Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposits in a Patient with Recent Deceased Donor Kidney Transplant Successfully Treated with Rituximab Monotherapy

Introduction: Proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMIDs) is a poorly understood monoclonal gammopathy of renal significance. The pathophysiology of this disease remains elusive; though is generally characterized by altered renal function, proteinuria and monoclonal immunoglobulin granular glomerular deposits. Prognosis is poor and treatment without consensus. Case Description: Patient is a 40-year-old male with history of end stage renal disease due to presumed post infectious C3 glomerular nephritis with secondary focal segmental glomerular sclerosis positive for APOL1; resistant to prolonged steroids. Patient is status post deceased donor kidney transplant in 2022 complicated by delayed graft function with hyperkalemia, hypertension, and secondary polycythemia. Post-transplant patient’s creatinine (Cr) nadir was 2.3 with uptrend to 2.8 without proteinuria. Serum immunofixation demonstrated IgA monoclonal protein with kappa light chain specificity, prompting biopsy. Immunofluorescence revealed mesangial deposits of 3+ C3, 1+ C1q, 3+ lambda light chains, 3+ IgG3. Bone marrow biopsy showed hypocellularity without evidence of malignancy. He completed seven of eight doses of Rituximab monotherapy complicated by neutropenia. Renal function improved (Cr 1.9-2.2) and he remained without proteinuria. His recovery course was complicated by severe clostridium difficile infection with acute kidney injury (peak Cr 5.0) one month after completion of Rituximab; likely interfering with optimal renal recovery. Discussion: Currently therapy for PGNMIDs is without established best practice. Data are from small heterogenous populations with varying intra study combinations of chemotherapy and immunosuppression. The literature supports targeted clonal approach with treatment of underlying hematologic malignancies when relevant. Empiric therapy with some combination of agents such as rituximab, cyclophosphamide, steroids and bortezomib shows promise in those without identifiable clones. It is notable that this patient is without identifiable clonal target and was able to achieve clinical remission with empiric Rituximab monotherapy.