Rethinking Proteinuria: Resolution of Donor Derived EXT2-Associated Membranous Nephropathy Following Renal Transplantation.

Exostosin-2 (EXT2)-associated membranous nephropathy (MN) represents a subgroup of immune complex-mediated renal diseases, where transplantation may facilitate clearance of immune deposits. We present a successful kidney transplantation from a 19-year-old deceased donor with previously undiagnosed EXT2-associated MN into a 75-year-old male recipient. Despite significant pretransplant donor proteinuria (> 300 mg/dL) and hypoalbuminemia, renal biopsies at procurement demonstrated well-preserved renal architecture with minimal interstitial fibrosis. Clinical follow-up showed improvement in recipient renal function, with serum creatinine decreasing from 3.56 mg/dL preoperatively to 0.96 mg/dL (reference range: 0.7-1.3 mg/dL) within 2 months posttransplant. Proteinuria, initially nephrotic-range, progressively resolved to subnephrotic by 4 months. At 6 months, the recipient had normalized renal function and sustained resolution of proteinuria. This case demonstrates that removing a kidney from its native pro-inflammatory environment, coupled with immunosuppression, can facilitate resolution of immune complex-mediated glomerulopathy.