Ankylosing Spondylitis

What is Ankylosing Spondylitis?

Ankylosing spondylitis (AS) is a rheumatic disease that causes arthritis of the spine and sacroiliac joints and can cause inflammation of the eyes, lungs, and heart valves. It varies from intermittent episodes of back pain that occur throughout life to a severe chronic disease that attacks the spine, peripheral joints and other body organs, resulting in severe joint and back stiffness, loss of motion and deformity as life progresses.

AS is a member of the family of diseases that attack the spine called spondylarthropathies. In addition to AS, these diseases include Reiter’s syndrome, some cases of psoriatic arthritis and the arthitis of inflammatory bowel disease.

Physician holding a picture of an x-ray depicting a human pelvis.



The cause of AS is not known, but all of the spondylarthropathies share a common genetic marker, called HLA-B27, in most affected individuals. In some cases, the disease occurs in these predisposed people after exposure to bowel or urinary tract infections.

Health Impact AS afflicts an estimated 129 out of 100,000 people in the United States. AS typically strikes adolescents and young adult males. The prevalence of AS varies by ethnic group and is most common in Native Americans.



Delayed diagnosis is common because symptoms are often attributed to more common back problems. A dramatic loss of flexibility in the lumbar spine is an early sign of AS. Although most symptoms begin in the lumbar and sacroiliac areas, they may involve the neck and upper back as well. Arthritis may also occur in the shoulder, hips and feet. Some patients have eye inflammation, and more severe cases must be observed for heart valve involvement.

At times, AS may presage the development of inflammatory bowel disease, and some patients have fever, fatigue, weight loss, anemia, eye inflammation (called iritis), and more severe cases may involve heart valve dysfunction. Other disorders of the internal organs and bones mimic spondylarthropathies and must be distinguished. Laboratory evaluation may reveal an elevated sedimentation rate (an indicator of inflammation), anemia and a positive HLA-B27 assay. X-rays and bone scans may show characteristic changes.


X-ray of a side-by-side image of a spine with and without anklosing spondylitis



The severity of joint involvement and the degree of systemic symptoms vary greatly from one individual to another. Early, accurate diagnosis and therapy may minimize years of pain and disability.

Medical treatment consists of nonsteroidal anti-inflammatory medications. Indomethacin is most effective, while sulfasalazine may benefit those with more severe involvement. Peripheral joint arthritis may respond to methotrexate.