Introduction
Epstein−Barr virus (EBV), also known as HHV-4, is a ubiquitous oncogenic lymphotropic
gamma herpes virus that infects the majority of adults. It evades the immune system,
staying dormant in B-lymphocytes. Reactivation occurs in situations of stress and
immunosuppression. Epstein−Barr virus can cause infectious mononucleosis, several
types of lymphoma, and nasopharyngeal carcinoma. It has also been associated with
autoimmune diseases such as systemic lupus erythematosus and multiple sclerosis.
1
Rare case reports describe the occurrence of acute interstitial nephritis,
2
acute tubular necrosis,
3
membranoproliferative glomerulonephritis (MPGN),
4
minimal change disease,
5
and membranous nephropathy
6
in the setting of EBV infection. There remains, however, a scarcity in the literature
about the association between EBV and glomerulonephritis (GN). Reactivation of EBV
has been implicated in the pathogenesis of monoclonal gammopathy, particularly when
T cells are depleted with anti-thymocyte globulin or alemtuzumab, as in stem-cell
transplantation.
7
Monoclonal proteins, through their physicochemical properties or via immunological
mechanisms, can cause a variety of renal diseases collectively labeled as monoclonal
gammopathies of renal significance (MGRS).
8
Although some antiviral drugs have activity against EBV, none has been approved so
far for its treatment.
9
Immune-complex mediated MPGN (IC-MPGN) is a rare form of GN characterized by the presence
of subendothelial nephritogenic immune complexes in the glomerular capillary wall,
mesangial interposition, and activation of the classical complement pathway. It can
be idiopathic or more commonly secondary to infections, autoimmune diseases, or paraproteinemia.S1
The coexistence of all 3 factors is distinctly unusual. Treatment of MPGN depends
on the cause. Infections such as hepatitis C or B are treated with antivirals. Immunosuppression
in such cases can be deleterious. Neoplasms such as chronic lymphocytic leukemia are
treated with chemotherapy or biotherapeutics, whereas autoimmune diseases are treated
with immunosuppressive drugs. The proper treatment of monoclonal gammopathy of renal
significance remains uncertain.S2
Case Presentation
A 51-year-old woman presented with anasarca and dyspnea following a flu-like illness.
She was found to have severe new-onset hypertension, pulmonary edema, and bilateral
pleural effusions. She had no B-symptoms, lymphadenopathy, or splenomegaly. Urinalysis
revealed an active sediment with 3+ protein and 3+ blood. Her 24-hour urine protein
was 3.63 g and serum albumin was 35 g/l. Serum creatinine was within normal range
at 85 μmol/l. C4 was normal, but C3 was low. Connective tissue serologies were negative.
Infectious serologies were positive for EBV early and nuclear antigens with a negative
IgM. She was treated with i.v. furosemide and required 4 additional antihypertensive
drugs, including a renin−angiotensin system (RAS) inhibitor. Renal biopsy revealed
marked endocapillary hypercellularity, neutrophils, and monocytes infiltration, and
focal karyorrhexis but no crescents (Figure 1a). Immunofluorescence study showed granular
glomerular capillary wall staining with antisera specific for IgG (1+), IgM (2+),
C3 (3+), C1q (1+), and kappa (3+) and lambda (1+) light chains. Staining for IgA and
fibrinogen was negative. On electron microscopy, the glomeruli showed multiple subendothelial
electron-dense deposits with focal mesangial interposition, basement membrane duplication,
and occasional mesangial deposits. Some of the deposits demonstrated organized substructure
composed of annular-tubular arrays suggestive of cryoglobulinemia (Figure 1b and 1c).
Cryoglobulins were negative on 2 occasions. The EBV viral load was 18.948 copies/ml.
Table 1 lists laboratory findings upon admission.
Figure 1
(a) A glomerulus showing endocapillary hypercellularity with neutrophil infiltration
(hematoxylin and eosin stain). (b) A glomerulus showing subendothelial electron dense
deposits (electron microscopy; low magnification). (c) Higher magnification of Figure 1b
demonstrating organized substructure of these deposits with annular-tubular arrays
appearance.
