Cryoglobulinemic Vasculitis Manifesting as Rapidly Progressive Glomerulonephritis: A Case Report

Cryoglobulinemic vasculitis is a small- to medium-vessel vasculitis involving the skin, joints, peripheral nerves, and kidneys, due to deposition of immune complexes containing cryoglobulins. Cryoglobulins are immunoglobulins that precipitate below 37°C and are classified into three types: type I (monoclonal) and types II and III (mixed). We report a rare case of mixed cryoglobulinemia associated with monoclonal gammopathy of renal significance (MGRS) presenting as rapidly progressive glomerulonephritis (RPGN). A 35-year-old man presented with generalized edema, frothy urine, microscopic hematuria, and lower limb numbness for three weeks. Laboratory evaluation revealed elevated serum creatinine (8.5 mg/dL), markedly reduced C4 complement (0.5 mg/dL), positive rheumatoid factor, and an IgM monoclonal band on immunofixation. Bone marrow biopsy showed no abnormal plasma cell proliferation. Renal biopsy demonstrated eosinophilic, periodic acid-Schiff (PAS)-positive globules in capillary loops consistent with cryoglobulin deposits, along with a membranoproliferative pattern. Immunofluorescence showed predominant IgM and kappa light chain deposition. A qualitative cryoglobulin assay was positive, confirming type II mixed cryoglobulinemia. The patient received five sessions of plasma exchange with corticosteroids, intravenous immunoglobulin, and rituximab. He required hemodialysis support until he achieved renal recovery. A follow-up visit showed significant improvement in his proteinuria and renal function. This case underscores the importance of considering cryoglobulinemic vasculitis in the differential diagnosis of RPGN and emphasizes the need for early recognition and prompt immunosuppressive therapy to prevent irreversible renal injury.