What causes ankylosing spondylitis (AS)?

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What causes ankylosing spondylitis (AS)?

About 95% of people who have AS have a variation of the human leukocyte antigen-B gene (HLA-B). This changed, or mutated, gene produces a protein called HLA-B27 that increases disease risk. However, most people with a mutated HLA-B gene don’t get AS. In fact, 80% of children who inherit the mutated gene from a parent with AS don’t develop the disease. More than 60 genes have been linked to the condition.

Having one of these conditions may also increase your risk:

  • Crohn’s disease.
  • Ulcerative colitis.
  • Psoriasis.

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