Pathologist's puzzle: Membranoproliferative glomerulonephritis-like features in cryoglobulinemic glomerulonephritis.

Mixed cryoglobulinemia is commonly related to chronic HCV infection, and renal complications occur frequently. Typical renal involvement presents with diffuse proliferative glomerular pathology, similar to membranoproliferative glomerulonephritis, with necrotizing arteritis of medium-sized vessels, referred to as cryoglobulinemic glomerulonephritis. However, the histological appearance may vary according to the clinical presentation and treatment applied. Not only membranoproliferative glomerulonephritis but also certain types of systemic vasculitis (Systemic Lupus Erythematosus, Polyarteritis Nodosa), thrombotic microangiopathy, and Waldenstrom's Macroglobulinemia may exhibit similar histopathological findings in the biopsy with cryoglobulinemic glomerulonephritis. For an optimal differential diagnosis, clinicopathological correlation and serological findings should accompany the pathological findings. We present a case of cryoglobulinemic glomerulonephritis, and discuss the differential diagnosis in detail.