Ankylosing spondylitis in nonhuman primates: the drill and the siamang

Nonhuman primates are known to be susceptible to many of the arthritides that afflict humans. Psoriatic like spondyloarthropathies have been reported in gorillas and skeletal hyperostosis in gibbons, rhesus monkeys, and gorillas, and additional cases of both of these conditions occurring in drills (baboons) are noted in this report. One western lowland gorilla and two rhesus monkeys with clinical features consistent with ankylosing spondylitis have been documented previously. Two additional nonhuman primate species with radiographic evidence of ankylosing spondylitis are described. A siamang (gibbon) and two drills (baboons) with the classic radiographic features of ankylosing spondylitis, namely a bamboo spine and sacroiliac joint fusion, are reported.