An unusual presentation of membranous nephropathy with primary and secondary features: a case report.

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults, broadly classified as primary or secondary based on etiology and pathologic findings. We present a single unusual case report of a 75-year-old woman with an 11-year course of MN featuring concurrent characteristics of both primary and secondary disease. On two separate kidney biopsies for the same patient, she demonstrated histopathologic features consistent with Class V lupus nephropathy alongside positive PLA2R staining - a combination that creates significant diagnostic uncertainty. Despite the overlapping features, the patient achieved remission on two separate occasions using different immunosuppressive regimens: cyclosporine initially, followed by Mycophenolate mofetil and prednisone upon relapse over a decade later. This case contributes to the emerging literature on PLA2R positivity in lupus membranous nephropathy and highlights the diagnostic and therapeutic challenges clinicians face when primary and secondary MN features coexist. The long-term follow-up and dual treatment response on a single patient reported here add to a limited body of published cases and carry implications for management of this increasingly recognized overlap syndrome.