[Membranous nephropathy secondary to rheumatoid arthritis occurring during anti-TNFalpha therapy and responsive to second-line treatment with rituximab].

We report the case of a patient with rheumatoid arthritis (RA) who developed a membranous nephropathy (MN) with nephrotic syndrome while receiving etanercept, a fusion protein that binds specifically to TNFalpha and blocks its interaction with TNFalpha receptors. A 62-year-old man with RA treated with etanercept was admitted to our unit in March 2008 because of a full-blown nephrotic syndrome. Renal biopsy showed a typical MN. Since no improvement of proteinuria was observed after withdrawal of etanercept, we administered rituximab (1 g two weeks apart repeated after 6 months). The signs and symptoms of RA improved and proteinuria decreased from 7.2 g/24h to 2.3 g/24h. MN is an immunological glomerulonephritis that may complicate other immune-mediated diseases or may be triggered by a number of drugs. The clinical improvement of both RA and MN after rituximab may indirectly confirm the role of antibodies in the pathogenesis of these diseases, although the mechanisms of action of this drug in immunological disorders remain to be elucidated.