Cast nephropathy associated with monoclonal immunoglobulin M-secreting mucosa-associated lymphoid tissue B-cell lymphoma
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The kidney is among the various anatomical sites involved in mucosa-associated lymphoid tissue (MALT) lymphoma. A variety of renal pathological types, including membranous glomerulopathy, membranoproliferative glomerulonephritis, crescentic IgA nephropathy, minimal change disease, and cryoglobulinemic glomerulopathy, have been reported in MALT lymphoma patients. However, cast nephropathy is extremely rare in MALT lymphoma. Herein, we describe the case of a patient with a history of MALT lymphoma of the stomach and small intestine 7 years before presenting with acute kidney failure 1 year after chemotherapy cessation. Monoclonal IgM-λ was detected in the serum, and kidney biopsy showed λ light chain deposition-based cast nephropathy. In addition, MALT recurrence was discovered in the stomach rather than intestinal tissue by gastrointestinal endoscope, and no lymphoplasmacytic infiltration was found in bone marrow. After 1 year of chemotherapy, renal function was partially restored, and the level of serum λ chain, serum IgM, and 24-hour urine protein all decreased. Our case illustrates that MALT lymphoma is prone to recurrence and grows slowly, moreover, with the characteristic of monoclonal immunoglobulin production and kidney infiltration.