Background: Membranous nephropathy (MN) is characterized by proteinuria and other symptoms of the nephrotic syndrome. In many cases, the etiology is unknown. Whether and how to treat MN is still a controversial question. Despite the use of corticosteroids and alkylating agents, up to 40% of patients still progress to end-stage renal failure.
Case report: A 40-year-old male patient with biopsy-proven idiopathic MN was initially treated with prednisolone and chlorambucil because of a proteinuria of 22 g/d. Treatment with cyclosporine was started because the nephrotic syndrome failed to improve. Proteinuria was reduced to a minimum of 4 g/d. Cyclosporine was stopped after 17 months leading to a fast relapse. Therapy with an ACE inhibitor and AT(1) receptor antagonist and retreatment with cyclosporine improved proteinuria. Cyclosporine was terminated after a total of 24 months. 5 months later, relapse occurred with a high proteinuria of 34 g/d. The monoclonal anti-CD20 antibody rituximab (375 mg/m(2)) was given four times every 4 weeks. 4 weeks and 4 months after the end of treatment, proteinuria decreased to 780 mg/d and <150 mg/d, but renal function remained impaired (creatinine clearance 65 ml/min, stage 2 according to K/DOQI). Now, remission of proteinuria (<150 mg/d) has been stable for almost 2 years. However, renal insufficiency progressed further (creatinine clearance 45 ml/min, stage 3 according to K/DOQI).
Conclusion: Rituximab offers the possibility for a targeted treatment of idiopathic MN. Based on the existing evidence and experience from this case, rituximab can be recommended as a new treatment option for MN, possibly before starting any treatment with cytotoxic agents and high-dose prednisolone carrying the risk of severe side effects. However, long-term results of this treatment are still lacking.