Generalized amyloidosis in rhesus monkeys

Necropsy materials from 57 cases of generalized amyloidosis in rhesus monkeys were reviewed. Clinically, animals with the disease were characterized by cachexia with muscle wasting, recurrent diarrhea, and arthritis. Gross lesions included hepatomegaly, splenomegaly, chronic/active colitis, fibrous strictures of the cecocolic junction, osteoarthritis, and generalized muscle atrophy. Histologic examination revealed minimal to severe deposits of amyloid in the small intestine (100%), spleen (93%), large intestine (67%), liver (40%), lymph nodes (71%), stomach and/or adrenal gland (32%). More amyloid was deposited in the spleen, liver, and small intestine than in other organs. Shigella sp. were isolated from feces in 23% of the cases and 84% had histologic evidence of colitis. Other findings indicated that 100% of the animals had lung mites, 25% had strictures of the cecocolic junction, and 40% had osteoarthritis. Thirty percent of the cases occurred in animals 10 months to 5 years of age, 10% in ages 6 to 10 years, and 60% in animals greater than 10 years old.