Rheumatoid arthritis and renal light-chain deposition disease: long-term effectiveness of TNF-α blockade with etanercept.

A 68-year-old woman diagnosed with erosive rheumatoid arthritis (RA) was treated with intramuscular methotrexate 15 mg weekly and oral prednisone 5 mg daily. A favorable outcome of 6 years was followed by RA flare and nephrotic syndrome (NS). Renal biopsy revealed non-amyloid light-chain deposition disease. Laboratory analysis and bone marrow biopsy excluded monoclonal protein and plasma cell dyscrasia. Addition of subcutaneous etanercept, 25 mg twice weekly allowed rapid control of both arthritis and NS. To date, after over 7-year follow-up, RA is in clinical remission, 24-h albuminuria is consistently below 0.5 g, and serum creatinine is 0.9 mg/dl.