch from their basic phagocytic
function to a secretory one (see sarcoidosis, p. 286), modulated by lymphokines from
T lymphocytes, notably interferon-γ.23, 43, 44 This change promotes the antibacterial
properties of the macrophage but also contributes to tissue necrosis, as outlined
below. After about 2 weeks some of the more centrally placed macrophages fuse to form
multinucleate cells of Langhans type. Small numbers of lymphocytes are mixed with
the epithelioid and giant cells and outside these, further lymphocytes form a dense
outer mantle. This localised collection of epithelioid macrophages, Langhans giant
cells and lymphocytes constitutes a tuberculous granuloma (Fig. 5.3.3
). Immunocytochemistry shows that the lymphocytes in the inner zone of the granuloma
are mainly T-helper (CD4) and memory (CD45RO) cells whereas the outer zone includes
both CD4 and CD8 (T-suppressor) lymphocytes, while immediately adjacent to the outer
zone and difficult to distinguish from it without immunocytochemistry there is a secondary
centre composed of B lymphocytes and active (Ki-67+) antigen-presenting cells (Fig.
5.3.4
).
45
Figure 5.3.3
A tuberculous granuloma consisting of a central collection of epithelioid macrophages
surrounded by lymphocytes. A Langhans giant cell is seen amongst the epithelioid cells.
Figure 5.3.4
Diagrammatic representation of a tuberculous granuloma. The central necrosis, which
harbours mycobacteria, is surrounded by an inner layer of antigen-presenting cells
and CD4+ T lymphocytes, within which CD8+ cells are scarce. The outer lymphocyte infiltrate
contains large numbers of CD8+ T cells and active (Ki-67+) centres with mycobacteria-containing
antigen-presenting cells and B cells surrounded by both CD4+ and CD8+ T cells.
(Redrawn from Ulrichs et al.
45
by permission of the Journal of Pathology.)
By the third week, the granuloma has usually grown sufficiently to be visible to the
naked eye as a small, grey nodule, or tubercle, which gives the disease its name.
As the tubercle enlarges, its centre turns yellow. Microscopical examination at this
stage shows that the granuloma has undergone necrosis (Fig. 5.3.5
). A ring of satellite tubercles then develops and as these undergo central necrosis
they fuse together (Fig. 5.3.6
). In this way the original granuloma gradually increases in size. The growth of a
tuberculous lesion by the progressive development and subsequent incorporation of
satellite tubercles is also seen in postprimary tuberculosis (see Fig. 5.3.19, p.
210).
Figure 5.3.5
A tuberculous granuloma showing central caseous necrosis.
Figure 5.3.6
Tuberculous granulomas clustered around more extensive areas of coagulative necrosis.
It is characteristic of the classic active tuberculous lesions that the tubercle bacilli
are scanty, probably reflecting a state of relatively strong immunity/hypersensitivity
(see below). Also characteristic of tuberculosis is prolonged survival of the tubercle
bacilli within the tissues, despite a vigorous host reaction. This is attributable
to the tubercle bacillus inhibiting the fusion of macrophage lysosomes and phagosomes
and so avoiding the bactericidal contents of the lysosomes.1, 2
The type of necrosis found in a classic tuberculous lesion is distinctive, being dry,
crumbling and cheesy (hence the term ‘caseous’ as a macroscopic description). It is
of the coagulative rather than liquefactive type, probably because of the relative
dearth of polymorphonuclear leukocytes. The necrosis is a hypersensitivity phenomenon;
no mycobacterial toxins have been identified. It represents apoptosis brought about
by cytotoxic T cells and macrophages activated by subsets of T-helper cells. The epithelioid
cells show strong immunoexpression of the proapoptotic proteins Bax and Fas, with
the antiapoptotic protein Bcl-2 being notably absent.46, 47
The elastic tissue of the lung persists for a long time in necrotising tuberculous
lesions. When stained appropriately, its distribution and pattern give information
about the position of blood vessels and of alveolar walls within the necrotic centre
that cannot be recognised clearly, if at all, in haematoxylin and eosin preparations.
Ultimately, however, all trace of the lung's elastin framework is lost.
In the comparatively small number of human cases in which there is an opportunity
to examine the lungs while the lesion of primary tuberculosis is still active, the
latter – often known as the ‘Ghon focus’
48
– is generally visible as a pale yellow, caseous nodule, a few millimetres to a centimetre
or two in diameter. Characteristically, it is situated in the peripheral part of the
lung underlying a localised area of chronic inflammation and thickening of the pleura.
Usually, only one such focus is present, but if the lungs are searched carefully,
preferably with the help of postmortem radiography, it will be found that there is
more than one focus in a small proportion of cases. It is a point of importance in
the distinction between primary and postprimary tuberculosis of the lungs that in
the latter the lesions are almost invariably in the apical region of an upper lobe,
whereas in the former they are found most frequently in the periphery of the lower
lobes, where airflow is greatest.
Studies on primary tuberculosis in both humans and experimental animals show that
within a few days of their deposition in subpleural alveoli some of the bacilli are
carried centripetally in the lymphatics to establish infection in hilar lymph nodes.
Thereafter, the granulomatous changes in the lung and lymph nodes, and the smaller
foci that may have formed along the course of the intrapulmonary lymphatics, all develop
at about the same rate but the caseating lesions in the lymph nodes tend to be larger
than the primary focus in the lung. This combination of a peripheral Ghon focus with
the corresponding focus of caseation in the regional lymph nodes is known as the primary
complex of Ranke (Figure 5.3.6, Figure 5.3.7
). The complex is the typical result of a primary tuberculous infection of the lungs.
Figure 5.3.7
Primary complex of tuberculosis with miliary spread. A small Ghon focus in the lower
lobe of the lung is accompanied by prominent caseating tuberculous lymphadenitis.
The infection has spread from one of the lymph nodes into a branch of a pulmonary
artery, resulting in miliary haematogenous tuberculosis of the lower lobe.
(Courtesy of the Curator of the Pathology Museum, Charing Cross and Westminster Medical
School, London, UK.)
The primary complex may undergo a series of reparative changes, or it may continue
to enlarge and in so doing implicate further structures and thus promote dissemination
of the infection. The pathological features of healing and progressive primary complexes
and the relative frequency of these processes will be considered next.
Reparative changes
The slow enlargement of the caseating primary complex is accompanied by the development
of a fibrous capsule that impedes further centrifugal dispersal of the bacilli should
any still remain alive. Later, there is often dystrophic calcification and even ossification,
within which fatty and sometimes haemopoietic marrow may form. Diffuse racemose (dendriform)
ossification (see p. 149) has also been reported in association with pulmonary tuberculosis.
49
These old foci of caseous necrosis, walled off by fibrous tissue, may contain viable
bacilli, despite an absence of inflammation. Such latent lesions, which are known
as quiescent tuberculosis, are potential sites of recrudescence. Active disease is
denoted by granulomatous inflammation.
Progressive changes
In a small proportion of cases of primary tuberculosis, the reparative changes fail
to stem the progress of the disease. As the infected tissues undergo caseation, the
bacilli tend to die in the central areas but to survive and multiply in the surviving
zone of granulation tissue that borders the lesion, leading to its peripheral extension.
As a result of this, a caseous mass, several centimetres in diameter, may form either
in the lung itself or in the now much enlarged and generally matted regional lymph
nodes. If the lesion erodes into a bronchus, loss of the necrotic material through
the airway leads to the creation of a cavity, often of a size little less than that
of the parent caseous mass, and surrounded by a ragged lining of partly necrotic tuberculous
granulation tissue. If the necrotic focus breaks through the pleura, the result is
pleural effusion, pneumothorax, tuberculous empyema (Fig. 5.3.8
) or pyopneumothorax. Sometimes this is the presenting manifestation of the disease,
and occasionally the only clinical evidence of the disease. In tuberculous empyema
the matter in the pleural sac is caseous and not purulent, despite the traditional
terminology, unless there is a secondary infection by pyogenic organisms.
Figure 5.3.8
Tuberculous empyema. The lung is compressed by a large cavity that was originally
filled by caseous material, loculated collections of which persist at the apex. The
walls of the cavity are formed by the thickened parietal and visceral layers of the
pleura.
(Courtesy of the curator of the Gordon Museum, Guy's Hospital, London, UK.)
Dissemination through the airways
Caseous material that enters the main respiratory passages is largely expectorated
but some is dispersed to other parts of the lungs by the deep inspiration that usually
accompanies coughing. Such dispersion of large numbers of organisms within the bronchial
tree may lead to widespread tuberculous bronchopneumonia (‘galloping consumption’),
an often fatal condition (Figure 5.3.9, Figure 5.3.10, Figure 5.3.11
). Smaller numbers of bacilli may infect the bronchial, tracheal or laryngeal mucosa,
or, by being swallowed, the intestine. Infection of a bronchus causes ulceration,
mucosal thickening or concentric scarring which may be complicated by collapse of
the distal lung.
Figure 5.3.9
Primary complex of tuberculosis comprising a large caseating Ghon focus and marked
enlargement of the infected mediastinal lymph nodes. A caseating lymph node to the
right of the lower end of the trachea has become adherent to the latter, and the tuberculous
process has extended through the tracheal wall to form a sinus. Aspiration of infective
material from this sinus has led to the development of the tuberculous bronchopneumonia,
represented by multiple small foci of consolidation scattered throughout the lung.
(Courtesy of the curator of the Gordon Museum, Guy's Hospital. London, UK.)
Figure 5.3.10
Dissemination of caseous material via the airways has led to widespread focal consolidation.
(Courtesy of Dr Max Millard, formerly of Florida, USA.)
Figure 5.3.11
Tuberculous bronchopneumonia. Almost the whole of the lung shows pale, confluent areas
of caseation.
(Courtesy of the curator of the Gordon Museum, Guy's Hospital. London, UK.)
Caseous hilar nodes may compress a bronchus and lead to absorption collapse (see middle-lobe
syndrome, p. 92).50, 51, 52 Partial obstruction may lead to air trapping and severe
distension of a lobe, proper ventilation of which may be obtainable only by surgical
evacuation of the caseous contents of the nodes responsible. Massive enlargement of
paratracheal nodes, particularly those of the right side, may result in compression
of the trachea, causing stridor and sometimes cyanosis.
A caseating hilar lymph node may also erupt into a bronchus. Very rarely, so much
matter escapes suddenly that the patient, usually a child, is quickly asphyxiated.
More often there is progressive change in the affected segment. This is the condition
known as epituberculosis.
Epituberculosis (segmental tuberculosis)
This condition
53
is a fairly frequent radiological finding in cases of primary pulmonary tuberculosis.
The radiographic picture is that of a segmental opacity. It is associated with little
clinical disturbance and usually resolves completely over a period of months. It was
once commonly assumed to represent absorption collapse due to compression of the segmental
bronchus by the lymph node component of the primary complex, but this explanation
is now recognised to be inadequate in many cases. The great majority of these lesions
represent inflammatory consolidation caused by the lymph node component of the complex
perforating into the segmental bronchus so that infected caseous material is disseminated
throughout the distal air passages.
The affected segment is pale grey and the lobular markings are accentuated by thickening
of the interlobular septa. There is exudation of both fluid and macrophages into the
alveoli, and lymphocytic infiltration of the alveolar walls. That the lesion is not
merely a non-specific obstructive pneumonitis is clear from the constant presence
of numerous epithelioid cell granulomas. Initially the granulomas are non-necrotising
but quite extensive caseation may develop. Tubercle bacilli are to be found in the
caseous node but are usually very sparse in the consolidated lung.
The lesion can be reproduced experimentally by introducing either killed tubercle
bacilli or the purified protein derivative of tuberculin into previously sensitised
animals. The condition is therefore considered to represent a local hypersensitivity
reaction to the aspiration of caseous material from the perforated hilar nodes. This
is supported by the acceleration of the resolution that is achieved by adding corticosteroids
to the usual specific antituberculous drugs, and by the dramatic reappearance of the
disease if the corticosteroids are withdrawn.
The natural outcome of epituberculosis is variable. There may be complete resolution
or patchy fibrosis with contracture and perhaps bronchiectasis. The perforation of
the bronchus usually heals with only minor scarring, but occasionally it causes fibrous
constriction of the bronchus similar to that caused by aerogenous spread to the bronchus
from a lesion in the lung, as described above. A rare sequel, comparable in pathogenesis
to the traction diverticula of the oesophagus, is the formation of a bronchial diverticulum.
Haematogenous dissemination
Tuberculous bacillaemia is a common early event in primary tuberculosis. Strom provided
evidence of this when he used radiolabelled tubercle bacilli to induce the disease
experimentally.54, 55 The bacilli are generally destroyed by phagocytes throughout
the body but occasional organisms may escape this fate and – after their lodgement
in a kidney, bone or joint, the central nervous system, an adrenal gland or some other
organ favourable to their growth – set up an isolated focus of tuberculosis that may
either remain latent for years or progress. The apices of the lungs are amongst the
tissues that favour the establishment of blood-borne tuberculosis. The reason for
this is described below under ‘Postprimary tuberculosis’.
When many bacilli enter the circulation simultaneously and a massive haematogenous
dissemination ensues, generalised miliary tuberculosis develops. In this condition,
as in all forms of bacteraemia, the organisms are removed from the circulating blood
by phagocytic cells lining sinusoids in the liver, spleen, bone marrow and elsewhere.
Although, to judge from experimental tuberculous bacillaemias, most of the circulating
bacilli are promptly destroyed by the phagocytes, enough survive ingestion to set
up innumerable small metastatic foci of infection.
The massive blood stream invasion by tubercle bacilli necessary to produce miliary
tuberculosis is often brought about by a caseating tuberculous focus involving the
wall of a neighbouring blood vessel. This is particularly likely to complicate the
hilar lymph node component of a primary complex, for these caseous masses are not
only larger than those in the lungs, but they develop in proximity to the large veins
in the mediastinum (see Fig. 5.3.7). The wall of the affected blood vessel becomes
replaced by tuberculous granulation tissue. In time, caseation develops, the lesion
ulcerates through the intima and tubercle bacilli escape into the blood stream. In
exceptional cases, the aorta may be eroded, with consequent rupture and rapidly fatal
bleeding. However, it is not always possible to demonstrate vascular erosion and it
seems likely that the organisms may on occasion reach the blood by way of the lymphatics.
Generalised miliary tuberculosis is usually fatal unless treated quickly and appropriately,
particularly if the infection has involved the central nervous system and given rise
to tuberculous meningitis. Necropsy in such cases shows enormous numbers of small,
grey tubercles, a millimetre or less in diameter, most notably in the liver, spleen,
bone marrow, lungs and meninges, and more sparsely in other organs (Fig. 5.3.12
). The term ‘miliary’ derives from a supposed likeness of the tubercles to millet
seeds. The preponderant distribution and typically uniform dispersal of tubercles
in the parts affected may be ascribed partly to the particularly large number of phagocytic
cells in the walls of the blood sinusoids of the tissues, and partly to the situation
of the vessel invaded: if it is a systemic vein in the mediastinum, or the main thoracic
duct, the bacilli are first carried to the lungs, where many are filtered out in the
pulmonary capillaries to give origin to a preponderance of the miliary tubercles in
the lungs; if it is a tributary of the pulmonary veins, they are carried to other
organs in the systemic arterial circulation.
Figure 5.3.12
Miliary tuberculosis. The lung is studded with numerous tubercles, each the size of
a millet seed.
(Courtesy of Dr M Kearney, Tromso, Norway.)
Histologically, miliary tubercles have a characteristic structure. A Langhans multinucleate
giant cell commonly forms the centre and is enclosed by a zone of epithelioid macrophages
and an outer shell of lymphocytes. If the patient survives for a month or more, the
tubercles will be larger and their centres show early caseation. These more advanced
lesions consist of small groups of satellite tubercles that have a general resemblance
to the original one and surround the central caseous area that has taken its place.
Today, when many of those patients who develop generalised haematogenous dissemination
of the infection are successfully treated, the progressive changes in the tubercles
in the lungs can sometimes be followed in serial radiographs and the findings compared
with those in histological preparations of the lungs of patients who died at the corresponding
stage. Gradually, during the weeks following the institution of the treatment the
finely dispersed opacities can be seen to regress until their presence is no longer
detectable radiologically. At this stage, microscopical examination of the tubercle
shows merely a minute scar composed almost wholly of hyaline collagen with no trace
of the former distinctive cellular structure. If a cure follows at a more advanced
stage of the disease, after caseation has occurred, the caseous material becomes calcified.
This results in a fine mottling of the lung fields that may be seen radiologically
for years after.
Subclinical primary tuberculosis
The true prevalence of tuberculous infection in the general population is very much
higher than overt clinical manifestations suggest. This inference is based on two
main sources of evidence: first, identification of healed tuberculous lesions in necropsy
studies on long series of consecutive cases of patients dying from all causes in large
general hospitals; and second, immunological surveys on large samples of the population
employing the tuberculin skin test as an indicator of previous infection.
The realisation that primary tuberculosis is followed by recovery in the great majority
of those infected was the most important outcome of a pioneer study by Naegeli at
the end of the nineteenth century in the postmortem room of the Zurich General Hospital.
Employing acceptable anatomical criteria for the identification of healed and active
tuberculous lesions, he reached two very significant conclusions: first, that practically
all the adults who had died in that hospital from diseases of all kinds had, at some
site in their body, recognisable tuberculous foci that, in the great majority, had
healed; and second, that in only a minority of these patients could death be attributed
to tuberculosis. Forty years later, a similar study was made at the same hospital,
and again traces of a previous tuberculous infection were detected in the bodies of
80–90% of all adult patients.
The interest and surprise aroused by Naegeli's work stimulated numerous similar studies
elsewhere: his general conclusions were fully confirmed and it was recognised that
signs of past tuberculous infection, notably calcified mediastinal and mesenteric
lymph nodes, were common in any population studied. Although in elderly people the
frequency of evidence of such healed infections changed little over the ensuing half-century,
in children and young adults it showed a decline that reflected the diminished incidence
of clinical tuberculosis in western countries. A much larger fraction of the population
than formerly became liable to reach adult life without a primary infection and, as
a corollary, also without the valuable, if partial, immunity that results from an
infection that has been overcome. Prophylactic immunisation in childhood was therefore
instituted and is now widely practised.
The tuberculin skin test
As well as first identifying the tubercle bacillus in 1882, Robert Koch went on to
develop a vaccine against the disease based upon the subcutaneous injection of a sterilised
extract of the bacteria. It was not successful therapeutically but von Pirquet used
Koch's ‘old tuberculin’ as a skin-testing agent after showing that reactivity to it
indicates that a person has been infected by the tubercle bacillus. In the original
test, a drop of old tuberculin was placed on the skin and a scratch was made through
the drop, but reagents are now administered by intradermal injection (the Mantoux
method) or by use of multiple-pronged devices (Heaf and tine tests). Old tuberculin
has given way to purified protein derivative but the principle of the test remains
unchanged and it provides a useful indication of the extent of transmission of tuberculosis
in countries where tuberculin reactivity has not been artificially induced by bacillus
Calmette–Guérin (BCG) vaccination (see below) or there is not heavy exposure to the
opportunistic environmental mycobacteria. To circumvent the problem of opportunistic
mycobacteria causing such spurious reactions, blood tests have been developed that
measure T-cell interferon release in vitro in response to antigens unique to the tubercle
bacillus.
56
The tuberculin skin test becomes positive within a few weeks of tuberculous infection
being acquired and remains so in the great majority for many years. Confidence in
the reliability and specificity of the test is based mainly upon evidence from two
sources. The first comes from surveys made on cattle just before slaughter: the result
of the test correlated very closely with the presence or absence of tuberculous lesions
in the carcass. The second is derived from tests on clinically tuberculous and clinically
non-tuberculous children under 5 years of age: 94% of the former, and only 12% of
the latter, were positive.
Tuberculin surveys have given incontestable support to the general conclusion drawn
from necropsy studies that tuberculosis has been widespread in urban populations.
In a tuberculin survey in London between the two world wars the percentage of positive
reactors was found to rise progressively from well below 10 in children under 2 years
to 90 in adults. Yet despite the great frequency of infection and the large number
of deaths from the disease, the case fatality rate – the only numerical indicator
of the probable outcome of an infection – is comparatively low. This is exemplified
by the figures set out in Table 5.3.2
, which shows that even in 1931 only one out of several thousand children who became
infected actually died from the disease: a fatal outcome is even less frequent today.
Table 5.3.2
Comparison by age of positive tuberculin reactors in a sample London population with
deaths from tuberculosis for England and Wales in 1931
Age group (years)
Positive reactors (%)
Deaths from tuberculosis (%)
0–5
12
0.076
6–10
30
0.026
11–20
61
0.060
The immunity and hypersensitivity that result from tuberculous infection
The frequency with which a primary tuberculous infection is overcome, usually without
the patient being aware of its presence, roused interest in the possibility that in
tuberculosis, as in many other infectious diseases, recovery from an attack might
leave a heightened resistance to infection in the event of subsequent exposure to
the same organism. Further, as some degree of immunity generally results from a natural
infection, the question was raised whether similar protection could be conferred by
some controllable prophylactic procedure. An affirmative answer has been given to
both these questions.
The first study that disclosed convincingly that a primary infection conferred some
protection was made by Heimbeck in Oslo. His conclusions were based on studying follow-up
records of positive and negative tuberculin reactors among probationer nurses entering
the municipal hospital in that city. Through a comparative study of the findings on
enrolment and the subsequent medical history while nursing, it became apparent that,
although all were equally exposed to the same general hospital environment and its
hazards, the incidence of overt tuberculosis was significantly less in those girls
who were positive reactors at the time of their entry.
Heimbeck's conclusions have since been scrutinised and confirmed in many studies elsewhere.
The most extensive of these – the Prophit Fund Tuberculosis Survey – was carried out
on nearly 10 000 young people, mainly nurses and medical students, in London over
the period from 1934 to 1944.
57
The results of this investigation are summarised in Table 5.3.3
, which shows that there was about three times as high an incidence of clinical tuberculosis
among young adults who were negative reactors at the start of the study as among similarly
exposed positive reactors in London. This is almost the same as the average ratio
derived from nearly 30 comparable surveys elsewhere in Europe and in America. It establishes
the conclusion that, although a primary infection does not confer absolute immunity,
it does give a valuable degree of protection against developing the disease in a clinical
form after subsequent exposure to the same organism.
Table 5.3.3
Incidence of clinical tuberculosis among positive and negative reactors to tuberculin
in London, 1934–44
57
Tuberculin reaction at outset
Number of people examined
Cases of tuberculosis recorded
Incidence (%)
Positive
7130
95
1.33
Negative
1745
69
3.95
Specific prophylactic immunisation
Numerous efforts have been made to confer immunity to tuberculosis through prophylactic
inoculation, many by veterinary surgeons who hoped to free cattle from the disease.
The most significant conclusion from their work was that, unlike what had been found
for many other infectious diseases, killed organisms were relatively impotent as immunising
agents. Protection could be conferred only through an infection that had been overcome.
In consequence of this, the search for an effective prophylactic agent became one
for strains of the bacillus that were of such low natural virulence, or that had been
so attenuated by appropriate methods of culture, that they could be inoculated safely
while still alive. Such strains, it was hoped, would produce only a self-limiting
infection. Of those that have been found, the organism now widely known, after those
who developed it, as bacillus Calmette–Guérin or BCG has established itself as the
agent of choice, and is now widely employed in antituberculosis schemes in many parts
of the world. Yet, although the effectiveness of BCG has been demonstrated on many
occasions (Table 5.3.4
), in other studies it appears to have conferred no protection whatsoever.
58
The reason for these marked differences is poorly understood but may be connected
with the fact that, since its introduction, numerous daughter strains of varying antigenicity
have developed, which is not surprising as being a live bacterium it has had to be
passaged in vitro over 1000 times.
59
Another possible reason is the variable prevalence of other mycobacteria in the environment
as these confer some protection against tuberculosis but also reduce the effectiveness
of BCG.
59a
Table 5.3.4 shows that BCG is most effective when administered soon after birth, i.e.
to the immunologically naïve.
Table 5.3.4
The protective effect of bacillus Calmette–Guérin (BCG) found in nine major studies
58
Group studied
Date of commencement
Duration (years)
Age range
Protection (%)
Native North American
1935–38
9–11
0–20 years
80
Chicago, USA
1937–48
12–23
3 months
75
Georgia, USA
1947
20
6–17 years
0
Illinois, USA
1947–48
19–20
Young adults
0
Puerto Rico
1949–51
5–7.5
1–18 years
31
Georgia/Alabama, USA
1950
14
Over 5 years
14
Great Britain
1950–52
15
14–15 years
78
South India (Bangalore)
1950–55
9–14
All ages
30
South India (Madras)
1969–71
7.5a
All ages
0
a
15-year follow-up has revealed some protection amongst those administered BCG as neonates.
In developing countries, where the prevalence of tuberculosis is high, BCG immunisation
of the newborn is recommended to prevent the dangerous forms of childhood tuberculosis,
but elsewhere it is only recommended for the Mantoux-negative members of certain high-risk
groups – health workers, including mortuary and laboratory staff, veterinarians, case
contacts, immigrants from countries with a high prevalence of tuberculosis together
with their children and infants wherever born, and those intending to stay in Asia,
Africa or Central or South America for longer than a month.
Although BCG inoculation is generally harmless, disastrous dissemination of the infection
has been known to occur.
60
Impaired host immunity may be presumed to account for these rare instances as the
dose and batch of the vaccine used in these exceptional cases have not differed from
those used successfully in other children. Cases have been reported in the context
of AIDS and inherited immunodeficiency states such as severe combined immunodeficiency
and chronic granulomatous disease. However, in half the cases reported no well-defined
inherited immunodeficiency state has been recognised. Some of these patients have
been able to mount a good granulomatous response against the infection but others
have developed disease similar to lepromatous leprosy, characterised by florid proliferation
of the bacilli and an apparently ineffective non-granulomatous macrophage response.
61
It follows that any form of immunosuppression is a contraindication to BCG immunisation:
this includes corticosteroid treatment and HIV infection.
BCG immunisation confers advantages other than protection against tuberculosis as
it has heterologous effects on the immune response to many organisms and thereby exerts
a beneficial influence on several human infections.
61a
It has also been suggested that children so immunised suffer less leukaemia and other
malignancies but such claims are somewhat tenuous.
62
However, BCG has been injected into the pleural cavity or the bladder of patients
with inoperable cancer of these regions in the hope that it would have a non-specific
adjuvant effect on the immune reaction to the cancer and, as with its use in preventing
tuberculosis, there are rare instances of the bacillus being disseminated widely throughout
the body.63, 64
The relationship of immunity to hypersensitivity in tuberculosis
The rapid translocation of tubercle bacilli to the regional lymph nodes, and perhaps
beyond, on first infection, is less likely in postprimary tuberculosis, indicating
some degree of acquired immunity, while the development of caseation at a time when
cellular immune mechanisms may be expected to take effect suggests that hypersensitivity
accompanies the immunity. Long ago, Rich showed that guinea pigs made allergic by
the injection of non-virulent tubercle bacilli still retained resistance after gradual
desensitisation with tuberculin, suggesting that hypersensitivity and immunity were
distinct,
65
a proposition for which there is now considerable support.66, 67 Hypersensitivity
and specific acquired immunity are both cell-mediated, but T-cell characterisation
indicates that different T-cell subsets are involved.
Antigens are processed by specific cells, such as dendritic cells, and are presented
in association with products of the major histocompatibility complex genes to T lymphocytes.
Cytotoxic (CD8-positive) T cells are activated by products of the class I major histocompatibility
genes (HLA-A and -B), which are expressed on the surface of antigen-presenting cells
if microbial proliferation proceeds unchecked within phagocytes, the bacteria-containing
phagocytes then being eliminated by the T cells. On the other hand, effective processing
of the bacteria results in the antigen-presenting cells expressing class II major
histocompatibility genes (HLA-D), the products of which activate (CD4-positive) T-helper
cells, so enhancing bacterial elimination.
68
Two types of T-helper cells are recognised, one concerned mainly in immunity and the
other with hypersensitivity. Type 1 T-helper lymphocytes (Th1) secrete interleukin-2
and the macrophage-activating cytokine interferon-γ, resulting in enhanced bacterial
elimination; however, it also results in the secretion of tumour necrosis factor by
the macrophage, which contributes to the hypersensitivity that derives from the activation
of type 2 helper T cells (Th2).
69
Th2 cells secrete interleukins-4, -5, -6 and -10, which prime tissue cells to the
necrotising action of tumour necrosis factor secreted by macrophages activated by
Th1 cells. Thus, type 1 reactions are essentially protective but also contribute to
the type 2 cell-mediated hypersensitivity (Fig. 5.3.13
).43, 44, 68, 70 Many chronic infections are first characterised by a Th1 response
which then shifts to a Th2 response, with detriment to the host. Animal models suggest
that necrosis occurs in T-cell-dependent granulomas when Th2 involvement is superimposed
on a Th1 reaction.
71
Figure 5.3.13
Types of T-helper cell (Th-) reactions. IFN, interferon-γ; IL, interleukin; TNF-α,
tumour necrosis factor-α.
(Redrawn after Grange.
68
)
Postprimary tuberculosis
In contrast to primary tuberculosis of the lungs, where the Ghon focus may develop
in any lobe, the early lesions in the postprimary disease are almost invariably found
near the apex of one of the upper lobes. Postprimary pulmonary tuberculosis obviously
involves considerable spread of the infection. The dissemination is believed to be
blood-borne. Using radiolabelled bacilli, Strom provided experimental evidence that
tuberculous bacillaemia is a common and early event in primary tuberculosis.54, 55
In the great majority of people, both the primary complex and its haematogenous dissemination
are quickly overcome, but in some the distant foci progress or remain latent. If tributaries
of the pulmonary veins are involved in the spread of the infection, the bacilli pass
out of the thorax, but if the blood stream is colonised via the lymphatics, the pulmonary
capillaries are the first to be reached, and so the infection returns to the lungs.
Oxygen tension governs the predilection for blood-borne tuberculosis to favour the
apical regions of the lungs and also sites such as the kidneys, meninges and metaphyses.
These extrapulmonary sites are well vascularised and therefore have a relatively high
oxygen tension. The tubercle bacillus is a strict aerobe and thrives in such organs.
In the lung, more complex factors govern oxygen tension. The apices of the lungs are
poorly perfused, but the pulmonary arteries bring deoxygenated blood. Ventilation
on the other hand promotes oxygen tension, but the apices are also the most poorly
ventilated parts of the lungs. The oxygen tension in the lungs is in fact dependent
upon the ventilation/perfusion ratio. In the upright position, this declines from
the apices to the bases of the lungs (Fig. 5.3.14
),72, 73, 74, 75 and the oxygen tension is therefore highest at the top of the lungs,
thus favouring the development of postprimary tuberculosis at the apices.
Figure 5.3.14
Regional differences in pulmonary blood flow, ventilation and ventilation/perfusion
ratios (VA/Q), consequent upon gravitational forces. These result in a higher oxygen
tension and poorer lymphatic drainage at the apices, thereby promoting the development
of tuberculosis at this site.
(Redrawn after West.
74
)
If the disease progresses, radiological opacities appear in the apex of one or both
of the upper lobes. They may resolve or progressively enlarge and ultimately cavitate.
Necropsy studies indicate that such lesions represent areas of caseating granulomatous
inflammation that ultimately develop large central areas of necrosis. It is through
the expulsion of this dead tissue through the regional bronchi that the cavities so
typical of the advanced lesions originate.
If the liquefying contents of a cavity escape into the bronchial tree, the bacilli
become widely dispersed to other parts of both lungs, as in progressive primary tuberculosis.
This diffuse bronchogenic infection gives rise to innumerable small areas of caseous
pneumonia, mostly in the lower lobes, and occasionally, a rapidly developing confluent
tuberculous bronchopneumonia involves almost the whole lower lobe. Microscopical examination
may show tubercle bacilli and macrophages in very large numbers in the consolidated
areas. Occasionally, such regions undergo caseation. They may become so confluent
as to involve a whole lobe.
At necropsy, the lungs of a patient with long-standing, progressive, postprimary tuberculosis
have a characteristic appearance. Large cavities may replace much of an upper lobe
and one or more smaller, but otherwise similar, cavities may be present in the apical
part of the lower lobe. The cavities may be filled with caseous material (Fig. 5.3.15
) or the contents may have been evacuated through communicating bronchi (Figure 5.3.16,
Figure 5.3.17, Figure 5.3.18
). The cavities may be several centimetres in diameter, with walls formed by tuberculous
granulation tissue in which the fibrotic remains of the larger bronchi and of branches
of the pulmonary arteries form coarse, irregular bands. Usually the disease is bilateral,
with similar, but often less advanced, changes in the opposite lung. As in progressive
primary tuberculosis, satellite nodules are evident at the advancing edge (Fig. 5.3.19
).
Figure 5.3.15
Postprimary tuberculosis. The upper lobe is consolidated and several large foci of
caseous necrosis are evident. Smaller foci are also seen in the lower lobe.
(Courtesy of the Curator of the Gordon Museum, Guy's Hospital, London, UK.)
Figure 5.3.16
Postprimary tuberculosis. The caseous contents of this cavitating upper-lobe lesion
have been partially evacuated through communicating airways.
(Courtesy of Dr M Kearney, Tromso, Norway.)
Figure 5.3.17
Postprimary tuberculosis. The upper lobe is replaced by a large air-filled cavity,
its caseous contents having emptied into the lobar bronchus with which the cavity
communicates.
Figure 5.3.18
Postprimary tuberculosis. Tuberculous bronchopneumonia is seen throughout the lower
lobe, the result of aerogenous dissemination of infection from the cavitating focus
at the apex of this lobe. A further focus of cavitating tuberculosis is seen in the
midzone of the upper lobe.
Figure 5.3.19
Postprimary pulmonary tuberculosis progressing by the incorporation of satellite tubercles.
Satellite tubercles are evident at the advancing edge of a chronic caseating focus
of infection.
The hilar lymph nodes are less obviously involved in the postprimary form of tuberculosis
than in the primary form of the disease but, on histological examination, tuberculous
foci, often with small areas of caseation, can generally be seen in them.
Histological examination of the wall of a cavity usually discloses several zones,
each grading into the next. The yellowish-grey lining is formed largely of granulation
tissue that has undergone caseation but not yet liquefied. Acid-fast bacilli can generally
be seen in this zone: their multiplication there and subsequent escape into the cavity
largely account for the high infectivity of the sputum expectorated by patients with
advanced pulmonary tuberculosis. Just deep to this is a zone of granulation tissue
containing a profusion of macrophages and lymphocytes and occasional multinucleate
giant cells. If the cavity has been infected secondarily by other organisms, as often
happens, this zone may also contain many neutrophils. Outside this zone there is generally
a mantle of satellite tubercles. Still deeper in the wall are traces of residual parenchyma,
often with alveoli obliterated by compression and fibrosis. The cavities enlarge by
incorporation of the satellite tubercles, more of which are constantly forming more
peripherally (see Fig. 5.3.19). In this way tuberculous granulation tissue extends
into the surrounding lung substance as its lining progressively caseates, liquefies
and is expectorated. Eventually the process of cavitation may reach the pleura, but
perforation into the sac hardly ever takes place, for the chronic pleurisy that accompanies
the changes within the lungs results in the formation of firm adhesions between the
visceral and parietal layers, with obliteration of the pleural sac.
Although the formation of a cavity is a serious development in the progress of a postprimary
tuberculous infection of the lung, it does not represent an irreversible stage in
the course of the disease. As long as it is small, a cavity may heal by scarring.
Ultimately, such a lesion may only be recognisable as an area of fibrosis that stands
out from the surrounding parenchyma because of its black pigmentation and the radiating
pale strands of fibrous tissue that pucker the neighbouring lung substance. Alternatively,
a balance may be achieved whereby the tubercle bacilli are not destroyed but their
spread is halted and the process is held in check, typically by a fibrous capsule
forming. Such an encapsulated mass of caseous material is sometimes termed a tuberculoma
(Fig. 5.3.20
). In such quiescent tuberculosis there is no inflammation but viable bacilli may
survive in the central caseation, ready to reactivate the disease should host defence
weaken. Any granulomatous inflammation in the vicinity of such a lesion indicates
active tuberculosis.
Figure 5.3.20
Quiescent tuberculosis forming a ‘tuberculoma’. Growth of this apical focus of tuberculosis
has been halted and its caseous contents walled off by a fibrous capsule. However,
the infection has not necessarily been overcome as viable bacilli may persist in the
caseous material and reactivate the disease if immunity wanes.
