KEY POINTS
Rare cases of systemic capillary leak syndrome (SCLS) have been reported worldwide
after vaccination with adenoviral vector and mRNA vaccines against SARS-CoV-2; a number
have occurred in patients with a history of SCLS.
Systemic capillary leak syndrome is a potentially life-threatening immune disorder
that is characterized by transient, recurrent episodes of vascular endothelial hyperpermeability
that are often triggered by viral upper respiratory infections.
Hypotension, hemoconcentration, hypoalbuminemia and anasarca are prominent features
of SCLS, reflecting the massive leakage of fluids and proteins into peripheral tissues.
Acute SCLS can rapidly evolve into shock and multiorgan failure, and treatment is
mostly aimed at correcting hypovolemia and avoiding end-organ damage; prophylactic
monthly administration of immunoglobulins can help prevent further episodes.
Adenoviral vector vaccines against SARS-CoV-2 are not advised for patients with a
history of SCLS.
A 66-year-old man presented to the emergency department with a 1-day history of generalized
malaise, nausea, abdominal pain and dizziness. On presentation the patient’s body
temperature was 36.5°C, blood pressure 112/78 mm Hg, heart rate 112 beats/min and
oxygen saturation 96% (room air), and his respiratory rate was normal. He reported
no allergies, no drug or alcohol misuse, and no current use of any medications or
over-the-counter products. Two days earlier, he had received his first dose of the
ChAdOx1 nCOV-19 (Oxford–AstraZeneca) vaccine.
The patient’s medical history included monoclonal gammopathy of uncertain significance
(immunoglobulin G [IgG] κ) and a cardiac arrest in 2017. At that time, he presented
with generalized weakness and a syncopal episode. Because his hemoglobin level was
elevated (210 [normal 130–180] g/L), polycythemia was suspected and phlebotomy was
performed. Soon after, the patient became hypotensive and went into pulseless electrical
activity arrest. He was successfully resuscitated, recovered without substantial deficits
and was discharged home 5 weeks later. His test result for influenza type A was positive,
and his shock was attributed to the viral infection.
At this presentation, the patient’s hemoglobin level was increased markedly at 224
g/L. He had hypoalbuminemia (28 [normal 34–55] g/L) and an elevated creatinine level
(133 [normal 62–115] μmol/L). Coagulation parameters, cardiac and liver enzymes, C-reactive
protein and procalcitonin were normal. Screening results for SARS-CoV-2 and extended
respiratory virus panel were negative. Examinations using chest radiography, abdominal
computed tomography, electrocardiography and focussed assessment with sonography for
trauma echocardiography were unremarkable (Table 1 and Table 2).
Table 1:
Laboratory test results for the patient during his 4-day stay in hospital
Laboratory test
Test result
At admission
4 h
12 h
24 h
48 h
72 h
96 h
Hemoglobin, g/L (normal 130–180 g/L)
224
226
223
184
142
131
136
Hematocrit, % (normal 39%–52%)
65
68.8
68
54.8
41.9
38.4
40
White blood cell count, × 109/L (normal 4.4–11.0 × 109/L)
14.5
19.7
24.5
21.5
11.4
7.6
6.9
Neutrophil count, × 109/L (normal 1.8–7.0 × 109/L)
10.5
15.7
21.3
16.7
7.6
4.6
4.3
Lymphocyte count, × 109/L (normal 1.0–4.0 × 109/L)
2.4
2.2
2.4
3.2
2.5
2.1
2
Platelets, × 109/L (normal 140–440 × 109/L)
222
237
251
202
173
164
174
Albumin, g/L (normal 34–55 g/L)
28
ND
ND
25
ND
ND
38
Creatinine, μmol/L (normal 62–115 μmol/L)
133
133
159
122
90
71
79
Lactate level, mmol/L (normal 0.5–2.2 mmol/L)
ND
ND
3.8
3.3
1.1
ND
ND
D-dimer level, μg/L (normal 0–500 μg/L)
353
ND
ND
ND
ND
ND
ND
Prothrombin time, INR (normal 0.9–1.1)
1.1
ND
ND
ND
ND
ND
ND
Partial prothrombin time, s (normal 20.1–26.4 s)
28.4
ND
ND
ND
ND
ND
ND
Note: ND = not done, INR = international normalized ratio.
