Infantile Cortical Hyperostosis, Rhesus Monkey

Infantile cortical hyperostosis in rhesus monkeys (Macaca mulatta) is encountered as a congenital enlargement of the diaphyses of long bone. Enlargements, or hyperostoses, are typically hard, bilaterally symmetric and widest at the mid-diaphysis (Fig. 128). The periosteum is mildly to moderately thickened and overlying soft tissues are atrophic, fibrotic and difficult to dissect from underlying bone. Longitudinal sections of long bones reveal morphologically normal epiphysis and physis. Cross-sections through affected diaphyses reveal a relatively normal medullary cavity with discernable cortical bone surrounded by hyperostotic proliferations. Gross features are particularly striking in radiographs (Fig. 129). Lesions are restricted to the musculoskeletal system.