Local complications of postprimary pulmonary tuberculosis
Pulmonary tuberculosis is often attended by minor episodes of haemoptysis. That the
involvement of blood vessels is not more frequently accompanied by haemoptysis is
accounted for by the fact that the destructive process usually advances slowly, so
that obliterative endarteritis leads to the closure of the lumen of the pulmonary
and bronchial arteries before their walls have been penetrated. However, caseation
sometimes advances too quickly for the artery to become completely blocked, and an
aneurysm may form where the muscular and elastic coats are destroyed on the side nearer
the cavity. It is through the rupture of such aneurysms (Rasmussen's aneurysms) that
sudden and sometimes fatal haemorrhages occur.
Large tuberculous cavities may persist indefinitely once the tuberculous infection
has been overcome. If the cavity is not able to drain freely into the bronchial tree,
secretion may accumulate in it and predispose to secondary bacterial infection, sometimes
with the formation of a lung abscess. Fungal colonisation may also take place, leading
to the formation of an aspergilloma or other variety of intracavitary ball colony
76
(see p. 231).
In some cases the cavity acquires an epithelial lining: the epithelial lining may
be of modified respiratory type or squamous. A squamous lining may be simple or stratified;
sometimes keratinisation develops, and the lumen of the cavity may become filled by
compressed desquamated cells, the appearances then being reminiscent of an epidermoid
cyst. Squamous carcinoma occasionally arises from such areas of metaplasia.
Chronic tuberculosis of the lungs is usually accompanied by pleurisy. Although this
begins in the neighbourhood of the most active lesions, in time it may extend to involve
the whole surface of the lung. The condition advances slowly, generally without the
formation of much exudate; by the time of necropsy the pleural lesions have usually
undergone fibrosis. The damaged lung becomes firmly attached to the chest wall – indeed,
the fibrosis may be so firm and extensive that the lung can be removed from the body
only by dissection outside the parietal pleura. Occasionally, the entire lung may
be enclosed by a dense white layer of hyaline connective tissue, several millimetres
thick.
Extrapulmonary complications of postprimary respiratory tuberculosis
The proliferation of tubercle bacilli that takes place in the caseating lining of
cavities in the lungs is often so great that it leads to heavy infection of the exudate
and secretions, most of which are expelled by coughing, sometimes aided by the adoption
of a posture that promotes gravitational drainage. These organisms form a potent reservoir
for infection of the upper respiratory tract and of the alimentary canal.
In advanced cases of chronic respiratory tuberculosis small ulcers, each a few millimetres
in diameter, often develop in the tracheobronchial mucosa,
77
as described above under the dissemination of primary pulmonary tuberculosis via the
airways. Occasionally it may mimic a neoplasm but generally there is just slight destruction
of tissue and the ulceration amounts to little more than loss of epithelium; occasionally,
it may extend more deeply and expose one or more rings of tracheal cartilage. Such
tracheobronchial disease was identified in 42% of cases in the preantibiotic era.
77
Subsequently, it was rarely encountered, until AIDS appeared, since when there have
been several reports of endobronchial tuberculosis.78, 79, 80, 81 Similar infection
may involve the larynx, particularly the glottis and the aryepiglottic folds; the
subsequent injury to the vocal cords leads both to hoarseness and to frequent stimulation
of the cough reflex.
The passage through the mouth of sputum teeming with tubercle bacilli may also lead
to infection of the oral mucous membrane. Most commonly, the lesions appear as ulcers
on the margin of the tongue: these are probably initiated by some minor damage to
the mucosa such as results from abrasion by a nearby carious tooth, the resulting
breach in the epithelial surface giving access to the organisms. Once these ulcers
form, they may penetrate deeply into the muscle. Sometimes, the organisms gain entry
to the tonsils and there produce typical changes.
Unless trained not to do so, many patients with respiratory tuberculosis swallow much
of their sputum and thus maintain a constant infection of the alimentary canal. Since
tubercle bacilli are relatively resistant to acid in the concentrations found in gastric
juice, they escape destruction in the stomach and enter the small intestine. The most
typical lesions occur in the lowest 2 m of the ileum; these are chronic, circumferentially
oriented ulcers that begin in, and finally destroy, Peyer's patches, and then extend
towards the mesentery along the mucosal lymphatics.
Amyloidosis is prone to develop in many cases of slowly progressive pulmonary tuberculosis.
Although many organs become infiltrated with the amyloid material, renal involvement
is the commonest serious manifestation and the lungs are seldom involved. As in other
forms of secondary amyloidosis, the amyloid is a polymer of the hepatic acute-phase
protein A.
Tuberculosis in the elderly and immunodeficient: non-reactive tuberculosis
In developed countries, miliary tuberculosis is now a commoner cause of death in the
elderly than the young.
82
It is thought to result from activation of old tuberculous foci, primary or postprimary,
as a consequence of waning of the immunological defences. In many cases the disease
takes a ‘cryptic’ form,82, 83, 84 characterised by insidious onset and progression,
and often lacking any evidence of miliary mottling in the chest radiograph. The diagnosis
is usually not made until necropsy. Both cryptic and overt miliary tuberculosis in
the elderly may be accompanied by changes in the blood, including pancytopenia and
leukaemoid reactions: these may be the first manifestation of the illness, and their
significance in such cases is sometimes overlooked. In the elderly, and especially
in the immunodeficient, the disease may be non-reactive. Non-reactive tuberculosis
differs from ordinary tuberculosis in lacking the usual giant cell granuloma formation.
At necropsy, disseminated miliary tuberculous lesions are found to be widespread.
Microscopy shows that the lesions comprise foci of virtually structureless necrotic
matter, sharply defined from the surrounding tissue, which shows little or no abnormality
(Fig. 5.3.21
). There is little or no granulomatous response. Appropriate staining shows that they
teem with tubercle bacilli, and, unlike the caseation of classic tuberculosis, the
necrotic material may contain much nuclear debris.41, 85, 86 Neutrophil polymorphonuclear
leukocytes are commonly seen.
Figure 5.3.21
Non-reactive tuberculosis in acquired immunodeficiency syndrome (AIDS). There is extensive
necrosis but no granulomatous reaction. Such lesions teem with tubercle bacilli.
Other forms of non-reactive tuberculosis include diffuse alveolar damage and vasculitis.
In the former tubercle bacilli are generally demonstrable in the hyaline membranes
86
while in the latter they teem within the vessel walls.
Non-reactive tuberculosis is the result of a deficiency in the body's cellular defences.
In some cases it develops as a complication of lymphoid neoplasia, particularly Hodgkin's
disease and leukaemia. In other cases it has followed treatment with immunosuppressant
drugs. More recently it has been seen in patients suffering from AIDS.41, 87 Often,
however, no predisposing cause is found; such patients are generally elderly.
If the diagnosis of non-reactive tuberculosis is suspected during life, tubercle bacilli
should be looked for in films of bone marrow. Biopsy may be helpful; any suggestion
of a tuberculous reaction is potentially an important diagnostic guide. When any biopsy
section includes unexplained areas of necrosis, particularly when there is little
in the way of a related cellular reaction, it is imperative to look for tubercle bacilli.
It is to be remembered that the tissues in this form of tuberculosis are highly infective.
Several cases of tuberculous infection in laboratory staff, including those working
in mortuaries, have been traced to this source.
Postmortem recognition of pulmonary tuberculosis
It is estimated that many cases of active tuberculosis of the lungs go unrecognised
until necropsy. This is particularly true of the elderly, whose resistance to the
infection is lowered as an accompaniment of ageing: dormant lesions become active,
and spread of the disease follows, often with little in the way of clinical manifestations
to indicate the seriousness of the danger. Similarly, at any age, patients, whose
resistance is lowered by conditions such as lymphoma and poorly controlled diabetes
mellitus, are prone to reactivation of dormant tuberculosis and vulnerable to exogenous
reinfection: often the presence of the infection is overlooked, even when it is the
immediate cause of death, until disclosed in the postmortem room. Now that the necropsy
rate is falling markedly in so many countries, many cases of active tuberculosis must
go unrecognised. The danger that persists after the patient's death is that the infection
may have been passed to relatives or associates without awareness of the need for
treatment.
Treatment of tuberculosis
The treatment of tuberculosis is based on a combination of drugs (classically triple
therapy) but is bedevilled by the emergence of drug-resistant strains, an inability
of many countries to provide the drugs and poor compliance on the part of the patient.88,
89, 90, 91
Infection by opportunistic mycobacteria
Bacteriology
The organisms responsible for tuberculosis and leprosy are only two of about 40 species
of mycobacteria, most of which live freely in the environment, particularly where
water abounds, and seldom infect humans. Occasionally, however, especially when resistance
is low, several of these environmental mycobacteria cause serious disease.92, 93 Their
distinction from M. tuberculosis is important because they require special drug regimens;
they do not respond to antituberculosis treatment. Formerly dismissed as ‘atypical’
or ‘anonymous’, these species are better described as the opportunistic mycobacteria.
They include M. marinum and M. ulcerans, the causes of swimming-pool granuloma and
Buruli ulcer respectively, and a group that causes disease that is very like tuberculosis.
In infection by members of the latter group, as in tuberculosis itself, the lungs
are the organs most often involved and there may be spread to lymph nodes, bone, meninges,
kidneys and elsewhere, or massive dissemination throughout the body akin to miliary
tuberculosis. The similarity to tuberculosis is also seen in that the gastrointestinal
tract is another important portal of entry.
94
The commonest opportunistic mycobacteria infecting the lungs are M. avium-intracellulare,
M. kansasii and M. xenopi. Less frequent causes of tuberculosis-like disease are M.
scrofulaceum, M. malmoense, M. szulgai, M. simiae, M. chelonei, M. fortuitum and M.
gordonae. M. avium-intracellulare and M. scrofulaceum are often said to comprise the
MAIS complex. They are all acid-fast but, unlike M. tuberculosis, many of them can
also be demonstrated with periodic acid–Schiff and Grocott's stains. M. kansasii has
a distinctive shape, being long, broad, beaded and bent.
95
Species-specific probes are available.
96, 97
Infection with these organisms comes from the environment, in contrast to tuberculosis,
which is always transmitted from an infected individual. The infection rate of tuberculosis
in the community bears a direct relation to the number of infectious cases but this
is not the case with the opportunistic mycobacteria. The prevalence of opportunistic
mycobacterial infection in a community is independent of that of tuberculosis and
is not controlled by public health measures aimed at reducing the spread of tuberculosis.
Interpretation of cultured isolates
The interpretation of cultured isolates must always take account of the possibility
that specimens may be contaminated with opportunistic mycobacteria from the environment.
Whereas M. tuberculosis is an obligate parasite and its isolation indicates tuberculosis,
the culture of opportunist mycobacteria does not necessarily indicate that they are
the cause of the disease being investigated. Their isolation from granulomatous tissue
strongly suggests that they have played a causative role, but sputum isolates need
to be obtained consistently over a period of weeks, and other causes of granulomatous
disease, especially tuberculosis, thoroughly excluded before a clinical diagnosis
of opportunistic mycobacterial infection can be advanced with confidence.
Predisposing causes
Factors predisposing to opportunistic mycobacterial infection may be general or local.
98
General factors include any congenital or acquired immunodeficiency, but especially
AIDS,94, 99, 100 therapeutic immunosuppression and autoimmune disease. Local factors
include pneumoconiosis, chronic bronchitis, cystic fibrosis, bronchiectasis and old
tuberculosis. The virulence of mycobacteria is enhanced by lipid
101
and the growth of opportunistic mycobacteria, especially M. fortuitum-chelonei, appears
to be promoted by lipid pneumonia.102, 103, 104 The aspiration of milk may explain
an observed association between achalasia and M. fortuitum-chelonei infection.105,
106
Only rarely is no predisposing cause recognised.107, 108 Although some impairment
of host defence is generally necessary for these bacteria to establish themselves
in humans, heavy exposure may result in healthy individuals being infected. An example
of this is the increasingly frequent presentation in affluent, non-immunocompromised
individuals of diffuse lung disease due to the inhalation of aerosols from hot tubs
and showers heavily infected by these bacteria. However, there are suggestions that
this may represent extrinsic allergic alveolitis rather than infection.96, 109, 110,
111, 112, 113, 114
Despite the above, there appears to be an increasing incidence of infection by opportunistic
mycobacteria in persons who are not obviously immunodeficient or heavily exposed.
These individuals are often women and it has been suggested that their infection may
be due to them suppressing their cough reflex for reasons of societal etiquette, an
unlikely scenario but one that has nevertheless entered the medical argot as the Lady
Windermere syndrome, a term taken from the fastidious character of the same name in
Oscar Wilde's play Lady Windermere's Fan.
115
A survey of such patients found that they were taller and leaner than controls, had
high rates of scoliosis, pectus excavatum, mitral valve prolapse and mutation of the
cystic fibrosis transmembrane conductance regulator gene. This categorised the condition
as one of women with a complex pre-existing morphotype, suggesting that there was
an underlying genetic defect.
116
Pathological changes
The pathological changes produced by opportunistic mycobacteria are generally very
similar, if not identical, to those of tuberculosis (Fig. 5.3.22
), but there is more airway involvement leading to bronchiectasis117, 118, 119 and
a higher proportion of cases that lack the classic granulomatous response.
120
In one study, four histological features were identified that favoured non-tuberculous
mycobacterial infection: the presence of microabscesses, the granulomas being ill
defined, an absence of necrosis and a comparatively small number of giant cells,
121
but these are not absolute points of distinction.
Figure 5.3.22
Mycobacterium avium-intracellulare infection. There is necrotising granulomatous inflammation
similar to that seen in tuberculosis.
Granulomatous disease indicates a strong immune response and the mycobacteria are
then scanty, as in classic tuberculosis. However, in very severe immunodeficiency,
as for example AIDS, the lesions may consist of numerous swollen macrophages, all
of which contain large numbers of acid-fast bacilli (Fig. 5.3.23
). Necrosis is not seen and granulomas are poorly formed or absent. The changes then
resemble those of lepromatous leprosy
94
or, if the macrophages are spindle-shaped, inflammatory myofibroblastic tumour (see
p. 620).122, 123, 124, 125 A leproma-like pattern has also been described in disseminated
BCG infection but is unusual in non-reactive tuberculosis
126
which is characterised by sheets of necrosis unattended by the usual granulomas, the
tubercle bacillus being more toxic to the macrophage than the opportunistic mycobacteria.
127
Figure 5.3.23
Mycobacterium avium-intracellulare/M. scrofulaceum (MAIS complex) infection in a patient
with acquired immunodeficiency syndrome (AIDS). Whereas the tissue reaction to opportunistic
mycobacteria is usually identical to that seen in tuberculosis, in the immunodeficient
it resembles the lepromatous form of leprosy, consisting of numerous macrophages with
abundant pale cytoplasm (A); Ziehl–Neelsen staining demonstrates that this contains
innumerable acid-fast bacilli (B). (C) Alternatively, the macrophages may be spindle-shaped
and the cytoplasm eosinophilic, resulting in an appearance simulating inflammatory
myofibroblastic tumour.
Treatment
The treatment of opportunist mycobacteriosis is less well defined than for tuberculosis,
there being few large clinical trials. However, the British Thoracic Society has published
a set of guidelines.
97
Brucellosis
Pneumonia is a rare form of brucellosis but has been reported in countries such as
Kuwait and Arabia128, 129 where this zoonosis is endemic, and in farmers and meat
packers in North America and Europe.130, 131 Cattle, sheep, goats and camels are common
sources of infection, which is usually acquired by consuming unpasteurised milk or
milk products. Close contact with infected animals or their carcasses may also be
responsible for transmission of the disease to humans, either orally or, in the case
of pneumonia, by inhalation.
Patients with Brucella pneumonia develop a cough productive of mucopurulent sputum
or present with fever of unknown cause.
132
Perihilar or peribronchial infiltrates, or less frequently coin lesions, are evident
radiographically. Pleural effusion with a predominance of monocytic or lymphocytic
infiltrates is also described.
133
Histology shows necrotising epithelioid and giant cell granulomas, very similar to
those of tuberculosis.128, 134, 135 Diagnosis is dependent upon excluding tuberculosis
and identifying brucellae by culture or brucellar DNA by polymerase chain reaction
in blood or tissue.
135
Examination of sputum and bronchial washings is generally unrewarding.
Chronic melioidosis
The general features and acute form of melioidosis have been described on page 186.
Chronic melioidosis is acquired in the same way as the acute form and may represent
persistence or recrudescence of acute disease or arise insidiously in someone unknown
to have had acute disease. The disease progresses gradually over months or years.
It takes the form of localised lesions that may affect any organ but most commonly
involve the lungs, where chronic cavitatory melioidosis may closely mimic tuberculosis
apart from relative sparing of the apices.136, 137, 138 Pleural effusion and empyema
are less common in chronic than acute disease. Before cavitation takes place, microscopy
shows areas of necrosis surrounded by granulomatous inflammation. The central necrotic
zones are often stellate, and may be suppurative or caseous. The surrounding granulomatous
reaction consists of epithelioid and Langhans giant cells and is itself encompassed
by a fibrous mantle. When necrosis is suppurative, the histological features mimic
those of cat scratch disease or lymphogranuloma venereum, and, especially in the lungs,
tularaemia (see p. 187) or sporotrichosis (see p. 244). When the necrosis is caseous,
the histological picture is very similar to that of tuberculosis. In contrast to the
acute form of the disease, the causative bacterium (Burkholderia pseudomallei) can
be difficult to demonstrate in tissue sections (see p. 186 for staining methods).
The diagnosis is then largely dependent upon serological techniques.
Actinomycosis
Bacteriology
Actinomycetaceae (which include the genera Actinomyces, Nocardia and Rhodococcus)
and Mycobacteriaceae (which include the genus Mycobacterium) are both families of
the order Actinomycetales. Although Actinomycetales are classed as bacteria and mycobacterial
diseases are invariably considered among bacterial infections, some of the pathogenic
Actinomycetaceae are often mistakenly referred to as fungi and the diseases they cause
are commonly grouped with those caused by the true fungi under the general heading
of mycoses. It will be difficult to correct this misconception, particularly in view
of such entrenched nosological nomenclature as actinomycosis, which by virtue of the
ending ‘-mycosis’ – its etymology is usually misinterpreted – is unlikely to be displaced
from its common association with the true mycoses, in spite of other well-understood
terminological paradoxes and pitfalls such as mycosis fungoides and mycotic aneurysm.
However, as well as differing from fungi in size, structure and metabolism, the Actinomycetaceae
are susceptible to antibacterial agents and resistant to specifically antifungal drugs.
Actinomyces israelii is by far the most frequent cause of actinomycosis in humans.
A. bovis, the cause of actinomycosis in cattle, is an exceptionally rare cause of
the disease in humans. Other species that occasionally cause actinomycosis in humans
include A. eriksonii, A. meyerii and A. naeslundii. A. propionicus (Arachnia proprionica),
an organism closely related to Actinomyces israelii, also causes disease indistinguishable
from actinomycosis.
A. israelii is a strictly anaerobic, Gram-positive bacterium, formed of branching
filaments 0.5–1.0 µm wide. The filaments readily break into bacillus-like fragments.
They are not acid-fast. Like those of the nocardiae (see below), fragments of the
Actinomyces may be mistaken for contaminant corynebacteria.
A. israelii is a common commensal or saprophyte in the human mouth and intestine and
it is probable that most infections by this organism are endogenous. About 60% of
cases of actinomycosis present with lesions in the region of the mouth, face or neck,
the portal of entry being dental or tonsillar. About 25% of cases of actinomycosis
involve the ileocaecal region and in the remaining 15% of cases the infection is in
the lungs. It is presumed that pulmonary actinomycosis is the outcome of aspiration
of infected matter from the tonsillar crypts or mouth, apart from the very small proportion
of cases in which the disease has extended from known foci of infection in the abdomen.
The diagnosis should therefore be particularly suspected in patients with dental caries
or a history of unconsciousness with aspiration. The incidence of actinomycosis is
in decline, probably due to a combination of improved dental hygiene and the early
initiation of antibiotic therapy, the bacterium being highly sensitive to penicillin.
Most cases of actinomycosis are of mixed microbial aetiology, the pathogenicity of
Actinomyces being enhanced by the synergistic action of other bacteria, notably microaerophilic
streptococci, other anaerobes such as Bacteroides and Fusobacterium, and aerobic streptococci
and staphylococci. Actinobacillus actinomycetem comitans is another constituent of
the mouth flora – one that is seldom recovered in pure culture
139
but is often found in association with Actinomyces israelii in actinomycotic lesions.
It secretes a powerful leukotoxin which probably contributes to the virulence of these
mixed infections.
Clinical features
Pulmonary actinomycosis is promoted by poor dental hygiene, smoking and heavy drinking
140
and is recorded in AIDS.
141
It is usually a disease of adults, though may rarely occur in children.142, 143 It
is characterised by fever and expectoration of mucopurulent sputum. Contrary to a
common belief, ‘sulphur granules’ – the yellow colonial granules of the organisms
– are not often to be found in the sputum. Haemoptysis is a significant complication
and may require surgical treatment.
144
The diagnosis depends on recognition of the fine, Gram-positive, sometimes branching
filaments in films, and isolation of the organism. It has to be remembered that the
organism may be present in sputum only in short bacillary forms that are liable to
be misinterpreted. The chest radiograph may show opacities of various sizes scattered
through both lungs, particularly in the middle and lower zones. Alternatively, there
may be a large pneumonic area, sometimes associated with an empyema: this type of
disease may be accompanied by new bone formation on the inner aspects of several contiguous
ribs due to elevation of the periosteum by the inflammatory infiltrate. Occasionally,
infiltration of the chest wall suggests malignancy (Fig. 5.3.24
). The presence of discharging sinuses on the chest wall is characteristic of advanced
thoracic actinomycosis
145
but this stage is seldom encountered today.146, 147 It is in the pus discharging from
these sinuses that the ‘sulphur granules’ referred to above are to be found. Recent
series have been characterised by less specific features that have suggested tuberculosis
or cancer.140, 141, 148 The diagnosis has often been made only after lung tissue has
been resected, but may be possible by biopsy, particularly when the process involves
major airways.141, 149 It should be confirmed by culture and, because A. israelii
is a strict anaerobe and will die on exposure to atmospheric oxygen, prompt delivery
to the laboratory for appropriate processing is imperative.
Figure 5.3.24
Actinomycosis. (A) Computed tomography shows a mass in the right middle lobe extending
through the chest wall and mimicking an invasive carcinoma. (B) The lobectomy specimen
shows colonies of Actinomyces (arrow) within abscesses that extend into the fat of
the chest wall.
Pathological findings
Actinomycosis of the lungs typically affects the lower lobes but may involve any part.
Characteristically, the affected tissue is riddled with chronic abscesses that range
in diameter from a few millimetres to 3 cm. These lesions may communicate with one
another, drain into the bronchial tree or extend to the pleural surface and open into
the pleural sac. ‘Sulphur granules’ are often to be found within the abscesses. These
colonies of Actinomyces consist of numerous radiating bacterial filaments that often
terminate in a prominent cap of eosinophilic material that represents immune material,
a reaction known as the Splendore–Hoeppli phenomenon (Fig. 5.3.25
). Fibrosis surrounds the suppurative foci and extends more widely through the lungs,
particularly involving the septa. The infection may spread to the pleura and on into
the spine and ribs, whether or not there is an actinomycotic empyema: the latter may
be loculated or involve the entire pleural sac. Obliteration of the sac prevents empyema
formation but does not present a barrier to the infection as it spreads outwards to
involve not only the thoracic skeleton but also the soft tissues and skin of the chest
wall, often with the establishment of the draining sinuses that are a classic, if
rare, feature of the disease. Actinomycotic bacteraemia is uncommon but arises more
frequently from pulmonary foci than from any other form of actinomycosis; it may give
rise to metastatic abscesses in other viscera, the skeleton or soft tissues. Actinomycosis
is occasionally complicated by amyloidosis.
Figure 5.3.25
Actinomycosis. Pus containing a colony of Actinomyces surrounded by an eosinophilic
mantle of immune material. The eosinophilic mantle is known as the Splendore–Hoeppli
phenomenon, although neither of these workers recognised its true nature. Splendore
described the eosinophilic material around Sporotrichum in 1908 and erroneously assumed
that it was a new species, while Hoeppli described the same material around schistosomes
in 1932 and erroneously suggested that it was secreted by the parasite. The material
is now considered to consist of immunoglobulin, complement and cellular debris. It
is especially striking in actinomycosis, botryomycosis and various fungal infections,
but may also be seen around parasites such as schistosomes and helminths, and even
around foreign material.
Nocardiosis
Bacteriology
Nocardiosis is caused by several genera of aerobic Actinomycetaceae. Nocardia asteroides
is the usual cause: N. brasiliensis and N. caviae are less common human pathogens.
None of these is part of the normal human flora. They are soil saprophytes that are
often found in decaying organic matter and human infection is exogenous. Nocardia
were first identified in cattle suffering from farcy in 1888.
150
Human disease was described shortly afterwards.151, 152
In contrast to A. israelii, N. asteroides is an aerobic bacterium. It is formed of
filaments measuring 0.5–1.0 µm in width, which are so highly branched that they have
been likened to Chinese characters. They often break into bacillus-like fragments
during preparation of films of infected exudate. They are Gram-positive but often
weakly so, and although commonly acid-fast, they are seldom as strongly so as tubercle
bacilli and they are not alcohol-fast; silver impregnation methods offer the best
means of demonstrating this organism in tissue sections. In contrast to A. israelii,
and to N. brasiliensis and N. caviae, N. asteroides does not form macroscopically
evident colonial granules in infected tissues.
Clinical features
Nocardiosis is typically acquired by inhalation but may extend beyond the respiratory
tract. Infection may develop in a previously healthy person,
153
but in most cases there are predisposing factors, particularly those that compromise
cellular immunity.154, 155, 156, 157 The disease is ordinarily chronic but may progress
rapidly in the severely immunocompromised. Predisposing factors include diseases such
as leukaemia and AIDS that interfere with resistance, therapeutic agents such as corticosteroids
and cytotoxic drugs that similarly suppress immunity and underlying pulmonary diseases,
including alveolar lipoproteinosis.158, 159 The overall incidence of nocardiosis appears
to be rising, probably in the main because of the increasing use of the drugs that
predispose to its occurrence. The disease is commoner in adults than children.
Pulmonary nocardiosis causes fever and cough productive of thick, sticky, purulent
sputum that may be streaked with blood. The radiological findings vary from minor
infiltrates to extensive consolidation, sometimes with abscess formation or empyema.160,
161 Less commonly, nocardiosis results in bronchial obstruction.162, 163, 164
Pathological findings
In general, the picture of nocardiosis is that of suppuration, with the development
of multiple abscesses. The lesions have a notable tendency to confluence. Pulmonary
nocardiosis may affect one or both lungs widely, with extensive consolidation round
the suppurative foci: the exudate in the alveoli of these pneumonic foci initially
contains much fibrinogen, and a fibrin coagulum forms, often with relatively little
leukocytic involvement. The organisms are present in the exudate, and may be very
numerous. Their number is often only inadequately disclosed by Gram or Ziehl–Neelsen
stains: the Grocott–Gomori method is generally more reliable (Fig. 5.3.26
).
165
Healing may result in extensive organising pneumonia.
166
Rarely, pulmonary nocardiosis may take the form of an intracavitary nocardioma
167
or invade contiguous vertebrae and compress the spinal cord.
168
N. asteroides has a particular affinity for the central nervous system; nocardial
brain abscess and nocardial meningitis are frequent complications of pulmonary infection.
Coexisting microbial agents are commonly identified. Treatment of nocardiosis is generally
medical, typically employing sulphonamides or co-trimoxazole. Abscesses and empyema
may require additional surgery.
Figure 5.3.26
Nocardiosis. Pus containing colonies of basophilic nocardia (A), which are better
demonstrated by Grocott staining (B).
Rhodococcus pneumonia
Rhodococcus equi (formerly Corynybacterium equi) is an aerobic, Gram-positive and
acid-fast bacillus belonging to the order Actinomycetales, and is therefore closely
related to the mycobacteria and Nocardia. Its natural habitat is the soil and its
transmission is aerogenous. It is best known as a pathogen in foals, cattle, swine
and sheep, where it is a lethal cause of suppurative granulomatous pneumonia, lymphadenitis,
mediastinitis and pyometra. It has only recently been recognised as pathogenic to
humans. Human infection often follows exposure to farm animals or to stockyards contaminated
with animal excreta. Virtually all Rhodococcus-infected patients have been severely
immunocompromised, typically suffering from AIDS, of which it is an infrequent complication.
169
The clinical presentation is often insidious, consisting of fatigue, fever and a non-productive
cough.
R. equi infection causes pneumonic consolidation with abscesses. The disease typically
affects the upper lobes and may simulate tuberculosis radiologically.170, 171, 172
Spread to sites such as the brain and bone may occur. The inflammation is histiocytic
in nature and may result in pulmonary malakoplakia.
Malakoplakia
Malakoplakia is a rare inflammatory disorder characterised by tumour-like accumulations
of swollen macrophages. It usually affects immunocompromised persons and is due to
a defect in macrophage function.
173
Bacteria are ingested normally but are not killed within the cell, suggesting that
the fault lies in the lysosomes. Malakoplakia usually affects the lower genitourinary
or gastrointestinal tracts and until recently few cases had been described with lung
involvement. However, several cases of malakoplakia confined to the lungs have now
been described, chiefly in the setting of AIDS but also associated with general debilitation,
organ transplantation, haematopoietic malignancy and alcoholism.170, 171, 174, 175,
176, 177, 178, 179, 180, 181, 182, 183
Bacteriology
Malakoplakia is associated with infection by various bacteria and fungi. In the urinary
tract the organism is usually Escherichia coli but in the lungs Rhodococcus equi (formerly
Corynebacterium equi) is generally involved, although rare cases associated with other
infections are described.
184
Rhodococci are Gram-positive coccobacilli that may be mistaken for commensal diphtheroids
in sputum. They are sometimes acid-fast. R. equi has been recognised as an agent causing
bronchopneumonia in horses and other domesticated animals since its first isolation
from infected foals in 1923. Its habitat is the soil. Infection of both humans and
beasts is thought to be acquired through the lungs. Human infection almost always
involves patients who have defects in cell-mediated immunity. A history of exposure
to animals is not invariably obtained.
Pathological and clinical features
Malakoplakia of the lungs may form solitary or multiple bilateral lesions, mimicking
either primary or metastatic neoplasms radiologically. The gross appearances also
mimic neoplastic disease. The lesions are well demarcated, firm and either solid or
cavitating. Microscopically, the lung tissue is replaced by sheets of swollen macrophages
with abundant eosinophilic, granular or vacuolated cytoplasm that stains well with
periodic acid–Schiff reagents and is diastase-resistant. The appearances may suggest
a granular cell tumour (see p. 640). A characteristic feature is the presence of Michaelis–Gutman
bodies in the macrophage cytoplasm or free between the cells. These are faintly basophilic,
round, target-like structures that measure up to 20 µm diameter (Fig. 5.3.27
). They contain calcium and are therefore well shown by von Kossa's stain. The Michaelis–Gutman
bodies represent mineralised bacteria-containing phagolysosomes.
183
Aggregates of bacteria can sometimes be demonstrated within macrophages by Gram stains.
Figure 5.3.27
Malakoplakia. A mass lesion composed of histiocytes with abundant eosinophilic cytoplasm.
Occasional Michaelis–Gutman bodies are evident (arrows).
Syphilis
Syphilitic lesions have never been particularly frequent in the lungs, and congenital
pulmonary syphilis (‘pneumonia alba’) has probably always been the commonest manifestation.
However, there has recently been an increase in syphilis and its protean manifestations
should not be forgotten.185, 186
Congenital pulmonary syphilis
The pallor and firmness of the lungs, which are larger than normal, account for this
condition's old name, pneumonia alba. It is usually seen in stillborn syphilitic babies
or those who die within a few hours of birth: in the latter, the aerated lobules stand
out above the indurated parts. Microscopically, there is widespread thickening of
the alveolar walls by fibroblastic connective tissue accompanied by an accumulation
of plasma cells with some lymphocytes. In places there are microscopical foci of necrosis,
maybe with histiocytic proliferation round them, as well as some accumulation of neutrophils:
these lesions occasionally merge to form gummatous foci that may be evident macroscopically.
Usually there is a conspicuous lining of cuboidal type II alveolar epithelial cells
and many alveoli may be filled with macrophages. Silver impregnation methods show
the presence of great numbers of treponemes in the tissues. The bacteria may also
be demonstrated immunohistochemically.
187
Imaging may show diffuse pulmonary infiltrates, which persist long after adequate
antibiotic treatment.
188
Somewhat similar macroscopical and microscopical changes may result from viral infections
in the neonatal period. Also, Pneumocystis pneumonia may be mistaken for syphilitic
pneumonia in those cases in which interstitial accumulation of plasma cells is particularly
marked (see p. 226).
Acquired pulmonary syphilis
Gummas and interstitial fibrosis are the manifestations of acquired syphilis in the
lungs. The gummas may be solitary or multiple, and small or large. They may occur
in the trachea and bronchi as ulcerative lesions, with a tendency to destroy the cartilage
of the wall. These cause cough and haemorrhage whereas gummas in the lung substance
may be clinically silent.
Bronchopulmonary gummas have the structure that is common to these lesions wherever
they occur in the body. They consist of a necrotic core surrounded by granulation
tissue that is heavily infiltrated by plasma cells and lymphocytes with scanty giant
cells. Satellite lesions, as seen in tuberculosis, are not a feature. As elsewhere,
gummas tend ultimately to produce dense scars that contract and produce deep cicatricial
fissures in the surface of the lungs, an appearance comparable to that of the classic
hepar lobatum of tertiary syphilis.
It is very important to consider and exclude other types of infection, particularly
mycobacterioses and mycoses, before a diagnosis of gumma can be sustained, even when
the patient's serological tests indicate the presence of syphilis. Moreover, primary
and secondary tumours are commoner causes of discrete shadows in chest radiographs
than gummas, even in patients with syphilis. The necrotic pulmonary lesions of Wegener's
granulomatosis and even pulmonary infarcts are among other conditions to be considered
in the differential diagnosis.
