Amyloidosis mimicking rheumatoid arthritis.

A 49-year-old man presented a clinical picture suggesting seronegative rheumatoid arthritis. He developed severe joint contractions, pasty synovial swelling, macroglossia and proteinurie. Subsequent investigations disclosed light-chain multiple myeloma and A1-amyloid deposits in synovial tissue and skin. A1-amyloidosis should be considered in the differential diagnosis of patients with seronegative polyarthritis. Clues to the diagnosis of amyloid arthropathy are a carpal tunnel syndrome, early occurrence of joint contractures in combination with a relatively mild synovitis and a low ESR as well as the presence of other possible organ involvement with amyloidosis.