Paraneoplastic glomerulonephritis and kidney infiltration by mantle cell lymphoma: A diagnostic challenge.

Mantle cell lymphoma (MCL) is a rare and aggressive type of lymphoma that can affect the kidneys. The disease can lead to kidney impairment, and glomerulonephritis (GN) is a rare but serious complication of MCL. We report a case of MCL with kidney interstitial infiltration and membranoproliferative glomerulonephritis with focal and segmental glomerulosclerosis. A 75-year-old man presented recurrent acute kidney failure and worsening of nephrotic syndrome. Kidney biopsy revealed membranoproliferative glomerulonephritis presented immunoglobulin and complement deposition, focal and segmental glomerulosclerosis of not otherwise specified type, and infiltration by mantle cell lymphoma. Bone marrow biopsy and PET/CT scan confirmed the diagnosis of mantle cell lymphoma. The patient was treated with R-CHOP21 chemotherapy with cyclophosphamide dose adjustment for nephroprotection. He achieved complete remission with normalization of hematological parameters, improvement of kidney function, and reduction of proteinuria and albuminuria. This case shows the importance of considering alternative diagnoses in patients with recurrent chronic kidney disease and worsening nephrotic syndrome. Early diagnosis and treatment of mantle cell lymphoma can lead to favorable outcomes.