Other thoracic manifestations of acquired syphilis include diffuse pulmonary fibrosis
of non-specific character, hilar lymphadenopathy and pleural fibrosis.185, 186
References
Tuberculosis
1
Armstrong
JA
D’Arcy Hart
P
Response of cultured macrophages to Mycobacterium tuberculosis with observations on
fusion of lysosomes and phagosomes
J Exp Med
134
1971
713
740
15776571
2
Lowrie
DB
Andrew
PW
Macrophage antimycobacterial mechanisms
Br Med Bull
44
1988
624
634
3076810
3
Gerston
KF
Blumberg
L
Tshabalala
VA
Viability of mycobacteria in formalin-fixed lungs
Human Pathology
35
2004
571
575
15138931
4
Fukunaga
H
Murakami
T
Gondo
T
Sensitivity of acid-fast staining for Mycobacterium tuberculosis in formalin-fixed
tissue
Am J Respir Crit Care Med
166
2002
994
997
12359660
5
Cserni
G
Auramine fluorescence for acid-fast bacilli in formalin-fixed paraffin-embedded tissues
Am J Clin Pathol
103
1995
114
6
Popper
HH
Auramine fluorescence for acid-fast bacilli in formalin-fixed paraffin-embedded tissues
– reply
Am J Clin Pathol
103
1995
114
7
Wockel
W
Auramine fluorescence for acid-fast bacilli in formalin-fixed, paraffin-embedded tissues
Am J Clin Pathol
103
1995
667
668
7537940
8
Ulbright
TM
Katzenstein
ALA
Solitary necrotizing granulomas of the lung
Am J Surg Pathol
4
1980
13
28
7361992
9
Tang
YW
Procop
GW
Zheng
XT
Histologic parameters predictive of mycobacterial infection
Am J Clin Pathol
109
1998
331
334
9495207
10
Chitkara
YK
Evaluation of cultures of percutaneous core needle biopsy specimens in the diagnosis
of pulmonary nodules
Am J Clin Pathol
107
1997
224
228
9024072
11
Ulrichs
T
Lefmann
M
Reich
M
Modified immunohistological staining allows detection of Ziehl–Neelsen-negative Mycobacterium
tuberculosis organisms and their precise localization in human tissue
J Pathol
205
2005
633
640
15776475
12
Mustafa
T
Wiker
HG
Mfinanga
SGM
Immunohistochemistry using a Mycobacterium tuberculosis complex specific antibody
for improved diagnosis of tuberculous lymphadenitis
Mod Pathol
19
2006
1606
1614
16980944
13
Cheng
VCC
Yam
WC
Hung
IFN
Clinical evaluation of the polymerase chain reaction for the rapid diagnosis of tuberculosis
J Clin Pathol
57
2004
281
285
14990600
14
Selva
E
Hofman
V
Berto
F
The value of polymerase chain reaction detection of Mycobacterium tuberculosis in
granulomas isolated by laser capture microdissection
Pathology
36
2004
77
81
14757561
15
Nopvichai
C
Sanpavat
A
Sawatdee
R
PCR detection of Mycobacterium tuberculosis in necrotising non-granulomatous lymphadenitis
using formalin-fixed paraffin-embedded tissue: a study in Thai patients
J Clin Pathol
62
2009
812
815
19734478
Park
JS
Kang
YA
Kwon
SY
Nested PCR in lung tissue for diagnosis of pulmonary tuberculosis
Eur Respir J
35
2010
851
857
19741027
16
Schulz
S
Cabras
AD
Kremer
M
Species identification of mycobacteria in paraffin-embedded tissues: frequent detection
of nontuberculous mycobacteria
Mod Pathol
18
2005
274
282
15475934
17
Schewe
C
Goldmann
T
Grosser
M
Inter-laboratory validation of PCR-based detection of Mycobacterium tuberculosis in
formalin-fixed, paraffin-embedded tissues
Virchows Arch
447
2005
573
585
15968546
18
Greco
S
Girardi
E
Navarra
A
Current evidence on diagnostic accuracy of commercially based nucleic acid amplification
tests for the diagnosis of pulmonary tuberculosis
Thorax
61
2006
783
790
16738037
19
Escombe
AR
Moore
DA
Gilman
RH
Upper-room ultraviolet light and negative air ionization to prevent tuberculosis transmission
PLoS Med
6
2009
e43
19296717
20
Callister
ME
Barringer
J
Thanabalasingam
ST
Pulmonary tuberculosis among political asylum seekers screened at Heathrow Airport,
London, 1995–9
Thorax
57
2002
152
156
11828046
21
Meredith
SK
Nunn
AJ
Byfield
SP
National survey of notifications of tuberculosis in England and Wales in 1988
Thorax
47
1992
770
775
1481174
22
Kolappan
C
Gopi
PG
Tobacco smoking and pulmonary tuberculosis
Thorax
57
2002
964
966
12403879
23
Levin
M
Newport
M
Unravelling the genetic basis of susceptibility to mycobacterial infection
J Pathol
181
1997
5
7
9071996
24
Murray
JF
Cursed duet: HIV infection and tuberculosis
Respiration
57
1990
210
220
2274719
25
Heckbert
SR
Elarth
A
Nolan
CM
The impact of human immunodeficiency virus infection on tuberculosis in young men
in Seattle-King county, Washington
Chest
102
1992
433
437
1643928
26
Brudney
K
Dobkin
J
Resurgent tuberculosis in New York City – human immunodeficiency virus, homelessness,
and the decline of tuberculosis control programs
Am Rev Respir Dis
144
1991
745
749
1928942
27
Kochi
A
The global tuberculosis situation and the new control strategy of the World Health
Organization
Tubercle
72
1991
1
6
1882440
28
Dolin
PJ
Raviglione
MC
Kochi
A
Global tuberculosis incidence and mortality during 1990–2000
Bulletin of the World Health Organization
72
1994
213
220
8205640
29
Busillo
CP
Lessnau
KD
Sanjana
V
Multidrug resistant Mycobacterium tuberculosis in patients with human immunodeficiency
virus infection
Chest
102
1992
797
801
1516405
30
Chawla
PK
Klapper
PJ
Kamholz
SL
Drug-resistant tuberculosis in an urban population including patients at risk for
human immunodeficiency virus infection
Am Rev Respir Dis
146
1992
280
284
1489113
31
Edlin
BR
Tokars
JI
Grieco
MH
An outbreak of multidrug-resistant tuberculosis among hospitalized patients with the
acquired immunodeficiency syndrome
N Engl J Med
326
1992
1514
1521
1304721
32
PablosMendez
A
Raviglione
MC
Laszlo
A
Global surveillance for antituberculosis-drug resistance, 1994–1997
N Engl J Med
338
1998
1641
1649
9614254
33
Kruijshaar
ME
Watson
JM
Drobniewski
F
Increasing antituberculosis drug resistance in the United Kingdom: analysis of National
Surveillance Data
BMJ
336
2008
1231
1234
18456593
34
World Health Organization
Global TB Control Report
www.who.int/tb
2009
Available online at
35
Selwyn
PA
Hartel
D
Lewis
VA
A prospective study of the risk of tuberculosis among intravenous drug users with
human immunodeficiency virus infection
N Engl J Med
320
1989
545
550
2915665
36
Centers for Disease Control
Nosocomial transmission of mutlidrug-resistant tuberculosis to health-care workers
and HIV-infected patients in an urban hospital – Florida
Mortality and Morbidity Weekly Reports
39
1990
718
722
37
Havlir
DV
Barnes
PF
Tuberculosis in patients with human immunodeficiency virus infection
N Engl J Med
340
1999
367
373
9929528
38
Goletti
D
Weissman
D
Jackson
RW
Effect of Mycobacterium tuberculosis on HIV replication. Role of immune activation
J Immunol
157
1996
1271
1278
8757635
39
Toossi
Z
Nicolacakis
K
Xia
L
Activation of latent HIV-1 by Mycobacterium tuberculosis and its purified protein
derivative in alveolar macrophages from HIV-infected individuals in vitro
J Acquir Immune Defic Syndr Hum Retrovirol
15
1997
325
331
9342251
40
Garrait
V
Cadranel
J
Esvant
H
Tuberculosis generates a microenvironment enhancing the productive infection of local
lymphocytes by HIV
J Immunol
159
1997
2824
2830
9300705
41
Hill
AR
Premkumar
S
Brustein
S
Disseminated tuberculosis in the acquired immunodeficiency syndrome era
Am Rev Respir Dis
144
1991
1164
1170
1952449
42
Medlar
EM
The behavior of pulmonary tuberculosis lesions: a pathological study
Am Rev Tuberc
71
1955
1
244
43
Rook
GAW
Al Attiyah
R
Cytokines and the Koch phenomenon
Tubercle
72
1991
13
20
1882441
44
Chensue
SW
Warmington
K
Ruth
J
Cytokine responses during mycobacterial and schistosomal antigen-induced pulmonary
granuloma formation – production of Th1 and Th2 cytokines and relative contribution
of tumor necrosis factor
Am J Pathol
145
1994
1105
1113
7977642
45
Ulrichs
T
Kosmiadi
GA
Trusov
V
Human tuberculous granulomas induce peripheral lymphoid follicle-like structures to
orchestrate local host defence in the lung
J Pathol
204
2004
217
228
15376257
46
Leong
ASY
Wannakrairot
P
Leong
TYM
Apoptosis is a major cause of so-called ‘caseous necrosis’ in mycobacterial granulomas
in HIV-infected patients
J Clin Pathol
61
2008
366
372
17761737
47
Mustafa
T
Wiker
H
Morkve
O
Differential expression of mycobacterial antigen MPT64, apoptosis and inflammatory
markers in multinucleated giant cells and epithelioid cells in granulomas caused by
Mycobacterium tuberculosis
Virchows Archiv
452
2008
449
456
18266005
48
Ober
WB
Ghon but not forgotten: Anton Ghon and his complex
Pathol Annu
18
1983
79
85
6371678
49
Chow
LTC
Shum
BSF
Chow
WH
Diffuse pulmonary ossification – a rare complication of tuberculosis
Histopathology
20
1992
435
437
1587494
50
Brock
RC
Cann
RJ
Dickinson
JR
Tuberculous mediastinal lymphadenitis in childhood; secondary effects on the lungs
Guy Hosp Rep
87
1937
295
317
51
MacPherson
AMC
Zorab
PA
Reid
L
Collapse of the lung associated with primary tuberculosis: a review of 51 cases
Thorax
15
1960
346
354
13764994
52
Husson
RN
Bramson
RT
Newton
AW
A 10-month-old girl with fever, upper-lobe pneumonia, and a pleural effusion – Pulmonary
tuberculosis, infantile
N Engl J Med
341
1999
353
360
10423471
53
Seal
RME
The pathology of tuberculosis
Br J Hosp Med
5
1971
783
790
54
Strom
L
Experiments with radioactive Calmette (BCG) vaccine
Acta Paed
39
1950
453
454
55
Strom
L
Rudback
L
On labelling tubercle bacteria with radioactive phosphorus
Acta tuberculosea Scandinavica
1949
98
101
56
Lalvani
A
Diagnosing tuberculosis infection in the 21st century: new tools to tackle an old
enemy
Chest
131
2007
1898
1906
17565023
57
Daniels
M
Ridehalgh
F
Springett
VH
Tuberculosis in young adults. Report on the Prophit tuberculosis survey 1935–1944
1948
HK Lewis
London
58
Grange
JM
Mycobacteria and Human Disease
1988
Edward Arnold
London
88
59
Behr
MA
Wilson
MA
Gill
WP
Comparative genomics of BCG vaccines by whole-genome DNA microarray [see comments]
Science
284
1999
1520
1523
10348738
Fine
PE
Variation in protection by BCG: implications of and for heterologous immunity
Lancet
346
1995
1339
1345
7475776
60
Abramowsky
C
Gonzalez
B
Sorensen
RU
Disseminated bacillus Calmette-Guerin infections in patients with primary immunodeficiences
Am J Clin Pathol
100
1993
52
8346737
61
Emile
J-F
Patey
N
Altare
F
Correlation of granuloma structure with clinical outcome defines two types of idiopathic
disseminated BCG infection
J Pathol
181
1997
25
30
9071999
Clark
IA
Heterologous immunity revisited
Parasitology
122
2001
S51
S59
11442196
62
Grange
JM
Stanford
JL
BCG vaccination and cancer
Tubercle
71
1990
61
64
2196727
63
Bakker
W
Nijhuis-Heddes
JM
Post-operative intrapleural BCG in lung cancer: a 5-year follow-up report
Cancer Immunol Immunother
22
1986
155
159
3719595
64
Tan
L
Testa
G
Yung
T
Diffuse alveolar damage in BCGosis: A rare complication of intravesical bacillus Calmette-Guerin
therapy for transitional cell carcinoma
Pathology
31
1999
55
56
10212925
65
Rich
AR
The pathogenesis of tuberculosis
2nd ed
1951
Charles C Thomas
Springfield, Ill
500–60
66
Youmans
GP
Mechanisms of immunity in tuberculosis
Ioachim
HL
Pathology Annual Vol. 9
1979
Raven Press
New York
137
157
67
Bothamley
GH
Grange
JM
The Koch phenomenon and delayed hypersensitivity: 1891–1991
Tubercle
72
1991
7
11
1882447
68
Grange
JM
The immunophysiology and immunopathology of tuberculosis
Davies
PDO
Tuberculosis
2nd ed
1998
Chapman and Hall
London
69
Schluger
NW
Recent advances in our understanding of human host responses to tuberculosis
Respir Res
2
2001
157
163
11686880
70
Myatt
N
Coghill
G
Morrison
K
Detection of tumour necrosis factor alpha in sarcoidosis and tuberculosis granulomas
using in situ hybridisation
J Clin Pathol
47
1994
423
426
8027394
71
Grange
JM
Stanford
JL
Rook
G
Tuberculosis and HIV: light after darkness
Thorax
49
1994
537
539
8016788
72
Dock
W
Apical localization of phthisis
Am Rev Tuberc
53
1946
297
305
21023380
73
West
JB
Dollery
CT
Distribution of blood flow and ventilation perfusion ratio in the lung, measured with
radioactive CO2
J Appl Physiol
15
1960
405
410
13844133
74
West
JB
Ventilation/Blood Flow and Gas Exchange
3rd ed
1977
Blackwell
Oxford
30
75
Goodwin
RA
Des Prez
RM
Apical localization of pulmonary tuberculosis, chronic pulmonary histoplasmosis, and
progressive massive fibrosis of the lung
Chest
83
1983
801
805
6839825
76
British Thoracic and Tuberculosis Association
Aspergilloma and residual tuberculous cavities – the results of a resurvey
Tubercle
51
1970
227
245
5495645
77
Auerbach
O
Tuberculosis of the trachea and major bronchi
Am Rev Tuberc
60
1949
604
620
15392764
78
Vandenbrande
P
Lambrechts
M
Tack
J
Endobronchial tuberculosis mimicking lung cancer in elderly patients
Respir Med
85
1991
107
109
1887126
79
Wasser
LS
Shaw
GW
Talavera
W
Endobronchial tuberculosis in the acquired immunodeficiency syndrome
Chest
94
1988
1240
1244
3191766
80
Lee
JH
Park
SS
Lee
DH
Endobronchial tuberculosis – clinical and bronchoscopic features in 121 cases
Chest
102
1992
990
994
1395814
81
Hoheisel
G
Chan
BKM
Chan
CHS
Endobronchial tuberculosis: diagnostic features and therapeutic outcome
Respir Med
88
1994
593
597
7991884
82
King
D
Davies
PDO
Disseminated tuberculosis in the elderly: still a diagnosis overlooked
J R Soc Med
85
1992
48
50
1548662
83
Proudfoot
AT
Cryptic disseminated tuberculosis
Br J Hosp Med
5
1971
773
780
84
Morris
CDW
Pulmonary tuberculosis in the elderly – a different disease
Thorax
45
1990
912
913
2281421
85
Singh
R
Joshi
RC
Christie
J
Generalised non-reactive tuberculosis: a clinicopathological study of four patients
Thorax
44
1989
952
955
2595638
86
Benatar
SR
Mark
EJ
McLoud
TC
A 44-year-old woman with pulmonary infiltrates, respiratory failure, and pancytopenia
– pulmonary tuberculosis, nonreactive and miliary, with diffuse alveolar damage (adult
respiratory distress syndrome), with miliary tuberculosis in the liver, spleen, adrenal
glands, bone marrow, and kidneys. Kaposi's sarcoma of the jejunum
N Engl J Med
333
1995
241
248
7791842
87
Nambuya
A
Sewankambo
N
Mugerwa
J
Tuberculous lymphadenitis associated with human immunodeficiency virus (HIV) in Uganda
J Clin Pathol
41
1988
91
96
88
Iseman
MD
Tuberculosis therapy: past, present and future
Eur Respir J Suppl
36
2002
87s
94s
12168751
89
Loddenkemper
R
Sagebiel
D
Brendel
A
Strategies against multidrug-resistant tuberculosis
Eur Respir J Suppl
36
2002
66s
77s
12168749
90
Blumberg
HM
Burman
WJ
Chaisson
RE
American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases
Society of America: treatment of tuberculosis
Am J Respir Crit Care Med
167
2003
603
662
12588714
91
Caminero
JA
de March
P
Statements of ATS, CDC, and IDSA on treatment of tuberculosis
Am J Respir Crit Care Med
169
2004
316
317
14718245
Opportunistic mycobacteria
92
Chester
AC
Winn
WC
Unusual and newly recognized patterns of nontuberculous mycobacterial infection with
emphasis on the immunocompromised host
Pathol Annu
21
1986
251
270
93
Grange
JM
Yates
MD
Infections caused by opportunist mycobacteria: a review
J R Soc Med
79
1986
226
229
3517327
94
Wallace
JM
Hannah
JB
Mycobacterium avium complex infection in patients with the acquired immunodeficiency
syndrome. A clinicopathologic study
Chest
93
1988
926
932
3359847
95
Smith
MB
Molina
CP
Schnadig
VJ
Pathologic features of Mycobacterium kansasii infection in patients with acquired
immunodeficiency syndrome
Arch Pathol Lab Med
127
2003
554
560
12708897
96
Kahana
LM
Kay
JM
Yakrus
MA
Mycobacterium avium complex infection in an immunocompetent young adult related to
hot tub exposure
Chest
111
1997
242
245
8996025
97
Management of opportunist mycobacterial infections: Joint Tuberculosis Committee Guidelines
1999. Subcommittee of the Joint Tuberculosis Committee of the British Thoracic Society
Thorax
55
2000
210
218
10679540
98
Sexton
P
Harrison
AC
Susceptibility to nontuberculous mycobacterial lung disease
Eur Respir J
31
2008
1322
1333
18515557
99
Rigsby
MO
Curtis
AM
Pulmonary disease from nontuberculous mycobacteria in patients with human immunodeficiency
virus
Chest
106
1994
913
919
8082377
100
Nash
G
Said
JW
Nash
SV
The pathology of AIDS – intestinal Mycobacterium avium complex (MAC) infection in
AIDS
Mod Pathol
8
1995
209
211
101
Laporte
R
A l’études des bacillus paratuberculeux. I Propriétés pathogènes II. Histo-cytologie
des lésions paratuberculeuses
Ann Inst Pasteur
65
1940
415
434
102
Guest
JL
Arean
VM
Brenner
HA
Group IV atypical mycobacterium infection occurring in association with mineral oil
granuloma of lungs
Am Rev Respir Dis
95
1967
656
662
6021127
103
Greenberger
PA
Katzenstein
ALA
Lipid pneumonia with atypical mycobacterial colonization. Association with allergic
bronchopulmonary aspergillosis
Arch Intern Med
143
1983
2003
2005
6625788
104
Jouannic
I
Desrues
B
Lena
H
Exogenous lipoid pneumonia complicated by Mycobacterium fortuitum and Aspergillus
fumigatus infections
Eur Respir J
9
1996
172
174
8834351
105
Gibson
JB
Infection of the lungs by ‘saprophytic’ mycobacteria in achalasia of the cardia, with
report of a fatal case showing lipoid pneumonia due to milk
J Pathol Bacteriol
65
1953
239
251
13035617
106
Burke
DS
Ullian
RB
Megaesophagus and pneumonia associated with Mycobacterium chelonei A case report and
a literature review
Am Rev Respir Dis
116
1977
1101
1107
931183
107
Levin
M
Newport
M
D'Souza
S
Familial disseminated atypical mycobacterial infection in childhood: a human mycobacterial
susceptibility gene?
Lancet
345
1995
79
83
7815885
108
Asano
T
Itoh
G
Itoh
M
Disseminated Mycobacterium intracellulare infection in an HIV-negative, nonimmunosuppressed
patient with multiple endobronchial polyps
Respiration
69
2002
175
177
11961434
109
Khoor
A
Leslie
KO
Tazelaar
HD
Diffuse pulmonary disease caused by nontuberculous mycobacteria in immunocompetent
people (hot tub lung)
Am J Pathol
115
2001
755
762
110
Kahana
LM
Kay
JM
Pneumonitis due to Mycobacterium avium complex in hot tub water: infection or hypersensitivity?
Chest
112
1997
1713
1714
9404787
111
Marras
TK
Wallace
RJ
Jr
Koth
LL
Hypersensitivity pneumonitis reaction to Mycobacterium avium in household water
Chest
127
2005
664
671
15706013
112
Cappelluti
E
Fraire
AE
Schaefer
OP
A case of ‘hot tub lung’ due to Mycobacterium avium complex in an immunocompetent
host
Arch Intern Med
163
2003
845
848
12695276
113
Hanak
V
Kalra
S
Aksamit
TR
Hot tub lung: presenting features and clinical course of 21 patients
Respir Med
100
2006
610
615
16194601
114
Zota
V
Angelis
SM
Fraire
AE
Lessons from Mycobacterium avium complex-associated pneumonitis: a case report
J Med Case Reports
2
2008
152
115
Reich
JM
Johnson
RE
Mycobacterium avium complex pulmonary disease presenting as an isolated lingular or
middle lobe pattern. The Lady Windermere syndrome
Chest
101
1992
1605
1609
1600780
116
Kim
RD
Greenberg
DE
Ehrmantraut
ME
Pulmonary Nontuberculous Mycobacterial Disease: Prospective Study of a Distinct Preexisting
Syndrome
Am J Respir Crit Care Med
178
2008
1066
1074
18703788
117
Fujita
J
Ohtsuki
Y
Suemitsu
I
Pathological and radiological changes in resected lung specimens in Mycobacterium
avium intracellulare complex disease
Eur Resp J
13
1999
535
540
118
Fujita
J
Ohtsuki
Y
Shigeto
E
Pathological findings of bronchiectases caused by Mycobacterium avium intracellulare
complex
Resp Med
97
2003
933
938
119
Fukuoka
K
Nakano
Y
Nakajima
A
Endobronchial lesions involved in Mycobacterium avium infection
Resp Med
97
2003
1261
1264
120
Christianson
LC
Dewlett
HJ
Pulmonary disease in adults associated with unclassified mycobacteria
Am J Med
29
1960
980
991
13693411
121
Kraus
M
Benharroch
D
Kaplan
D
Mycobacterial cervical lymphadenitis: the histological features of non-tuberculous
mycobacterial infection
Histopathology
35
1999
534
538
10583577
122
Loo
KT
Seneviratne
S
Chan
JKC
Mycobacterial infection mimicking inflammatory ‘pseudotumour’ of the lung
Histopathology
14
1989
217
219
2707756
123
Umlas
J
Federman
M
Crawford
C
Spindle cell pseudotumor due to Mycobacterium-avium-intracellulare in patients with
acquired immunodeficiency syndrome (AIDS) – positive staining of mycobacteria for
cytoskeleton filaments
Am J Surg Pathol
15
1991
1181
1187
1720931
124
Chen
KTK
Mycobacterial spindle cell pseudotumor of lymph nodes
Am J Surg Pathol
16
1992
276
281
1309172
125
Suster
S
Moran
CA
Blanco
M
Mycobacterial spindle-cell pseudotumor of the spleen
Am J Clin Pathol
101
1994
539
542
8160649
126
Sekosan
M
Cleto
M
Senseng
C
Spindle cell pseudotumors in the lungs due to Mycobacterium tuberculosis in a transplant
patient
Am J Surg Pathol
18
1994
1065
1068
8092397
127
Lucas
SB
Mycobacteria and the tissues of man
Ratledge
C
Stanford
JL
Grange
JM
Biology of Mycobacteria
Vol. 3
1989
Academic Press
London
107
176
Brucellosis
128
Lubani
MM
Lulu
AR
Araj
GF
Pulmonary brucellosis
Q J Med
71
1989
319
324
2594962
129
Al-Jam’a
AH
Elbashier
AM
Al-Faris
SS
Brucella pneumonia: a case report
Ann Saudi Med
13
1993
74
77
17587997
130
Greer
AE
Pulmonary brucellosis
Dis Chest
29
1956
508
519
13305445
131
Hunt
AC
Bothwell
PW
Histological findings in human brucellosis
J Clin Pathol
20
1967
267
272
5632572
132
Saltoglu
N
Tasova
Y
Midikli
D
Fever of unknown origin in Turkey: evaluation of 87 cases during a nine-year-period
of study
J Infect
48
2004
81
85
14667795
133
Pappas
G
Bosilkovski
M
Akritidis
N
Brucellosis and the respiratory system
Clin Infect Dis
37
2003
e95
e99
13130417
134
Weed
LA
Sloss
PT
Clagett
OT
Chronic localised pulmonary brucellosis
JAMA
161
1956
1044
1047
135
Theegarten
D
Albrecht
S
T+Âtsch
M
Teschler
H
Neubauer
H
Al Dahouk
S
Brucellosis of the lung: case report and review of the literature
Virchows Archiv
452
2008
97
101
17952458
Chronic melioidosis
136
Piggott
JA
Hochholzer
L
Human melioidosis. A histopathologic study of acute and chronic melioidosis
Arch Pathol
90
1970
101
111
5433595
137
Wong
KT
Puthucheary
SD
Vadivelu
J
The histopathology of human melioidosis
Histopathology
26
1995
51
55
7713483
138
Dhiensiri
T
Puapairoj
S
Susaengrat
W
Pulmonary melioidosis: clinical-radiologic correlation in 183 cases in northeastern
Thailand
Radiology
166
1988
711
715
3340766
Actinomycosis
139
Bowker
CM
Connellan
SJ
Freeth
MG
A case of thoracic Actinobacillus infection
Respir Med
86
1992
53
54
1565818
140
Hsieh
MJ
Liu
HP
Chang
JP
Thoracic actinomycosis
Chest
104
1993
366
370
8339619
141
Cendan
I
Klapholz
A
Talavera
W
Pulmonary actinomycosis – a cause of endobronchial disease in a patient with AIDS
Chest
103
1993
1886
1887
8404119
142
Lee
JP
Rudoy
R
Pediatric thoracic actinomycosis
Hawaii Med J
62
2003
30
32
12685278
143
Mabeza
GF
Macfarlane
J
Pulmonary actinomycosis
Eur Respir J
21
2003
545
551
12662015
144
Lu
MS
Liu
HP
Yeh
CH
The role of surgery in hemoptysis caused by thoracic actinomycosis; a forgotten disease
Eur J Cardiothorac Surg
24
2003
694
698
14583300
145
Bates
M
Cruickshank
G
Thoracic actinomycosis
Thorax
12
1957
99
124
13442954
146
Brown
JR
Human actinomycosis. A study of 181 subjects
Hum Pathol
4
1973
319
330
4756858
147
Slade
PR
Slesser
BV
Southgate
J
Thoracic actinomycosis
Thorax
28
1973
73
85
4568119
148
Dalhoff
K
Wallner
S
Finck
C
Endobronchial actinomycosis
Eur Respir J
7
1994
1189
1191
7925892
149
Ariel
I
Breuer
R
Kamal
NS
Endobronchial actinomycosis simulating bronchogenic carcinoma. Diagnosis by bronchial
biopsy
Chest
99
1991
493
495
1989815
Nocardiosis
150
Nocard
ME
Note sur la maladie des boeufs de la Guadeloupe connue sous le nom de farcin
Ann Inst Pasteur
2
1888
293
302
151
Eppinger
H
Ueber eine neue pathogene Cladothrix und eine durch sie hervorgerufene Pseudotuberculose
Wien Klin Wschr
3
1890
321
152
Eppinger
H
Uber eine neue, pathogene Cladothrix und eine durch sie hervorgerufene Pseudotuberculosis
(cladothrichica)
Beitr Pathol Anat
9
1891
287
328
153
Brechot
JM
Capron
F
Prudent
J
Unexpected pulmonary nocardiosis in a non-immunocompromised patient
Thorax
42
1987
479–440
154
Saltzman
HA
Chick
EW
Conant
NF
Nocardiosis as a complication of other diseases
Lab Invest
11
1962
1110
1117
13991193
155
Uttamchandani
RB
Daikos
GL
Reyes
RR
Nocardiosis in 30 patients with advanced human immunodeficiency virus infection: clinical
features and outcome
Clin Infect Dis
18
1994
348
353
8011814
156
Menendez
R
Cordero
PJ
Santos
M
Pulmonary infection with Nocardia species: a report of 10 cases and review
Eur Respir J
10
1997
1542
1546
9230244
157
Hui
CH
Au
VWK
Rowland
K
Pulmonary nocardiosis re-visited: experience of 35 patients at diagnosis
Resp Med
97
2003
709
717
158
Burbank
B
Morrione
TG
Cutler
SS
Pulmonary alveolar proteinosis and nocardiosis
Am J Med
28
1960
1002
1007
13805962
159
Summers
JE
Pulmonary alveolar proteinosis. Review of the literature with follow-up studies and
report of two new cases
Calif Med
104
1966
428
436
5336559
160
Frazier
AR
Rosenow
ECI
Roberts
GD
Nocardiosis: a review of 25 cases occurring during 24 months
Mayo Clin Proc
50
1975
657
663
1186297
161
Wada
R
Itabashi
C
Nakayama
Y
Chronic granulomatous pleuritis caused by nocardia: PCR based diagnosis by nocardial
16S rDNA in pathological specimens
J Clin Path
56
2003
966
969
14645361
162
McNeil
KD
Johnson
DW
Oliver
WA
Endobronchial nocardial infection
Thorax
48
1993
1281
1282
8303641
163
Fielding
DI
Oliver
WA
Endobronchial nocardial infection
Thorax
49
1994
385
164
Casty
FE
Wencel
M
Endobronchial nocardiosis
Eur Respir J
7
1994
1903
1905
7828703
165
Robboy
SJ
Vickery
AL
Jr
Tinctorial and morphologic properties distinguishing actinomycosis and nocardiosis
N Engl J Med
282
1970
593
596
4189913
166
Camp
M
Mehta
JB
Whitson
M
Bronchiolitis obliterans and Nocardia asteroides infection of the lung
Chest
92
1987
1107
1108
3315480
167
Murray
JF
Finegold
SM
Froman
S
The changing spectrum of nocardiosis. A review and presentation of nine cases
Am Rev Respir Dis
83
1961
315
330
13727022
168
Petersen
JM
Awad
I
Ahmad
M
Nocardia osteomyelitis and epidural abscess in the nonimmunosuppressed host
Cleve Clin Q
50
1983
453
459
6365359
Rhodococcus infection and malakoplakia
169
TorresTortosa
M
Arrizabalaga
J
Villanueva
JL
Prognosis and clinical evaluation of infection caused by Rhodococcus equi in HIV-infected
patients – A multicenter study of 67 cases
Chest
123
2003
1970
1976
12796176
170
Kwon
KY
Colby
TV
Rhodococcus equi pneumonia and pulmonary malakoplakia in acquired immunodeficiency
syndrome – pathologic features
Arch Pathol Lab Med
118
1994
744
748
7517660
171
Scott
MA
Graham
BS
Verrall
R
Rhodococcus equi – an increasingly recognized opportunistic pathogen: report of 12
cases and review of 65 cases in the literature
Am J Clin Pathol
103
1995
649
655
7741114
172
Hamrock
D
Azmi
FH
ODonnell
E
Infection by Rhodococcus equi in a patient with AIDS: histological appearance mimicking
Whipple's disease and Mycobacterium avium-intracellulare infection
J Clin Pathol
52
1999
68
71
10343616
173
Biggar
WD
Keating
A
Bear
RA
Malakoplakia: evidence for an acquired disease secondary to immunosuppression
Transplantation
31
1981
109
112
7020170
174
Gupta
RK
Schuster
RA
Christian
WD
Autopsy findings in a unique case of malacoplakia. A cytoimmunohistochemical study
of Michaelis–Gutmann bodies
Arch Pathol Lab Med
93
1972
42
48
175
Colby
TV
Hunt
S
Pelzmann
K
Malakoplakia of the lung. A report of two cases
Respiration
39
1980
295
299
6997951
176
Hodder
RV
St George-Hyslop
P
Chalvardjian
A
Pulmonary malakoplakia
Thorax
39
1984
70
71
6364445
177
Crouch
E
Wright
J
White
V
Malakoplakia mimicking carcinoma metastatic to lung
Am J Surg Pathol
8
1984
151
156
6367503
178
Byard
RW
Thorner
PS
Edwards
V
Pulmonary malacoplakia in a child
Pediatr Pathol
10
1990
417
424
2349158
179
Scannel
KA
Portoni
EJ
Finkel
HI
Pulmonary malakoplakia and Rhodococcus equi infection in a patient with AIDS
Chest
97
1990
1000
1001
2323228
180
Schwartz
DA
Ogden
PO
Blumberg
HM
Pulmonary malakoplakia in a patient with the acquired immunodeficiency syndrome –
differential diagnostic considerations
Arch Pathol Lab Med
114
1990
1267
1272
2252424
181
Mollo
JL
Groussard
O
Baldeyrou
P
Tracheal malacoplakia
Chest
105
1994
608
610
8306775
182
Deperalta-Venturina
MN
Clubb
FJ
Kielhofner
MA
Pulmonary malacoplakia associated with Rhodococcus equi infection in a patient with
acquired immunodeficiency syndrome
Am J Clin Pathol
102
1994
459
463
7942603
183
Yuoh
G
Hove
MGM
Wen
J
Pulmonary malakoplakia in acquired immunodeficiency syndrome: an ultrastructural study
of morphogenesis of Michaelis–Gutmann bodies
Mod Pathol
9
1996
476
483
8733761
184
Bastas
A
Markou
N
Botsi
C
Malakoplakia of the lung caused by Pasteurella multocida in a patient with AIDS
Scand J Infect Dis
34
2002
536
538
12195882
Syphilis
185
Edmonds
LC
Stubbs
SE
Ryu
JH
Syphilis – a disease to exclude in diagnosing sarcoidosis
Mayo Clin Proc
67
1992
37
41
1732690
186
Dooley
DP
Tomski
S
Syphilitic pneumonitis in an HIV-infected patient
Chest
105
1994
629
631
8306785
187
Guarner
J
Greer
PW
Bartlett
T
Congenital syphilis in a newborn: An immunopathologic study
Modern Pathol
12
1999
82
87
188
Austin
R
Melhem
RE
Pulmonary changes in congenital syphilis
Pediatr Radiol
21
1991
404
405
1749670
5.4
Fungal infections
Chapter Contents
Pneumocystosis
223
Aspergillosis
226
Predisposing causes and types of pulmonary aspergillosis 228
Saprophytic aspergillosis
231
Aspergilloma 231
Obstructive aspergillosis 233
Invasive and septicaemic aspergillosis
233
Invasive aspergillosis 233
Septicaemic aspergillosis 233
Chronic necrotising Aspergillus pneumonia (acute cavitary pulmonary aspergillosis) 233
Pseudomembranous Aspergillus tracheobronchitis 234
Mucormycosis
234
Candidosis (moniliasis)
235
Cryptococcosis
236
Histoplasmosis
238
Primary pulmonary histoplasmosis 239
Histoplasmoma 239
Cavitary histoplasmosis 239
Acute (‘epidemic’) pulmonary histoplasmosis 240
Progressive disseminated histoplasmosis 240
Fibrosing mediastinitis 240
African histoplasmosis 240
Coccidioidomycosis
241
Blastomycosis (‘North American’ blastomycosis)
242
Paracoccidioidomycosis ('South American blastomycosis’)
243
Rare pulmonary mycoses
243
Torulopsosis 244
Sporotrichosis 244
Adiaspiromycosis 244
Malasseziosis 244
Pseudallescheriosis (monosporiosis) 244
Penicillium marneffei infection 245
Microsporidiosis 245
References
245
In certain regions of the world, environmental soil conditions support the saprophytic
phase of pathogenic fungi such as Histoplasma capsulatum, Blastomyces dermatitidis,
Coccidioides immitis and Paracoccidioides brasiliensis that are able to cause disease
in previously healthy people. Other fungi invade the tissues only because of lowering
of the patient's resistance by some other disease or as a side-effect of treatment.
Some of the fungi that cause these so-called opportunistic infections are seldom,
if ever, responsible for illness in healthy individuals: this is particularly so of
mucormycetes. Others cause disease in healthy individuals of a type very different
from the progressive, destructive, disseminated infection that they set up in those
whose resistance has been reduced: asthma from sensitisation to aspergilli and saprophytic
growth in previously formed cavities are examples of such disease.
Many fungi that infect humans are dimorphic – that is, they grow as yeast-like organisms
at certain temperatures and in mycelial form at others. Sporulating conidiophores
(or ‘fruiting heads’) form on the mycelial hyphae when oxygen is plentiful and release
spores into the atmosphere. The spores are particularly likely to be inhaled and germinate
into hyphae in the lungs. The size and shape of the fungus in its various forms often
enable the histopathologist to identify the genus (Box 5.4.1
) but speciation generally requires culture.
Box 5.4.1
Microscopical differentiation of common fungi in lung tissue
Yeasts
Small
Pneumocystis
Histoplasma
Torula
Medium-sized
Candida
Cryptococcus
Blastomyces
Paracoccidioides
Large
Coccidioides
Hyphae
Short
Candida (pseudohyphae)
Long and regular
Aspergillus
Long and irregular
Mucormycetes
The ease and frequency of international travel make many hitherto ‘exotic’ diseases
the immediate practical concern of doctors who have no personal experience in their
recognition and management. The fact that fungi which are frequently the cause of
disease in other parts of the world are not indigenous where the doctor is in practice
is no longer an excuse for not considering the possibility that a patient may have
acquired infection while visting another country or through exposure to contaminated,
imported materials. Neither histoplasmosis nor coccidioidomycosis, for instance, occurs
naturally in western Europe, yet every year in countries such as the UK patients are
seen whose symptoms are due to these diseases: the cardinal importance of the patient's
geographical history, and of the doctor's knowledge of geographical medicine, is self-evident.
Pneumocystosis1, 2
Microbiology
Pneumocystosis is caused by organisms discovered in the early twentieth century by
Chagas and soon after by Carini. They both thought the organism to be a stage in the
life cycle of trypanosomes as they found it in the lungs of rats experimentally infected
with trypanosomiasis. The Delanoës recognised that it was a distinct species, Pneumocystis
carinii. Pneumocystis organisms were first identified as a cause of human disease
in 1942, in Belgium, in association with cases of the condition, previously of unknown
causation, that had been described in 1937 as interstitial plasma cell pneumonia.
