Chronic lymphocytic leukemia with associated renal invasion and light chain-restricted deposition membranous nephropathy: a case report and literature review.

Chronic lymphocytic leukemia (CLL) is a prevalent hematological malignancy that significantly affects the kidneys as an extramedullary organ. Reports from autopsy studies have shown the infiltration of CLL cells into the renal parenchymal in 63-93% of cases. Glomerular diseases associated with CLL are relatively rare, occurring in approximately 2% of patients and often presenting as nephrotic syndrome. The most common histological pattern observed in CLL-associated glomerular diseases is membranoproliferative glomerulonephritis, followed by minimal change disease and membranous nephropathy. In this report, we presented a case of a 69-year-old male patient with CLL who developed nephrotic syndrome. The diagnosis of CLL was confirmed through bone marrow and renal biopsies, which revealed the presence of CLL tumor cells in the renal interstitium along with membranous nephropathy characterized by light chain-restricted deposits. The tumor cells present in the renal interstitium and glomeruli of the patient expressed identical light chain restrictions, which suggested that the membranous nephropathy was secondary and possibly induced by the deposition of tumor-associated antigens. Treatment with a combination of fludarabine, cyclophosphamide, and rituximab led to the remission of both the CLL and nephrotic syndrome, with no recurrence observed during the follow-up period.