Parvovirus B19-Induced Membranoproliferative Glomerulonephritis in an Immunocompetent Adult Patient: A Case Report.

A 41-year-old woman without significant medical history was admitted for edema and a 10 kg weight gain. Two months earlier, she had experienced a flu-like syndrome treated with amoxicillin. At admission, she presented with severe hypertension and stage 1 acute kidney injury. Work-up revealed nephrotic syndrome, microscopic hematuria, and transient biological hemolysis. Type II cryoglobulinemia was identified, along with complement consumption. Autoimmune and viral serologies were negative. Renal biopsy revealed a full-house membranoproliferative glomerulonephritis (MPGN). She was initially treated as having type II cryoglobulinemic MPGN with rituximab, corticosteroids, and nephroprotection. Subsequently, an acute coexisting parvovirus B19 infection was confirmed by seropositivity for IgG and IgM and high viremia. This was associated with an inflammatory articular flare. Rituximab was stopped and replaced by intravenous immunoglobulin (IVIg), leading to clinical and renal remission and viral clearance over a 10-month period. Although rare, parvovirus B19 is a known cause of lupus-like MPGN, even in immunocompetent adults. Failure to recognize primary parvovirus B19 infection exposes patients to diagnostic delay and unwarranted treatment. Timely IVIg therapy avoids persistent disease and prevents treatment escalation.