Outbreaks of the latter occurred during the Second World War, and for some years after,
in orphanages and other institutions that housed malnourished children, particularly
in eastern Europe and the Middle East.
3
The causative role of the Pneumocystis in this type of pneumonia in young children
was generally recognised following work of Jirovec in Czechoslovakia in the years
immediately after the war.4, 5 Subsequently it has been recognised that the human
pathogen is a separate species, P. jirovecii. Although pneumocysts were long thought
to be protozoal, they are now regarded as a primitive fungus in which the mycelium
is reduced to a unicellular state but is still able to sporulate.6, 7, 8 Despite this,
various forms of the fungus are still referred to as sporozoa or trophozoites, as
if it was a protozoa.
Electron microscopy6, 9, 10, 11, 12 provides an insight into the structure of the
organism and the pathogenesis of Pneumocystis pneumonia. It shows that the organism
forms cysts measuring 3–6 µm in diameter, which have a thick wall or pellicle (Fig.
5.4.1
). The pellicle is particularly thick at one point, a feature that is evident by light
microscopy in silver-stained preparations as a peripheral dot on the cyst wall. The
pellicle is triple-layered, consisting of an outer electron-dense zone about 75 nm
thick, an electron-lucent intermediate zone 250 nm thick and an inner 7-nm membrane.
Numerous small tubular structures are associated with the inner layer. Up to eight
nucleated intracystic bodies or sporozoa are also probably derived from this membrane.
These are released when the cyst ruptures (Fig. 5.4.2
). Collapsed cysts are largely empty and the innermost membrane of the wall is either
detached or absent. The released sporozoa grow from about 1.5 to 6 µm, have a thin
pellicle and are highly irregular in shape (Fig. 5.4.3
). They are now known as trophozoites and possibly undergo binary fission before entering
a precyst stage in which their pellicles thicken (Fig. 5.4.4
).
Figure 5.4.1
Pneumocystis jirovecii. Cyst form. The cyst wall has three layers: an outer electron-dense
zone about 75 nm thick, an electron-lucent intermediate zone 250 nm thick and an inner
7-nm membrane. Numerous small tubular structures are associated with the inner layer,
which also spawns up to eight intracystic bodies or sporozoites, one of which is visible
here. Electron micrograph.
(Reproduced from Corrin & Dewar (1992).
12
)
Figure 5.4.2
Pneumocystis jirovecii. Collapsed cyst releasing its contents. Electron micrograph
(Reproduced from Corrin & Dewar (1992).
12
)
Figure 5.4.3
Pneumocystis jirovecii. Trophozoites. These are irregular in shape and have a thin
unit membrane wall. Electron micrograph.
(Reproduced from Corrin & Dewar 1992.
12
)
Figure 5.4.4
Proposed life cycle of Pneumocystis jirovecii. (A) Cystic form containing two intracystic
bodies. Note the focal thickening of the pellicle. (B) Discharge of cyst contents
and collapse of the cyst. (C–E) Trophozoites, which possibly undergo binary fission.
(F) Trophozoite in precystic stage.
Cysts tend to be sparse near the alveolar walls, which are bordered chiefly by trophozoites,
suggesting that limitation of some nutritional factor promotes cyst formation. In
successfully treated cases only empty cysts are found, indicating that all viable
forms of the parasite, whether free-living or encysted, are vulnerable to chemotherapy.
Although there is not a heavy cellular reaction within the alveoli, cysts and trophozoites
may fill these air spaces.
Electron microscopy also shows that the trophozoites attach to type I alveolar epithelial
cells, eventually causing these cells to slough away from the alveolar walls.
13
Tracer studies show that there is increased permeability in the lung, even before
epithelial cells are lost.
14
In severe cases, trophozoites are observed within the alveolar interstitium. From
here they may gain access to the blood stream and disseminate widely.
15
Epidemiology
The epidemic Pneumocystis pneumonia mentioned above as a feature of malnourished children
is no longer seen in Europe but is still encountered in parts of the world where poverty
and malnutrition are rife. Pneumocystis pneumonia is also recognised as a complication
of immunodeficiency states, both congenital and acquired. Until the appearance of
the acquired immune deficiency syndrome (AIDS), such immunodeficiency was generally
due to lymphoproliferative disease or immunosuppressive therapy but interest now centres
on Pneumocystis pneumonia as being by far the commonest opportunistic infection in
AIDS (see Table 5.1.1, p. 167). P. jirovecii is kept in check by T lymphocytes and
suppression of these cells, as in AIDS, allows the parasite to proliferate and cause
pneumonia. In very severe T-lymphocyte depletion extrapulmonary dissemination is found
(see below). Patients who have undergone heart/lung transplantation are also at risk
of developing Pneumocystis pneumonia,
16
as are those with cancer.
17
Whatever the cause of the immunoparesis, Pneumocystis pneumonia in immunodeficient
individuals lacks the intense plasma cell infiltration seen in malnourished children.
Antibodies to P. jirovecii can be detected in most of the population by the age of
4 years
18
but the absence of the organism from normal lungs suggests that the pneumonia represents
reinfection rather than reactivation.8, 19, 20 Infection is presumed to be by inhalation
from an as yet poorly characterised environmental source. Although P. jirovecii has
been found in a wide range of animals it shows host specificity and is the species
prevalent in humans.
Autopsy in cases of Pneumocystis pneumonia presents no danger except in AIDS where
there is a possibility of mortuary staff being infected by the HIV virus.
Clinical features
Pneumocystis pneumonia is characterised by breathlessness, cough and fever, generally
of insidious onset. Untreated, the disease progresses with mounting tachypnnoea, hypoxaemia
and cyanosis. Radiographs typically show widespread bilateral opacification. Late
features include calcification, cavitation and pneumothorax. Diagnosis requires demonstration
of the organisms, for which sputum production is generally induced by the inhalation
of a saline aerosol or bronchoalveolar lavage is undertaken.
21
The organisms may be demonstrated with toluidine blue, Giemsa stain, Grocott's methenamine
silver stain or by immunofluorescence, but detection of Pneumocystis DNA by the polymerase
chain reaction is much more sensitive.22, 23, 24, 25, 26, 27, 28
Morbid anatomy
Fatal Pneumocystis pneumonia is generally characterised by widespread bilateral consolidation
with relative sparing of the bases and apices of the lungs (Fig. 5.4.5
). Rarely, the disease takes the form of solid or cavitating pulmonary nodules.29,
30
Figure 5.4.5
Pneumocystis jirovecii pneumonia. The lung shows diffuse consolidation.
(Courtesy of the late Dr AA Liebow, San Diego, USA and Dr T Jelihovsky, Sydney, Australia.)
Histological appearances
Microscopically, the alveoli are filled by a foamy, pale, eosinophilic exudate (Fig.
5.4.6
). The parasite is unstained in haematoxylin and eosin preparations but with Grocott's
methenamine silver stain the alveoli are seen to contain numerous round cysts that
measure about 5 µm across. Crescent-shaped forms (Fig. 5.4.7
) represent collapsed cysts and their presence is helpful if there is concern that
erythrocytes have not been successfully differentiated in the staining procedure,
especially if bronchial washings or bronchoalveolar lavage fluids are being examined
and the topographical features provided by a biopsy cannot be studied. Another helpful
feature is a dot, generally seen on the edge of the cyst (see Fig. 5.4.7); this represents
a focal thickening of cyst wall.
31
Various quick modifications of fixation and processing and of the Grocott stain have
been introduced to speed the diagnosis,32, 33, 34 but the importance of fixation in
killing any concomitant human immunodeficiency virus (HIV) should not be overlooked.
Other special stains that find favour include the Gram Weigert and Giemsa methods35,
36 and those using monoclonal antibodies (Fig. 5.4.8
).
22
The last two methods stain the trophozoite as well as the encysted form of the parasite,
but as the cysts are invariably present in Pneumocystis pneumonia (and are shown by
Grocott's stain), this is a dubious advantage: the Grocott stain is clearer and has
the advantage of staining any other fungi that may also be present.
37
However, in sputa and other cytological specimens where the pneumocysts may be sparse
the greater sensitivity of immunochemical stains and molecular techniques is advantageous.23,
24, 25, 26, 27 In situ hybridisation has also been used to demonstrate pneumocysts
in tissue sections.
38
Figure 5.4.6
Pneumocystis jirovecii pneumonia. The alveoli are filled by a foamy exudate and the
alveolar walls are thickened by a lymphoid infiltrate.
Figure 5.4.7
Pneumocystis jirovecii demonstrated by Grocott's methenamine silver stain. The smaller
group includes crescentic forms representing collapsed cysts and other cysts that
show a characteristic dot representing focal thickening of the cyst wall.
Figure 5.4.8
Immunocytochemical staining of Pneumocystis jirovecii demonstrates the trophozoites
as well as the cysts.
The alveolar exudate in which the parasites are found is virtually free of host cells
except for a mild increase in the number of alveolar macrophages. The reaction to
the parasite is largely an interstitial infiltrate of lymphocytes and plasma cells
(see Fig. 5.4.6). In most immunodeficient patients the infiltrate is generally mild
but in malnourished children it is intense, warranting the original descriptive term
interstitial plasma cell pneumonia.
Changes other than the classic one of foamy alveolar exudates may be found in Pneumocystis
pneumonia, particularly in AIDS (Table 5.4.1
and Fig. 5.4.9
),29, 30, 39, 40, 41, 42, 43, 44, 45, 46 demonstrating that pathological changes in
infective disorders are dependent on host factors as well as the parasite. In addition
to the cavitating nodules mentioned above,29, 30 necrotising granulomatous inflammation,26,
39, 42, 43, 44, 47 diffuse alveolar damage,
41
calcification,40, 45, 48 lymphoid interstitial pneumonia (particularly in children)49,
50, 51 and interstitial52, 53 and vascular invasion have been described, the latter
sometimes resulting in a necrotising vasculitis.
30
The invasion of the interstitium and pulmonary blood vessels probably causes the necrosis
that underlies the cavitating nodules.30, 53, 54 The cavities develop into air cysts,
which are prone to rupture into the pleural cavities, resulting in both pneumothorax
and Pneumocystis infection of the pleura.55, 56 Alternatively, there may be interstitial
spread and infection of the pleural cavities in the absence of any direct fistulous
communication.
52
Table 5.4.1
Pneumocystis jirovecii pneumonia: atypical histological features
43
No. of cases
%
Fibrosis
77
63
Interstitial
44
36
Intraluminal
23
19
Absence of typical exudates
11
9
Numerous alveolar macrophages
6
5
Granulomatous inflammation
5
4
Hyaline membranes
4
3
Marked interstitial pneumonitis
3
2
Parenchymal cavities
3
2
Interstitial microcalfication
2
2
Minimal histological reaction
1
1
Vascular permeation
1
1
Figure 5.4.9
Atypical reactions to Pneumocystis jirovecii in severely immunodeficient patients.
(A, B) Necrotising, granulomatous inflammation. (C) Necrosis, cavitation and dystrophic
calcification. (D) Invasion of the interstitium, evident from the foamy exudate expanding
alveolar walls as well as occupying alveoli.
(Courtesy of Dr R Steele, Brisbane, Australia; and Professor F Capron and Dr I Abdalsamad,
Paris, France.)
In view of the vascular invasion it is not surprising that widespread blood-borne
dissemination is also reported, particularly in AIDS.15, 39, 57, 58, 59, 60, 61 The
fact that this sometimes develops in the absence of obvious pneumonia has been attributed
to the prophylactic use of inhaled pentamidine which reduces the risk of Pneumocystis
pneumonia but does not prevent the organism spreading to other organs. Restitution
of the immune response following effective antiviral therapy is sometimes accompanied
by an ‘immune reaction inflammation syndrome’ (IRIS)
62
and this may ultimately result in widespread interstitial pulmonary fibrosis.
Although opportunistic infections are often multiple, there appears to be a special
relationship between P. jirovecii and cytomegalovirus because these two organisms
coexist particularly frequently in the infected lung (Fig. 5.4.10
). It has been suggested that P. jirovecii acts as an intermediate host for cytomegalovirus.
63
Figure 5.4.10
Pneumocystis jirovecii and cytomegalovirus pneumonia. As well as the foamy exudate
of Pneumocystis pneumonia there are prominent viral inclusions (centre).
Differential diagnosis
The differential diagnosis of classic Pneumocystis pneumonia is from pulmonary oedema
and alveolar lipoproteinosis. These three conditions are all characterised by the
alveoli being filled by a largely acellular material, but whereas in oedema the material
is amorphous, in lipoproteinosis it is granular and in Pneumocystis pneumonia it has
a foamy appearance. Alveolar lipoproteinosls is further distinguished from Pneumocystis
pneumonia by the presence of cholesterol crystal clefts and a few foamy fat-filled
macrophages in the alveolar deposit and by the strong periodic acid–Schiff-positivity
of the deposit (compare Fig. 5.4.6 with Fig. 6.2.18A, p. 319).
Aspergillosis
Mycology
Aspergilli are common saprophytes found throughout the world in decaying organic matter
where their spores may be so numerous that they can be seen as a dense dust cloud
when piles of such material are disturbed. Several species have been identified as
causes of human disease but Aspergillus fumigatus is by far the most frequent, particularly
in European cases of pulmonary disease and septicaemia. Other species responsible
for disease in humans include A. flavus and A. niger, the latter more common in the
USA.
Definitive diagnosis requires culture but this is not always successful. In histological
preparations an aspergillus has a characteristic appearance and can be generically
identified by the morphology of its hyphae (Fig. 5.4.11
). Aspergillus hyphae are usually visible in haematoxylin and eosin preparations,
and sometimes are so intensely haematoxyphil that they are immediately evident at
low magnifications. Although the periodic acid–Schiff stain and the Gridley stain
for fungi facilitate their recognition, the Grocott–Gomori methenamine silver nitrate
method is very much more reliable. The hyphae are septate and their hyphal diameter,
which varies from 3 to 6 µm, is fairly regular. Typically, the hyphae branch dichotomously
at relatively narrow angles (35–45°), the branches then tending to orient themselves
parallel to each other. Rare fungi of similar morphology, such as
Chaetomium globosum, can be distinguished by immunocytochemistry, culture or molecular
methods.64, 65, 66, 67
Figure 5.4.11
Aspergillus hyphae are septate, of fairly uniform thickness (3-6 µm diameter) and
branch dichotomously. Grocott's methenamine silver stain.
The conidiophores (or fruiting heads), that are so striking a feature of aspergilli
when growing as saprophytes, are seen in infected tissues only when the fungus is
exposed to air: they are never found within the solid structure of colonised organs
and tissues, but may occasionally be seen in the lung if the lesion communicates with
a bronchus (Fig. 5.4.12
). Species identification is based on colonial characteristics and on the structure
of the conidiophores, which is best studied in culture (Figure 5.4.13, Figure 5.4.14
).
Figure 5.4.12
The fruiting heads or conidiophores of Aspergillus in a pulmonary cavity that communicated
with the bronchi, so affording the fungus the oxygen that stimulates this form of
reproduction. (A) Grocott's methenamine silver stain; (B) lactophenol cotton blue
stain.
Figure 5.4.13
Aspergillus colonies in culture. The hyphal mycelium is white in all species but the
conidiophores’ colour is distinctive. (A) A. fumigatus; (B) A. niger.
Figure 5.4.14
Aspergillus conidiophores. The structure of the conidiophores shows marked species
variation. (A) Diagrammatic appearances of A. fumigatus on the left and A. flavus
on the right. (B) A conidiophore in culture.
Oxalate crystal deposition
Crystals of calcium oxalate have been identified in tissues infected by aspergilli,
particularly A. niger, of which oxalic acid is a fermentation product. In some cases
local tissue injury and even generalised acute oxalosis and renal failure have resulted
from the production of oxalic acid by the fungus.68, 69 Its widespread deposition
as insoluble calcium oxalate may be accompanied by sudden hypocalcaemia.
70
Tissue toxicity is attributed to calcium oxalate complexing with iron, resulting in
the production of free oxidants.
71
Oxalosis is commonest with saprophytic aspergillosis but is also recorded with the
allergic and invasive varieties of the infection (described below). The demonstration
of oxalate crystals in biopsy and cytology specimens can be a useful aid in the diagnosis
of pulmonary aspergillosis.72, 73, 74 The crystals are birefringent (Fig. 5.4.15
), stain with alizirin red
75
and can be confirmed as oxalate by crystallography and X-ray diffraction.
76
Figure 5.4.15
Calcium oxalate crystal deposition in the tissues bordering an aspergilloma viewed
with (A) non-polarised and (B) polarised light. As is usually the case, much of the
fungal colony is dead but here the adjacent host tissue is also necrotic; this change
is attributable to oxalic acid secretion by the fungus. The oxalic acid combines with
free calcium ions in the tissues to precipitate as insoluble, birefringent crystals.
Predisposing causes and types of pulmonary aspergillosis77, 78
Although exposure to Aspergillus spores is common, the fungus is not a frequent pathogen.
Only if the individual is atopic, or the lungs have been previously damaged, or general
resistance is lowered by other conditions are ill-effects likely to occur. Bronchopulmonary
disease caused by aspergilli may accordingly be classified respectively as allergic,
saprophytic and invasive.77, 79 Rarely, different forms of pulmonary aspergillosis
occur in the same patient. For example, an aspergilloma may be complicated by allergic
aspergillosis,80, 81 even in a non-atopic patient, whilst an aspergilloma may develop
within the bronchiectasis resulting from allergic aspergillosis.82, 83
Allergic bronchopulmonary aspergillosis
Persons suffering from this form of aspergillosis are generally atopic and give a
history of asthma.84, 85, 86, 87 There is also an increased incidence of allergic
aspergillosis in patients with cystic fibrosis, but nearly half those so affected
are also atopic.
88
It is important to reiterate that this form of aspergillosis is not characterised
by invasion of the tissues by the fungus: it is an allergic response to Aspergillus
that remains confined to the airways. Furthermore, as the disease is a hypersensitivity
phenomenon, hyphae are very sparse and have to be searched for diligently, in contrast
to both the other main forms of aspergillosis (saprophytic and invasive) in which
hyphae are numerous.
The allergic reaction in the lung is frequently reflected in a raised blood eosinophil
count: eosinophilia is also seen in lung tissue and sputum. Circulating precipitating
antibodies to Aspergillus antigens may be demonstrable and immunoglobulin E, both
total and specific, is generally raised; indeed, these immunological tests, together
with the demonstration of immediate (and late) skin reactions to Aspergillus antigens,
are now the main means of confirming the clinical diagnosis of allergic aspergillosis.
There is, however, a wide range of specific antibodies to various antigenic components
of the fungus, and concentration of the serum may be necessary to detect them for
they are often not present in the high concentrations found in association with an
aspergilloma. Poor antigens may give false-negative results and corticosteroids may
depress the antibody response and thus both skin and serological reactions. Culture
of the sputum is not always positive and on occasion the diagnosis of allergic bronchopulmonary
aspergillosis is first made by the histopathologist after surgery has been undertaken
for a suspected malignancy (Fig. 5.4.16
and see Fig. 9.8, p. 464).
89
Figure 5.4.16
Allergic bronchopulmonary aspergillosis identified as the cause of a pulmonary opacity
thought to be neoplastic. (A) Several bronchi are distended by plugs of viscous mucus.
(B, C) Microscopy shows alternating eosinophilic bands, the pink ones representing
mucus and the red conglomerations of eosinophils. In (C) the walls of the bronchi
also show chronic inflammation, which weakens them and leads to proximal bronchiectasis.
(Courtesy of Professor DH Wright, Southampton, UK.)
The term ‘allergic bronchopulmonary aspergillosis’ is generally limited to a syndrome
that is chiefly characterised by the expectoration of mucous plugs or the impaction
of such plugs and the consequent development of bronchiectasis. However, allergy to
Aspergillus may have further bronchopulmonary consequences, notably bronchocentric
granulomatosis and eosinophilic pneumonia, both of which are dealt with elsewhere
(see pp. 461 and 464). Attention here will be limited to mucoid impaction.
Mucoid impaction
In some asthmatic individuals particularly large mucous plugs develop, typically 1–2 cm
thick and 2–5 cm long. They generally form in proximal bronchi (see Fig. 5.4.16) and
can be clearly seen in plain radiographs as finger-like opacities near the hilum of
the lung. They are frequently expectorated spontaneously (Fig. 5.4.17
). The airway involved is dilated and its wall shows non-specific chronic inflammatory
changes which vary from a mild infiltrate to a severe reaction that includes many
eosinophils. The affected airway may be merely distended and therefore returns to
normal after the plug is expectorated, or its wall may be largely destroyed by the
inflammation so that there is permanent bronchiectasis (Fig. 5.4.18
). The proximal distribution of this form of bronchiectasis contrasts with that of
the postinfective form, which generally affects the bases.
Figure 5.4.17
A mucous plug spontaneously expectorated by a patient with allergic bronchopulmonary
apergillosis. Such plugs are short and stubby, very different from the long, many-tailed
plugs expectorated in plastic bronchitis (compare with Fig. 3.20, p. 109).
(Courtesy of Dr T Jelihovsky, Sydney, Australia.)
Figure 5.4.18
Allergic bronchopulmonary aspergillosis. The proximal bronchi (top) are dilated and
some contain mucous plugs. More peripherally there is coagulative necrosis representing
bronchocentric granulomatosis and beyond that pale foci of eosinophilic pneumonia
are seen.
(Courtesy of the late Dr AA Liebow, San Diego, USA.)
The mucous plugs undergo inspissation and often have the consistency of hard rubber.
Although they may form casts of several generations of bronchi, they tend to be shorter
and stubbier than the long stringy casts expectorated in plastic bronchitis (see p.
109). The microscopic appearances also differ. Mucous plugs characteristically consist
of bands of agglutinated eosinophils alternating with layers of mucus (see Fig. 5.4.16).
The bands of eosinophils are arranged parallel to the airway wall and frequently diminish
in length towards the centre of the lumen so that wedges of alternating cellular and
mucous bands point inwards, presenting an appearance that has been likened to fir
trees.
90
Sparse Aspergillus hyphae are generally to be found in the mucous plugs.
In exceptional cases other fungi are responsible for similar changes, resulting in
reports of allergic bronchopulmonary stemphyliosis, curvulariosis, drechsleriasis,
candidosis, helminthosporiosis, penicilliosis, torulopsosis, fusariosis and pseudallescheriosis.91,
92, 93, 94, 95, 96 and the term ‘allergic bronchopulmonary fungal disease’ is therefore
sometimes preferred.
97
Extrinsic allergic alveolitis
Extrinsic allergic alveolitis may also be a manifestation of allergy to Aspergillus,
but here it is heavily exposed non-atopic individuals who are affected. One example
is ‘malt worker's lung’, which occurs in brewery staff working with mouldy barley;
the species of Aspergillus involved here is usually A. clavatus. Extrinsic allergic
alveolitis may also develop in patients harbouring an aspergilloma.
81
These forms of allergy to Aspergillus are similar, both clinically and pathologically,
to the extrinsic allergic alveolitis that develops in response to other allergens
(see p. 279).
Saprophytic aspergillosis
Aspergilli may grow saprophytically within stagnant secretions in the bronchi in cases
of chronic bronchitis and, less often, bronchiectasis. In certain circumstances this
may be very marked, resulting in obstructive aspergillosis (see below). Other varieties
of saprophytic aspergillosis include the colonisation of an infarct,
98
a tumour,
99
the bronchial anastomosis following transplantation100, 101 and a preformed cavity,
resulting in the last case in the formation of an aspergilloma (intracavitary Aspergillus
ball colony).
102
Aspergilloma
In an aspergilloma the fungus grows in the lumen of a cavity in the lung without invading
the tissues to any appreciable extent, drawing its nutriment from such exudate as
may be present. The ball usually forms in an existing cavity, particularly an old
tuberculous cavity,
102
but sometimes in a cavity resulting from conditions such as sarcoidosis (see Fig.
6.1.37, p. 289), bronchiectasis, abscess or emphysema, or in a congenital cyst. Aspergilloma
formation has been observed both in the bronchiectatic lung distal to an obstructing
carcinoma and within the cavity resulting from necrosis at the centre of a peripheral
carcinoma.
103
Although usually single, aspergillomas may be present in cavities in both lungs, and
in some cases there are several such lesions.
The term ‘mycetoma’ is frequently misapplied to intracavitary fungal balls, such as
aspergillomas. The term is correctly limited to a type of fungal granuloma that is
characterised by the formation of multiple sinuses and is usually the outcome of penetration
of the soft tissues by a thorn, or the like, contaminated by the causative organism.
Such lesions are most frequent on the extremities and ‘Madura foot’ is the type example.
In this sense a mycetoma represents a lesion caused by invasion of the tissues by
the organism concerned, in contrast to an intracavitary fungal ball, which is essentially
outside the tissues and does not, except in unusual circumstances, lead to extension
of the infection into the wall of the cavity itself. Many varieties of fungus cause
mycetomas: most of them seldom, if ever, cause other disease.
While most intracavitary fungal ball colonies are formed by A. fumigatus, other species
of Aspergillus have been identified in some cases and, exceptionally, fungi such as
Pseudallescheria (Petriellidium) boydii,
104
Cladosporium cladosporidioides
105
and species of Penicillium, Candida or Syncephalastrum
106
have been responsible. Also, ball colonies similar to an aspergilloma may on rare
occasions consist solely of bacteria (see nocardioma on p. 215 and botryomycoma on
p. 192).
Radiology
The radiological appearances of an aspergilloma are often characteristic. The fungal
ball appears as a sharply demarcated radiopaque spheroid that rests on the wall of
the dependent part of the cavity and is separated from it elsewhere by a crescent
of air (Fig. 5.4.19
). In cases of long standing the colony may fill the cavity completely but the fungal
ball is often able to move within the cavity in accordance with the patient's posture.
However, although these features are characteristic of an aspergilloma, they may also
be given by an indolent necrotising form of invasive aspergillosis which is considered
below. A true aspergilloma is often demonstrated in radiographs over a period of several
years, sometimes with little or no detectable change in its appearance, sometimes
with appreciable phases of shrinkage and enlargement.
Figure 5.4.19
Aspergilloma. Computed tomography shows a cavity in the apical segment of the right
lower lobe, containing an intracavitary body consistent with an aspergilloma, which
was confirmed following lobectomy.
Antibody production
Most patients with an aspergilloma have strong serum precipitins against Aspergillus
antigens but, unless allergy with asthma has developed, skin tests against extracts
of the fungus are negative. Occasionally the circulating precipitins combine with
fungal antigen disseminated via the airways to produce the changes of extrinsic allergic
alveolitis elsewhere in the lung or there may be immune complex-mediated vasculitis
elsewhere in the body.
Morbid anatomy
The fungal colony appears macroscopically as a grey or reddish brown, rarely white
or green-tinged mass, sometimes firm or rubbery in consistency but often friable or
pultaceous (Fig. 5.4.20
). Old colonies may have a gritty feel, from deposition of calcium salts, and exceptionally
there may be so much calcification that the ball becomes stony and may be classified
among the so-called ‘pneumonoliths’.
Figure 5.4.20
An Aspergillus fungal ball (an aspergilloma) filling an apical cavity. In its fresh
state the fungal ball forms a soft, brown, pultaceous mass but as seen here after
fixation, it is more friable.
Histological appearances
Microscopically, an aspergilloma consists of a dense feltwork of hyphae, most of which
are dead. Only the hyphae at the surface are well preserved. The tips of these may
be abundantly coated with hyaline eosinophilic material of probable immune origin
(Splendore–Hoeppli phenomenon; see Fig. 5.3.25, p. 215), giving the edge of the aspergilloma
a distinctive appearance (Fig. 5.4.21
). The lining of the cavity that contains an aspergilloma varies according to the
nature of the condition that has given rise to it. The wall of an old tuberculous
cavity may consist of dense, hyaline fibrous tissue, sometimes devoid of an epithelial
covering; in other cases there may be a lining zone of chronic inflammatory granulation
tissue, which usually is without specific features of tuberculosis or other former
disease. When present, an epithelial lining may be of either respiratory or squamous
type.
Figure 5.4.21
Aspergilloma. (A) The centre of the fungus ball consists of a dense feltwork of dead
fungal hyphae. Only at the periphery is the fungus viable. (B) The edge of the fungus
ball is coated by a layer of eosinophilic immune material (Splendore–Hoeppli phenomenon).
Chronic inflammatory changes in the lining of the cavity that are attributable to
the fungal ball are variable but their presence underlies any enlargement of the cavity.
It is mentioned above that numerous calcium oxalate crystals are occasionally present.
These are found in the cavity lining, particularly near the surface and in relation
to the sides of blood vessels that face the fungus ball (see Fig. 5.4.15). The toxic
nature of oxalic acid contributes to the progressive enlargement of the cavity but
proteinases secreted by the fungus are probably more important in this respect.
107
Sometimes non-specific chronic inflammation is due to secondary bacterial infection.
It is exceptional for the fungus to invade the tissues, although this has been observed.
Such a change from saprophytosis to invasive growth is more likely to occur when the
patient's resistance is lowered, particularly by immunosuppressant and cytotoxic therapy
and less often by administration of corticosteroids.
Haemorrhage
Haemoptysis is a common feature of aspergilloma. Usually it causes no more than anaemia,
but in some cases it has been massive and death has resulted. It often accompanies
the development of further excavation of the lung tissue round the colonised lesion.
The rich capillary bed of a granulation tissue lining is generally the source of the
haemorrhage,
108
but larger vessels are occasionally involved; the endarteritis obliterans usually
found in chronic inflammation fails to seal them completely. The blood supply to the
wall of an aspergilloma cavity ultimately derives from the bronchial circulation and
the haemoptysis can sometimes be controlled by cannulation of the bronchial arteries
concerned under radiographic control and the introduction of occlusive synthetic emboli
(see Fig. 8.1.15, p. 412).
Obstructive aspergillosis
This form of aspergillosis was first described in patients with AIDS
109
and subsequently in the recipients of organ transplants.
110
It is characterised by a progressive cough, which is sometimes productive of bronchial
casts composed entirely of Aspergillus hyphae, in contrast to the mucous plugs of
allergic bronchopulmonary aspergillosis in which hyphae are scanty. There is no wheezing
or eosinophilia but the patient rapidly develops hypoxaemia. Chest radiographs show
areas of collapse and at bronchoscopy some airways are found to be completely obstructed
by fungal casts. When these are removed the bronchial mucosa appears normal. The condition
therefore represents saprophytic infection. Nevertheless, it is probably a precursor
of the locally invasive pseudomembranous Aspergillus tracheobronchitis, described
below.
Invasive and septicaemic aspergillosis
Excluding saprophytic colonisation of pulmonary infarcts and superficial invasion
round an aspergilloma – each a relatively rare occurrence – most instances of Aspergillus
pneumonia are due to the patient's resistance being undermined by factors that cause
prolonged granulocytopenia, such as lymphoproliferative disease, leukaemia and corticosteroid
therapy.111, 112, 113, 114, 115 Less often, invasive pulmonary aspergillosis complicates
influenza or other viral infection116, 117 or chronic obstructive pulmonary disease.117a,
118 AIDS is another predisposing cause119, 120, 121 but the incidence of invasive
aspergillosis is nevertheless lower than that of many other opportunistic infections
in this group of patients,109, 122, 123 probably because the HIV attacks lymphocytes
rather than granulocytes. Rarely, the patient is apparently immunocompetent.
124
In severely immunodeficient patients the infection spreads quickly and often disseminates
via the blood stream, whereas in less debilitated patients infection results in more
indolent localised lesions.
Invasive aspergillosis
In neutropenic patients invasive aspergillosis is characterised by star-like clusters
of radiating hyphae that extend widely throughout the lung tissue (Fig. 5.4.22
). There is vascular invasion leading to thrombosis, infarction and generalisation
of the infection through the body. Non-neutropenic patients are more likely to show
neutrophilic and monocytic exudates and inflammatory necrosis.
125
Figure 5.4.22
Invasive aspergillosis. The fungal hyphae grow through all constituents of the lung
tissue, including blood vessels, which thrombose, resulting in infarction.
Septicaemic aspergillosis
Septicaemic aspergillosis is commonly first recognised at necropsy, and often not
until the tissues are examined with the microscope. In many cases the portal of invasion
of the blood stream by the fungus is not apparent. In others it is a recognisable
local infection such as Aspergillus pneumonia. There may be a rapidly overwhelming
septicaemia, with little to show in the way of focal lesions, or there may be many
large foci of necrosis, most frequently in the brain, heart and kidneys. The lesions
are often so heavily colonised by the Aspergillus that, very soon after exposure to
the air at necropsy, condiophores develop and colour the necrotic tissue – green in
the case of A. fumigatus and A. flavus and black if the fungus is A. niger. There
may even be an obvious growth of the pigmented mould on the surface. Microscopical
examination often shows that the hyphae of the invading fungus are surrounded by a
spreading zone of necrosis in advance of their progress through the tissues: this
is probably a result of diffusion from the infected part of toxins and degradative
enzymes produced by the Aspergillus.68, 107 Occasionally, the lesions are suppurative.
Infection by other fungi may be present at the same time.
Chronic necrotising Aspergillus pneumonia (acute cavitary pulmonary aspergillosis)
This is a localised form of invasive aspergillosis in which the necrotic lung tissue
may separate away as a sequestrum and mimic an aspergilloma both radiographically
and macroscopically (Fig. 5.4.23
)126, 127, 128, 129, 130, 131, 132, 133, 134; microscopically, however, infected lung
tissue is easily distinguishable from an intraluminal ball colony of fungus, even
though both are largely necrotic.
Figure 5.4.23
Chronic necrotising Aspergillus pneumonia. The lung contains a cavity partly lined
by a plaque of Aspergillus nigra. The appearances simulate those of an aspergilloma
but the cavity is newly formed and its contents consist of necrotic lung tissue heavily
infiltrated by the fungus. Compare the colour of this non-sporing mycelium with the
cultured colony of the same species, which is exposed to oxygen and is therefore producing
black conidiophores (Fig. 5.4.13b).
(Reproduced from Wiggins et al. (1989) by permission of the editor of Thorax.
130
)
Pseudomembranous Aspergillus tracheobronchitis
Pseudomembranous Aspergillus tracheobronchitis involves only a narrow zone of tissue
bordering the major airways; the intervening lung parenchyma is spared.135, 136, 137,
138, 139, 140 In this form of invasive aspergillosis the airways are occluded by a
mixture of necrotic debris and fungal hyphae (Fig. 5.4.24
). It may be preceded by the obstructive form of saprophytic aspergillosis, described
above. A granulomatous response to the fungus may develop, mimicking bronchocentric
granulomatosis.141, 142
Figure 5.4.24
Pseudomembranous Aspergillus bronchitis. Many airways are plugged by fungal hyphae
and necrotic debris. Invasion is generally limited but in this patient the process
has already affected the adjacent pulmonary artery. (A) Gross appearances; (B) microscopy.
Mucormycosis
Mycology
Mucormycosis (formerly zygomycosis or phycomycosis) is the name most widely familiar
for any infection caused by a fungus that is a member of the class Zygomycetes (formerly
Phycomycetes). This class includes the orders Mucorales and Entomophthorales. They
are found in soil, dung and dust throughout the world and are common causes of food
spoilage. The classic form of mucormycosis is rhinocerebral, where the fungi grow
from an infected ulcer in the nasal space to invade the cranial cavity, cerebral blood
vessels and the contents of one or both orbits.143, 144 Some of the mucormycoses are
primary subcutaneous or orificial mucosal infections, occurring without predisposing
disease. Very rarely, dissemination of the fungus from these primary sites results
in visceral infection, including pulmonary mucormycosis due to the Entomophthorales
Basidiobolus haptosporus (B. meristosporus) and Conidiobolus coronatus (Entomophthora
coronata). Much more commonly, pulmonary mucormycosis is direct and attributable to
lowering of resistance to invasion of the tissues by Mucorales of the species Absidia,
Mucor and Rhizopus which ordinarily are saprophytes on decaying organic matter. It
is quite exceptional for one of these moulds to set up progressive infection in a
patient who is otherwise in good health.
145
The Mucorales that cause pulmonary infection are recognisable as such in histological
sections by their characteristic morphology (Fig. 5.4.25A
) but this does not allow identification of genus or species, which requires immunohistochemistry.
