Amyloidosis in rheumatoid arthritis.

The clinical and pathological features of amyloidosis are reviewed with special references to amyloidosis associated with rheumatoid arthritis. Data concerning the nature of the amyloid substance are presented. The amyloid fibril which is the unique and principal component of all amyloid substances, can be constituted by different protein subunits. The amyloid fibril protein AA is a major subunit of the amyloid fibrils particularly seen in secondary amyloidosis including that associated with rheumatoid arthritis. The immunological and chemical properties of protein AA and a structurally related serum protein (SAA) are discussed. Increased knowledge of the nature of amyloid and its precursor proteins may provide better methods for the diagnosis and treatment of amyloidosis.