Table 1
Patient’s admission laboratory results
CBC differential
WBC
5.74
109/l
RBC
L 3.87
1012/l
HGB
111
g/l
HCT
0.32
l/l
MCV
82.7
fL
PLT
210
109/l
Peripheral blood morphology
Few reactive lymphocytes and mild thrombocytopenia
Urine chemistry
Creatinine, random urine
11.68
mmol/l
Protein, random urine
4.29
g/l
PCR, random urine
3.23
g/g
Urinalysis
Protein
3+
pH
6.5
Blood
3+
WBC
6-10/hpf
RBC
31-40/hpf
Infectious serology
Hepatitis Bs antigen
Nonreactive
Hepatitis C virus antibody
Nonreactive
Streptozyme
Negative
CMV IgM antibody
Nonreactive
Parvo virus B19, IgM antibody
Nonreactive
Parvo virus B19, IgG antibody
Reactive
EBV IgM
<10 (n = <20)
U/ml
EBV early antigen
135 (n = <9)
U/ml
EBV nuclear antigen
54 (n = <5)
U/ml
Autoimmune serology
C-ANCA (PR3)
<3.1
U/mL
P-ANCA (MPO)
<3.1
U/mL
ANCA IF
Negative
ANA
Negative
Anti-GBM antibody
Negative
Units
Cryoglobulin
Absent × 2
Rheumatoid factor
Not done
Protein electrophoresis, serum
No monoclonal spike
Protein electrophoresis, urine
No monoclonal spike
Urine immunofixation
Free kappa light chains
ANA, antinuclear antibody; ANCA, antineutrophil cytoplasmic antibody; EBV, Epstein−Barr
virus; CBC, complete blood count; CMV, cytomegalovirus; GBM, glomerular basement membrane;
HCT, hematocrit; HGB, hemoglobin; IF, immunofluorescence; MCV, mean corpuscular volume;
MPO, myeloperoxidase; PCR, polymerase chain reaction; PLT, platelet; RBC, red blood
cells; WBC, white blood cell.
The initial diagnostic impression was acute GN secondary to EBV infection, and thus
no immunosuppressive therapy was prescribed. Over the following 3 months, proteinuria
decreased to a protein/creatinine ratio (P/Cr) of 1.67 g/g, serum albumin and complement
levels increased, and renal function remained stable. Although serum and urine protein
electrophoresis were negative, free kappa light chains were present on urine immunofixation.
Serum level of free lambda chains was normal, whereas that of kappa chains was increased
with κ:λ ratio of 5.84 (N 0.26−1.65) consistent with the presence of paraproteins.
Bone marrow biopsy findings were normal, with 2% plasma cells. Light chain restriction
could not be assessed.
Liver enzymes increased in a mixed pattern, and ultrasound showed cholelithiasis,
whereas magnetic resonance cholangiopancreatography (MRCP) was negative for choledocholithiasis.
This was followed by a nephrotic relapse accompanied by a marked decrease in C4 levels
and an increase of EB viral load to 34,600 copies/ml. Oral prednisone 60 mg daily
was initiated when the P/Cr showed a marked increase to 13.5 g/g but was soon reduced
to 40 mg daily because of poor tolerance. Despite a transient decrease in P/Cr to
3.94 g/g over the following 2 months, EB viral load increased further to 94,600 copies/ml.
The patient was administered a dose of rituximab (700 mg), and prednisone was further
tapered. Proteinuria continued to decrease, reaching a P/Cr of 1.64 g/g months later
but then increased again to P/Cr of 11.36 g/g with a decline in eGFR to 34 ml/min
(Modification of Diet in Renal Disease [MDRD] equation). Additional doses of rituximab
(1 g each) were given, allowing for a brief CD-19 cell recovery in between. Tacrolimus
was added, maintaining a level of 3.5 to 5 mg/l over the following year. By 6 months
after the first rituximab dose, the EB viremia had completely resolved. Proteinuria
continued to decrease and estimated glomerular filtration rate (eGFR) to increase,
both returning to normal in less than 1 year. Urinalysis, complement levels, free
kappa light chain, and Κ/λ ratio all normalized. Antihypertensive drug requirements
decreased to 1 drug. Three-and-a-half years after the last dose of rituximab, the
patient remains in complete clinical, biochemical, hematological remission, with no
detectable viremia. Subsequent in situ hybridization on the kidney tissue was negative
for EBV. Figure 2 tracks changes in laboratory results, while showing therapeutic
interventions from the time of diagnosis.
Figure 2
Relevant laboratory results and therapeutic interventions from the time of presentation
until the last follow-up.
Discussion
Glomerulonephritis is an inflammatory condition in which tissue damage is mediated
by antibodies, immune complexes, and/or complement activation. It can be precipitated
by infection or chemical exposure; however, the trigger is often unclear. Among different
infectious agents, hepatitis B, hepatitis C, and human immunodeficiency viruses are
commonly associated with glomerular diseases.S2 Although many humans are infected
with EBV, it is rarely implicated as a cause of GN. However, EBV has been associated
with cases of GN, interstitial nephritis, and monoclonal gammopathy.
4
In some of those cases, the presence of the virus was demonstrated in the kidney.
EBV has a special ability to transform B-lymphocytes, reliably and efficiently.S3
This can explain its association with lymphomas as well as with autoimmune diseases.
Paraproteins are markers for the clonal proliferation of B-lymphocytes and plasma
cells and can mediate a number of renal diseases when they deposit in kidney tissue.