66
The hyphae are characteristically of variable but generally broad diameter, ranging
from 3 to 20 µm. They tend to branch perpendicularly, and septation of the hyphae
is absent or at most very infrequent. A false impression of septum formation may be
given by folds that result from shrinkage. Because of their irregular appearance and
the sometimes striking effects of shrinkage during histological processing the hyphae
have been likened to lengths of crushed ribbon. Although visible in haematoxylin and
eosin preparations, the mucoraceous fungi are best shown by special methods: the methenamine
silver stain is often useful, but better results may be obtained by the silver impregnation
methods used in the demonstration of reticulin fibres. As in the case of aspergilli,
such morphologically specific structures as sporangiophores develop only when the
mould is growing in air: they are seldom, if ever, seen in pulmonary lesions in the
fresh state, but they may form if a specimen has inadvertently been left exposed before
being placed in fixative solution. Culture often fails and histology may then be the
first means of identification, supplemented if required by molecular techniques.
67
The distinction from aspergilli is important because the treatment differs.
Figure 5.4.25
Mucor. (A) Mucor hyphae have few septa and are irregular in outline. The rounded structures
that resemble spores are hyphae cut transversely. (B) Mucormycosis in a lung excised
because of massive haemoptysis. Haemorrhage surrounds a partially thrombosed ruptured
blood vessel. (C) The wall of the ruptured vessel shows necrotising granulomatous
angiitis.
Predisposing causes
Conditions predisposing to visceral mucormycosis include AIDS, leukaemia, pancytopenia,
myelomatosis, diabetes mellitus and immunosuppression to prevent graft rejection.142,
146, 147 Certain therapeutic measures also predispose to these infections, particularly
desferrioxamine and the administration of cytotoxic and immunosuppressant drugs, including
corticosteroids. Cannulation of blood vessels, when long continued, is a further occasional
factor, being a potential portal of infection. Burns, too, have repeatedly become
not merely a site of superficial infection but the source of haematogenous dissemination.
The predisposing factors to some extent determine the site of predominant infection.
For instance, the syndrome of naso-orbitomeningingocerebral mucormycosis occurs usually
as a complication of diabetes mellitus or renal failure: these metabolic disorders
are comparatively seldom responsible for the development of pulmonary or primarily
septicaemic mucormycosis, which in most cases occur as complications of severe blood
disease or of the resistance-lowering side-effects of drugs. Similarly, severe malnutrition
predisposes to mucormycosis of the stomach or intestine.
Pathological findings
Mucormycotic lesions in the lungs vary greatly in size and number. Multiple lesions
are usually the result of haematogenous dissemination, as may occur in cases of naso-orbitocerebral
mucormycosis, whereas lesions that are single or few may be the result of direct infection
of the lungs by way of the airways. The lesions are firm, hyperaemic or haemorrhagic,
and often necrotic. If they extend to the pleura, a fibrinous exudate is found over
them and there are often petechial or larger foci of bleeding. Central lesions tend
to be spherical and peripheral ones wedge-shaped,
148
the former resembling chronic necrotising pulmonary aspergillosis (see above) and
the latter representing infarcts.
Microscopically, the most significant finding is fungal invasion of blood vessels
of all sizes, with thrombosis and colonisation of the thrombus by the fungus, and
infarction (Fig. 5.4.25B, C). It is clear that many strains of these fungi are thrombogenic,
and staining the lesions with phosphotungstic acid haematoxylin or by other appropriate
methods clearly demonstrates the formation of fine radiating threads of fibrin on
the surface of the hyphae within the blood vessels. Perineural invasion is also commonly
seen.
144
The hyphae may be present in great number, not only in the thrombi but throughout
the resulting infarcts. The latter soon liquefy, and there may be secondary bacterial
infection. Calcium oxalate crystal deposition, as described in aspergillosis (see
above), is rarely reported in mucormycosis.
149
As with other fungal infections occurring as a consequence of predisposing illnesses
and drug-induced failure of resistance, mucormycosis is often accompanied by one or
more other opportunistic infections, even of the same part. Frequent associations
are of mucormycosis with aspergillosis or candidosis but bacterial, viral and protozoal
infections may also be present.
Candidosis (moniliasis)
Candida is a yeast-like fungus that forms round or oval budding cells (blastospores),
septate hyphae and intermediate structures called pseudohyphae (Fig. 5.4.26
). Candidosis generally represents infection by Candida albicans (formerly known as
Monilia albicans) but other species may be involved.
150
Speciation requires culture as the species are morphologically identical. C. (Torulopsis)
glabrata is dealt with separately (see p. 244).
Figure 5.4.26
‘Mycotic’ candidal aneurysm of a pulmonary artery complicating surgery for complex
congenital heart disease. (A) Severe inflammation of the artery has led to mural necrosis
(below) and thrombosis. (B) Grocott staining reveals Candida spores and hyphae within
the thrombosed vessel. Note: the term ‘mycotic’ is applied to any aneurysm caused
by infected emboli regardless of whether the infection is fungal or bacterial.
The commonest form of candidosis is oral thrush, but the organism can attack any mucous
or moist cutaneous surface. The fungus is often found in the sputum but its presence
there generally represents no more than saprophytic growth. The diagnosis of bronchopulmonary
candidosis therefore often depends on finding the organism histologically. It is found
as a secondary invader of the lower respiratory tract in cases of chronic bronchitis,
bronchiectasis and bronchial carcinoma, and in severely ill patients with immunosuppression,
including AIDS.
119
In sections, Candida may be seen within a pseudomembrane consisting of purulent exudate
on the surface of a bronchus, or very rarely in lung tissue as a cause of pneumonia
or even lung abscess. In agranulocytic patients there is necrosis with minimal inflammation.
Candida pneumonia may represent a peripheral extension of Candida bronchitis or result
from haematogenous dissemination complicating diseases or therapeutic measures that
lower resistance. Pulmonary vascular candidosis may complicate endocarditis or infection
of central venous catheters inserted for prolonged parenteral feeding (see Fig. 5.4.26).151,
152 Features that distinguish Candida from P. jirovecii and other yeast-forming fungi
such as Histoplasma include the mixture of budding yeast cells with pseudohyphae and
the pyogenic or necrotising host reaction. The invariable presence of yeasts distinguishes
candidosis from aspergillosis and mucormycosis.
Cryptococcosis
Mycology
Cryptococcosis, a disease of worldwide distribution, is caused by the monomorphic
yeast-like fungus, Cryptococcus neoformans. This organism was formerly known as Torula
histolytica, and the disease as torulosis. Because it was first recognised in Europe,
and is caused by a fungus the cells of which reproduce by budding, cryptococcosis
was also sometimes known as European blastomycosis, in contrast to the so-called North
and South American blastomycoses (now blastomycosis and paracoccidioidomycosis respectively).
Although perhaps most familiar as a complication of leukaemia or lymphoma, in which
the infection typically presents as a progressive meningoencephalitis, cryptococcosis
is also known as a primary disease of the lungs without predisposing conditions, particularly
when Cryptococcus neoformans var. gattii is involved.153, 154 The lung is the principal
portal of entry and infection of the lungs is probably much commoner than at present
recognised. The primary pulmonary lesion of cryptococcosis is comparable to the initial
lesion of histoplasmosis and coccidioidomycosis and to the Ghon focus of tuberculosis.
Other diseases predisposing to secondary pulmonary cryptococcosis include alveolar
lipoproteinosis and AIDS.119, 155, 156 Cryptococcal inflammatory pseudotumours are
recorded in HIV-positive patients.
157
C. neoformans is a spheroidal or ovoid organism (Fig. 5.4.27
). A characteristic feature is variability in size, the cell body measuring from 3
to 20 µm in diameter, although in many instances it is within the range of 6–9 µm.
Another prominent feature is single, narrow-based budding, as opposed to the single,
broad-based budding of Blastomyces dermatitidis and the multiple narrow-based budding
of Paracoccidioides brasiliensis (Fig. 5.4.27A). The organism has a mucoid capsule
that usually stains with mucicarmine, a reaction that is not given by any other pathogenic
yeast-like fungus. Cryptococci can be seen in haematoxylin and eosin preparations
because they are refractile and, in polarised light, birefringent. They can also be
demonstrated by any of the special methods for staining fungi (Fig. 5.4.27B). The
capsule is sometimes deficient, in which case the fungus is not mucicarminophilic.
158
However, in most cases of capsule-deficient cryptococcosis some carminophilic capsular
material can be identified around a few yeasts. A Masson–Fontana stain can also help
in the recognition of capsule-deficient cryptococci because, unlike other yeasts,
cryptococci produce a melanin-like pigment.
159
Alternatively, capsule-deficient strains may be identified by immunohistochemistry.
Figure 5.4.27
Cryptococcosis. (A) A single Cryptococcus exhibiting single narrow-based budding (haematoxylin
and eosin stain).
(Courtesy of Dr A Paiva-Correia, formerly of Oporto, Portugal.)
(B) Cryptococci demonstrated by periodic acid–Schiff staining. (C) A necrotising 4-cm
cryptococcoma excised after its chance radiographic discovery.
(Courtesy of Dr M Jagusch, formerly of Auckland, New Zealand).
(D) Fungal spores (arrows) are seen amongst neutrophils in an immunosuppressed patient
with disseminated disease.
(B and D courtesy of Dr PM Cury, Rio Preto, Brazil.)
The cryptococci may be found in the sputum in cases of pulmonary involvement. They
may be seen on microscopical examination of wet films, particularly when the sputum
has been mixed with India ink or nigrosin to display the capsule. In dry films the
fungal cells disintegrate or become smudged and usually cannot be recognised, although
sometimes staining with mucicarmine is conclusive. Cultures are generally the preferred
means of confirming the diagnosis, but some strains of the cryptococcus do not grow
well and several attempts may have to be made before the organism is isolated. It
is notable that the cryptococcus is only exceptionally, if ever, found in sputum in
the absence of infection, in spite of its near ubiquity in our environment.
The fungus is often found in the dried droppings of birds, particularly pigeons and
starlings; these provide a good culture medium and pathogenic cryptococci can often
be isolated from buildings on which these birds roost.
160
Isolation from soil is less frequent, probably because of the avidity with which cryptococci
are phagocytosed by soil amoebae. As in the case of histoplasmosis, cryptococcosis
has been known to develop in people who have worked in bird-infested buildings, particularly
during demolition. The infection in such patients is slow to appear, in contrast to
the acute pneumonic form of histoplasmosis. It is clear that exposure to cryptococci
must occur very frequently: equally, the great majority of people must have a high
immunity, for cryptococcosis is rare in any population.
It is important to remember that any patient with active cryptococcosis is at risk
of developing infection of the central nervous system because of the peculiar affinity
of the organism for the brain and meninges and the frequency of its dissemination
in the blood.
Clinical features
Clinical features range from asymptomatic pulmonary involvement to life-threatening
meningitis and overwhelming cryptococcaemia. Imaging shows single or multiple well-circumscribed
masses, poorly demarcated opacities or segmental consolidation.
Morbid anatomy
Pulmonary cryptococcosis takes several forms: primary, cryptococcoma, cavitary, pneumonic,
miliary and inflammatory pseudotumour.153, 155, 156, 157, 161, 162, 163 Isolated,
discrete, encapsulated, subpleural granulomas are occasionally seen at necropsy: these
are healed or healing lesions, and the implication of their presence is that they
are a manifestation of a primary and non-progressive infection. Less rarely, there
are one or more focal lesions in the lungs, up to several centimetres in diameter,
that prove to be foci of progressive cryptococcal infection. These are known as cryptococcomas
(formerly torulomas) (Fig. 5.4.27C). They are firm, pale tan and rather sharply defined
but are encapsulated only when healing. Their cut surface may be dry or gelatinous:
the latter is the case when there is less inflammatory reaction to the organisms,
which, packed closely in great numbers, account for the mucoid appearance and consistence
of such lesions. Cryptococcal inflammatory pseudotumours are solid, firm and grey.
Progressive cavitary disease occurs in about 10% of cases. Confluence and continuing
enlargement of multiple foci may produce a gelatinous pneumonia involving a segment
or the greater part of one or more lobes. In cases of generalised haematogenous dissemination
of cryptococcosis both lungs may be studded with miliary or larger foci: close inspection
of these discloses their gelatinous nature; they tend to be sharper in outline than
miliary tubercles or pyaemic abscesses. The gelatinous collection of cryptococci at
the centre of the lesion may be washed out during examination of the tissue, leaving
a minute cavity.
Histological appearances
Microscopically, the lesions may be composed largely of the cryptococci themselves,
with little cellular reaction: the alveoli and interstitial tissue contain the closely
packed organisms, their cell bodies separated by the variable extent of their mucoid
capsule. In other cases, particularly those involving capsule-deficient strains, there
may be a tuberculoid reaction, the fungal cells being found within the cytoplasm of
multinucleate giant cells and of mononuclear macrophages as well as free in the tissue
spaces. In lesions of long standing, lymphocytes and plasma cells may be present in
large numbers, and fibrosis may be a feature, although not often conspicuous. Occasionally,
neutrophils accumulate in considerable numbers (Fig. 5.4.27D), particularly in miliary
haematogenous lesions, but in the absence of bacterial infection frank suppuration
is not found. Caseation is a rare development, and has to be distinguished from the
somewhat similar appearance that may result when large numbers of cryptococci have
died and disintegrated into an amorphous, finely granular, eosinophile mass. Cryptococcal
inflammatory pseudotumours are composed of plump spindle cells mixed with lymphocytes,
plasma cells and the yeast forms of the fungus.
Histoplasmosis
The first report of Histoplasma infection was in 1905 by Samuel Darling, a US Army
pathologist stationed in Panama around the time of the building of the canal. Darling
observed the organisms in histiocytes (hence the prefix ‘histo’), likened them to
plasmodia (hence ‘plasma’) and incorrectly assumed that an artefactual clear space
around each organism was a capsule (hence ‘capsulatum’).
Mycology
Two species of Histoplasma are pathogenic in humans, H. capsulatum and H. duboisii.
The latter is found exclusively in tropical Africa and the disease that it causes
differs significantly from that caused by H. capsulatum, an organism that is geographically
far more widespread. In general, when the word histoplasmosis is used without elaboration
it refers to disease caused by H. capsulatum.
The histoplasmas are dimorphic fungi, growing as ovoid, yeast-like organisms in cultures
at 37°C and in infected tissues (parasitic phase), and in mycelial form, producing
characteristic tuberculate macroconidia, in cultures at laboratory temperature (about
18°C) and in their free-living state in the soil (saprophytic phase). Spores released
by the macroconidia are inhaled and at body temperature germinate into yeasts that
grow by binary fission.
Histoplasmas can rarely be demonstrated in sputum, even by culture, but complement
fixation and precipitin tests may be helpful. However, on occasion, biopsy may be
necessary. When this is undertaken, the opportunity to set up cultures must not be
lost, although histology is more sensitive than culture.
164
The fungi may be quite focal in their distribution, and therefore difficult to find,
but within these foci the spores are usually present in large numbers within the cytoplasm
of macrophages or in areas of necrosis. They are readily seen in haematoxylin and
eosin preparations, but only if recently viable. They measure 1–3 × 3–5 µm and may
contain a distinct nucleus. Histoplasmas that have been dead for some time may escape
detection in such preparations, although sometimes birefringence, induced by histological
processing, may make a proportion of them visible in polarised light. Fortunately,
the methenamine silver stain commonly demonstrates histoplasmas very clearly, even
when they have long been dead. Unfortunately, they are difficult to distinguish from
other budding yeasts but a granulomatous reaction, their intracellular location and
an absence of pseudohyphae help separate them from Candida species and P. jirovecii.
Epidemiology
H. capsulatum is a soil-inhabiting fungus that requires organic nitrates for growth.
These are generally provided by bird droppings. Histoplasmosis results from inhalation
of infective spores and the geographical distribution of the disease is determined
by environmental conditions. In regions where the fungus cannot survive to complete
its saprophytic phase in soil or other organic debris, histoplasmosis does not occur
naturally – infection does not ordinarily take place from person to person, the tissue
form of the fungus being in general unable to convey the disease. In those parts of
the world where the soil or the climate is unsuitable for the saprophytic phase of
H. capsulatum, the disease is found only among those who have acquired the infection
in lands where the fungus is present in the environment, or, much more rarely, as
a result of exposure to imported materials contaminated by the infective spores
165
or to laboratory cultures of the saprophytic phase, which develops when the tissue
form is grown at laboratory temperature.
Histoplasmosis is endemic in many parts of North, Central and South America, Asia
and Africa. In North America, infection is particularly common in the basin of the
Ohio and Mississippi river valleys, where as many as 90% of the population give a
positive reaction to the histoplasmin skin test. The histoplasmin test has the same
significance in relation to histoplasmosis as the tuberculin test in relation to infection
by Mycobacterium tuberculosis. In Africa, infection by H. capsulatum is endemic over
an area far greater than that in which infection by the ‘African histoplasma’, H.
duboisii, occurs. Histoplasmosis is also endemic in India and South-east Asia but
it has not been recognised as an indigenous infection in Australia. Its occurrence
in Europe, other than as a result of travel to an endemic area or accidental exposure
to the fungus, is exceptionally rare.
Most people who acquire histoplasmosis have no more than a subclinical infection.
It has been estimated that clinical manifestations occur in only about 1% of cases
and that few of these patients develop serious illness. Histoplasmosis is seen in
rural communities exposed to bird droppings and in urban dwellers exposed to demolition
and building sites. Bat guano is rich in organic phosphates and histoplasmas and the
likely cause of an acute illness of cave explorers. Several forms of histoplasmosis
are desribed, which will now be considered.
Primary pulmonary histoplasmosis
The primary focus of histoplasmosis resembles that of tuberculosis. As with mycobacteria,
the main line of host defence is the macrophage. Specific T-cell immunity appears
about 10–14 days after infection and macrophages so activated usually terminate the
infection. If not, the organisms continue to grow within the macrophage cytoplasm.
The disease is spread during its primary stage by infected macrophages migrating to
the regional lymph nodes and beyond to disseminate by the blood stream to all organs,
but being filtered out particularly well by those rich in reticuloendothelial cells
so that the liver and spleen are commonly involved.
The primary lesion may be solitary or there may be two or more, sometimes many, primary
lesions in the lungs, the number depending on the heaviness of the exposure to the
infecting spores. Primary lesions may occur in any part of the lungs. Generally, and
especially when solitary, it is larger than the corresponding lesion of primary tuberculosis
but otherwise similar, showing epithelioid and giant cell granulomatous inflammation.
Caseation develops within a few weeks of infection and its appearance is believed
to coincide with the development of skin reactivity to histoplasmin, an observation
comparable to the corresponding events in tuberculosis. Early calcification and the
formation of a fibrous capsule are common (Fig. 5.4.28
). As in tuberculosis, there is spread of the infection to the hilar lymph nodes,
which undergo comparable changes. It is a characteristic of calcified lesions of histoplasmosis
that they have a massively chalky appearance and often show a peculiar stippled pattern
in radiographs, particularly lesions in lymph nodes. Occasionally, the calcified foci
in the lungs have a target-like radiographic shadow because of concentric zones of
greater and lesser transradiancy.
Figure 5.4.28
Histoplasmosis. A chest radiograph shows multiple bilateral calcific nodules in a
patient with quiescent histoplasmosis.
Histoplasmoma
The name histoplasmoma is given to any circumscribed, persistent focus of Histoplasma
infection in a lung. The lesion is an outcome of a primary focus, akin to a tuberculoma
rather than an aspergilloma. It occurs typically just under the pleura, and is roughly
spherical and from 1 to 4 cm, sometimes more, in diameter (Fig. 5.4.29
). Both in radiographs and when examined with the naked eye it has a characteristically
concentric pattern of closely set laminae, which may contain appreciable amounts of
calcium salts, although by no means invariably. This laminar structure is so characteristic
of chronic caseous granulomas of fungal origin that in some centres it is regarded
as proof of the non-neoplastic nature of ‘coin shadows’: this is not necessarily justified,
for it has been known for carcinoma to arise in the fibrotic capsular zone round such
a long-standing mycotic lesion. In general, histoplasmomas are altogether benign in
outlook, and may be left in situ with little chance that the infection will be activated
and progress; they may become more heavily calcified as the years pass. If resected,
they usually prove to be sterile on culture. The causative organism may then be demonstrated
most reliably by the methenamine silver stain, even though it is no longer viable.
Figure 5.4.29
Histoplasmoma representing quiescent disease.
Cavitary histoplasmosis
Histoplasmosis may closely reproduce the clinical and radiological picture of cavitating
pulmonary tuberculosis. Moreover, if such patients are exposed to a substantial risk
of infection by Mycobacterium tuberculosis, as may occur if they are nursed in company
with tuberculous patients, tuberculosis may be superimposed on the histoplasmic lesions,
with detriment to the chances of successfully treating either infection. In general,
cavitary histoplasmosis is seen most frequently in older patients, particularly men
with emphysema or other chronic lung disease.
166
It is attributed to a local breakdown in immunity at the site of dormant subapical
histoplasmic granulomas. In some cases it is possible that the condition is due to
reinfection, thus adding to the similarities between histoplasmosis and tuberculosis.
Like the cavities of chronic pulmonary tuberculosis, the lesion of cavitary histoplasmosis
may become the site of an aspergilloma. Tuberculoid granulomatous tissue in the lining
and vicinity of the cavities contains typical intracellular histoplasmas.
Acute (‘epidemic’) pulmonary histoplasmosis
The condition that has been described as ‘epidemic’ pulmonary histoplasmosis is a
form of acute histoplasmosis characterised by a severe influenza-like illness that
occurs as a result of a particularly heavy inhalational infection in an unprotected
individual.
167
The epithet ‘epidemic’ has been applied because such cases are commonly seen in several
patients simultaneously, all of them exposed on the same occasion to a massive contamination
of the air by infective spores. It is an unfortunate name, for such cases may occur
singly when individuals are so unfortunate as to stir up large numbers of spores when
working alone in a contaminated environment. These outbreaks have occurred when infected
dust is disturbed in the course of cleaning or demolishing buildings, ranging from
hen houses to city halls, that have harboured birds that over years have left the
droppings that so perfectly favour the growth of the saprophytic phase of H. capsulatum.
Similarly, those who enter caves where bat and bird droppings have encouraged the
Histoplasma to proliferate may suffer comparable group outbreaks of acute histoplasmic
pneumonia. The multiple foci of histoplasmosis that form in the lungs of heavily infected
patients have the same structure and run the same course as the solitary primary foci
described above. However, in some cases the infection is so heavy, and the resulting
changes in the lungs are so widespread, that death occurs. Those who have not previously
had a histoplasmic infection tend to suffer the severest illness in these outbreaks,
but even those already known to have had a primary infection may develop fatal pneumonic
lesions under such conditions of massive reinfection. Fatal opportunistic Histoplasma
pneumonia is recorded
168
but immunosuppression is by no means necessary.
Progressive disseminated histoplasmosis
Mention has been made above of haematogenous dissemination of the infection during
its primary stage. In most such cases the widespread lesions heal without ill effects.
However, there is another form of disseminated histoplasmosis in which the disease
progresses and eventually kills the patient. In some cases of this sort there are
no obvious predisposing causes but in most the patient's resistance is lowered by
the presence of serious underlying disease leading to defective T-cell function.
169
AIDS is now an important cause of such progressive disease (Fig. 5.4.30
).170, 171
Figure 5.4.30
Progessive disseminated histoplasmosis in a patient dying of acquired immunodeficiency
syndrome (AIDS). (A) A pulmonary vessel shows only slight granulomatous inflammation
but (B) Grocott staining shows extensive infiltration of the vessel by histoplasmas.
(Courtesy of Dr PM Cury, Rio Preto, Brazil.)
Fatal disseminated histoplasmosis is characterised by heavy parasitisation of the
reticuloendothelial cells resulting in hepatosplenomegaly and leukoerythroblastic
anaemia. Painful ulcers develop at mucocutaneous junction zones or within the orifices
of the body or in the pharynx and larynx. Organising pneumonic exudates and thin-walled
cavities may be found in the lungs. Well-formed granulomas are not usually found.
Fatal adrenal cortical insufficiency is another important manifestation.
Fibrosing mediastinitis
In those countries where histoplasmosis is prevalent mediastinal fibrosis with obstruction
of some, or all, of the mediastinal contents is recorded as a complication of such
infection.
172
African histoplasmosis
Histoplasma duboisii, an organism larger than H. capsulatum, has been recognised as
a cause of disease throughout much of Africa between the Sahara and the Zambesi. Its
distribution overlaps that of H. capsulatum, which, however, is much more widespread
on the continent. The source of the infection and the portal of entry of the fungus
remain debatable. There is growing evidence that the organism has a saprophytic phase,
probably in soil, and that it may enter the body either through the lungs or, in certain
cases, by inoculation into the skin. Pulmonary disease as one of its manifestations
has attracted less attention than cutaneous and skeletal involvement, but it is possible
that in many cases the lesions in the skin, like those in bones, are the result of
dissemination in the blood from inapparent pulmonary foci.
A feature typical of African histoplasmosis is that the fungal cells provoke a foreign-body
giant cell reaction, not a simple histiocytosis with or without tuberculoid metamorphosis,
as occurs in cases of infection by H. capsulatum. The organism is ovoid, has a distinct
cell wall and some internal structure, and measures 5–12 µm in its longer dimension.
It stains well with all the fungal stains, but is unlikely to be overlooked by the
careful microscopist in haematoxylin and eosin preparations.
Coccidioidomycosis173, 174, 175
Epidemiology
This disease is endemic in certain parts of North and South America, occurring especially
in hot semiarid regions such as Arizona and the San Joaquin valley of California,
but also in other such areas of the Americas down to Argentina. It is caused by the
fungus Coccidioides immitis, the saprophytic, free-living form of which requires special
environmental conditions of soil and climate for its survival: these determine its
geographical distribution. C. immitis grows best in soils free of competing microflora,
losing out to competitors when the soil is irrigated. Upsurges of infection may follow
dust storms that release the fungus into the air. The fungus may also be transported
on inanimate objects such as crops or native artefacts and infect persons outside
endemic areas, and of course patients may travel to non-endemic regions while incubating
the disease.
176
For example, the 2001 model airplane-flying world championship was held in an endemic
region of California and several of those attending from other areas were found to
have contracted coccidioidomycosis when they returned home.
177
Mycology
C. immitis is a dimorphic fungus. Saprophytically, it grows as a mould that produces
highly infective arthroconidia: these, inhaled in soil dust, establish the disease.
As a parasite, the organism is found almost exclusively in the form of spherules:
hyphae develop occasionally in the wall of coccidioidal cavities when air is admitted
by them communicating with an airway, but this is exceptional: only spherules and
their released spores are usually present, even when air is admitted (Figure 5.4.31,
Figure 5.4.32
).
Figure 5.4.31
Life cycle of Coccidioides immitis. 1–3: Saprophytic phase in soil; 4–6: parasitic
phase in lungs. Mycelial strands (1) growing in soil mature into chains of barrel-shaped
arthroconidia (2), which disarticulate (3), become air-borne, and are returned to
the soil or are inhaled. The parasitic phase in the lungs begins with the enlargement
of the inhaled arthroconidia and their development into thick-walled spherules (4),
within which endospores form (5). Released spores (6) can initiate the development
of a new spherule in the lungs or if infected material returns to the soil, mycelia
(1), so completing the cycle.
Figure 5.4.32
Coccidioidomycosis. Spherules discharging their spores within lung tissue. Grocott
methenamine silver stain.
(Courtesy of Dr JT Gmelich, formerly of Pasadena, USA.)
Coccidioides is one of the most dangerous of all organisms in terms of risk of accidental
infection of laboratory personnel. It is imperative that clinicians communicate to
the laboratory any suspicion that a specimen may contain C. immitis. Laboratories
dealing with coccidioidal cultures must operate with stringent precautions, including
the exclusion of staff not known to have acquired some natural immunity through previous
infection. The coccidioidin skin reaction is an invaluable screening test.
Once in the lungs, the arthroconidia develop into endosporulating spherules. These
range from 30 to 60 µm or more in diameter and contain from scores to hundreds of
endospores (see Fig. 5.4.32). The maturing spherule is usually accompanied by a histiocytic
reaction, with the formation of many multinucleate giant cells: the parasite may be
enclosed by the latter or lie free in the tissues. The mature spherule attracts neutrophils,
which collect to form microabscesses at the centre of the histiocytic granulomatous
foci. When the spherule ruptures, the freshly released spores, which range from 5
to 10 µm in diameter, at first lie free in the purulent exudate but soon are engulfed
by mononucleate or multinucleate macrophages. They grow, and eventually become transformed
into further spherules, thus repeating the cycle and leading to extension of the infection.
The fungal cells are usually well seen in haematoxylin and eosin preparations, except
in the early stages when only a few, newly released spores are present, which may
be so inconspicuous as to escape detection. The methenamine silver and other stains
for fungi demonstrate all forms of the organism very clearly. Whilst the mature or
even ruptured spherule is diagnostic, immature spherules or free spores are not: the
former may be confused with Blastomyces or Paracoccidioides and the latter with cryptococci
or histoplasmas.
Clinical features
The initial coccidioidal infection is symptomless in about 60% of persons.
178
When disease develops, there is usually an influenza-like fever, which characteristically
may be accompanied by erythema nodosum – hence its popular name of ‘the bumps’ in
the San Joaquin valley, where it is also called ‘valley fever’. In most cases there
is spontaneous recovery from the primary infection. When the disease is more severe,
which is likelier to be the case in patients of African or Asian ethnic origin, it
may mimic tuberculosis in any of its manifestations. In severe infections generalisation
through the blood is a frequent and particularly grave complication. Meningitis is
another common complication. Many patients are left with quiescent pulmonary foci.
Pathological findings
At necropsy, the lungs may show focal consolidation, necrotic haemorrhagic areas or
extensive necrotic excavating granulomatous nodules. Histologically, there may be
a suppurative exudate in the alveoli, or necrotic haemorrhagic and fibrinous lesions,
or a tuberculoid granulomatous reaction. Granulomatous inflammation is in general
associated with good resistance, and purulent inflammation with poor resistance. However,
when a spherule ruptures to release its spores (see Fig. 5.4.32), there may be a transient
neutrophil response whatever the underlying pattern of inflammation. Also, the type
of reaction is partly determined by the maturity of the developing fungal cells. Patients
whose resistance is lowered by other diseases may develop generalised haematogenous
coccidioidomycosis as a consequence of activation of a dormant pulmonary focus. The
lesion of quiescent pulmonary coccidioidomycosis is typically a fibrocaseous nodule
containing a few viable organisms (Fig. 5.4.33
).
Figure 5.4.33
Coccidioidomycoma representing quiescent disease.
Blastomycosis (‘north american’ blastomycosis)
Epidemiology
It is now recognised that infection with Blastomyces dermatitidis occurs very widely
throughout Africa and that the geographical designation ‘North American’, intended
to distinguish this disease from ‘European blastomycosis’ (cryptococcosis) and ‘South
American blastomycosis’ (paracoccidioidomycosis), is inappropriate.
In North America, the greatest prevalence is in the south-eastern and north central
USA, the area drained by the Mississippi, Missouri and Ohio rivers, the Great Lakes
region and the eastern provinces of Canada.179, 180 The natural habitat of the fungus
is soil, particularly that subjected to flooding. Infection is believed to occur by
inhalation.
In Africa, lung disease is not so predominant. Many patients present with bone lesions
or skin disease. Also, the antigenic make-up of the fungus differs from that encountered
in North America, suggesting that there are at least two variants of blastomycosis,
one seen in North America and in scattered foci in other countries (Mexico, Lebanon,
Israel, Saudi Arabia and India), the other restricted to Africa.
Mycology
Like the histoplasmas, B. dermatitidis is a diphasic fungus.
181
In tissues and in cultures at 37°C it grows as a yeast whereas in cultures at laboratory
temperature, and presumably in nature, it grows as a mycelium from which project special
slender hyphae known as conidiophores which bear conidia, the infective agents. The
yeasts are rounded and usually within the range of 7–15 µm in diameter, although some
cells may be as much as 30 µm across (Fig. 5.4.34
). They have a thick wall, which may give them a double-contoured appearance, but
they differ from the spores of Cryptococcus neoformans, which they otherwise resemble,
in lacking a capsule and therefore failing to stain with mucicarmine. It is a special
feature of B. dermatitidis that it reproduces in tissues by the formation of a single
broad-necked bud that protrudes from the surface of the parent cell, enlarging even
until it has reached as much as half the diameter of the latter, or more, before the
two separate.
Figure 5.4.34
Blastomycosis. There is a neutrophil and giant cell reaction to Blastomyces dermatitidis
yeasts, several of which have been ingested by giant cells. (A) Haematoxylin and eosin;
(B) Grocott stain.
Clinical features
As with several other fungi, Blastomyces causes a variety of clinical syndromes, including
primary, progressive and disseminated disease. Asymptomatic disease is rarely documented,
probably because there are no reliable skin or serological tests of infection. The
disease is generally first identified on cytology or histology with subsequent positive
culture.181, 182 Most patients are immunocompetent.
Primary blastomycosis is characterised by the abrupt onset of chills and cough accompanied
by patchy radiographic opacities. Such illness may be self-limiting or followed by
progressive disease, which is sometimes first manifest many months or years later,
affecting either the lung or extrapulmonary sites. Some patients who have no history
of pulmonary involvement develop blastomycosis in tissues such as the skin, the fungus
probably having spread there during the course of asymptomatic primary lung infection.
Pathological features
The lungs are the usual portal of entry and within the lungs the upper lobes are predominantly
involved.
183
The histological reaction to the fungus is characterised by necrotising granulomas
that are typically suppurative, the fungal cells either lying free in the purulent
exudate or engulfed by phagocytes. Although neutrophils are generally conspicuous,
tuberculoid granulomas also form. A characteristic feature is the so-called ‘suppurating
pseudotubercle’, in which a central microabscess is enclosed within a complex of epithelioid
histiocytes and multinucleate giant cells (see Fig. 5.4.34). Alternatively, an overwhelming
infection may cause diffuse alveolar damage.184, 185 The infection is usually confined
to the lungs and hilar lymph nodes but dissemination by the blood stream may occur,
particularly if immunity is impaired.
186
However, blastomycosis is not a common manifestation of AIDS.
Paracoccidioidomycosis ('south american blastomycosis’)187, 188
Epidemiology
Infection with Paracoccidioides brasiliensis is limited to Latin American countries
from Mexico to Argentina but does not occur in all countries in this area. The endemic
regions are the tropical and subtropical forests, particularly those of Brazil, Venezuela
and Colombia. Paracoccidioidomycosis has not been proved to occur in any other part
of the world. Cases reported from North America
189
and England
190
had all lived in South or Central America. The fungus is thought to live in the soil
but its exact ecological niche is still unknown. Humans are the only known naturally
infected animal host. Person-to-person transmission is of little importance in the
epidemiology of the disease, which is thought to be acquired by inhalation.
Mycology
P. brasiliensis is a dimorphic fungus that grows as a mould at ambient temperatures
and as a yeast at 37°C. Infection is acquired by inhalation of conidia produced in
the mycelial phase. The spores that form its tissue form are round or ovoid and vary
in size from 5 to 30 µm. A characteristic feature is that they reproduce by the development
of multiple buds over the surface of the parent cell. The buds have been likened to
the handles of a ship's wheel or Mickey Mouse's ears (Fig. 5.4.35
). The presence of buds distinguishes Paracoccidioides from Coccidioides and their
multiplicity from Blastomyces.
Figure 5.4.35
Paracoccidioides brasiliensis. The larger of the organisms illustrated is forming
multiple buds. Grocott's methenamine silver stain.
(Courtesy of Dr PM Cury, Rio Preto, Brazil.)
Clinicopathological features
Both pulmonary and disseminated forms of the disease are described.
187
After the establishment of a primary complex in the lung and hilar lymph nodes there
may be haematogenous dissemination. Primary infection occurs in childhood and generally
heals spontaneously. The sexes are affected equally in childhood but the development
of the yeasts is inhibited by oestrogens and in adults the disease is largely limited
to male agricultural workers. It is also described in patients with AIDS.
191
Disseminated disease tends to be acute and generalised in children and chronic and
localised in adults. Chronic disseminated disease may take the form of lymphadenopathy,
painful oropharyngeal ulceration or destruction of tissues such as the adrenal glands.
Progressive pulmonary paracoccidioidomycosis is characterised by multiple cavities
that mimic tuberculosis, or by progressive fibrosis of the lower lobes with traction
bronchiectasis and paracicatricial emphysema in a bilaterally symmetrical distribution.
192
The tissue response is generally granulomatous but may be purulent (Fig. 5.4.36
). Calcification is not a prominent feature. The diagnosis is established by recognising
the spores in smears or culture of sputum or pus, or in tissue sections, or by serology.
Biopsy is an excellent diagnostic procedure. The spores are best recognised with silver
stains.
Figure 5.4.36
Paracoccidioidomycosis. There is a giant cell and neutrophil reaction to numerous
spores of Paracoccidioides brasiliensis.
