Ankylosing spondylitis (AS) is a type of arthritis in which there is a long-term inflammation of the joints of the spine. Typically the joints where the spine joins the pelvis are also affected.Occasionally other joints such as the shoulders or hips are involved.
Eye and bowel problems may also occur. Back pain is a characteristic symptom of AS, and it often comes and goes. Stiffness of the affected joints generally worsens over time.
Although the cause of ankylosing spondylitis is unknown, it is believed to involve a combination of genetic and environmental factors.