Rituximab-Induced Remission in Proliferative Glomerulonephritis With Monoclonal Immunoglobulin G Deposits: A Case Report With Serial Kidney Biopsies

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) is a rare form of monoclonal gammopathy of renal significance (MGRS). The natural history and optimal treatment are poorly defined, particularly when circulating monoclonal proteins or hematologic clones are undetectable. We report a 57-year-old woman with biopsy-confirmed PGNMID who underwent 3 sequential kidney biopsies. The initial biopsy showed a classic membranoproliferative pattern with monotypic IgG-kappa deposits, whereas bone marrow examination showed no clonal plasma cell or B-cell proliferation. Despite corticosteroid-based immunosuppression, proteinuria persisted, and histology worsened on the second biopsy. Rituximab was administered 10 months after diagnosis; a third biopsy 3 months later showed resolution of immune deposits and glomerular proliferation. At 8 months post-rituximab, the patient remained in clinical remission with stable kidney function. This case underscores the value of sequential kidney biopsies to monitor disease activity and treatment response in PGNMID. Rituximab can induce clinical and histologic remission, even when circulating monoclonal proteins are undetectable.