Resumen

Chronic lymphocytic leukemia (CLL) is a mature B cell neoplasm characterized by a progressive accumulation of monoclonal B lymphocytes in the blood, bone marrow, lymph nodes and spleen. Although up to 90% of CLL cases present kidney infiltration, renal involvement generally remains clinically undetected. Nephrotic syndrome (NS) in CLL is a rare complication that occurs in less than 2% of the cases. To date, there are only 13 cases of CLL-related membranous nephropathy (MN) reported in literature. We present a 67-year-old male who was diagnosed with CLL on 2011; no therapy was started at that time. On 2016 he presented edema in his lower extremities; laboratory results were, hemoglobin: 11.8 g/dl, urea: 63 mg/dl, creatinine: 2.02 mg/dl; urinary protein excretion: 10.25 g/24 h, serum proteins: 5.36 g/dl, serum albumin: 4 g/dl and white
blood cells: 19,600/mm3. We contacted the Nephrology Department, a percutaneous renal biopsy
was performed and a diagnosis of MN was given.
Furthermore a lymphocyte perivascular infiltration was present; immunofluorescent staining  revealed deposition of IgG, IgM, C3 and C1q. The diagnosis was membranous nephropathy type II secondary to CLL. Treatment with rituximab and cyclophosphamide (CYS) was started and the patient has reached
remission of his CLL; proteinuria has been improving with CYS orally. The current follow up of his case
is 31 months. From all the cases in literature, our approach to this extremely rare condition is unique, as
we avoid the use of fludarabine because of its myelotoxicity in older patients.