What causes ankylosing spondylitis?

Although the cause of AS is unknown, genetics play a large role in an individual’s susceptibility. In particular, the human leukocyte antigen HLA-B27 is strongly correlated with AS.^[1] Men are more likely to present with the radiographic signs of AS, but spondyloarthritis occurs with a more even frequency.^[2] The absence of radiographic indications among women can result in a diagnostic delay, during which time the disease can progress unmanaged.^[3]