#6598 STUNNING RENAL FUNCTION RECOVERY AFTER TREATMENT WITH DARATUMAMB IN A CASE OF C3 GLOMERULOPATHY WITH MONOCLONAL GAMMOPATHY

Abstract

Abstract Background and Aims 38 years old man with C3GN linked to Monoclonal Gammopathy recovers from dialysis after treatment with Daratumamb. Case report C3 glomerulonephritis related to monoclonal gammopathy is a challenging entity and the efficacy of treatment with Daratumumab is not clearly defined yet. We would like to describe the case of a stunning renal response to Daratumumab in a young man with MGUS and C3 glomerulonephritis. In July 2021 a 38 years old man presented to our nephrology division with full nephrotic syndrome, creatinine 1.2 mg/dl, low C3 and little IgG lambda spike of 2 g/dL on serum electrophoresis. Kidney biopsy revealed a membranoproliferative GN with bright C3 staining by immunofluorescence, no other positive immune-reactant and no masked deposits on pronase digested tissue. Electron microscopy confirmed the presence of subendothelial electron dense deposits. The diagnosis was consistent with C3 glomerulonephritis. Complement genetic test and C3 nephritic factor were negative. Assuming a form of C3GN associated to monoclonal gammopathy (MGRS), a bone marrow biopsy was performed and revealed a small clonal plasma cells population. In November 2021 he was started on velcade/dexamethasone but unfortunately stopped early due to severe side effects. Subsequently he begun cyclophosphamide and steroids without clinical or serological response. In few months renal function rapidly worsened requiring dialysis since April 2022. A repeat kidney biopsy confirmed C3GN with still moderate activity and low chronicity. In May 2022 he was started on Daratumamab/Lenalidome/Dexamethasone. After eight months of dialysis the diuresis progressively increased and the renal function improved so remarkably that dialysis was discontinued since December 2022. At present the patient renal function is stable with creatinine 3.5 mg/dl, proteinuria 3g/L, and monoclonal component decreased to 1.1 g/L from 3.5 g/L. He continues Daratumumab single agent monthly and we have scheduled a further renal biopsy in the next week. To our knowledge this is the first time a patient recovers from dialysis after treatment with Daratumamb for a C3GN linked to a monoclonal gammopathy. It definitely makes this case unique and inspiring for further studies and considerations regardinf this intriguing field of MGRS.