Thirty years after its discovery, the association between HLA-B27 and ankylosing spondylitis remains the strongest known relationship between a major histocompatibility complex (MHC) antigen and a disease.

Epidemiological studies in the 1960s and early 1970s identified close links between several distinct forms of arthritis that were given the collective title of the seronegative spondarthritides. Recognition that HLA-B27 was a genetic marker for these diseases led to a review of the composition of the group, resulting in the exclusion of Whipple’s disease and Behcet’s syndrome and the inclusion of other conditions such as undifferentiated and formes frustes of spondarthritis and HLA-B27 associated isolated peripheral enthesitis. Notwithstanding a 28–44% prevalence of HLA-B27 in affected patients, Whipple’s disease was excluded after being found to be caused by the actinobacterium Tropheryma whipplei, whilst Behcet’s syndrome forfeited its place for many reasons including a lack of association with HLA-B27.

Source: HLA-B27