Membranoproliferative Glomerulopathy with Masked Monoclonal Deposit: A Case Report

Introduction: Membranoproliferative glomerulonephritis [MPGN] is diagnosed on immunofluorescence. Some cases are influenced by the dysregulation of the alternative complement pathway. Larsen et al. have described the unmasking of immunoglobulin deposits when tissue is treated with paraffin and hence exposing immunoglobulin previously staining negative on immunofluorescence. Here, we describe a case of monoclonal gammopathy of renal significance presenting as MPGN with masked monoclonal deposit. Case Description: 42-year-old male with history of intravenous drug use on methadone who presented with elevated creatinine and lower extremity swelling. No prior history of kidney disease or family history of kidney disease. Labs notable for creatinine 1.81, hemoglobin 7.9 [83.7] and albumin 3. Urine analysis showed +3 protein, RBC and WBC. Spot urine protein/creatinine ration showed 10 mg/mg with >4,400 mg/g albumin to creatinine ratio. Hepatitis B, C, Cryoglobulin, C3 and HIV were unremarkable. Serum kappa/lambda light chain ratio 1.91 and immunofixation positive for Monoclonal component detected in the gamma region in serum and characterized as IgM lambda. Renal biopsy revealed MPGN with masked monoclonal deposit with subsequent bone marrow aspirate showing findings are of a moderately hypocellular marrow with 10% lambda monoclonal plasma cells consistent with involvement by a plasmocytic neoplasm. CYBORD (Cyclophosphamide + Bortezomib + Dexamethasone) and lisinopril was started with improvement in protein/creatinine ratio to 3.42 mg/mg in 1 month and recent creatinine improvement to 1.2. Discussion: This case is unique as it signifies the importance of Monoclonal gammopathy of Renal Significance. Early detection with renal biopsy and initiation of treatment was instrumental in preserving renal function