What is ankylosing spondylitis (AS)?

AS is a chronic (long-lasting) and inflammatory disease of the spine. It is systemic, meaning that other joints throughout the body may be involved, as well as other organ systems. People with the condition have pain and stiffness in the spine. The disease may be mild to severe. The vertebrae, or the bones of the spine, may fuse over time, causing a rigid spine. This fusing is known as ankylosis. Finding and treating AS early may help control the symptoms and prevent physical weakness and disability.

Who gets ankylosing spondylitis (AS)?

AS usually starts in late adolescence to early adulthood. It is rare for AS to begin after age 45. The disease is more common in men. It is also more common in Caucasians, Asians, and Hispanics. The incidence is 1 in 1,000 persons. In the US, about 500,000 people have the disease.

What causes ankylosing spondylitis (AS)?

The cause of AS is unknown, but genetics may play a part. About 90% of Caucasian people with AS have the HLA B27 gene. The gene is seen in about 8% of normal Caucasians. Research is indicating that other genetic variations may be involved. There are no known infectious or environmental causes. More than one person in a family may have the disease, but it cannot be said to be completely inherited.

What are the signs and symptoms of ankylosing spondylitis (AS)?

  • Pain and stiffness in the buttocks and low back due to sacroiliac joint involvement. Importantly, the pain and stiffness is worse in the morning and improves as the day progresses. Back pain may also wake the patient up at night. Sacroiliitis occurs when the joints between the pelvic bones and the lowest part of the spine become inflamed. Sacroiliitis is considered the hallmark of AS.
  • Movement up from the base of the spine to involve the low back, chest, and neck. Ultimately, the bones may fuse together, causing limited range of motion of the spine and of the body itself.
  • Shoulders, hips and sometimes other joints may be involved.
  • AS may affect tendons and ligaments. For example, the heel may be involved with Achilles tendonitis and plantar fasciitis.
  • AS may also be associated with inflammatory bowel disease and psoriasis
  • Fever, fatigue, bowel, or eye inflammation (anterior uveitis) may occur.
  • Rarely, there can be heart or lung involvement. However, AS is typically not life-threatening. Usually, it gets worse slowly. Most people are able to work and function normally.

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