The frequency of gastric amyloidosis in baboons. A 22-year survey at a large primate facility

Background: Systemic amyloidosis, caused by abnormal tissue accretion of plasma proteins, affects several organs of the gastrointestinal (GI) tract. Gastric amyloidosis, rare in humans, has only been reported once in animals. Materials and Methods: Gastric amyloidosis was sought for in baboons with systemic amyloidosis. Results: During the past 22 years (between January 1986 and January 2007) a mean of 3,315 baboons/year (range 2,578-3,931) were housed at the Southwest National Primate Research Center. Gastric amyloidosis was found in 9 (10.2%) of the 88 baboons having a diagnosis of systemic amyloidosis. Consequently, the prevalence of gastric amyloidosis occurring since 1986 at this facility was 0.41 baboons/year. Gastric amyloid deposits were found in the interstitial aspect of the lamina propria, replacing normal mucosal structures, in the submucosal stroma along the interface with the muscularis mucosae and in the interstitial tissue of submucosal lymphoid aggregates. In one of the animals, lumps of amyloid deposits with giant cells were found in the gastric mucosa. Conclusion: Baboons with systemic amyloidosis usually show increasing frequency of amyloid deposits in the liver, large intestine, lymph nodes, spleen and the small intestine. We now demonstrate that it may also involve the stomach. Why certain organs of the GI tract in baboons are more susceptible than others to be affected by the process of systemic amyloidosis remains unexplained. The apparent natural resistance of the stomach of baboons to be affected by systemic amyloidosis deserves further investigation. The review of the literature indicates that this is only the second report on gastric amyloidosis in baboons.