September 2, 2014
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Ankylosing Spondylitis

 Health Home >> Ankylosing Spondylitis >> About ankylosing spondylitis (AS) 


What is ankylosing spondylitis (AS)?

Ankylosing spondylitis (pronounced ankle-o-sing spawn-dill-eye-tis), or AS for short, is more than just chronic back pain. AS is a type of arthritis or inflammation of the joints that usually involves the spine. Sometimes, other joints such as those in the hip, knees, or shoulders, and other body parts such as the eye are affected. The characteristic feature of AS is the involvement of the joints at the base of the spine that join the spine and the pelvis, called the sacroiliac joints (pronounced sack-row-illy-ack).

Figure 1

About 150,000 to 300,000 Canadians live with AS. AS can develop at any age, but it tends to affect young adults and symptoms usually appear between the ages of 15 and 30. Men are 3 times more likely than women to develop AS. 80% of people with AS develop it before the age of 30.

AS is a type of rheumatic disease, a disease that causes pain and inflammation of joints and muscles. It can even affect internal organs such as the heart. AS is also known as an inflammatory disease. Other examples of rheumatic diseases include rheumatoid arthritis and psoriatic arthritis.

The pain associated with AS is a result of inflammation of the joints of the vertebrae (the backbones). In severe cases, when there is long-term inflammation, the vertebrae can fuse together, causing severely reduced mobility and function. Chest expansion can also be limited because the joints between the spine, ribs, and breast bone can become stiff. Read more about the symptoms of AS here.

The cause of ankylosing spondylitis is not known. Experts believe that the symptoms of AS are triggered by an environmental factor, such as bacteria, causing the immune system to become overactive and attack the healthy joints and nearby areas. It is not clear what causes the immune system to become overactive.

Though the cause of AS is unclear, researchers do know that some people have a higher risk of AS. These include:

  • people who have a tissue type called HLA-B27. HLA-B27 does not cause AS, but having it means there is a higher chance of developing AS. About 90% of people with AS have this tissue type. Many people inherit this tissue type from their parents, so people who have a family history of AS are at higher risk of AS.
  • men (men are 3 times as likely as women to get AS)
  • people from northern countries or of Inuit or Haida descent

The pain, stiffness, and disability caused by AS can have an enormous impact on a person's quality of life. People with AS may not be able to work, play sports, do hobbies, or participate in social activities as they once did or as other people do.

The good news is that treatment is available. Appropriate treatment can reduce AS symptoms, improve physical function, and allow people with AS to take control of their lives.

You can learn more about AS by talking to your doctor or a rheumatologist (a doctor who specializes in arthritic diseases).

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