Amyloid arthritis simulating rheumatoid disease in five patients with multiple myeloma.

Abstract Five patients with multiple myeloma, three of whom had kappa light chain disease, presented with a symmetrical polyarthritis simulating rheumatoid arthritis. In all instances amyloid infiltration of synovial tissues appeared to account for the articular manifestations. Synovial fluids examined in four of these cases lacked the inflammatory characteristics of rheumatoid synovial fluid and three of them contained M components. In the course of synovial fluid analysis, small fragments of amyloid-containing material were detected in the aspirates from three of the patients, thereby establishing the diagnosis prior to confirmation by tissue biopsy. In the past patients with verified amyloidosis involving synovial tissues have been erroneously considered to have rheumatoid arthritis.