When Monoclonality Meets Crescents: A Case of Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposits with Rapidly Progressive Glomerulonephritis

Introduction: Proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) is a rare glomerulonephritis caused by deposition of a monoclonal immunoglobulin within the glomeruli. The triggers and management for PGNMID are incompletely understood, particularly when associated with rapidly progressive glomerulonephritis (RPGN). Case Description: A 40-year-old woman, who had pre-eclampsia two years prior, presented to the hospital with hypertensive emergency and fatigue. Her serum creatinine was at 4.2 mg/dL (0.98 mg/dL six months prior) and albuminuria at 8.7 g/g. In the previous month, she was taking 600-1200 mg of ibuprofen daily for flu-like symptoms. Her creatinine rose to 8.6 mg/dL at 7 days and to 12.27 mg/dL at 10 days after the admission. She received intravenous methylprednisolone followed by 40 mg of prednisone daily. Kidney biopsy revealed PGNMID with IgG-3-lambda deposits and prominent cellular crescents (76%) as well as acute tubular injury. Serum protein electrophoresis showed no abnormal bands and free light chain ratio was normal at 1.04. Antibodies against myeloperoxidase, proteinase 3, glomerular basement membrane, antinuclear, and complements C3 and C4 were unremarkable. Parvovirus was positive. There was no identifiable malignancy. Bone marrow biopsy showed no identifiable clone. Since empiric clone-directed therapy had shown benefit in some cases of PGNMID, the patient received 1 g of rituximab. Unfortunately, her kidney function did not improve, and she was transitioned to hemodialysis with monitoring for renal recovery and possible second dose of rituximab with daratumumab. Discussion: This rare case of RPGN in the setting of PGNMID is possibly related to an infection, including parvovirus. Other possible associations include pregnancy, although it concluded two years prior to the onset of RPGN, and ibuprofen. More data is needed to effectively manage this rare glomerulonephritis.