Anti-CD20 Monoclonal Antibody (Rituximab) for the Treatment of Recurrent Idiopathic Membranous Nephropathy in a Renal Transplant Patient

Idiopathic membranous nephropathy (IMN) remains the most common histologic entity associated with adult-onset nephrotic syndrome. The therapy for IMN is challenging. Steroids and various other immunosuppressive agents have been tried in IMN; however, current agents have not altered the course of IMN, are nonspecific and can be very toxic. In native kidneys affected by IMN, rituximab, a monoclonal antibody against the B-cell surface antigen CD20, has been shown to reduce proteinuria and prevent disease progression. In this report, we describe a 39-year-old white male with end-stage renal disease secondary to IMN that, 4 months post living unrelated kidney transplant, developed recurrent IMN with 18 g/day of proteinuria. In addition to angiotensin converting enzyme inhibitor and statins, the patient was treated with 4 weekly doses of 375 mg/m² of rituximab with significant reduction in proteinuria, a corresponding increase in serum albumin and improvement in hypercholesterolemia. At 3 years post-transplant, his kidney function remains stable with 0.5 g/day of proteinuria.