Mixed cryoglobulinemic membranoproliferative glomerulonephritis due to monoclonal gammopathy of undetermined significance: A case report

RATIONALE: Membranoproliferative glomerulonephritis (MPGN) can be induced by autoimmune diseases, chronic infection, chronic hepatitis, and paraproteins (including cryoglobulinemia). In addition, the mixed cryoglobulinemic MPGN is reported to be highly correlated with hepatitis C virus (HCV) infection. PATIENT CONCERNS: We reported a rare case of a 61-year-old woman without a history of viral hepatitis infection; she presented with bilateral leg edema and proteinuria. Renal pathology revealed MPGN with multiple positive immunofluorescent staining. The consequent serum survey revealed positive cryoglobulin and monoclonal gammopathy of kappa type of immunoglobulin M. However, bone marrow study showed no obvious plasma cell proliferation, indicating that multiple myeloma was less likely. DIAGNOSES: This patient's cryoglobulinemic MPGN could be related to monoclonal gammopathy of undetermined significance. INTERVENTIONS: Oral immunosuppressant. OUTCOMES: After steroid treatment, her renal function normalized and proteinuria kept in low level. LESSONS: We demonstrated a rare cause of cryoglobulinemic MPGN without HCV infection, which led to a favorable prognosis after receiving steroid therapy. Moreover, the diagnosis of monoclonal gammopathy should be considered when facing such case and aggressive steroid therapy might be beneficial.