Table 2:
Causes of polycythemia, hypoalbuminemia and hypotension and the reasons for exclusion
in our patient
Presentation
Differential diagnosis
Reason for exclusion
Polycythemia
Primary polycythemia
Inherited:
Congenital heart defects
Normal transthoracic echocardiogram
Acquired:
Polycythemia vera
Absence of Janus kinase 2 (JAK-2) mutation (Val671Phe)
Leukemia
Absence of BCR-ABL t(9;22) mutation
Secondary polycythemia
Chronic hypoxia or cardiopulmonary abnormalities
No clinical symptoms of obstructive sleep apnea and low risk according to the STOP-BANG
score
No known chronic pulmonary disease
No obesity hypoventilation syndrome and no daytime hypercapnia
No elevation of erythropoietin level: 4.6 (normal range 5.0–16.0) IU/L
Normal hemoglobin and hematocrit levels between acute episodes
No history of high-altitude travel
Erythropoietin-secreting tumours
Level of erythropoietin not high
Relative polycythemia
DehydrationCapillary leak syndrome
Not excluded
Hypoalbuminemia
Nephrotic syndrome
No proteinuria, negative urine protein-to-creatinine ratio: undetectable (normal <
0.15 g protein/g creatinine)
No evidence of hyperlipidemia that may be associated with nephrotic syndrome (normal
fasting lipid profile)
Poor nutrition or liver cirrhosis
Rapid correction of serum albumin levels is inconsistent with hypoalbuminemia from
poor nutrition or cirrhosis
No features of liver cirrhosis or ascites on abdominal CT
Hypotension and shock
Sepsis
Normal procalcitonin level 0.28 (normal 0.00–0.39) μg/L and C-reactive protein level
4.9 (normal 0.0–10.0) mg/L
No evidence of infection on chest radiography and abdominal CT
Two negative results for blood cultures
Negative result for urine culture
Negative result for screening (RT–PCR) test for SARS-CoV-2 (COVID-19 direct diagnostic
kit)
Negative result for serology screening test for SARS-CoV-2 IgG
Negative results for screening for common respiratory viruses and pathogens: syncytial
respiratory virus; influenza type A (H1 and H3); influenza type B; parainfluenza viruses
1, 2, 3 and 4; human metapneumovirus; entero-rhinovirus, coronavirus NL 63, HKU1,
OC43 and 229E; adenovirus; Bordetella pertussis and parapertussis; Chlamydophilia
pneumoniae; or Mycoplasma pneumoniae
Negative results for serology screening test for HIV-1 and -2 (p24 combo)
Cardiogenic and obstructive shock
Normal FAST ultrasonography in the emergency department
Normal electrocardiogram
Normal transthoracic echocardiography and negative result for exercise stress test
(recent outpatient investigations)
Absence of pulmonary edema and raised central venous pressure
Normal cardiac enzymes (troponin < 3 [normal 0–18] ng/L) and D-dimer levels (353 [normal
< 500] μg/L)
Negative V/Q
Anaphylaxis
Absence of typical clinical signs or symptoms associated with anaphylaxis (e.g., respiratory
compromise, rash, pruritus, angioedema or persistent gastrointestinal symptoms)
Normal tryptase level: 3.0 (normal < 11) μg/L
Hereditary angioedema
Normal C4 esterase activity (0.20 [normal 0.13–0.40] g/L) and C1 esterase activity
(0.97 [normal 0.69–1.42] g/L)
Other diseases excluded
Cancer drug reactionsHemophagocytic lymphohistiocytosisViral hemorrhagic feverSnakebite
envenomation
Absence of the epidemiologic factors usually associated with these diagnoses
Note: CT = computed tomography, FAST = focussed assessment with sonography for trauma,
IgG = immunoglobulin G, RT–PCR = reverse transcription–polymerase chain reaction.
