====== HLA-B27 ======


Although the cause of [[ankylosing spondylitis]] is unknown, it is believed to involve a combination of genetic and environmental factors.

More than 90% of those affected have a specific [[human leukocyte antigen]] known as the [[HLA-B27]] antigen. The underlying mechanism is believed to be autoimmune or autoinflammatory.
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but only 2% of people with HLA-B27
develop clinical AS.
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[[Reiter syndrome]] (after Hans Reiter, a German bacteriologist): a reactive arthritis (usually
1–3 weeks following certain bacterial infections) with involvement of at least one other
non-joint area (urethritis, uveitis/conjunctivitis, skin lesions, mucosal ulcerations…). 75%
are [[HLA-B27]] positive