Retroperitoneal fibromatosis and acquired immunodeficiency syndrome in macaques. Pathologic observations and transmission studies.

A peculiar fibroproliferative syndrome called retroperitoneal fibromatosis (RF) has been observed in Macaca nemestrina, Macaca mulatta, Macaca fascicularis, and Macaca fuscata at the Washington Regional Primate Research Center. RF is characterized by the aggressive proliferation of highly vascular fibrous tissue subjacent to the peritoneum covering the ileocecal junction and associated mesenteric lymph nodes. In the early, proliferative phase of the disease, most of the fibroblastlike cells contain Factor VIII-related antigen. Two syndromes have been recognized: localized, in which fibroproliferative lesions occur only in solitary nodules; and progressive, in which fibromatosis occurs throughout the abdominal cavity. RF-affected monkeys often develop a simian acquired immunodeficiency syndrome (SAIDS) with severe thymic and lymphoid atrophy, chronic enterocolitis, and wasting. Experimental intraperitoneal inoculation with suspensions of RF tissue in two separate experiments resulted in the development of SAIDS in 5 of 16 and RF-SAIDS in 3 of 16 macaques. RF associated with SAIDS appears to be an excellent model for the Kaposi's sarcoma associated with AIDS.