8
A monoclonal protein can also be a target antigen for antibodies, leading to complement
activation and vasculitis, as in the case of type II cryoglobulinemia. Alternatively,
it can directly activate complement, as in some cases of type I cryoglobulinemia and
proliferative GN with monoclonal immunoglobulin deposition.S4
Our patient is unique in that the acute GN was accompanied by a progressive EB viremia
and kappa light chain proteinuria. Immunofluorescence suggested the presence of immune
complexes of a monoclonal IgM kappa and a polyclonal IgG in a manner akin to rheumatoid
factor and type II cryoglobulinemia. Although serum cryoglobulins were negative on
2 occasions, the presence of the characteristic ultrastructure on EM was highly suggestive.
The negative in situ hybridization argues against a direct cytopathic effect of EBV
on the kidney. It is more plausible that a clonal transformation of a B-lymphocyte
resulted in the production of a small amount of IgM kappa paraprotein that acted as
a neoantigen, inducing a humoral immune response as in the paraneoplastic syndromes.
Epstein−Barr virus infection in humans is mostly in a latent phase as a result of
the expression of specific viral proteins. Reactivation occurs as the virus enters
a phase of lytic replication and is important in the pathogenesis of some EBV-related
diseases. Glucocorticoids have been shown to induce lytic replication by a dose-dependent
upregulation of the expression of the immediate early gene BZLF1, which produces the
protein Zebra.
1
,
S5 The source of glucocorticoids can be endogenous, as in stress situations, or exogenous
when taken for a therapeutic indication, as is often the case in idiopathic or autoimmune-associated
MPGN. On the other hand, rituximab, by depleting B cells, can reduce the risk of EBV-associated
diseases, as has been reported in immunosuppressed organ transplant recipients.S6
Rituximab has also been proposed to treat monoclonal gammopathies when the source
of the culprit clone is a lymphocyte, as in the case of macroglobulinemia of Waldenstrom,
as opposed to that of a plasma cell as in multiple myeloma.S2
Our patient’s kidney disease was preceded by a flu-like illness consistent with a
viral prodrome. Epstein−Barr virus viremia was documented early in her disease course
and increased with her first nephrotic relapse. The patient’s age and the absence
of IgM EBV antibodies support a reactivation rather than a primary EBV infection.
Following a brief partial nephrotic remission with prednisone, she had a severe nephrotic
relapse, and the EB viral load increased to 94,600 copies/ml. Following the first
dose of rituximab, EB viremia completely resolved and the proteinuria improved. With
subsequent doses, the patient achieved a complete remission in all disease manifestations
including urinary protein excretion, hematuria, renal impairment, hypocomplementemia
and paraproteinemia. This persisted for more than 3 years following the last dose
of rituximab.
Our patient presented in 2011, when the evidence for rituximab use in kidney diseases
was limited. The initial immunosuppression used consisted of tapered glucocorticoids,
and tacrolimus was added subsequently.S7 In the absence of a standard rituximab regimen
for MPGN, we dosed it every 6 to 9 months while monitoring for B-cell recovery and
immunoglobulin levels. The treatment continued until the complete resolution of disease
activity with several doses afterward to reduce the possibility of a clonal disorder
relapse.
In conclusion, we present a case of lytic reactivation of EBV infection associated
with a probable IgM kappa monoclonal gammopathy in the form of MPGN-Ig with type II
cryoglobulinemia-like features. The kidney disease failed to respond to glucocorticoid
therapy, which enhanced viral replication and exacerbated the glomerulopathy. Treatment
with a multi-dose rituximab regimen achieved a complete durable clinical, biochemical,
and hematological remission (Table 2). The co-occurrence of EBV infection, monoclonal
gammopathy, and the renal pathological findings as well as the parallel responses
to therapeutic interventions suggest that our case represent an MGRS. As in type II
cryoglobulinemic glomerulonephritic MGRS, the mechanism of renal injury is indirect,
and a circulating IgM kappa monoclonal protein cannot be found in about half of the
cases.S8
,
S9 The mounting evidence of the relationship between EBV and paraproteinemia provides
additional support.
Table 2
Teaching points
1.
Patients with GN including MPGN should be evaluated for underlying infections, auto-immune
diseases, and paraproteinemia. If no secondary cause can be identified, it is labeled
as idiopathic.
2.
Treatment of secondary GN should be directed at the underlying etiology.
3.
EBV can cause GN by several mechanisms, including the transformation of B-lymphocytes, resulting
in the development of a monoclonal gammopathy and the subsequent formation of nephritogenic
immune complexes.
4.
The use of glucocorticoids and other immunosuppressive agents in infection-associated
GN can result in the exacerbation of the infection and worsening of the kidney disease.
5.
Rituximab, by depleting B-lymphocytes, has a unique role in the treatment of EBV-associated
pathology by clearing both the viremia and the pathogenic paraprotein-producing clone.
EBV, Epstein−Barr virus; GN, glomerulonephritis; MPGN, membrano-proliferative glomerulonephritis.
Disclosure
All the authors declared no competing interests.