Rare pulmonary mycoses
Fungi responsible for extrinsic allergic alveolitis are listed in Table 6.1.4 (p.
279) and the occurrence of intracavitary colonies of various fungi is mentioned on
page 231. Allergic bronchopulmonary candidosis, helminthosporiosis, penicilliosis
and curvulariosis, similar to the more familiar allergic aspergillosis, have all been
described on rare occasions.
97
Pulmonary mycoses not dealt with above are rare and ordinarily occur as a result of
lowering of the body's resistance by other diseases or their treatment.
193
Some examples are dealt with below. Others include infection by the common saprophytic
mould Geotrichum candidum, Trichosporon cutaneum, the organism of white piedra (tinea
alba),194, 195
Chaetomium globosum,
65
Paecilomyces lilacinus,
196
Dactylaria gallopava
197
and Ochroconis galloparvum.
198
Chromomycosis (caused by species of Phialophora or Cladosporium) and rhinosporidiosis
(caused by Rhinosporidium seeberi) are very occasionally found as infections of the
lungs; in most cases such infection has spread, by the airways or in the blood, from
a site elsewhere in the body.
Torulopsosis
Torulopsis glabrata, also known as Candida glabrata, is a common yeast on the body
surface, and is frequently isolated as a contaminant of urine cultures. Human infection
is usually opportunistic, taking the form of pneumonia, septicaemia, pyelonephritis
or endocarditis in debilitated or immunocompromised patients, particularly those with
AIDS or advanced cancer or being treated with wide-spectrum antibiotics.199, 200 Pulmonary
infection is often by aspiration. Unlike Candida albicans it does not form hyphae.
Its cells are nearly invisible in haematoxylin and eosin sections but are easily seen
in Grocott preparations. They are difficult to distinguish from those of Histoplasma
capsulatum but are rounded rather than ovoid.
Sporotrichosis
Sporotrichosis is usually seen as an indurated ulcer of the finger acquired from the
prick of a thorn. Pulmonary involvement is rare and when present is generally secondary
to disseminated lymphocutaneous sporotrichosis. Primary pulmonary sporotrichosis (involvement
of the lung in the absence of cutaneous disease) is distinctly unusual.201, 202, 203
However, because it mimics tuberculosis, its incidence may be greater than is generally
recognised. The causative agent, Sporothrix schenckii, is a yeast-like fungus that
occurs worldwide on decaying vegetation, contaminated soil and living plants, especially
roses. Primary pulmonary sporotrichosis is acquired by inhalation of the spores and
usually presents as a chronic, cavitary, bilateral, apical disease, most often in
a clinical setting of alcoholism and chronic obstructive airway disease: less often
it forms a solitary, necrotising, peripheral pulmonary nodule.
202
Fungal stains demonstrate many round or ovoid budding yeast forms, 2–4 µm in size,
in the areas of necrosis. Hyphae bearing sessile budding yeasts are found infrequently.
Adiaspiromycosis204, 205, 206, 207, 208, 209, 210, 211, 212
Adiaspiromycosis is caused by a remarkable fungus, Emmonsia (also known as Chrysosporium),
which is a dimorphic filamentaous soil saprophyte of worldwide distribution. Its principal
species are E. crescens and E. parva. The term ‘adiaspiromycosis’ derives from the
conidia of this fungus, which are quite small but at 37°C exhibit the unique property
of progressive enlargement, perhaps a million-fold in volume, without replication,
when they are known as adiaspores.
The disease is ordinarily limited to wild rodents but has been seen exceptionally
in humans. It is characterised by the formation of tuberculoid granulomas around the
inhaled adiaspores, which are usually solitary. The adiaspores have a prominent yellowish
wall, up to about 8 µm in thickness, surrounding a central mass of amorphous cytoplasm
in which there is a single nucleus. The adiaspores are remarkable for the great size
that they may reach – as much as 600 µm in diameter. They are too large to be effectively
mobilised by the host cells and the granulomatous response usually maintains a bronchiolocentric
distribution indicative of inhalational infection. Dissemination is unusual but is
recorded in AIDS.
210
Diagnosis relies on recognition of the fungus in tissue sections, as serology and
culture are unreliable.
Light infection may result in a solitary adiaspiromycotic granuloma which would only
be found incidentally in an asymptomatic individual. Widespread adiaspiromycotic granulomas
are indicative of heavy infection and patients so affected may complain of fever,
cough and dyspnoea and show a diffuse, micronodular pattern on chest radiographs.
207
Death is very unusual.
208
Healing is by progressive fibrosis and calcification.
Malasseziosis
Malassezia furfur, the causative organism of tinea versicolor (pityriasis versicolor),
is dependent for its growth on high concentrations of fatty acids and is normally
limited to the skin. Systemic infection has however complicated prolonged lipid infusions
through central venous catheters, in which circumstances the small yeast-like organisms
have been noted infiltrating the walls of pulmonary arteries and in small pulmonary
thromboemboli.213, 214 As is so often the case with fungi, identification of the species
depends upon cultural characteristics.
Pseudallescheriosis (monosporiosis)
Pseudallerscheria boydii (syn. Petriellidium boydii, Allescheria boydii) is a fungus
of worldwide distribution in soils, and is of low pathogenicity. It is the commonest
cause of mycetoma in Europe and North America, gaining access to the subcutaneous
tissues through cuts and abrasions in the skin. Pulmonary involvement may occur through
the inhalation of airborne spores, taking the form of an intracavitary fungal ball,
comparable to an aspergilloma, or in conditions such as leukaemia it may be invasive
and disseminate widely.104, 215, 216, 217, 218 Allergic bronchopulmonary pseudallescheriosis
is also described.
96
Pseudallerscheria boydii usually grows in hyphal form within the body but within air-filled
cavities conidia may develop. The conidial state is known as Monosporium (syn. Scedosporium)
apiospermum and infection showing such growth may be termed monosporiosis. The hyphae
are slender, thin-walled and of fairly constant diameter with numerous septa and branching
points. The hyphae are slightly indented at the septa. They are more slender and their
branches less clearly dichotomous than those of aspergilli but the differences are
insufficient to discriminate between them with confidence morphologically. This requires
immunohistochemistry.
66
The distinction of these two fungi is important because their drug sensitivities differ.
217
Penicillium marneffei infection
Penicillium marneffei is a dimorphic fungus endemic in South-east Asia.
219
At room temperature it grows as a mould with red to black conidia whereas in tissue
it forms a 3–5-µm yeast-like cell that divides by binary fission. The yeasts therefore
display clear central septation, unlike H. capsulatum and other fungi that divide
by budding. Infection, which is highest after the rainy season, is by inhalation but
the pulmonary changes are usually overshadowed by systemic features such as hepatosplenomegaly,
skin lesions and bone marrow involvement. However, there may be diffuse infiltration,
mass lesions or cavities in the lungs. While it can affect the immunocompetent, infection
is mainly associated with AIDS, for which it is a clinical marker in the endemic areas.
220
Microsporidiosis
Microsporidia, once thought to be protozoa, are now regarded as extremely reduced
fungi. They are obligate intracellular parasites that infect many animals and have
emerged as important opportunistic pathogens in AIDS.221, 222 They are also being
increasingly recognised in HIV-negative individuals.
223
Four microsporidian genera, Enterocytozoon, Encephalitozoon, Pleistophora and Nosema,
have been reported to infect humans. Infection generally involves the gastrointestinal
tract but may become generalised.223, 224 Pulmonary involvement is unusual but heavy
infestation of the tracheobronchial mucosa is recorded.225, 226, 227, 228, 229 The
infected respiratory epithelium may show focal proliferation with little inflammation
or there may be a lymphocytic infiltrate of the airway epithelium similar to that
seen in the bowel; heavy infestations cause sloughing and ulceration of the tracheobronchial
mucosa and severe subacute inflammation. In haematoxylin and eosin-stained sections
the parasite appears as a supranuclear ‘blue body’ but the staining is weak and it
is easily overlooked, even when infestation is heavy. It is ovoid or spherical, and
measures approximately 2 µm in length, and is Gram-positive. Microsporidia differ
from cryptosporidia, which attach to the outer surface of infected epithelial cells,
in being obligate intracellular parasites. Immunocytochemistry, electron microscopy
and in situ hybridisation are useful for confirming the diagnosis.
230
Antiretroviral therapy has been shown to improve gastrointestinal symptoms, presumably
through restoring immunity,
231
and albendazole has also been effective in some patients.
References
Pneumocystosis
1
Watts
JC
Chandler
FW
Evolving concepts of infection by Pneumocystis carinii
Pathol Annu
26
1991
93
138
1707512
2
Miller
R
Huang
L
Pneumocystis jirovecii infection
Thorax
59
2004
731
733
15333844
3
Dutz
W
Jennings-Khodadad
E
Post
C
Marasmus and Pneumocystis carinii pneumonia in institutionalised infants. Observations
during an endemic
Z Kinderheilk
117
1974
241
258
4213237
4
Vanek
J
Jivorec
O
Luckes
J
Interstitial plasma cell pneumonia in infants
Ann Pediatr
180
1953
1
21
5
Lunseth
JH
Kirmse
TW
Prezyna
AP
Interstitial plasma cell pneumonia
J Pediatr
46
1955
137
145
13234007
6
Haque
A
Plattner
SB
Cook
RT
Pneumocystis carinii. Taxonomy as viewed by electron microscopy
Am J Clin Pathol
87
1987
504
510
3493682
7
Edman
JC
Kovacs
JA
Masur
H
Ribosomal RNA sequence shows Pneumocystis carinii to be a member of the fungi
Nature
334
1988
519
522
2970013
8
Sidhu
GS
Cassa
ND
Pei
ZH
Pneumocystis carinii: An update
Ultrastruct Pathol
27
2003
115
122
12746203
9
Ham
EK
Greenberg
SD
Reynolds
RC
Ultrastructure of Pneumocystis carinii
Exp Mol Pathol
14
1971
362
372
5316979
10
Campbell
WG
Ultrastructure of Pneumocystis in human lung
Arch Pathol
93
1972
312
324
4536969
11
Sueishi
K
Hisano
S
Sumiyoshi
A
Scanning and transmission electron microscopic study of human pulmonary pneumocystosis
Chest
72
1977
213
216
301812
12
Corrin
B
Dewar
A
Respiratory diseases
Papadimitriou
JM
Henderson
DW
Spagnolo
DV
Diagnostic Ultrastructure of Non-Neoplastic Diseases
1992
Churchill Livingstone
Edinburgh
264
286
13
Lanken
PN
Minda
M
Pietra
GG
Alveolar response to experimental Pneumocystis carinii pneumonia in the rat
Am J Pathol
99
1980
561
588
6966893
14
Yoneda
K
Walzer
PD
Mechanism of pulmonary alveolar injury in experimental Pneumocystis carinii pneumonia
in the rat
Br J Exp Pathol
62
1981
339
346
6975112
15
Coker
RJ
Clark
D
Claydon
EL
Disseminated Pneumocystis carinii infection in AIDS
J Clin Pathol
44
1991
820
823
1960214
16
Gryzan
S
Paradis
IL
Zeevi
A
Unexpectedly high incidence of Pneumocystis carinii infection after heart–lung transplantation.
Implications for lung defense and allograft survival
Am Rev Respir Dis
137
1988
1268
1274
3144196
17
Varthalitis
I
Aoun
M
Daneau
D
Pneumocystis carinii pneumonia in patients with cancer – an increasing incidence
Cancer
71
1993
481
485
8422642
18
Pifer
LL
Hughes
WT
Stagno
S
Pneumocystis carinii infection: evidence for high prevalence in normal and immunosuppressed
children
Pediatrics
61
1978
35
41
400818
19
Peters
SE
Wakefield
AE
Sinclair
K
A search for latent Pneumocystis carinii infection in post-mortem lungs by DNA amplification
J Pathol
166
1991
195
198
20
Miller
RF
Mitchell
DM
AIDS and the lung – Update 1992 .1. Pneumocystis carinii pneumonia
Thorax
47
1992
305
314
1585297
21
Young
JA
Stone
JW
McGonigle
RJS
Diagnosing Pneumocystis carinii pneumonia by cytological examination of bronchoalveolar
lavage fluid: report of 15 cases
J Clin Pathol
39
1986
945
949
2428843
22
Elvin
KM
Bjorkman
A
Linder
E
Pneumocystis carinii pneumonia: detection of parasites in sputum and bronchoalveolar
lavage fluid by monoclonal antibodies
BMJ
297
1988
381
384
3044514
23
Wakefield
AE
Pixley
FJ
Banerji
S
Detection of Pneumocystis carinii with DNA amplification
Lancet
336
1990
451
453
1974987
24
Lipschik
GY
Gill
VJ
Lundgren
JD
Improved diagnosis of Pneumocystis carinii infection by polymerase chain reaction
on induced sputum and blood
Lancet
340
1992
203
206
1353136
25
Leigh
TR
Gazzard
BG
Rowbottom
A
Quantitative and qualitative comparison of DNA amplification by PCR with immunofluorescence
staining for diagnosis of Pneumocystis carinii pneumonia
J Clin Pathol
46
1993
140
144
8459034
26
Wakefield
AE
Miller
RF
Guiver
LA
Granulomatous Pneumocystis carinii pneumonia: DNA amplification studies on bronchoscopic
alveolar lavage samples
J Clin Pathol
47
1994
664
666
8089227
27
Eisen
D
Ross
BC
Fairbairn
J
Comparison of Pneumocystis carinii detection by toluidine blue O staining, direct
immunofluorescence and DNA amplification in sputum specimens from HIV positive patients
Pathology
26
1994
198
200
7522318
28
Armbuster
CH
Pokieser
L
Hassl
A
Diagnosis of Pneumocystis carinii pneumonia by bronchoalveolar lavage in AIDS patients.
Comparison of Diff-Quik, Fungifluor stain, direct immunofluorescence test and polymerase
chain reaction
Acta Cytol
39
1995
1089
1093
7483981
29
Barrio
JL
Suarez
M
Rodriguez
JL
Pneumocystis carinii pneumonia presenting as cavitating and noncavitating solitary
pulmonary nodules in patients with the acquired immunodeficiency syndrome
Am Rev Respir Dis
134
1986
1094
1096
3490810
30
Liu
YC
Tomashefski
JF
Tomford
JW
Necrotizing Pneumocystis carinii vasculitis associated with lung necrosis and cavitation
in a patient with acquired immunodeficiency syndrome
Arch Pathol Lab Med
113
1989
494
497
2785375
31
Watts
JC
Chandler
FW
Pneumocystis carinii pneumonitis. The nature and diagnostic significance of the methenamine
silver-positive ‘intracystic bodies’
Am J Surg Pathol
9
1985
744
751
2415010
32
Mahan
CT
Sale
GE
Rapid methenamine silver stain for Pneumocystis and fungi
Arch Pathol
102
1978
351
352
33
Musto
L
Flanigan
M
Elbadawi
A
Ten-minute silver stain for Pneumocystis carinii and fungi in tissue sections
Arch Pathol
106
1982
292
294
34
Shimono
LH
Hartman
B
A simple and reliable rapid methenamine silver stain for Pneumocystis carinii and
fungi
Arch Pathol Lab Med
110
1986
855
856
3489450
35
Kim
H-K
Hughes
WT
Comparison of methods for identification of Pneumocystis carinii in pulmonary aspirates
Am J Clin Pathol
60
1973
462
466
4126522
36
Cameron
RB
Watts
JC
Kasten
BL
Pneumocystis carinii pneumonia: an approach to rapid laboratory diagnosis
Am J Clin Pathol
72
1979
90
93
88179
37
Amin
MB
Mezger
E
Zarbo
RJ
Detection of Pneumocystis carinii – comparative study of monoclonal antibody and silver
staining
Am J Clin Pathol
98
1992
13
18
1615917
38
Kobayashi
M
Urata
T
Ikezoe
T
Simple detection of the 5S ribosomal RNA of Pneumocystis carinii using in situ hybridisation
J Clin Pathol
49
1996
712
716
9038753
39
LeGolvan
DP
Heidelberger
KP
Disseminated, granulomatous Pneumocystis carinii pneumonia
Arch Pathol
95
1973
344–318
40
Weber
WR
Askin
FB
Dehner
LP
Lung biopsy in Pneumocystis carinii pneumonia. A histopathologic study of typical
and atypical features
Am J Clin Pathol
67
1977
11
19
64112
41
Askin
FB
Katzenstein
AA
Pneumocystis infection masquerading as diffuse alveolar damage. A potential source
of diagnostic error
Chest
79
1981
420
422
6164519
42
Cupples
JB
Blackie
SP
Road
JD
Granulomatous Pneumocystis carinii pneumonia mimicking tuberculosis
Arch Pathol Lab Med
113
1989
1281
1284
2684091
43
Travis
WD
Pittaluga
S
Lipschik
GY
Atypical pathologic manifestations of Pneumocystis carinii pneumonia in the acquired
immune deficiency syndrome. Review of 123 lung biopsies from 76 patients with emphasis
on cysts, vascular invasion, vasculitis, and granulomas
Am J Surg Pathol
14
1990
615
624
2192568
44
Birley
HDL
Buscombe
JR
Griffiths
MH
Granulomatous Pneumocystis carinii pneumonia in a patient with the acquired immunodeficiency
syndrome
Thorax
45
1990
769
771
2247869
45
Lee
MM
Schinella
RA
Pulmonary calcification caused by Pneumocystis carinii pneumonia – a clinicopathological
study of 13 cases in acquired immune deficiency syndrome patients
Am J Surg Pathol
15
1991
376
380
2006717
46
Foley
NM
Griffiths
MH
Miller
RF
Histologically atypical Pneumocystis carinii pneumonia
Thorax
48
1993
996
1001
8256247
47
Blumenfeld
W
Basgoz
N
Owen
WF
Granulomatous pulmonary lesions in patients with the acquired immunodeficiency syndrome
(AIDS) and Pneumocystis carinii infection
Ann Intern Med
109
1988
505
507
3261957
48
Nash
G
Said
JW
Nash
SV
The pathology of AIDS – bronchiectasis, pulmonary fibrosis with honeycombing, necrotizing
bacterial pneumonia, invasive fungal infection consistent with aspergillosis, cytomegalovirus
pneumonia, and healed pneumocystis pneumonia with pulmonary calcification
Mod Pathol
8
1995
203
205
49
Travis
WD
Fox
CH
Devaney
KO
Lymphoid pneumonitis in 50 adult patients infected with the human immunodeficiency
virus – lymphocytic interstitial pneumonitis versus nonspecific interstitial pneumonitis
Hum Pathol
23
1992
529
541
1314778
50
Moran
CA
Suster
S
Pavlova
Z
The spectrum of pathological changes in the lung in children with the acquired immunodeficiency
syndrome: an autopsy study of 36 cases
Hum Pathol
25
1994
877
882
8088762
51
Saldana
MJ
Mones
JM
Pulmonary pathology in AIDS: atypical Pneumocystis carinii infection and lymphoid
interstitial pneumonia
Thorax
49
1994
S46
S55
7974327
52
Mariuz
P
Raviglione
MC
Gould
IA
Pleural Pneumocystis carinii infection
Chest
99
1991
774
776
1995246
53
Murry
CE
Schmidt
RA
Tissue invasion by Pneumocystis carinii – a possible cause of cavitary pneumonia and
pneumothorax
Hum Pathol
23
1992
1380
1387
1468775
54
Ferre
C
Baguena
F
Podzamczer
D
Lung cavitation associated with Pneumocystis carinii infection in the acquired immunodeficiency
syndrome – a report of six cases and review of the literature
Eur Respir J
7
1994
134
139
8143812
55
Lazard
T
Guidet
B
Meynard
JL
Generalized air cysts complicated by fatal bilateral pneumothoraces in a patient with
AIDS-related Pneumocystis carinii pneumonia
Chest
106
1994
1271
1272
7924511
56
Light
RW
Hamm
H
Pleural disease and acquired immune deficiency syndrome
Eur Resp J
10
1997
2638
2643
57
Grimes
MM
LaPook
JD
Bar
MH
Disseminated Pneumocystis carinii infection in a patient with acquired immunodeficiency
syndrome
Hum Pathol
18
1987
307
308
3493199
58
Ragni
MV
Dekker
A
Derubertis
FR
Pneumocystis carinii infection presenting as necrotizing thyroiditis and hypothyroidism
Am J Clin Pathol
95
1991
489
493
2014774
59
Matsuda
S
Urata
Y
Shiota
T
Disseminated infection of Pneumocystis carinii in a patient with the acquired immunodeficiency
syndrome
Virchows Arch A Pathol Anat Histopathol
414
1989
523
527
2499110
60
Deroux
SJ
Adsay
NV
Ioachim
HL
Disseminated pneumocystosis without pulmonary involvement during prophylactic aerosolized
pentamidine therapy in a patient with the acquired immunodeficiency syndrome
Arch Pathol Lab Med
115
1991
1137
1140
1747032
61
Fishman
JA
Mattia
AR
Lee
MJ
A 29-year-old man with AIDS and multiple splenic abscesses – disseminated Pneumocystis
carinii infection and Mycobacterium avium complex infection involving the spleen and
liver
N Engl J Med
332
1995
249
257
7808492
62
Shelburne
SA
III
Hamill
RJ
The immune reconstitution inflammatory syndrome
AIDS Rev
5
2003
67
79
12876896
63
Wang
N-S
Huang
S-N
Thurlbeck
WM
Combined Pneumocystis carinii and cytomegalovirus infection
Arch Pathol
90
1970
529
535
4320869
Aspergillosis
64
Verweij
PE
Smedts
F
Poot
T
Immunoperoxidase staining for identification of Aspergillus species in routinely processed
tissue sections
J Clin Pathol
49
1996
798
801
8943743
65
Yeghen
T
Fenelon
L
Campbell
CK
Chaetomium pneumonia in a patient with acute myeloid leukaemia
J Clin Pathol
49
1996
184
186
8655695
66
Jensen
HE
Salonen
J
Ekfors
TO
The use of immunohistochemistry to improve sensitivity and specificity in the diagnosis
of systemic mycoses in patients with haematological malignancies
J Pathol
181
1997
100
105
9072010
67
Bialek
R
Konrad
F
Kern
J
PCR based identification and discrimination of agents of mucormycosis and aspergillosis
in paraffin wax embedded tissue
J Clin Pathol
58
2005
1180
1184
16254108
68
Nime
FA
Hutchins
GM
Oxalosis caused by Aspergillus infection
Johns Hopkins Med J
133
1973
183
194
4200601
69
Roehrl
M
Croft
W
Liao
Q
Hemorrhagic pulmonary oxalosis secondary to a noninvasive Aspergillus niger fungus
ball
Virchows Archiv
451
2007
1067
1073
17786471
70
Bryan
RL
Hubscher
SG
Aspergillosis associated with calcinosis and hypocalcaemia following liver transplantation
J Pathol
155
1988
353A
71
Ghio
AJ
Peterseim
DS
Roggli
VL
Pulmonary oxalate deposition associated with Aspergillus niger infection – an oxidant
hypothesis of toxicity
Am Rev Respir Dis
145
1992
1499
1502
1596026
72
Lee
SH
Barnes
WG
Schaetzel
WP
Pulmonary aspergillosis and the importance of oxalate crystal recognition in cytology
specimens
Arch Pathol Lab Med
110
1986
1176
1179
3778147
73
Benoit
G
de Chauvin
MF
Cordonnier
C
Oxalic acid level in bronchoalveolar lavage fluid from patients with invasive pulmonary
aspergillosis
Am Rev Respir Dis
132
1985
748
751
4051310
74
Nakajima
M
Niki
Y
Manabe
T
False-positive antineutrophil cytoplasmic antibody in aspergillosis with oxalosis
Arch Pathol Lab Med
120
1996
425
426
75
Proia
AD
Brinn
NT
Identification of calcium oxalate crystals using alizarin red S stain
Arch Pathol Lab Med
109
1985
186
189
2579619
76
Kurrein
F
Green
GH
Rowles
SL
Localized deposition of calcium oxalate around a pulmonary Aspergillus niger fungus
ball
Am J Clin Pathol
64
1975
556
563
1199978
77
Soubani
AO
Chandrasekar
PH
The clinical spectrum of pulmonary aspergillosis
Chest
121
2002
1988
1999
12065367
78
Kradin
RL
Mark
EJ
The pathology of pulmonary disorders due to Aspergillus spp
Arch Pathol Lab Med
132
2008
606
614
18384212
79
Barth
PJ
Rossberg
C
Koch
S
Pulmonary aspergillosis in an unselected autopsy series
Pathol Res Pract
196
2000
73
80
10707362
80
Makker
H
McConnochie
K
Gibbs
AR
Postirradiation pulmonary fibrosis complicated by aspergilloma and bronchocentric
granulomatosis
Thorax
44
1989
676
677
2678580
81
Ein
ME
Wallace
RJ
Jr
Williams
TW
Jr
Allergic bronchopulmonary aspergillosis-like syndrome consequent to aspergilloma
Am Rev Respir Dis
119
1979
811
820
378049
82
McCarthy
DS
Pepys
J
Allergic bronchopulmonary aspergillosis. Clinical immunology: (1) Clinical features
Clin Allergy
1
1971
261
286
83
Reich
JM
Pneumothorax due to pleural perforation of a pseudocavity containing aspergillomas
in a patient with allergic bronchopulmonary aspergillosis
Chest
102
1992
652
653
84
Hinson
KFW
Moon
AJ
Plummer
NS
Broncho-pulmonary aspergillosis: a review and report of eight cases
Thorax
7
1952
317
333
13015523
85
Sanerkin
NG
Seal
RME
Leopold
JG
Plastic bronchitis, mucoid impaction of the bronchi and allergic broncho-pulmonary
aspergillosis, and their relationship to bronchial asthma
Ann Allergy
24
1966
586
594
5923425
86
Bosken
CH
Myers
JL
Greenberger
PA
Pathologic features of allergic bronchopulmonary aspergillosis
Am J Surg Pathol
12
1988
216
222
3344888
87
Zander
DS
Allergic bronchopulmonary aspergillosis: an overview
Arch Pathol Lab Med
129
2005
924
928
15974818
88
Nelson
LA
Callerame
ML
Schwartz
RH
Aspergillosis and atopy in cystic fibrosis
Am Rev Respir Dis
120
1979
863
873
507513
89
Aubry
MC
Fraser
R
The role of bronchial biopsy and washing in the diagnosis of allergic bronchopulmonary
aspergillosis
Modern Pathol
11
1998
607
611
90
Jelihovsky
T
The structure of bronchial plugs in mucoid impaction, bronchocentric granulomatosis
and asthma
Histopathology
7
1983
153
167
6852779
91
Benatar
S
Allan
B
Hewitson
R
Allergic broncho-pulmonary stemphyliosis
Thorax
35
1980
515
518
7192017
92
Glancy
JJ
Elder
JL
McAleer
R
Allergic bronchopulmonary fungal disease without clinical asthma
Thorax
36
1981
345
349
7314002
93
McAleer
R
Kroenert
D
Elder
J
Allergic bronchopulmonary disease caused by Curvularia lunata and Drechslera hawaiiensis
Thorax
36
1981
338
344
7314001
94
Halwig
JM
Brueske
DA
Greenberger
PA
Allergic bronchopulmonary curvulariosis
Am Rev Respir Dis
132
1985
186
189
4040344
95
Backman
KS
Roberts
M
Patterson
R
Allergic bronchopulmonary mycosis caused by Fusarium vasinfectum
Am J Respir Crit Care Med
152
1995
1379
1381
7551398
96
Miller
MA
Greenberger
PA
Amerian
R
Allergic bronchopulmonary mycosis caused by Pseudallescheria boydii
Am Rev Respir Dis
148
1993
810
812
8368653
97
Travis
WD
Kwonchung
KJ
Kleiner
DE
Unusual aspects of allergic bronchopulmonary fungal disease – report of two cases
due to Curvularia organisms associated with allergic fungal sinusitis
Hum Pathol
22
1991
1240
1248
1748430
98
Buchanan
DR
Lamb
D
Saprophytic invasion of infarcted pulmonary tissue by Aspergillus species
Thorax
37
1982
693
698
6760449
99
Smith
FB
Beneck
D
Localized Aspergillus infestation in primary lung carcinoma – clinical and pathological
contrasts with post-tuberculous intracavitary aspergilloma
Chest
100
1991
554
556
1864137
100
Mehrad
B
Paciocco
G
Martinez
FJ
Spectrum of aspergillus infection in lung transplant recipients – Case series and
review of the literature
Chest
119
2001
169
175
11157600
101
Nunley
DR
Gal
AA
Vega
JD
Saprophytic fungal infections and complications involving the bronchial anastomosis
following human lung transplantation
Chest
122
2002
1185
1191
12377840
102
British Thoracic and Tuberculosis Association
Aspergilloma and residual tuberculous cavities – the results of a resurvey
Tubercle
51
1970
227
245
5495645
103
McGregor
DH
Papasian
CJ
Pierce
PD
Aspergilloma within cavitating pulmonary adenocarcinoma
Am J Clin Pathol
91
1989
100
103
2642636
104
McCarthy
DS
Longbottom
JL
Riddell
RW
Pulmonary mycetoma due to Allescheria boydii
Am Rev Respir Dis
100
1969
213
216
4979745
105
Kwon-Chung
KJ
Schwartz
IS
Rybak
BJ
A pulmonary fungus ball produced by Cladosporium cladosporioides
Am J Clin Pathol
64
1975
564
568
1239189
106
Kirkpatrick
MB
Pollock
HM
Wimberley
NE
An intracavitary fungus ball composed of Syncephalastrum
Am Rev Respir Dis
120
1979
943
947
574368
107
Iadarola
P
Lungarella
G
Martorana
PA
Lung injury and degradation of extracellular matrix components by Aspergillus fumigatus
serine proteinase
Exp Lung Res
24
1998
233
251
9635248
108
Awe
RJ
Greenberg
SD
Mattox
KL
The source of bleeding in plumonary aspergillomas
Texas Medicine
80
1984
58
61
109
Denning
DW
Follansbee
SE
Scolaro
M
Pulmonary aspergillosis in the acquired immunodeficiency syndrome
N Engl J Med
324
1991
654
662
1994248
110
Hummel
M
Schuler
S
Hempel
S
Obstructive bronchial aspergillosis after heart transplantation
Mycoses
36
1993
425
428
7935576
111
Williams
AJ
Zardawi
I
Walls
J
Disseminated aspergillosis in high dose steroid therapy
Lancet
i
1983
1222
112
Lake
KB
Browne
PM
Van Dyke
JJ
Fatal disseminated aspergillosis in an asthmatic patient treated with corticosteroids
Chest
83
1983
138
139
6848318
113
Karam
GH
Griffin
FM
Invasive pulmonary aspergillosis in non immunocomprised non neutropenic hosts
Rev Infect Dis
8
1986
357
363
3726394
114
Gerson
SL
Talbot
GH
Hurwitz
S
Prolonged granulocytopenia: the major risk factor for invasive pulmonary aspergillosis
in patients with acute leukemia
Ann Intern Med
100
1984
345
351
6696356
115
Vaideeswar
P
Prasad
S
Deshpande
JR
Invasive pulmonary aspergillosis: A study of 39 cases at autopsy
J Postgrad Med
50
2004
21
26
15047994
116
Variwalla
AG
Smith
AP
Melville-Jones
G
Necrotising aspergillosis complicating fulminating viral pneumonia
Thorax
35
1980
215
216
6992331
117
Lewis
M
Kallenbach
J
Ruff
P
Zaltzman
M
Invasive pulmonary aspergillosis complicating influenza A pneumonia in a previously
healthy patient
Chest
87
1985
691
693
3872776
Rello
J
Esandi
ME
Mariscal
D
Gallego
M
Domingo
C
Valles
J
Invasive pulmonary aspergillosis in patients with chronic obstructive pulmonary disease:
report of eight cases and review
Clin Infect Dis
256
1998
1473
1475
118
Ali
ZA
Ali
AA
Tempest
ME
Invasive pulmonary aspergillosis complicating chronic obstructive pulmonary disease
in an immunocompetent patient
J Postgrad Med
49
2003
78
80
12865577
119
Marchevsky
A
Rosen
MJ
Chrystal
G
Pulmonary complications of the acquired immunodeficiency syndrome: a clinicopathologic
study of 70 cases
Hum Pathol
16
1985
659
670
3874142
120
Nash
G
Irvine
R
Kerschmann
RL
Pulmonary aspergillosis in acquired immune deficiency syndrome: Autopsy study of an
emerging pulmonary complication of human immunodeficiency virus infection
Hum Pathol
28
1997
1268
1275
9385932
121
Mylonakis
E
Barlam
TF
Flanigan
T
Pulmonary aspergillosis and invasive disease in AIDS: Review of 342 cases
Chest
114
1998
251
262
9674477
122
Klapholz
A
Salomon
N
Perlman
DC
Aspergillosis in the acquired immunodeficiency syndrome
Chest
100
1991
1614
1618
1959405
123
Miller
WT
Sais
GJ
Frank
I
Pulmonary aspergillosis in patients with AIDS – clinical and radiographic correlations
Chest
105
1994
37
44
8275779
124
Cornet
M
Mallat
H
Somme
D
Fulminant invasive pulmonary aspergillosis in immunocompetent patients – a two-case
report
Clin Microbiol Infect
9
2003
1224
1227
14686988
125
Stergiopoulou
T
Meletiadis
J
Roilides
E
Host-dependent patterns of tissue injury in invasive pulmonary aspergillosis
Am J Clin Pathol
127
2007
349
355
17276936
126
Gefter
W
Weingrad
T
Ochs
RH
‘Semi-invasive’ pulmonary aspergillosis. A new look at the spectrum of Aspergillus
infections of the lung
Radiology
140
1981
313
321
7255704
127
Binder
RE
Faling
LJ
Pugatch
RD
Chronic necrotizing pulmonary aspergillosis: a discrete clinical entity
Medicine (Baltimore)
61
1982
109
124
7038373
128
Slevin
ML
Knowles
GK
Phillips
MJ
The air crescent sign of invasive pulmonary aspergillosis in acute leukaemia
Thorax
37
1982
554
555
7135303
129
Kibbler
CC
Milkins
SR
Bhamra
A
Apparent pulmonary mycetoma following invasive aspergillosis in neutropenic patients
Thorax
43
1988
108
112
3281310
130
Wiggins
J
Clark
TJH
Corrin
B
Chronic necrotising pneumonia caused by Aspergillus niger
Thorax
44
1989
440
441
2763249
131
Yamaguchi
M
Nishiya
H
Mano
K
Chronic necrotising pulmonary aspergillosis caused by Aspergillus niger in a mildly
immunocompromised host
Thorax
47
1992
570
571
1412104
132
Yousem
SA
The histological spectrum of chronic necrotizing forms of pulmonary aspergillosis
Hum Pathol
28
1997
650
656
9190998
133
Kradin
RL
Drucker
EA
Malhotra
A
An 83-year-old woman with long-standing asthma and rapidly progressing pneumonia –
Chronic necrotizing pulmonary aspergillosis (Aspergillus fumigatus), with elements
of bronchocentric granulomatosis
N Engl J Med
339
1998
1228
1236
9786749
134
Hiltermann
TJ
Bredius
RG
Gesink-vd Veer
BJ
Bilateral cavitary pulmonary consolidations in a patient undergoing allogeneic bone
marrow transplantation for acute leukemia
Chest
123
2003
929
934
12628896
135
Pervez
NK
Kleinerman
J
Kattan
M
Pseudomembranous necrotizing bronchial aspergillosis. A variant of invasive aspergillosis
in a patient with haemophilia and acquired immune deficiency syndrome
Am Rev Respir Dis
131
1985
961
963
4003949
136
Hines
DW
Haber
MH
Yaremko
L
Pseudomembranous-tracheobronchitis caused by Aspergillus
Am Rev Respir Dis
143
1991
1408
1411
2048829
137
Niimi
T
Kajita
M
Saito
H
Necrotizing bronchial aspergillosis in a patient receiving neoadjuvant chemotherapy
for non-small-cell lung carcinoma
Chest
100
1991
277
279
1647938
138
Kramer
MR
Denning
DW
Marshall
SE
Ulcerative tracheobronchitis after lung transplantation – a new form of invasive aspergillosis
Am Rev Respir Dis
144
1991
552
556
1654038
139
Tait
RC
O'Driscoll
BR
Denning
DW
Unilateral wheeze caused by pseudomembranous Aspergillus tracheobronchitis in the
immunocompromised patient
Thorax
48
1993
1285
1287
8303643
140
Nicholson
AG
Sim
KM
Keogh
BF
Pseudomembranous necrotising bronchial aspergillosis complicating chronic airways
limitation
Thorax
50
1995
807
808
7570422
141
Tron
V
Churg
A
Chronic necrotizing pulmonary aspergillosis mimicking bronchocentric granulomatosis
Pathol Res Pract
181
1986
621
626
3786254
142
Tazelaar
HD
Baird
AM
Mill
M
Bronchocentric mycosis occurring in transplant recipients
Chest
96
1989
92
95
2661162
Mucormycosis
143
Brown
RB
Lau
SK
Gonzalez
RG
A 59-year-old diabetic man with unilateral visual loss and oculomotor-nerve palsy
– Invasive fungal sinusitis and osteomyelitis due to mucormycosis. (Diabetes mellitus.)