We started intravenous fluids and empiric treatment with piperacillin–tazobactam,
despite the unlikelihood of an infectious process. Twelve hours later, the patient
had received more than 6 L of fluid, but his blood pressure had deteriorated to 93/60
mm Hg, his heart rate was 125 beats/min and his polycythemia persisted (hemoglobin
223 g/L). We admitted the patient to the intensive care unit (ICU). In the absence
of other causes of impending shock, we diagnosed systemic capillary leak syndrome
(SCLS).
During the first 24 hours of his admission, the patient received more than 10 L of
intravenous fluid, but his hemoglobin and lactic acid levels remained elevated (Table
1), and his creatinine level continued to rise. Central venous pressure was consistently
0–1 mm Hg. He did not need vasopressors and he required oxygen therapy only transiently.
He developed substantial anasarca and gained 15 kg. Eventually, his hemodynamic status
improved, laboratory abnormalities resolved, and he was discharged 4 days later.
We considered various causes of hypotension, polycythemia and hypoalbuminemia, and
eliminated all of them (Table 2). Because his SCLS developed 2 days after vaccination
against SARS-CoV-2 and we identified no other triggers, we suspected a possible adverse
reaction to the ChAdOx1 nCOV-19 vaccine and reported the reaction to our local department
of public health.
Interpretation
Systemic capillary leak syndrome is a rare disorder associated with recurrent episodes
of extravasation of fluid and protein into the interstitial space.1,2 Fewer than 500
cases have been reported. Recognizing SCLS may be challenging, because presentation
has often been preceded by a prodrome of flu-like symptoms and may be mistaken for
sepsis. There are no specific diagnostic criteria for SCLS. Once other causes of shock
have been excluded, the classical triad of hypotension, hemoconcentration and hypoalbuminemia
supports the diagnosis of SCLS.2 Together with generalized edema, those 3 features
are manifestations of the vascular hyperpermeability and extreme hypovolemia that
occur with this syndrome.
The exact pathophysiology of SCLS is mostly unknown. Typically, exacerbations can
be triggered by viral upper respiratory infections.1,3–5 An overwhelming immune response
and upregulation of soluble inflammatory and angiogenic mediators during flares appear
to be linked to vascular endothelial hyperpermeability. 2 Monoclonal gammopathy of
uncertain significance (predominantly IgG κ) is observed in 68%–85% of patients with
SCLS, although a pathogenic role for the paraprotein has yet to be established.2 Reports
exist of patients with SCLS who had a cardiac arrest triggered by influenza type A,
similar to the experience of our patient in 2017.5,6 It is likely that his cardiac
arrest at that time occurred during an unrecognized episode of SCLS; he had hypoalbuminemia
(29 g/L), hemoconcentration and hypovolemia. However, SCLS was not suspected until
this admission.
Our patient’s near-fatal episodes illustrate that unrecognized SCLS can be life-threatening;
SCLS is associated with an estimated 10-year mortality rate of 25%–34%.1,4 In addition
to shock and renal and cardiopulmonary failure arising from intravascular volume depletion,
thromboembolic events and compartment syndrome can occur. Systemic capillary leak
syndrome can be classified as grade 1 (hypotension responding to oral hydration),
grade 2 (intravenous fluids without hospital admission), grade 3 (life threatening
and requiring admission to an ICU) and grade 4 (fatal).1
No interventions other than fluid resuscitation have been shown to halt or delay progression
of a flare of SCLS.2 Most episodes are self-limited and resolve within 4 days.1 The
frequency of recurrence of SCLS varies, ranging from once weekly to once every 10
years. Administration of prophylactic monthly intravenous Igs can reduce the frequency
of episodes.1,2
The World Health Organization (WHO) reports that 3.8 billion doses of vaccines against
SARS-CoV-2 have been administered worldwide (as of July 29, 2021; WHO Coronavirus
[COVID-19] Dashboard, available at https://covid19.who.int). Adverse effects are usually
mild and local in nature; however, rare serious adverse reactions can occur, such
as pericarditis or myocarditis, anaphylaxis, Guillain–Barré syndrome and thromboembolic
events with concurrent low platelet levels (the latter occurring mostly with adenoviral
vector vaccines).7
In April 2021, the European Medicines Agency (EMA) reported 6 cases of SCLS following
receipt of the ChAdOx1 nCOV-19 vaccine (including 1 fatality).8 Three of those patients
had a previous history of SCLS. More than 78 million doses of the ChAdOx1 nCOV-19
vaccine have been administered in Europe, with a reported rate of 1 case of SCLS per
13 million doses.8 In June 2021, Health Canada issued the first report of SCLS in
a patient who had received a ChAdOx1 nCOV-19 vaccine in Canada.9 The United Kingdom’s
Medicines & Healthcare products Regulatory Agency (MHRA) reported 8 potential cases
of SCLS that occurred shortly after administration of the ChAdOx1 nCOV-19 vaccine.7
Our patient had a score of at least 4 on the Naranjo Adverse Drug Reaction Probability
Scale,10 making this a possible case of exacerbation of SCLS induced by the ChAdOx1
nCOV-19 vaccine.
