Amyloidosis in rhesus monkeys with rheumatoid arthritis and enterocolitis.

Generalized amyloidosis was diagnosed by light and electron microscopy in 4 of 5 monkeys (Macaca mulatta) that had a history of chronic arthritis or chronic intermittent diarrhea, or both. Clinical signs and lesions of arthritis in the monkeys were compatible with diagnostic criteria for rheumatoid arthritis. Shigella sp was cultured from 1 monkey, and 2 other monkeys had colonic lesions characteristic of shigellosis. At necropsy, gross changes attributed to amyloid were seen only in the liver. Amyloid deposits in the liver, spleen, mesenteric lymph nodes, kidney, heart, adrenal glands, and other organs were determined by staining reactions and fine structural characteristics.