N Engl J Med
344
2001
286
293
11172157
144
Frater
JL
Hall
GS
Procop
GW
Histologic features of zygomycosis – Emphasis on perineural invasion and fungal morphology
Arch Pathol Lab Med
125
2001
375
378
11231486
145
Matsushima
T
Soejima
R
Nakashima
T
Solitary pulmonary nodule caused by phycomycosis in a patient without obvious predisposing
factors
Thorax
35
1980
877
878
7221986
146
Murray
HW
Pulmonary mucormycosis: one hundred years later
Chest
72
1977
1
3
872637
147
Bigby
TD
Serota
ML
Tierney
LM
Clinical spectrum of pulmonary mucormycosis
Chest
89
1986
435
439
3081299
148
Harada
M
Manabe
T
Yamashita
K
Pulmonary mucormycosis with fatal massive hemoptysis
Acta Pathol Jpn
42
1992
49
55
1557988
149
Rassaei
N
Shilo
K
Lewin-Smith
MR
Deposition of calcium salts in a case of pulmonary zygomycosis: histopathologic and
chemical findings
Human Pathology
40
2009
1353
1357
19454361
Candidosis (moniliasis)
150
Hopfer
RL
Fainstein
V
Luna
MP
Disseminated candidiasis caused by four different Candida species
Arch Pathol Lab Med
105
1981
454
455
6895015
151
Knox
WF
Hooton
VN
Barson
AJ
Pulmonary vascular candidiasis and use of central venous catheters in neonates
J Clin Pathol
40
1987
559
565
3584509
152
O'Driscoll
BRC
Cooke
RDP
Mamtora
H
Candida lung abscesses complicating parenteral nutrition
Thorax
43
1988
418
419
3143161
Cryptococcosis
153
Campbell
GD
Primary pulmonary cryptococcosis
Am Rev Respir Dis
94
1965
236
243
154
Torda
A
Kumar
RK
Jones
PD
The pathology of human and murine pulmonary infection with Cryptococcus neoformans
var. gattii
Pathology
33
2001
475
478
11827415
155
Douketis
JD
Kesten
S
Miliary pulmonary cryptococcosis in a patient with the acquired immunodeficiency syndrome
Thorax
48
1993
402
403
8511742
156
Nash
G
Said
JW
Nash
SV
Degirolami
U
The pathology of AIDS – pulmonary cryptococcosis
Mod Pathol
8
1995
202
203
157
Sing
Y
Ramdial
PK
Cryptococcal inflammatory pseudotumors
Am J Surg Pathol
31
2007
1521
1527
17895752
158
Harding
SA
Scheld
WM
Feldman
PS
Pulmonary infection with capsule-deficient Cryptococcus neoformans
Virchows Arch A Pathol Anat Histopathol
382
1979
113
118
159
Lazcano
O
Speights
VO
Strickler
JG
Combined histochemical stains in the differential diagnosis of Cryptococcus neoformans
Mod Pathol
6
1993
80
84
7678937
160
Levitz
SM
The ecology of Cryptococcus neoformans and the epidemiology of cryptococcosis
Rev Infect Dis
13
1991
1163
1169
1775849
161
Baker
RD
The primary pulmonary lymph node complex of crytptococcosis
Am J Clin Pathol
65
1976
83
92
1246992
162
Haugen
RK
Baker
RD
The pulmonary lesions in cryptococcosis with special reference to subpleural nodules
Am J Clin Pathol
24
1954
1381
1390
13228372
163
McDonnell
JM
Hutchins
GM
Pulmonary cryptococcosis
Hum Pathol
16
1985
121
128
3972394
Histoplasmosis
164
Weydert
JA
Van Natta
TL
Deyoung
BR
Comparison of fungal culture versus surgical pathology examination in the detection
of Histoplasma in surgically excised pulmonary granulomas
Arch Pathol Lab Med
131
2007
780
783
17488166
165
Symmers
WStC
Histoplasmosis contracted in Britain: a case of histoplasmic lymphadenitis following
clinical recovery from sarcoidosis
BMJ
2
1956
786
789
13364326
166
Goodwin
RA
Loyd
JE
Des Prez
RM
Histoplasmosis in normal hosts
Medicine (Baltimore)
60
1981
231
266
7017339
167
Lehan
PH
Furculow
ML
Epidemic histoplasmosis
J Chronic Dis
5
1957
489
503
13416360
168
Peterson
MW
Pratt
AD
Nugent
KM
Pneumonia due to Histoplasma capsulatum in a bone marrow transplant recipient
Thorax
42
1987
698
699
3317978
169
Sathapatayavongs
B
Batteiger
BE
Wheat
J
Clinical and laboratory features of disseminated histoplasmosis during two large urban
outbreaks
Medicine
62
1983
263
270
6312246
170
Wheat
LJ
Conolly-Stringfield
PA
Baker
RL
Disseminated histoplasmosis in the acquired immune deficiency syndrome: clinical findings,
diagnosis and treatment, and review of the literature
Medicine
69
1990
361
374
2233233
171
Levitz
SM
Mark
EJ
Ko
JP
A 19-year-old man with the acquired immunodeficiency syndrome and persistent fever
– Disseminated histoplasmosis. Acquired immunodeficiency syndrome
N Engl J Med
339
1998
1835
1843
9867564
172
Godwin
RA
Nickell
JA
Des Prez
AM
Mediastinal fibrosis complicating healed primary histoplasmosis and tuberculosis
Medicine
51
1972
227
246
4623262
Coccidioidomycosis
173
Bayer
AS
Fungal pneumonias; pulmonary coccidioidal syndromes (part 1)
Chest
79
1981
575
583
7014124
174
Bayer
AS
Fungal pneumonias: pulmonary coccidioidal syndromes (part 2)
Chest
79
1981
686
691
7226957
175
Feldman
BS
Snyder
LS
Primary pulmonary coccidioidomycosis
Semin Respir Infect
16
2001
231
237
11740823
176
Panackal
AA
Hajjeh
RA
Cetron
MS
Fungal infections among returning travelers
Clin Infect Dis
35
2002
1088
1095
12384843
177
Centers for Disease Control and Preventation
Coccidioidomycosis among persons attending the world championship of model airplane
flying – Kern County, California, October 2001
JAMA
287
2002
312
11817355
178
Kirkland
TN
Fierer
J
Coccidioidomycosis: a reemerging infectious disease
Emerg Infect Dis
2
1996
192
199
8903229
Blastomycosis
179
Sarosi
GA
Davies
SF
Blastomycosis
Am Rev Respir Dis
120
1979
911
938
116580
180
Bradsher
RW
Chapman
SW
Pappas
PG
Blastomycosis
Infect Dis Clin North Am
17
2003
21
40
vii
12751259
181
Taxy
JB
Blastomycosis: contributions of morphology to diagnosis: a surgical pathology, cytopathology,
and autopsy pathology study
Am J Surg Pathol
31
2007
615
623
17414110
182
Lemos
LB
Guo
M
Baliga
M
Blastomycosis: organ involvement and etiologic diagnosis. A review of 123 patients
from Mississippi
Ann Diagn Pathol
4
2000
391
406
11149972
183
Patel
RG
Patel
B
Petrini
MF
Clinical presentation, radiographic findings, and diagnostic methods of pulmonary
blastomycosis: a review of 100 consecutive cases
South Med J
92
1999
289
295
10094269
184
Meyer
KC
McManus
EJ
Maki
DG
Overwhelming pulmonary blastomycosis associated with the adult respiratory distress
syndrome
N Engl J Med
329
1993
1231
1236
8413389
185
Lemos
LB
Baliga
M
Guo
M
Acute respiratory distress syndrome and blastomycosis: presentation of nine cases
and review of the literature
Ann Diagn Pathol
5
2001
1
9
11172200
186
Guccion
JG
Rohatgi
PK
Saini
NB
Disseminated blastomycosis and acquired immunodeficiency syndrome: a case report and
ultrastructural study
Ultrastruct Pathol
20
1996
429
435
8883326
Paracoccidioidomycosis
187
Londero
AT
Ramos
CD
Paracoccidioidomycosis: a clinical and mycologic study of forty-one cases observed
in Santa Maria, RS, Brazil
Am J Med
52
1972
771
775
5030174
188
Bethlem
EP
Capone
D
Maranhao
B
Paracoccidioidomycosis
Curr Opin Pulm Med
5
1999
319
325
10461538
189
Murray
HW
Littman
ML
Roberts
RB
Disseminated paracoccidioidomycosis (South American blastomycosis) in the United States
Am J Med
56
1974
209
220
4590780
190
Bowler
S
Woodcock
A
Da Costa
P
Chronic pulmonary paracoccidioidomycosis masquerading as lymphangitis carcinomatosa
Thorax
41
1986
72
73
3704971
191
Goldani
LZ
Martinez
R
Landell
GAM
Paracoccidioidomycosis in a patient with acquired immunodeficiency syndrome
Mycopathologia
105
1989
71
74
2747786
192
Funari
M
Kavakama
J
Shikanai-Yasuda
MA
Chronic pulmonary paracoccidioidomycosis (South American blastomycosis): high-resolution
CT findings in 41 patients
AJR Am J Roentgenol
173
1999
59
64
10397100
Rare pulmonary mycoses
193
Huang
S-N
Harris
LS
Acute disseminated penicilliosis. Report of a case and review of pertinent literature
Am J Clin Pathol
39
1963
167
174
13955352
194
Saul
SH
Khachatoorian
T
Poorsattar
A
Opportunistic Trichosporon pneumonia
Arch Pathol Lab Med
105
1981
456
459
6895016
195
Ito
T
Ishikawa
Y
Fujii
R
Disseminated Trichosporon capitatum infection in a patient with acute leukaemia
Cancer
61
1988
585
588
3422174
196
Ono
N
Sato
K
Yokomise
H
Lung abscess caused by Paecilomyces lilacinus
Respiration
66
1999
85
87
9973699
197
Mazur
JE
Judson
MA
A case report of a dactylaria fungal infection in a lung transplant patient
Chest
119
2001
651
653
11171754
198
Odell
JA
Alvarez
S
Cvitkovich
DG
Multiple lung abscesses due to Ochroconis gallopavum, a dematiaceous fungus, in a
nonimmunocompromised wood pulp worker
Chest
118
2000
1503
1505
11083712
199
Aisner
J
Schimpff
SC
Sutherland
JC
Torulopsis glabrata infections in patients with cancer. Increasing incidence and relationship
to colonisation
Am J Med
61
1976
23
28
945692
200
Srivastava
S
Kleinman
G
Manthous
CA
Torulopsis pneumonia – a case report and review of the literature
Chest
110
1996
858
861
8797445
201
Beland
JE
Mankiewicz
E
MacIntosh
DJ
Primary pulmonary sporotrichosis
Can Med Assoc J
99
1968
813
816
5681077
202
England
DM
Hochholzer
L
Primary pulmonary sporotrichosis
Am J Surg Pathol
9
1985
193
204
3993831
203
England
DM
Hochholzer
L
Sporothrix infection of the lung without cutaneous disease. Primary pulmonary sporotrichosis
Arch Pathol Lab Med
111
1987
298
300
3827535
204
Watts
JC
Callaway
CS
Chandler
FW
Human pulmonary adiaspiromycosis
Arch Pathol
99
1975
11
15
1167442
205
Schwarz
J
Adiaspiromycosis
Pathol Annu
13
1978
41
53
364386
206
Rippon
JW
Medical Mycology: The Pathogenic Fungi and the Pathogenic Actinomycetes
3rd ed
1988
W.B. Saunders
Philadelphia
p. 718–21
207
Filho
JVB
Amato
MBP
Deheinzelin
D
Respiratory failure caused by adiaspiromycosis
Chest
97
1990
1171
1175
2331914
208
Peres
LC
Figueiredo
F
Peinado
M
Fulminant disseminated pulmonary adiaspiromycosis in humans
Am J Trop Med Hyg
46
1992
146
150
1539748
209
England
DM
Hochholzer
L
Adiaspiromycosis – an unusual fungal infection of the lung – report of 11 cases
Am J Surg Pathol
17
1993
876
886
8352373
210
Echavarria
E
Cano
EL
Restrepo
A
Disseminated adiaspiromycosis in a patient with AIDS
J Med Vet Mycol
31
1993
91
97
8483061
211
Nuorva
K
Pitkanen
R
Issakainen
J
Pulmonary adiaspiromycosis in a two year old girl
J Clin Pathol
50
1997
82
85
9059367
212
Denson
JL
Keen
CE
Froeschle
PO
Adiaspiromycosis mimicking widespread malignancy in a patient with pulmonary adenocarcinoma
J Clin Pathol
62
2009
837
839
19734484
213
Redline
RW
Redline
SS
Boxerbaum
B
Systemic Malassezia furfur infections in patients receiving intralipid therapy
Hum Pathol
16
1988
852
854
214
Shek
YH
Tucker
MC
Viciana
AL
Malassezia furfur – Disseminated infection in premature infants
Am J Clin Pathol
92
1989
595
603
2510495
215
Tadros
TS
Workowski
KA
Siegel
RJ
Pathology of hyalohyphomycosis caused by Scedosporium apiospermum (Pseudallescheria
boydii): An emerging mycosis
Hum Pathol
29
1998
1266
1272
9824105
216
Nonaka
D
Yfantis
H
Southall
P
Pseudallescheriasis as an aggressive opportunistic infection in a bone marrow transplant
recipient
Arch Pathol Lab Med
126
2002
207
209
11825121
217
Raj
R
Frost
AE
Scedosporium apiospermum fungemia in a lung transplant recipient
Chest
121
2002
1714
1716
12006471
218
Jayamohan
Y
Ribes
JA
Pseudallescheriasis: a summary of patients from 1980–2003 in a tertiary care center
Arch Pathol Lab Med
130
2006
1843
1846
17149961
219
Deng
Z
Ribas
JL
Gibson
DW
Infections caused by Penicillium marneffei in China and Southeast Asia: review of
eighteen published cases and report of four more Chinese cases
Rev Infect Dis
10
1988
640
652
3293165
220
McShane
H
Tang
CM
Conlon
CP
Disseminated Penicillium marneffei infection presenting as a right upper lobe mass
in an HIV positive patient
Thorax
53
1998
905
906
10193382
221
Shadduck
JA
Orenstein
JM
Comparative pathology of microsporidiosis
Arch Pathol Lab Med
117
1993
1215
1219
8250691
222
Schwartz
DA
Sobottka
I
Leitch
GJ
Pathology of microsporidiosis: emerging parasitic infections in patients with acquired
immunodeficiency syndrome
Arch Pathol Lab Med
120
1996
173
188
8712897
223
Orenstein
JM
Diagnostic pathology of microsporidiosis
Ultrastruct Pathol
27
2003
141
149
12775504
224
Tosoni
A
Nebuloni
M
Ferri
A
Disseminated microsporidiosis caused by Encephalitozoon cuniculi III (Dog type) in
an Italian AIDS patient: a retrospective study
Modern Pathol
15
2002
577
583
225
Schwartz
DA
Bryan
RT
Hewanlowe
KO
Disseminated microsporidiosis (Encephalitozoon hellem) and acquired immunodeficiency
syndrome – autopsy evidence for respiratory acquisition
Arch Pathol Lab Med
116
1992
660
668
1616428
226
Weber
R
Kuster
H
Keller
R
Pulmonary and intestinal microsporidiosis in a patient with the acquired immunodeficiency
syndrome
Am Rev Respir Dis
146
1992
1603
1605
1456583
227
Schwartz
DA
Visvesvara
GS
Leitch
GJ
Pathology of symptomatic microsporidial (Encephalitozoon hellem) bronchiolitis in
the acquired immunodeficiency syndrome – a new respiratory pathogen diagnosed from
lung biopsy, bronchoalveolar lavage, sputum, and tissue culture
Hum Pathol
24
1993
937
943
7504651
228
Cowley
GP
Miller
RF
Papadaki
L
Disseminated microsporidiosis in a patient with acquired immunodeficiency syndrome
Histopathology
30
1997
386
389
9147092
229
Scaglia
M
Sacchi
L
Croppo
GP
Pulmonary microsporidiosis due to Encephalitozoon hellem in a patient with AIDS
J Infect
34
1997
119
126
9138134
230
Velasquez
JN
Carnevale
S
Labbe
JH
In situ hybridization: A molecular approach for the diagnosis of the microsporidian
parasite Enterocytozoon bieneusi
Hum Pathol
30
1999
54
58
9923927
231
Maggi
P
laRocca
AM
Quarto
M
Effect of antiretroviral therapy on cryptosporidiosis and microsporidiosis in patients
infected with human immunodeficiency virus type 1
Eur J Clin Microbiol Infect Dis
19
2000
213
217
10795595
5.5
Parasitic infestations
Chapter Contents
Protozoa
252
Toxoplasmosis 252
Amoebiasis 252
Malaria 253
Leishmaniasis 253
Cryptosporidiosis 253
Trichomoniasis 254
Helminths
254
Trematodes 254
Cestodes 256
Nematodes 257
Hookworm infestation 258
Arthropods
259
Pulmonary acariasis 259
Pentastomiasis 260
Myiasis 260
References
260
This chapter describes infestation of the lungs by certain parasitic protozoa, helminths
and arthropods, of which man may be either the natural or the accidental host.
Protozoal diseases of the lungs include toxoplasmosis, leishmaniasis and amoebic abscess
while severe malaria may be complicated by acute respiratory failure. Also, parasites
usually confined to other organs may be identified in the lungs, for example cryptosporidia
in AIDS and trichomonas in aspiration lesions.
Helminths of all three major classes may infest the lung. Trematodes include the blood
flukes (genus Schistosoma), the lung flukes (genus Paragonimus) and certain liver
flukes (genus Opisthorchis). The cestodes are represented by the larval forms of Echinococcus
and Taenia, which are responsible for hydatid disease and cysticercosis respectively,
whilst nematodes found in the lung include immature forms of Ascaris, Strongyloides,
Ancylostoma, Necator, Wuchereria and Brugia and the adult forms of heartworm (Dirofilaria)
and gapeworm (Syngamus).
Arthropods include the ticks and mites (arachnids), adult forms of which may cause
pulmonary acariasis. Pulmonary pentastomiasis is a manifestation of infestation by
larvae of Linguatula or of Armillifer.
The mode of transmission is variable. Some of these parasites are transmitted by an
insect bite e.g. those causing tropical pulmonary eosinophilia, dirofilariasis and
malaria, while some penetrate the skin directly e.g. Strongyloides, hookworms and
schistosomes, and others are ingested e.g. Paragonimus, Entamoeba and Echinococcus.
The human lungs may be involved in the life-cycle of these parasites in various ways:
1
The lungs may be the natural location of the parasite, for example Paragonimus and
Syngamus.
2
The larval form of the parasite may encyst in the lungs, for example Echinococcus.
3
The lung may be a migratory route for the larvae of the parasite: this includes most
of the nematodes listed above and the larvae responsible for pentastomiasis.
4
The parasite may reach the lungs as an embolus: most schistosomal ova and the dead
adult canine heartworm, Dirofilaria, are examples of this.
5
The parasite may invade the lung through the diaphragm from the liver, for example
Entamoeba histolytica and the liver fluke Opisthorchis.
6
The lungs may be involved in disseminated parasitosis, for example microsporidiosis
in the acquired immune deficiency syndrome.
Although immunodeficient patients are particularly prone to parasitic infestation,
most of these pulmonary parasites are capable of infecting and causing disease in
the immunocompetent; only a few are opportunists (e.g. Cryptosporidium spp.). Many
of them have a characteristic distribution, often in tropical or subtropical countries.
In the developed world parasitic diseases of the lung mainly affect immigrants and
tourists.
Protozoa
Protozoa are unicellular eukaryotic microbes that reproduce vegetatively (as trophozoites)
but encyst when conditions are unfavourable. Some are parasitic to man. A comprehensive
review of those that affect the human lungs, including their taxonomy and treatment,
has recently been provided.
1
Toxoplasmosis
Toxoplasmosis represents infection with the coccidian parasite Toxoplasma gondii,
this name deriving from the crescentic bow shape of the parasite's tachyzoites and
its discovery in the gondi, a North African rodent used as a laboratory animal. The
domestic cat is the usual definitive host from which man is infected but the disease
occurs in many species of wild and domestic birds and mammals, all of which provide
a ready source of human infection. Ingestion of infected animal material is the usual
route of infection of adults but neonatal disease generally reflects placental transmission.
Toxoplasmosis is one of the most prevalent protozoal infections of man but the parasite
rarely harms its host and the vast majority of human infections remain occult throughout
life, causing damage only when cellular immunity is impaired. Gametogenesis and oocyst
formation take place in the intestine of animals such as cats; outside the body, sporozoites
are liberated which can infect other species, including man. Only asexual cysts containing
dormant bradyzoites are formed in normal accidental hosts but if immunity fails the
cysts liberate motile tachyzoites and it is these that swarm through the host tissues
causing cell damage and inflammation.
Pulmonary toxoplasmosis is rare and most cases have been in patients suffering from
generalised disease attributable to immunodeficiency from diseases such as lymphoma
and AIDS. Transplant recipients are also liable to develop toxoplasmosis. Because
many of these patients undergo toxoplasma sero-conversion after they receive new organs,
it is likely that the parasite is introduced in the donor tissues in which it presumably
lay dormant. In lung transplant patients, recognition of the parasites in transbronchial
biopsies is important in distinguishing infection from the changes of graft rejection.
Because of the size of the parasite relative to the thickness of tissue sections,
many laboratories involved in transplantation work cut serial sections through these
small biopsies.
Pulmonary infection is initially non-specific. There is an interstitial infiltrate
of lymphocytes, and alveolar macrophages are increased. Hyaline membranes may develop,
indicating necrosis of the alveolar epithelium, and the changes are then those of
diffuse alveolar damage. Alveoli adjacent to those lined by hyaline membranes show
type II pneumocyte hyperplasia. Up to this stage the parasites are scanty but if immunity
is sufficiently impaired, enormous numbers of tachyzoites develop. These cause necrosis
on a major scale. Air spaces may be filled with necrotic debris or broad tracts of
the lung undergo coagulative necrosis.2, 3, 4, 5, 6, 7 In one case macrophages filled
with toxoplasma trophozoites formed a mass lesion.
8
Individual tachyzoites are very difficult to recognise in histological sections but
their identification is facilitated by immunocytochemistry,6, 7 which is superior
to the Giemsa stain formerly used. The tachyzoites are crescentic in shape and measure
within the range 4–7 × 2–3 µm with a prominent central nucleus.
9
The intracystic bradyzoites tend to be shorter and more rounded. The cysts, which
represent the latent form of the parasite, lie free in the intercellular tissues and
provoke no inflammatory response (Fig. 5.5.1
). They vary considerably in size but are commonly of the order of 60 µm in diameter.
Single tachyzoites are difficult to identify but they invade and proliferate within
host cells to form distinctive collections known as pseudocysts. These resemble true
cysts in size and appearance but are intracellular and lack an outer membrane. Cysts
and pseudocysts are easier to recognise than individual tachyzoites but both are generally
very rare.
Figure 5.5.1
A Toxoplasma cyst exciting little inflammatory reaction in the surrounding lung.
Treatment with pyrimethamine and sulfonamides is effective if initiated promptly.
10
The mortality for toxoplasma pneumonia is 55%, although survival is much better in
the immunocompetent.
11
Amoebiasis
Entamoeba histolytica, the causative organism of amoebic dysentery, is a protozoon
with a trophozoite and a cystic stage that is endemic in much of sub-Saharan Africa,
South America and southern Asia. Infection is acquired by the ingestion of food or
water contaminated by amoebic cysts. Trophozoites develop in the small intestine and
are carried to the large bowel, which they ulcerate. From there they may spread in
the blood, giving rise to metastatic foci of infection. These are found most frequently
in the liver, lungs and brain, in that order. Although the lesions in these organs
are conventionally described as abscesses, they are not accompanied by suppuration
unless there is secondary bacterial infection.
If there is amoebic ulceration of the lower part of the rectum, amoebae may reach
the rectal venous plexus and, bypassing the liver, make their way directly in the
systemic circulation to the lungs. More often, amoebic pulmonary abscesses are secondary
to those in the liver: the amoebae pass though the diaphragm to infect the lungs and
are therefore commoner in the right lung. Whether the pleural cavity becomes infected
in the course of this extension of the disease from liver to lung depends on whether
adhesions have formed that bind the apposed pleural surfaces sufficiently to protect
the cavity from invasion. Pleuropulmonary complications develop in less than 5% of
patients with intestinal amoebiasis but in 50% of those with liver abscesses. They
may include bronchohepatic fistulas.
12
An amoebic abscess in the lung, like one in the liver, is essentially a focus of localised
destruction in which part of the lung is converted into a cavity filled with reddish-brown,
viscous fluid. There is little inflammatory reaction in the surrounding tissues but
amoebae with their characteristic ingested erythrocytes may be seen in the zone bordering
the cavity or on aspiration cytology.
13
Often the area of destruction extends to involve one of the bronchi, and much of the
contents, often blood-stained, may then be expectorated. Should this happen, there
may be secondary bacterial infection of the cavity. Metronidazole is the treatment
of choice.
12
In addition to E.histolytica, certain free-living amoebae have occasionally caused
disease in man, of which two, Acanthamoeba spp. and Balamuthia mandrillaris have been
responsible for pulmonary disease.
14
Malaria
Severe Plasmodium falciparum malaria may be complicated by acute respiratory failure.15,
16, 17 This is usually due to non-cardiogenic oedema, reflecting increased permeability
of the alveolar capillaries.
18
Alternatively, patients may display the acute respiratory distress syndrome, which
as usual has diffuse alveolar damage as its pathological basis.
It is suggested that the various cytokines that have been identified in the general
circulation in complicated forms of malaria19, 20, 21 may be more important than the
ischaemia occasioned by heavy erythrocyte parasite burdens rendering the red blood
cells less deformable and so inclined to occlude capillaries. However, blood sludging
undoubtedly takes place in the lungs as well as the brain and elsewhere. The pulmonary
capillaries are engorged with parasitised erythrocytes, pigment-laden macrophages
and neutrophils. This is contributed to by endothelial activation and increased expression
of intercellular adhesion molecule-1
22
as well as the non-deformability of the parasitised cells. The alveoli are filled
with protein-rich or haemorrhagic oedema fluid, often containing pigment-laden macrophages,
or show the hyaline membranes of diffuse alveolar damage.
The parasites in the lung are largely early trophozoites or ring forms rather than
the later schizonts that predominate in cerebral vessels, possibly because the higher
oxygen levels in the lung inhibit plasmodium maturation.
23
Therapeutic measures resulting in fluid overload and oxygen toxicity may aggravate
the respiratory distress. Even after treatment, altered pulmonary function in malaria
is common, with airflow obstruction, impaired ventilation, impaired gas transfer,
and increased pulmonary phagocytic activity. This occurs in both vivax and falciparum
malaria suggesting common underlying inflammatory mechanisms.
24
Leishmaniasis
Visceral leishmaniasis, which is contracted by the bite of an infected sandfly, is
characterised by fever, weight loss, splenomegaly and hepatomegaly. Most patients
also complain of cough but there are few reports of pulmonary involvement. As in the
spleen and liver, the leishmania are contained within macrophages (Fig. 5.5.2
) but are difficult to find. One study identified chronic interstitial pneumonitis
in 10 of 13 cases of visceral leishmaniasis, accompanied in 7 by focal interstitial
fibrosis.
25
Leishmania donovani were identified in only 3 cases but leishmanial antigenic material
was recognised immunocytochemically in all cases showing pneumonitis and in none of
the others.
Figure 5.5.2
Pulmonary involvement in disseminated leishmaniasis. The protozoa are seen within
macrophages in alveoli and capillaries.
(Courtesy of Dr J DeGaetano, Malta.)
Cryptosporidiosis
Cryptosporidia species cause diarrhoea in many species.
26
In man, enteric cryptosporidiosis was first recognised in an immunodeficient patient
and the disease has now become a serious problem in AIDS.
27
It also affects the immunocompetent and is a common cause of short-term diarrhoea
in day nurseries and in travellers. Infection is by faecal–oral transmission of an
encysted form and generally involves drinking contaminated water. A small number of
immunocompromised patients show respiratory as well as enteric infection, complaining
of cough and chest pain (Fig. 5.5.3
).28, 29, 30, 31
Figure 5.5.3
Cryptosporidia (arrows) are seen in the bronchial lumen of a patient suffering from
acquired immunodeficiency syndrome (AIDS).
(Courtesy of Dr M Antoine, Paris, France.)
Cryptosporidia are extracellular protozoan parasites which adhere to the surface of
lining epithelia. They are seen as faintly haematoxyphil dots measuring up to 5 µm
arrayed along the mucosal surface. In the respiratory tract they have been identified
on the surface and glandular epithelium of the trachea and bronchi and in the lung
parenchyma, associated with extensive squamous metaplasia of the conductive airways.
29
The superficial location of cryptosporidia helps distinguish them from microsporidia,
which are found within the cytoplasm of epithelial cells. Electron microscopy shows
that cryptosporidia occupy a vacuole that communicates with the cell surface: they
lie just beneath the level of cell membrane but are nevertheless extracellular.
Treatment may require immune reconstitution as well as the administration of drugs
such as paromomycin, azithromycin and nitazoxanide, for which varying success is reported.26,
32, 33
Trichomoniasis
The finding of trichomonads in human lungs is rare. Trichomonas hominis, the intestinal
trichomonas, has spread to the pleura via an enteropleural fistula, and T.vaginalis
has been isolated from the respiratory tracts of newborn babies, but pulmonary trichomoniasis
is usually caused by aspirated T.tenax.34, 35, 36 Trichomonads cannot persist without
associated bacterial infection and T.tenax is generally found as a harmless commensal
in patients with poor oral hygiene, surviving in carious teeth where it feeds on the
bacteria responsible for the dental decay. Pulmonary trichomoniasis is usually found
as part of a mixed infection in adult men with chronic purulent or necrotic lung disease
such as lung abscess or bronchiectasis. The flagellated protozoan may be identified
by microscopic examination of wet-smear, Gram-stained or Papanicolaou-stained preparations
but cultural identification is reputed to be superior to these methods.
34
Aspirated pulmonary trichomoniasis is an opportunistic infection of dubious pathogenicity,
but it seems advisable that it be treated appropriately (with metronidazole).
Helminths
Trematodes
Schistosomiasis
Pulmonary schistosomiasis (bilharziasis) may be due to any of the three most important
species of human blood fluke, Schistosoma haematobium, S.mansoni and S.japonicum.
Although involvement of the lung is relatively infrequent as a cause of clinical disease
in comparison with the major locations of schistosomal infestation, it is recognised
wherever schistosomiasis is endemic. However, with increased international travel,
it seems that the non-endemic population has a higher incidence of pulmonary involvement
once infected.37, 38 Specific changes are found in the lungs in a third of cases of
clinically evident schistosomiasis in Egypt but contribute to death in only about
2% of these patients.39, 40 The frequency of pulmonary involvement is least in the
Far East where schistosomiasis is due to S.japonicum.
The schistosomal cercariae thrive in fresh water and penetrate the skin to to transform
into immature adults, which are transported in the blood to mature in venous plexuses
around the bladder or rectum, where they reproduce. Pulmonary infestation generally
comes from ova being carried to the lungs in the blood, either bypassing the portal
venous circulation or having been produced by flukes inhabiting plexuses that drain
directly into the inferior vena cava. Alternatively, if adult parasites are present
within the pulmonary vasculature itself, ova are produced locally.
The ova, which measure from 70 to 170 µm in length by 50 to 70 µm in breadth, according
to the species, are bound by their dimensions to lodge in blood vessels of corresponding
calibre; local thrombosis and organisation result, with the formation of a characteristic
tuberculoid granuloma round the egg itself (Figure 5.5.4, Figure 5.5.5
).
39
Medial hypertrophy, intimal fibrosis, thrombosis, necrotising angiitis and angiomatoid
lesions (see p. 422) develop in the obstructed arteries.39, 41 Eosinophils may be
conspicuously numerous in the vicinity of the ova. It is uncertain whether the necrotising
arteritis and consequent angiomatoid lesions are attributable to vascular obstruction
by the ova, to an allergic response to the parasite, or to the ‘pipestem’ hepatic
fibrosis that is commonly found in schistosomiasis permitting vasoconstrictive substances
that normally are metabolised in the liver to reach the pulmonary arteries.
41
Cor pulmonale may complicate pulmonary schistosomiasis and aneurysmal dilatation of
the pulmonary trunk has been observed in long standing cases.
Figure 5.5.4
Schistosomiasis. Schistosomal ova are evident (centre) within the alveolar interstitium,
which also shows a lymphocytic infiltrate.
Figure 5.5.5
Schistosomiasis. Lodgement of the schistosomal eggs in the pulmonary microcirculation
has provoked a vigorous granulomatous response.
The ova also pass through the walls of the pulmonary vessels and initiate parenchymal
lesions characterised by a similar granulomatous reaction and more widespread lymphocytic
infiltrate and interstitial fibrosis. Although the ova may be much distorted during
tissue processing, they are readily seen and recognised, particularly if they were
viable at the time when the specimen was obtained (see Fig. 5.5.4). Dead ova often
become heavily calcified but may long retain identifiable traces of the contained
embryo. Eosinophilic infiltration and necrotising angiitis are only seen in the presence
of viable ova. The presence of eggs, viable or dead, is generally the clue to the
diagnosis, but in some cases pulmonary arterial lesions, including thrombosis and
arteritis, develop where no ova are demonstrable.
Occasionally, ova reach the respiratory bronchioles and cause a local tuberculoid
bronchiolitis. Sometimes a tumour-like mass forms in the lungs, abutting and obstructing
a bronchus: this proves to be a confluent growth of granulomatous tissue and scarring
around great numbers of schistosome ova.
When adult flukes reach the lungs they appear to cause no reaction while alive, any
associated lesions being caused by the presence of their ova. However, when the flukes
die, thrombosis and arteritis result, and there is commonly an accompanying focal
consolidation of the adjacent parenchyma. This gives rise to nodules up to 1 cm and
more in diameter that show as small ‘coin’ shadows in chest radiographs.
Katayama fever
As well as the classic chronic form of schistosomiasis described above, pulmonary
symptoms such as cough feature in the severe form of acute schistosomiasis known as
Katayama disease.
15
This systemic illness signifies seroconversion and develops about 3–6 weeks after
penetration of the skin by water-borne cercariae. It is almost exclusively a disease
of non-immune visitors to endemic areas and has been reported in several groups of
tourists returning from such areas, especially those participating in water sports.
The disease is self-limiting but recognition and treatment are important to avoid
the sequelae of chronic infection.
Paragonimiasis
Infestation by lung flukes is endemic in the Far East, and to a lesser extent in central
Africa and parts of the Americas. 42, 43, 44 In its early stages the disease is characterised
by chest pain or discomfort. Later, when it has become chronic, there is persistent
cough and recurrent haemoptysis. Characteristic operculate eggs can then be found
in the sputum; they are golden-brown and measure about 90 µm in length. In some cases
the presence of the parasite is borne well; in others it leads to anorexia and debility.
As long as the flukes remain in the lungs the disease is rarely fatal, but should
they reach the brain, as happens in a minority of cases, the prognosis is grave. Occasionally
the disease mimics lung cancer.
45
Rapid and reliable immunodiagnostic methods are now available, and there are PCR techniques
that distinguish individual species.46, 47
The species most frequently responsible are Paragonimus westermani in the Far East
and P.kellicotti in the Americas.
44
Morphologically these differ from each other only slightly. The adults infest the
lungs of many predatory animals: P westermani in the dog, cat and pig, and P.kellicotti
in the mink. Small groups of them become sexually mature within the lung tissue, where
necrosis and the formation of a fibrous capsule produce characteristic ‘worm cysts’
(abscess cavities) that eventually enlarge and break into the bronchial lumen (Fig.
