The cause of ankylosing spondylitis in unknown but it is a known fact that the illness to a certain extent is associated with a specific tissue type (HLA-B27). This means that if a person in the immediate family has ankylosing spondylitis there is an increased risk of developing the illness.
Ninety percent of all patients with ankylosing spondylitis have the tissue type HLA-B27, while only 10 percent of healthy people have this tissue composition. If a person has back and joint pain and at the same time has this tissue type it supports the suspicion of ankylosing spondylitis.