Many health agencies have concluded that SCLS, albeit rare, should be considered a
serious and potentially fatal adverse effect of the ChAdOx1 nCOV-19 vaccine, and are
now advising against its use in patients with known SCLS.7–9 After the EMA’s July
2021 report of 3 cases of severe SCLS, 2 with fatal outcomes, which were potentially
linked to the Ad26.COV2.S vaccine (Johnson & Johnson–Janssen; an adenoviral vector
vaccine), similar advice against using the Ad26.COV2.S vaccine in patients with a
history of SCLS was made.8
In June 2021, a case series described 3 patients who presented with acute SCLS within
2 days of receiving a SARS-CoV-2 vaccine.11 They all had monoclonal gammopathy of
uncertain significance and pre-existing SCLS. The 3 patients received different vaccines:
Ad26.COV2.S, mRNA-1273 (Moderna) and BNT162b2 (Pfizer–BioNTech). To our knowledge,
no other cases of SCLS have been reported that were associated with mRNA SARS-CoV-2
vaccines, and thus far no warnings or recommendations related to SCLS have been released
regarding the mRNA-1273 or BNT162b2 vaccines. Whether exacerbations are triggered
by adenoviral vectors themselves or by SARS-CoV-2 antigen (spike protein) remains
to be determined.
Administration of mRNA SARS-CoV-2 vaccines can still be used in patients with a history
of SCLS, if the benefits are considered to outweigh the risks. After vaccination,
physicians and patients must be extra vigilant, because exacerbations can develop
quickly and patients may require urgent medical assessment. In our opinion, patients
should be monitored closely during the 7–10 days after vaccination with home surveillance
of blood pressure, heart rate, weight and urine output; hemoglobin and albumin levels
should be measured at least once or twice. We also suggest that prophylaxis with intravenous
immunoglobulins be started before vaccination, if not already given monthly.
Conclusion
We presented the case of a patient with an acute exacerbation of SCLS after ChAdOx1
nCOV-19 vaccination. Early recognition and treatment of acute SCLS is crucial. When
a patient presents with generalized edema, malaise, hypotension, hemoconcentration
or hypoalbuminemia shortly after administration of a SARS-CoV-2 vaccine, regardless
of which vaccine was administered, SCLS should be considered. A history of SCLS is
now considered a contraindication to adenoviral vector vaccines against SARS-CoV-2.
Health care professionals should report any suspected adverse reactions to SARS-CoV-2
vaccines to their public health agency.
The section Cases presents brief case reports that convey clear, practical lessons.
Preference is given to common presentations of important rare conditions, and important
unusual presentations of common problems. Articles start with a case presentation
(500 words maximum), and a discussion of the underlying condition follows (1000 words
maximum). Visual elements (e.g., tables of the differential diagnosis, clinical features
or diagnostic approach) are encouraged. Consent from patients for publication of their
story is a necessity. See information for authors at www.cmaj.ca.