Clone-Directed Therapy for Monoclonal Gammopathy of Renal Significance in a Patient with Sjögren Syndrome

Introduction: Monoclonal gammopathy of renal significance (MGRS) is defined by a circulating paraprotein, renal impairment with a biopsy demonstrating monoclonal immunoglobulin related renal pathology by a B-cell or plasma cell clone. We present a case report of a MGRS who received treatment with adequate response. Case Description: A woman of 83-year-old. Who has in her background Sjögren syndrome since 2021 in treatment with Hydroxychloroquine 200 mg/day. She presented muscle weakness, loss of weight, fever and rapid progressive glomerulonephritis with a previous serum creatinine of 1.0 mg/dl and she showed up with a serum creatinine of 3.6 mg/dl and hyperazotemia (BUN 93), therefore a kidney biopsy was performed. In the biopsy there were observed CD138 cells, Kappa and IgA were all three stains positive in the IF and IHC, confirming monotypic and plasma cell deposits. The rest of stains were all negative. Others immunological tests were rolled out resulting negative. CT was run with absents of some tumoral lesion. Related to the findings in the biopsy, we searched for infiltration of plasma cells in bone marrow, however the diagnosis of multiple myeloma was ruled out. Serum protein electrophoresis demonstrated a monoclonal spike of kappa chain and serum free light chains assay demonstrated concentration of kappa of 899 mg/dl and lambda of 217 mg/dl, a Kappa/Lambda index of 4.1 mg/dl. With no evidence of plasma cell infiltration in the bone marrow, the diagnosis of monoclonal gammopathy of renal significance was reached by the hematology service. Therefore, she started treatment aimed at plasma cloning based on Bortezomib, Lenalidomide and Dexamethasone (four cycles). After completing treatment, improvements in hemoglobin, kidney function (serum creatinine of 1.9 mg/dl) and general clinical improvement were observed. Discussion: Till now, treatment in a MGRS is no stablished. This case is an example of how starting treatment for MGRS led to stable kidney function and general clinical improvement in this patient.