Ankylosing Spondylitis (AS)
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ABOUT ANKYLOSING SPONDYLITIS
Ankylosing spondylitis (pronounced ank-kih-low-sing spon-dill-eye-tiss), or AS, is a form of arthritis that primarily affects the spine, although other joints can become involved. It causes inflammation of the spinal joints (vertebrae) that can lead to severe, chronic pain and discomfort. In the most advanced cases (but not in all cases), this inflammation can lead to new bone formation on the spine, causing the spine to fuse in a fixed, immobile position, sometimes creating a forward-stooped posture. This forward curvature of the spine is called kyphosis. More information on kyphosis and fusion can be found in the complications section.
AS can also cause inflammation, pain and stiffness in other areas of the body such as the shoulders, hips, ribs, heels and small joints of the hands and feet. Sometimes the eyes can become involved (known as Iritis or Uveitis), and rarely, the lungs and heart can be affected. See the Complications of Spondylitis: How is a Person Affected? page for more information.
The hallmark feature of ankylosing spondylitis is the involvement of the sacroiliac (SI) joints during the progression of the disease, which are the joints at the base of the spine, where the spine joins the pelvis.
Is There a Cure?
Currently, there is no known cure for AS, but there are treatments and medications available to reduce symptoms and manage the pain. Recent studies show that the new biologic medications can potentially slow or halt the disease progression in some people. Please refer to the AS Treatment and Medications sections for more information.
AS is in a Group of Diseases
AS is the primary disease in the group of diseases known as Spondylitis, Spondyloarthropathy or Spondyloarthritis.
Ankylosis means "fusion", which may be fibrous, or bony. Spondylitis means "inflammation of the spine."
Causes of Ankylosing Spondylitis
Although the exact cause of AS is unknown, we do know that genetics play a key role in AS. Most individuals who have AS also have a gene that produces a "genetic marker" - in this case, a protein - called HLA-B27. This marker is found in over 95% of people in the caucasian population with AS (the association between ankylosing spondylitis and HLA-B27 varies greatly between ethnic and racial groups, see our AS Diagnosis section for more information). It is important to note, however, that you do not have to be HLA-B27 positive to have AS. Also, a majority of the people with this marker never contract ankylosing spondylitis.
Scientists suspect that other genes, along with a triggering environmental factor, such as a bacterial infection, are needed to trigger AS in susceptible people. HLA-B27 probably accounts for about 40% of the overall risk, but then there are other genes working in concert with B27. There are probably five or six genes involved in susceptibility toward AS. It is thought that perhaps AS starts when the defenses of the intestines start breaking down and bacteria from the intestines pass into the bloodstream directly into the region where the sacroiliac joints are located.
Who is At Risk?
The risk factors that predispose a person to ankylosing spondylitis include:
Unlike other forms of arthritis and rheumatic diseases, general onset of AS commonly occurs in younger people, between the ages of 17-35. However, it can affect children and those who are much older. AS is more common in men, but occurs in women as well.
- Testing positive for the HLA-B27 marker
- A family history of AS
- Frequent gastrointestinal infections
Prevalence of AS
There are at least half a million people with AS in the United States but likely more because the disease is under-recognized. AS is more prevalent than multiple sclerosis, cystic fibrosis and Lou Gehrig's Disease combined. Click here to learn how you can help make a difference.
The severity of AS varies greatly from person to person, and not everyone will experience the most serious complications or have spinal fusion. Some will experience only intermittent back pain and discomfort, but others will experience severe pain and stiffness over multiple areas of the body for long periods of time. AS can be very debilitating, and in some cases, lead to disability.
Almost all cases of AS are characterized by acute, painful episodes (also known as "flares") followed by temporary periods of remission where symptoms subside.
Overheard in a Message Board Conversation, "Not all of us have flares and remissions. Some of us had rapid and severe onset that never let up, and was rather quickly degenerative." - poster Mary Beth
It is important to know that ankylosing spondylitis is a chronic, or life long disease and that the severity of AS has nothing to do with age or gender. It can be just as severe in women and children as it is in men.
Remember that even if you have AS and are experiencing only mild symptoms, which you are able to manage quite well, it is important to see your rheumatologist once a year in order to detect and treat any underlying complications.
Please visit the following sections for more information: AS Symptoms, Diagnosis, Treatment of AS and AS Medications. We also offer a wide variety of Educational Materials on ankylosing spondylitis and related diseases. Click here to view what we have to offer.