Gout

Gout is arthritis described in various human populations and has not been observed in non-human primates. The arthritis results from increased serum levels of uric acid, with crystallization of urates within and about joints, due to hyperuricemia. It may occur as a primary or a secondary condition, due to impaired excretion of uric acid by the kidney, or from increased production of uric acid. The presenting signs are pain and redness of the first metatarso-phalangeal joint and microscopic examination of late stage tissue samples, shows needle shaped negatively birefringent crystals of sodium urate precipitate in chalky deposits (tophi). Gout has not been described in non-human primates.

Calcium pyrophosphate dihydrate crystal arthropathy (pseudogout) is also common in humans and has also been seen in a few non-human primates, such as the rhesus macaque, Barbary ape and mandrill.