5.5.6
). The ova that thus escape pass up the respiratory tract and are either expectorated
or swallowed, to be eventually excreted in the stools. The life cycle of the fluke
is a complex one: after several weeks in water or moist earth, the ovum hatches into
a miracidium, a free-swimming form that eventually enters and parasitises water snails
of the genus Melania. After its larval life in the snail, the fluke emerges as a cercaria,
which in turn parasitises small fresh-water crabs and crayfish. It is through the
consumption of these crustaceans, raw or insufficiently cooked, that man becomes infested.
Pickling the crabs does not destroy the parasite. The disease may also be acquired
by eating the flesh of another host, such as a pig, that has eaten infected crabs
or crayfish. On reaching the duodenum of the human host, the parasite penetrates the
gut wall and thence passes by way of the peritoneal cavity and diaphragm to the pleura
and the lungs. It grows to a length of 12 mm and attains maturity about five weeks
after reaching the lungs and so completing its life cycle.
Figure 5.5.6
Paragonimiasis. (A) A ‘worm cyst’ including several Paragonimus eggs in the chronic
inflammatory granulation tissue that borders the central necrosis. (B) Paragonimus
eggs removed from the lung (scale divisions = 10 µm).
In man the flukes often lie singly in the connective tissue ‘worm cysts’, the number
of which rarely exceeds ten, each about 1 to 2 cm across. They may excite an eosinophilic
pneumonia, give rise to a pleural effusion or cause pneumothorax.
48
Sometimes the young worms go astray and reach the liver, spleen, kidneys or brain.
Occasionally dead worms in the lungs are associated with distant tissue reactions
that probably have a hypersensitivity basis. The diagnosis is based on the demonstration
of the eggs in bronchial secretions, pleural fluid or faeces.
Opisthorchiasis
Liver flukes generally remain within the hepatic bile ducts but in Thailand Opisthorchis
viverrini has on rare occasions made its way from the liver through the diaphragm
to the right lung.
49
Cestodes
Hydatid disease (larval echinococcosis)
This disease has long been endemic in sheep-raising countries, notably Australia,
New Zealand, Wales, parts of South Africa and South America, and the Middle East.
50
Control measures are steadily lessening its incidence. The dog is the usual host of
the mature tapeworm, Echinococcus granulosus, and sheep the commonest host of its
larval stage. The ova in the faeces of the dog reach sheep or man in contaminated
food or water and, after hatching in the small intestine, larvae penetrate the gut
wall and enter the portal circulation. Most are retained in the liver, but some negotiate
the hepatic barrier to reach the systemic venous circulation and the lungs. The larval
forms of this helminth thus tend to occur most frequently in the liver and the lungs.
They take the form of hydatid cysts (Fig. 5.5.7
). If a hydatid cyst is demonstrated in the lung, others are almost always present
in the liver. Pulmonary hydatid cysts are usually solitary but bilateral instances
are recorded.50, 51, 52
Figure 5.5.7
Hydatid cyst, the encysted larval form of the Echinococcus granulosus tapeworm, filled
with numerous ‘daughter’ cysts.
The wall of a hydatid cyst is formed of a semipermeable laminated capsule, which is
composed of chitin, and an inner germinal layer. Outside these is the pericyst, formed
of a layer of chronic inflammatory granulation tissue or a fibrous capsule, these
representing the host reaction to the parasite (Figure 5.5.8, Figure 5.5.9
). The germinal layer gives rise to brood capsules and from the germinal layer of
these arise scolices. Free brood capsules and scolices form the hydatid ‘sand’ that
can be seen as minute white grains in the otherwise clear cyst fluid (Fig. 5.5.10
). When sheep tissues containing hydatid cysts are eaten by a dog, the scolices attach
to the intestinal mucosa and develop into the adult worms, thus completing the life
cycle. Scolices also have the potential to develop into secondary cysts if released
by cyst rupture. They also form daughter cysts within the mother cyst, each daughter
cyst being an exact true replica of the mother cyst. The daughter cysts may be packed
together in the mother cyst or float freely in the mother cyst cavity. In older cysts,
the contents degenerate into gelatinous material known as the matrix, which may be
mistaken for pus. The cysts are usually bacteriologically sterile but they may become
infected, resulting in true suppuration. Calcification commonly develops in the pericyst
without affecting the viability of the parasite but calcification of the endocyst
indicates that it is dead.
Figure 5.5.8
Hydatid cyst. The encysted larva of the Echinococcus granulosus tapeworm has died
and the parasite's capsule has collapsed away from the fibrous capsule formed by its
human host.
Figure 5.5.9
Hydatid cyst. The convoluted chitinous layer of a collapsed dead hydatid cyst.
Figure 5.5.10
Hydatid cyst. An echinococcal scolex from a ruptured hydatid cyst is surrounded by
pus.
Because the parasite has evolved mechanisms to avoid host immunity, the infection
is often asymptomatic until a mechanical complication occurs.
53
Thus, most cases of pulmonary hydatid disease are discovered on routine chest radiography.
Symptoms stem from compression, infection or rupture into a bronchus. The sudden escape
of a large amount of its fluid contents may give rise to a grave, even fatal, anaphylactic
reaction. Rupture of a hydatid cyst into a bronchus may also cause bronchocentric
granulomatosis
54
or lymphoid hyperplasia. Aspiration of the cyst contents should not be undertaken
because of the risk of spillage and a consequent hypersensitivity reaction. The treatment
of choice for compressive cysts is surgical resection, with particular care being
exercised to avoid rupture of the cyst, and postoperative drug therapy using albendazole.55,
56, 57
Cysticercosis (larval taeniasis)
Cysticercosis occurs when man becomes the intermediate host of the porcine tapeworm,
Taenium solium, through the ingestion of the worm's eggs present in faecally contaminated
water or food or on soiled hands, or by the eggs hatching within the intestine of
those harbouring the adult worm.58, 59 The disease is common in Africa, China, south
east Asia and South America. Once hatched, the embryo penetrates the intestinal wall
and is disseminated by the blood stream, giving rise to an encysted larva. Such cysticerci
may form anywhere but the brain is particularly vulnerable. The lungs are seldom affected
but may be the seat of either solitary or multiple lesions, the latter generally as
part of disseminated disease, which probably reflects immune impairment. The larva
has an inverted scolex and lies within clear fluid bounded by a thin fibrous capsule.
Little inflammation is induced while the larvae are alive but after their death a
variable response is seen, often culminating in calcification.
Nematodes
Ascariasis and toxocariasis (‘visceral larva migrans’)
Although essentially an intestinal parasite, the large roundworm Ascaris lumbricoides
passes through the lungs during one phase of its complex life cycle. Infection is
endemic in much of Africa, Asia and South America. The infestation is acquired by
ingesting food or water contaminated with ova passed in the faeces of an earlier host.
The ova hatch in the small intestine, where the larvae quickly penetrate the mucosa
and are carried either to the liver in the portal bloodstream or in lymph to the systemic
veins, reaching the lungs about five or six days after ingestion of the eggs. In the
lungs, the larvae pierce the alveolar wall to reach the air space, whence they are
cleared to the pharynx to be swallowed. Maturation, copulation and ovulation occur
in the small intestine.
Toxocara canii and cati are respectively the corresponding roundworms of dogs and
cats, human infection by which is acquired through close contact with these animals
or with soil contaminated by their faeces. Toxocarae do not complete their life-cycle
in man but dissemination of their larvae simulates visceral ascariasis, resulting
in what is known as visceral larva migrans.
Migration of these worms through the lungs may cause self-limiting pulmonary eosinophilia
(Löffler's syndrome, see p. 460) during which eosinophils and Charcot–Leyden crystals
are often conspicuous in the sputum, although the larvae themselves are rarely seen.
The illness is usually over within three weeks but in exceptional cases respiratory
distress becomes so severe that the patient may die.
60
Microscopical studies of the pulmonary lesions have been infrequent except in the
rare fatal cases, or when the parasites are present by chance in lungs examined as
a result of other disease. The larvae may be found in capillaries, the interstitial
tissues, or air spaces, accompanied by eosinophils and neutrophils. When a larva dies,
an intense reaction may develop, with dense local accumulation of eosinophils, lesser
numbers of macrophages and neutrophils, and fibrin. Identifiable remnants of larvae
may be seen, sometimes in multinucleate giant cells. There may be local haemorrhage.
The larvae of A.lumbricoides, the ascarid parasite of man, are difficult to distinguish
from those of other ascarids, such as species of Toxocara, that may also be found
in human lung tissue or pleural fluid.
61
Morphological differentiation of these larvae in histological preparations is commonly
beyond the ability even of professional parasitologists but investigation by means
of specific immunocytochemical staining may be decisive. The larvae of the toxocarae
have a greater tendency than those of A.lumbricoides to die in the lungs when they
infest man: they then cause pulmonary eosinophilia and tuberculoid granulomas that
eventually lead to fibrous encapsulation of the remains of the parasites.
Strongyloidiasis
Strongyloides stercoralis is another intestinal parasite that at one stage in its
development passes through the lungs. Infection is endemic in much of the tropics
and subtropical regions. The filariform larvae of strongyloides, like those of hookworms
and schistosomal cercariae, have the ability to penetrate intact human skin, following
which they are carried to the lungs where they penetrate the alveoli and migrate via
the airways and upper gastrointestinal tract to the small intestine. Here they mature
into parthenogenetic adult females, the eggs of which release rhabditiform larvae
within the intestine, unlike the eggs of other intestinal helminths which are passed
intact in the faeces to embryonate in the soil. The rhabditiform larvae of Strongyloides
may pass with the faeces to complete a free-living sexual cycle in the soil or differentiate
within the intestine into filariform larvae, which are capable of penetrating the
bowel wall or the perianal skin to repeat their parasitic asexual cycle, an endogenous
process known as autoinfection. This difference between Strongyloides and other intestinal
helminths is important in maintaining the infection and, in immunocompromised hosts,
leading to potentially fatal hyperinfestation.
Chronic strongyloidiasis has been well described among individuals who were prisoners
of the Japanese during the second world war: decades later, it affected a fifth of
the survivors of those who worked on the notorious Burma railway.62, 63 Most infestations
cause at most a creeping skin eruption (larva migrans) or chronic diarrhoea but there
is a real danger of fatal hyperinfestation if the individual becomes immunosuppressed.
This may happen when corticosteroid drugs are administered, particularly in the treatment
of unrelated conditions but also because of resistant asthma caused by unrecognised
strongyloidiasis. In cases of such asthma the dose of corticosteroids may be progressively
increased when the patient would have been better treated with anti-helminthic drugs.
64
Worsening asthma as the steroid dosage is increased should alert the clinician to
the possibility of hyperinfestation. Heavy infestation is often associated with blood
eosinophilia and fleeting pulmonary opacities that represent eosinophilic pneumonia
but these features may be absent in those who are immunosuppressed. Other risk factors
include advanced age, chronic lung disease and altered cellular immunity, particularly
that found in adult T-cell leukaemia complicating human T-lymphotropic retrovirus
(HTLV-1) infection.65, 66, 67, 68
The respiratory features in hyperinfestation may be those of the acute respiratory
distress syndrome. At necropsy in such cases, the larvae are seen in huge numbers
within the lumen and walls of airways of all sizes down to the alveoli and within
interlobular septa (Fig. 5.5.11
). They excite an inflammatory response, chiefly of plasma cells with smaller numbers
of lymphocytes and eosinophils. Diffuse alveolar haemorrhage may be seen.
69
More chronic infestation may result in restrictive lung disease due to interlobular
septal fibrosis
70
or a mass lesion.
71
Figure 5.5.11
Strongyloides stercoralis filaria in the lung in a case of strongyloides superinfection.
(Courtesy of the late Professor BE Heard, Brompton, UK.)
Hookworm infestation
The larval forms of the hookworms Ancylostoma duodenale and Necator americanus, like
those of Ascaris lumbricoides and Strongyloides stercoralis, migrate through the heart,
lungs and trachea to reach the intestine where they mature. On their way through the
lungs, they may similarly cause fleeting eosinophilic pneumonia.
Filariasis: tropical eosinophilia
Filariasis is endemic in the tropics. The adult nematodes, Wuchereria bancrofti, Brugia
malayi, Brugia pahangi and Onchocerca volvulus inhabit lymphatics where they produce
eggs from which are released embryos known as microfilariae. These circulate in the
blood and disseminate widely in the tissues, to be transmitted to others by mosquitoes.
Some of those infected present with ‘tropical eosinophilia’, a name that was given
to a condition that was initially described from the coast of southern India but is
now known to have a far wider distribution in the tropics.
72
The clinical signs are fever, loss of weight, dyspnoea and asthmatic attacks; there
is marked blood eosinophilia and radiographs show nodular shadows in the lungs. The
condition is benign and little is known of the changes in the lungs. Such reports
as have been published describe whitish nodules 3 to 5 mm in diameter, scattered irregularly
throughout the lungs. Histologically, the nodules are composed of groups of alveoli
consolidated by eosinophils enmeshed in fibrin. In the centre of some of the nodules,
the alveolar walls are destroyed and the area becomes an ‘eosinophil abscess’. In
others, a central collection of epithelioid cells becomes arranged in a palisade manner
round deeply eosinophilic hyaline material that probably represents inspissated granules
of eosinophil leukocytes. Giant cells and fibrosis are seen in some lesions and microfilariae
are sometimes observed.73, 74 The condition is thought to represent an immunopathological
response to the parasite rather than direct damage by the microfilariae because it
is confined to those individuals who are highly sensitised to filarial antigens.
Tropical eosinophilia is readily distinguished from other forms of eosinophilia (which
are described in Chapter 9) by the patient's history of residence in the tropics,
by the presence of extraordinarily high levels of both serum IgE and antifilarial
antibodies, and by a dramatic therapeutic response to the filaricide diethylcarbamazine.
Dirofilariasis (heartworm infestation)
Pulmonary dirofilariasis occurs when man becomes an alternative host of the canine
heartworm, Dirofilaria immitis, after being bitten by a mosquito or sandfly infested
with the microfilariae. Early development occurs in a subcutaneous nodule, whence
after a few weeks’ development the young adult worm migrates to the right side of
the heart and the pulmonary arteries. In man, the adult worm typically dies while
it is immature and is carried from the heart to the lungs as a parasitic embolus to
occlude a small pulmonary artery. This generally causes no symptoms. A necrotising
granuloma forms about the dead worm and this is seen as an incidental ‘coin’ lesion
in chest radiographs,
75
often prompting a needless thoracotomy as carcinoma is the principal differential
diagnosis. The diagnosis is almost always made only when resected tissue is submitted
to microscopy. The granuloma is rounded rather than wedge-shaped and is not haemorrhagic,
appearances favouring an immune reaction to the worm rather than infarction. The young
adult worm in the centre of the granuloma is about 3cm in length but the mature female
measures up to 30cm x 2mm with the male about 20cm x 2mm. Very rarely an embolic tangle
of worms results in major pulmonary infarction (Fig. 5.5.12A
).
Figure 5.5.12
Dirofilaria immitis, the dog heart worm. (A) A tangle of Dirofilaria worms that was
removed surgically from the pulmonary artery of a merchant seaman. Magnification ×1.8.
(Courtesy of Professor F Ho, Hong Kong.)
(B–D) Dirofilaria immitis causing a 3-cm, rounded, necrotising nodule in the lung
of a man who had lived rough in tropical countries. (B) Gross appearances; (C) microscopy;
(D) elastin stain showing the worm situated within a pulmonary artery.
(B–D courtesy of Dr M Jagusch, Auckland, New Zealand.)
Heartworm is enzootic in the Gulf states of America but since the first report of
human infestation in 1961 it has become recognised in dogs throughout the United States
and in southern parts of Canada. Human cases have now been reported also from Japan,
Australia, Brazil and various other countries.76, 77, 78, 79, 80, 81 The smaller D.repens,
which is common in Italy, may result in a similar pulmonary nodule but the lung is
a relatively rare locus for this species.82, 83, 84
The lesions in man are usually solitary, peripheral and lower lobar in distribution
(Fig. 5.5.12B), but multiple bilateral nodules have been reported. They range in size
from 1 to 4 cm. Most patients are asymptomatic but some complain of cough, chest pain,
haemoptysis and fever, with up to 20% showing eosinophilia. Microscopically, a large
central area of coagulative necrosis is surrounded by a thin band of chronic inflammatory
granulomatous tissue containing occasional giant cells (Fig. 5.5.12C).80, 85, 86 Eosinophils
may be numerous but are often absent. The diagnosis is made by identifying the dead
worm within a thrombosed artery in the central area of necrosis (Fig. 5.5.12D). This
may require step sections, which are therefore advisable when examining any necrobiotic
nodule of obscure aetiology. Methenamine silver and elastin stains aid the identification
and localisation of the parasite (Fig. 5.5.12D), which has a thick cuticle and in
man seldom measures more than 300 µm in diameter.
Syngamiasis (gapeworm infestation)
Gapeworms of the Syngamidae family infest domestic mammals, rodents and birds, producing
in domestic fowl a disease known as ‘the gapes’, which is characterised by dyspnoea
and an asphyxial death due to the worms obstructing the bird's trachea and bronchi.
Human infection is rare but isolated cases have been reported from the West Indies,
Brazil, the Philippines and Korea.87, 88, 89, 90 Affected patients complain of dyspnoea,
cough, wheeze and pain or a feeling of tightness in the chest. Ova and adult worms
may be found in the sputum or on bronchoscopy. The adults live off the host's blood
and are therefore bright red. The female measures up to 2 cm and the male a quarter
of this. They live in permanent copulation and since the vulva opens in the mid region
of the female's body, each pair forms a characteristic Y shape. It must be disconcerting
to see the paired worms wriggling away from the bronchoscopy forceps.
87
Arthropods
Pulmonary acariasis
Adult ticks and mites are occasionally found in the sputum of those exposed to organic
dust in tropical climates, probably representing bronchial saprophytes. This is known
as pulmonary acariasis. Mites were found in the sputum of 5% of Chinese grain workers.
91
Pentastomiasis
The upper or lower respiratory passages of some dogs, birds and snakes are inhabited
by certain arthropods of debatable taxonomic standing, the so-called ‘tongueworms’
or pentastomes, which include Linguatula and Armillifer. 92, 93 The eggs of Armillifer
may be transmitted to snake handlers in Africa and the Far East and those of Linguatula
are transmitted to dog handlers worldwide. Larvae develop in the human intestine and
penetrate the wall to reach many viscera, including the lungs, where in their natural
host they mature to adults but where in man they die. A recognisable larva is occasionally
encountered in human lungs but more often, barely recognisable parasitic remnants
are observed within encapsulated, partly calcified, necrotic debris. Their identification
from other metazoal remnants may be impossible, even for professional parasitologists.
Myiasis
Myiasis is caused by parasitic dipterous fly larvae feeding on the host's necrotic
or living tissue. The disease is a serious problem in the livestock industry and is
fairly common in rural human populations in tropical and subtropical regions. The
insect that attacks man is Dermatobia hominis, the human bot-fly. The infestation
is usually cutaneous but many other parts of the body may be affected, including the
respiratory tract on rare occasions. Respiratory involvement is usually identified
when a patient complaining of cough or haemoptysis coughs up a recognisable maggot.
References
1
Martinez-Giron
R
Esteban
JG
Ribas
A
Protozoa in respiratory pathology: a review
Eur Respir J
32
2008
1354
1370
18978136
Toxoplasmosis
2
Marchevsky
A
Rosen
MJ
Chrystal
G
Pulmonary complications of the acquired immunodeficiency syndrome: a clinicopathologic
study of 70 cases
Hum Pathol
16
1985
659
670
3874142
3
Tschirart
D
Klatt
EC
Disseminated toxoplasmosis in the acquired immunodeficiency syndrome
Arch Pathol Lab Med
112
1988
1237
1241
3190410
4
Bergin
C
Murphy
M
Lyons
D
Toxoplasma pneumonitis – fatal presentation of disseminated toxoplasmosis in a patient
with AIDS
Eur Respir J
5
1992
1018
1020
1426192
5
Artigas
J
Grosse
G
Niedobitek
F
Anergic disseminated toxoplasmosis in a patient with the acquired immunodeficiency
syndrome
Arch Pathol Lab Med
117
1993
540
541
8489347
6
Schurmann
D
Ruf
B
Extracerebral toxoplasmosis in AIDS – Histological and immunohistological findings
based on 80 autopsy cases
Pathol Res Pract
189
1993
428
436
8351245
7
Nash
G
Kerschmann
RL
Herndier
B
The pathological manifestations of pulmonary toxoplasmosis in the acquired immunodeficiency
syndrome
Hum Pathol
25
1994
652
658
8026824
8
Monso
E
Vidal
R
de Gracia
X
Pulmonary toxoplasmoma presenting as obstructive pneumonia
Thorax
41
1986
489
490
3787527
9
Dubey
JP
Lindsay
DS
Speer
CA
Structures of Toxoplasma gondii tachyzoites, bradyzoites, and sporozoites and biology
and development of tissue cysts
Clin Microbiol Rev
11
1998
267
299
9564564
10
Mariuz
P
Bosler
EM
Luft
BJ
Toxoplasma pneumonia
Semin Respir Infect
12
1997
40
43
9097375
11
Pomeroy
C
Filice
GA
Pulmonary toxoplasmosis: a review
Clin Infect Dis
14
1992
863
870
1576281
Amoebiasis
12
Lyche
KD
Jensen
WA
Pleuropulmonary amebiasis
Semin Respir Infect
12
1997
106
112
9195675
13
Bhambhani
S
Kashyap
V
Amoebiasis: diagnosis by aspiration and exfoliative cytology
Cytopathology
12
2001
329
333
11722513
14
Visvesvara
GS
Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris,
Naegleria fowleri, and Sappinia diploidea
FEMS immunology and medical microbiology
50
2007
1
26
17428307
Malaria
15
Johnson
S
Wilkinson
R
Davidson
RN
Acute tropical infections and the lung
Thorax
49
1994
714
718
8066570
16
Torres
JR
Perez
H
Postigo
MM
Acute non-cardiogenic lung injury in benign tertian malaria
Lancet
350
1997
31
32
17
Taylor
WR
White
NJ
Malaria and the lung
Clin Chest Med
23
2002
457
468
12092039
18
Taylor
WR
Pulmonary manifestations of malaria: recognition and management
Treatments in respiratory medicine
5
2006
419
428
17154671
19
Kern
P
Hemmer
JC
Van Damme
J
Elevated tumour necrosis factor alpha and interleukin-6 serum levels as markers for
complicated Plasmodium falciparum malaria
Am J Med
87
1989
139
143
2667356
20
Kwiatkowski
D
Hill
AVS
Sambou
I
Tumour necrosis factor concentration in fatal cerebral, non-fatal cerebral, and uncomplicated
Plasmodium falciparum malaria
Lancet
336
1990
1201
1204
1978068
21
Davis
TME
Sturm
M
Yue-Rong
Z
Platelet-activating factor and lipid metabolism in acute malaria
J Infect
26
1993
279
285
8505562
22
Turner
GDH
Morrison
H
Jones
M
An immunohistochemical study of the pathology of fatal malaria – evidence for widespread
endothelial activation and a potential role for intercellular adhesion molecule-1
in cerebral sequestration
Am J Pathol
145
1994
1057
1069
7526692
23
Macpherson
GG
Warrell
MJ
White
NJ
Human cerebral malaria, a quantitative ultrastructural analysis of parasitised erythrocyte
sequestration
Am J Pathol
119
1985
385
401
3893148
24
Anstey
NM
Jacups
SP
Cain
T
Pulmonary manifestations of uncomplicated falciparum and vivax malaria: cough, small
airways obstruction, impaired gas transfer, and increased pulmonary phagocytic activity
J Infect Dis
185
2002
1326
1334
12001051
Leishmaniasis
25
Duarte
MI
da Matta
VLR
Corbett
CEP
Interstitial pneumonitis in human visceral leishmaniasis
Trans Roy Soc Trop Med Hyg
83
1989
73
76
Cryptosporidiosis
26
Davies
AP
Chalmers
RM
Cryptosporidiosis
BMJ
339
2009
b4168
19841008
27
Chen
XM
Keithly
JS
Paya
CV
Current concepts: Cryptosporidiosis
N Engl J Med
346
2002
1723
1731
12037153
28
Travis
WD
Schmidt
K
MacLowry
JD
Respiratory cryptosporidiosis in a patient with malignant lymphoma. Report of a case
and review of the literature
Arch Pathol Lab Med
114
1990
519
522
2185714
29
Moore
JA
Frenkel
JK
Respiratory and enteric cryptosporidiosis in humans
Arch Pathol Lab Med
115
1991
1160
1162
1747035
30
Meynard
JL
Meyohas
MC
Binet
D
Pulmonary cryptosporidiosis in the acquired immunodeficiency syndrome
Infection
24
1996
328
331
8875287
31
Clavel
A
Arnal
AC
Sanchez
EC
Respiratory cryptosporidiosis: case series and review of the literature
Infection
24
1996
341
346
8923043
32
Maggi
P
laRocca
AM
Quarto
M
Effect of antiretroviral therapy on cryptosporidiosis and microsporidiosis in patients
infected with human immunodeficiency virus type 1
Eur J Clin Microbiol Infect Dis
19
2000
213
217
10795595
33
Palmieri
F
Cicalini
S
Froio
N
Pulmonary cryptosporidiosis in an AIDS patient: successful treatment with paromomycin
plus azithromycin
Int J STD AIDS
16
2005
515
517
16004637
Trichomoniasis
34
Hersh
SM
Pulmonary trichomoniasis and Trichomonas tenax
J Med Microbiol
20
1985
1
10
3894667
35
McLaren
LC
Davis
LE
Healy
GR
Isolation of Trichomonas vaginalis from the respiratory tract of infants with respiratory
disease
Pediatrics
71
1983
888
890
6602324
36
Radosavljevicasic
G
Jovanovic
D
Radovanovic
D
Trichomonas in pleural effusion
Eur Respir J
7
1994
1906
1908
7828704
Schistosomiasis
37
Schwartz
E
Rozenman
J
Perelman
M
Pulmonary manifestations of early schistosome infection among nonimmune travelers
Am J Med
109
2000
718
722
11137487
38
Schwartz
E
Pulmonary schistosomiasis
Clin Chest Med
23
2002
433
443
12092037
39
Shaw
AFB
Ghareeb
AA
The pathogenesis of pulmonary schistosomiasis in Egypt with special reference to Ayerza's
disease
J Pathol Bacteriol
46
1938
401
423
40
Cheever
AW
Kamel
IA
Elwi
AM
Schistosoma mansoni and S. haematobium infections in Egypt
Am J Trop Med Hyg
27
1978
55
75
626283
41
Harris
P
Heath
D
The Human Pulmonary Circulation. Its Form and Function in Health and Disease
3rd ed
1986
Churchill Livingstone
Edinburgh
Paragonimiasis
42
Mukae
H
Taniguchi
H
Matsumuto
L
Clinicoradiologic features of pleuropulmonary Paragonimus westermani on Kyusyu Island,
Japan
Chest
120
2001
514
520
11502652
43
DeFrain
M
Hooker
R
North American paragonimiasis – Case report of a severe clinical infection
Chest
121
2002
1368
1372
11948081
44
Castilla
EA
Jessen
R
Sheck
DN
Cavitary mass lesion and recurrent pneumothoraces due to Paragonimus kellicotti infection
– North American paragonimiasis
Amer J Surg Pathol
27
2003
1157
1160
12883250
45
Watanabe
S
Nakamura
Y
Kariatsumari
K
Pulmonary paragonimiasis mimicking lung cancer on FDG-PET imaging
Anticancer Res
23
2003
3437
3440
12926086
46
Sugiyama
H
Morishima
Y
Kameoka
Y
Polymerase chain reaction (PCR)-based molecular discrimination between Paragonimus
westermani and P. miyazakii at the metacercarial stage
Mol Cell Probes
16
2002
231
236
12144775
47
Nakamura-Uchiyama
F
Mukae
H
Nawa
Y
Paragonimiasis: a Japanese perspective
Clin Chest Med
23
2002
409
420
12092035
48
Al Mohaya
SA
Al Sohaibani
M
Bukhari
H
Pulmonary paragonimiasis presenting as a hemorrhagic pleural effusion
Eur J Respir Dis
71
1987
314
316
3691686
Opisthorchiasis
49
Prijyanonda
B
Tandhanand
S
Opisthorchiasis with pulmonary involvement
Ann Intern Med
54
1961
795
799
13738024
Hydatid disease (larval echinococcosis)
50
Tor
M
Atasalihi
A
Altuntas
N
Review of cases with cystic hydatid lung disease in a tertiary referral hospital located
in an endemic region: A 10 years’ experience
Respiration
67
2000
539
542
11070459
51
Scully
RE
Mark
EJ
McNeely
WF
A 34-year-old woman with one cystic lesion in each lung – Bilateral pulmonary echinococcal
cysts
N Engl J Med
341
1999
974
982
10498494
52
Eroglu
A
Kurkcuoglu
C
Karaoglanoglu
N
Bilateral multiple pulmonary hydatid cysts
Eur J Cardiothorac Surg
23
2003
1053
12829089
53
Baden
LR
Elliott
DD
Miseljic
S
Case 4–2003: A 42-year-old woman with cough, fever, and abnormalities on thoracoabdominal
computed tomography – Echinococcus granulosus infection
N Engl J Med
348
2003
447
455
12556547
54
Den Hertog
RW
Wagenaar
SjSc
Westermann
CJJ
Bronchocentric granulomatosis and pulmonary echinococcosis
Am Rev Respir Dis
126
1982
344
347
7103261
55
Dakak
M
Genc
O
Gurkok
S
Surgical treatment for pulmonary hydatidosis (a review of 422 cases)
J R Coll Surg Edinb
47
2002
689
692
12463709
56
Kabiri e, Caidi
M
al Aziz
S
Surgical treatment of hydatidothorax. Series of 79 cases
Acta Chir Belg
103
2003
401
404
14524160
57
Ayed
AK
Alshawaf
E
Surgical treatment and follow-up of pulmonary hydatid cyst
Med Princ Pract
12
2003
112
116
12634467
Cysticercosis (larval taeniasis)
58
Walts
AE
Nivatpumin
T
Epstein
A
Pulmonary cysticercus
Mod Pathol
8
1995
299
302
7617658
59
Mauad
T
Battlehner
CN
Bedrikow
CL
Case report: massive cardiopulmonary cysticercosis in a leukemic patient
Pathol Res Pract
193
1997
527
529
9342760
Ascariasis and toxocariasis (‘visceral larva migrans’)
60
Heggers
JP
Muller
MJ
Elwood
E
Ascariasis pneumonitis: a potentially fatal complication in smoke inhalation injury
Burns
21
1995
149
151
7766327
61
Jeanfaivre
T
Cimon
B
Tolstuchow
N
Pleural effusion and toxocariasis
Thorax
51
1996
106
107
8658358
Strongyloidiasis
62
Gill
V
Bell
DR
Strongyloidiasis in ex-prisoners of war in south-east Asia
BMJ
280
1982
1319
63
Gill
GV
Bell
DR
Strongyloides stercoralis infection in Burma Star veterans
BMJ
294
1987
1003
1004
64
Higenbottam
TW
Heard
BE
Opportunistic pulmonary strongyloidiasis complicating asthma treated with steroids
Thorax
31
1976
226
232
781904
65
Ting
YM
Pulmonary strongyloidiasis – case report of 2 cases
Kaohsiung J Med Sci
16
2000
269
274
10969524
66
O'Doherty
MJ
Van de Pette
JE
Nunan
TO
Recurrent Strongyloides stercoralis infection in a patient with T-cell lymphoma-leukaemia
Lancet
1
1984
858
67
Newton
RC
Limpuangthip
P
Greenberg
S
Strongyloides stercoralis hyperinfection in a carrier of HTLV-I virus with evidence
of selective immunosuppression
Am J Med
92
1992
202
208
1543206
68
Robinson
RD
Lindo
JF
Neva
FA
Immunoepidemiologic studies of Strongyloides stercoralis and human T lymphotropic
virus type I infections in Jamaica
J Infect Dis
169
1994
692
696
8158055
69
Kinjo
T
Tsuhako
K
Nakazato
I
Extensive intra-alveolar haemorrhage caused by disseminated strongyloidiasis
Int J Parasitol
28
1998
323
330
9512996
70
Lin
AL
Kessimian
N
Benditt
JO
Restrictive pulmonary disease due to interlobular septal fibrosis associated with
disseminated infection by Strongyloides stercoralis
Am J Respir Crit Care Med
151
1995
205
209
7812554
71
Mayayo
E
Gomez-Aracil
V
Azua-Blanco
J
Strongyloides stercolaris infection mimicking a malignant tumour in a non-immunocompromised
patient. Diagnosis by bronchoalveolar cytology
J Clin Pathol
58
2005
420
422
15790710
Filariasis: tropical eosinophilia
72
Udwadia
FE
Tropical eosinophilia – a review
Respir Med
87
1993
17
21
8438095
73
Webb
JGK
Job
CK
Gault
EW
Tropical eosinophilia : demonstration of microfilariae in lung, liver, and lymph nodes
Lancet
1
1960
835
842
13843264
74
Danaraj
TJ
Pacheco
G
Shanmugaratnam
K
The etiology and pathology of eosinophilic lung (tropical eosinophilia)
Am J Trop Med Hyg
15
1966
183
189
5910525
Dirofilariasis (heartworm infestation)
75
Kido
A
Ishida
T
Oka
T
Pulmonary dirofilariasis causing a solitary lung mass and pleural effusion
Thorax
46
1991
608
609
1926037
76
Awe
RJ
Mattox
KL
Alvarez
BA
Solitary and bilateral pulmonary nodules due to Dirofilaria immitis
Am Rev Respir Dis
112
1975
445
449
1163897
77
Merrill
JD
Otis
J
Logan
WD
The dog heartworm (Dirofilaria immitis) in man. An epidemic pending or in progress?
JAMA
243
1980
1066
1068
7354565
78
Tsukayama
C
Manabe
T
Miura
Y
Dirofilarial infection in human lungs
Acta Pathol Jpn
32
1982
157
162
7072495
79
Chesney
TM
Martinez
LC
Painter
MW
Human pulmonary dirofilarial granuloma
Ann Thorac Surg
36
1983
214
217
6882080
80
Nicholson
CP
Allen
MS
Trastek
VF
Dirofilaria immitis – a rare, increasing cause of pulmonary nodules
Mayo Clin Proc
67
1992
646
650
1434897
81
deCampos
JRM
Barbas
CSV
Filomeno
LTB
. Human pulmonary dirofilariasis: Analysis of 24 cases from São Paulo, Brazil
Chest
112
1997
729
733
9315807
82
Pampiglione
S
Rivasi
F
Paolino
S
Human pulmonary dirofilariasis
Histopathology
29
1996
69
72
8818697
83
Pampiglione
S
Rivasi
F
Angeli
G
Dirofilariasis due to Dirofilaria repens in Italy, an emergent zoonosis: report of
60 new cases
Histopathology
38
2001
344
354
11318900
84
Pampiglione
S
Rivasi
F
Gustinelli
A
Dirofilarial cases in the Old World, attributed to Dirofilaria immitis: a critical
appraisal
Histopathology
54
2009
192
204
19207944
85
Flieder
DB
Moran
CA
Pulmonary dirofilariasis: A clinicopathologic study of 41 lesions in 39 patients
Hum Pathol
30
1999
251
256
10088541
86
Hiroshima
K
Iyoda
A
Toyozaki
T
Human pulmonary dirofilariasis: report of six cases
Tohoku J Exp Med
189
1999
307
314
10739166
Syngamiasis (gapeworm infestation)
87
Basden
RDE
Jackson
JW
Jones
EI
Gapeworm infestation in man
Br J Dis Chest
68
1974
207
209
4279103
88
Grell
GAC
Watty
EI
Muller
RL
Syngamus in a West Indian
BMJ
2
1978
1464
89
Delara
TDC
Barbosa
MA
Deoliveira
MR
Human syngamosis – two cases of chronic cough caused by Mammomonogamus laryngeus
Chest
103
1993
264
265
8417893
90
Kim
HY
Lee
SM
Joo
JE
Human syngamosis: the first case in Korea
Thorax
53
1998
717
718
9828862
Acariasis
91
Li
C
Li
L
Human pulmonary acariasis in Anhui Province: an epidemiological survey
Zhongguo Ji. Sheng Chong. Xue Yu Ji. Sheng Chong. Bing. Za Zhi
8
1990
41
44
2364504
Pentastomiasis
92
Guardia
SN
Sepp
H
Scholten
T
Pentastomiasis in Canada
Arch Pathol Lab Med
115
1991
515
517
2021321
93
Morsy
TA
El Sharkawy
IM
Lashin
AH
Human nasopharyngeal linguatuliasis (Pentasomida) caused by Linguatula serrata
J Egypt Soc Parasitol
29
1999
787
790
12561918