Ankylosing Spondylitis




Ankylosing spondylitis is a disorder that primarily affects the spine. It is a form of chronic inflammatory arthritis characterized by back pain and stiffness. These symptoms typically appear in adolescence or early adulthood. As the condition progresses, back movement can gradually become limited as the bones of the spine (vertebrae) fuse together. Joint stiffness or a limited range of motion in certain joints is called ankylosis.

The earliest symptoms of this disorder result from inflammation of the joints between the base of the spine (the sacrum) and the hipbones (the ilia). These joints are called sacroiliac joints, and inflammation in this region is known as sacroiliitis. The disorder also causes inflammation of the joints between vertebrae, which is called spondylitis. Ankylosing spondylitis can involve other joints as well, including the shoulders, hips, and, less often, joints in the limbs. Over time, this disorder can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe.

Ankylosing spondylitis affects the eyes in up to 40 percent of cases, leading to episodes of eye inflammation called acute iritis. Acute iritis causes eye pain and increased sensitivity to light (photophobia). Rarely, ankylosing spondylitis can also have serious complications involving the heart and lungs.

Causes, incidence, and risk factors

The cause of ankylosing spondylitis is unknown, but genetic factors seem to play a role. The disease starts with intermittent hip and/or lower-back pain that is worse at night, in the morning, or after inactivity.

Back pain begins in the sacroiliac joint (between the pelvis and the spine) and may progress to include the lumbosacral spine and the thoracic spine (chest portion of the spine).

Pain may be eased by assuming a bent posture. Limited expansion of the chest occurs because of the involvement of the joints between the ribs. The symptoms may worsen, go into remission, or stop at any stage.

With progressive disease, deterioration of bone and cartilage can lead to fusion in the spine or peripheral joints, affecting mobility. It can be extremely painful and crippling. The heart, the lungs, and the eyes may also become affected.

The disease most frequently begins between age 20 and 40, but may begin before age 10. It affects more males than females. Risk factors include a family history of ankylosing spondylitis and male gender. About 0.21% of Americans over age 15 are affected.

What genes are related to ankylosing spondylitis?

Variations of the HLA-B gene increase the risk of developing ankylosing spondylitis.

Ankylosing spondylitis is likely caused by a combination of genetic and environmental factors, most of which have not been identified. Researchers have determined, however, that a particular version of the HLA-B gene (called HLA-B27) increases the risk of developing this disorder.

The HLA-B gene provides instructions for making a protein that plays an important role in the immune system. HLA-B is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). The HLA-B gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign invaders. Although many patients with ankylosing spondylitis have the HLA-B27 variation, most people with this version of the HLA-B gene never develop the disorder. It is not known how HLA-B27 increases the risk of developing ankylosing spondylitis.

Other genes are believed to affect the chances of developing ankylosing spondylitis and influence the progression of the disorder. Some of these genes likely play a role in the immune system, while others may have different functions. Researchers are working to identify these genes and clarify their role in ankylosing spondylitis.



How do people inherit ankylosing spondylitis?

Although ankylosing spondylitis occurs in more than one person in some families, it is not a purely genetic disease. Multiple genetic and environmental factors likely play a part in determining the risk of developing this disorder. Inheriting the HLA-B27 variation from a parent does not mean that a person will develop ankylosing spondylitis, even in families where more than one family member has the disorder. In fact, about 80 percent of children who inherit HLA-B27 from a parent with ankylosing spondylitis do not develop the disorder.

Symptoms
  • low-back pain that is worse at night, in the morning, or after inactivity
  • stiffness and limited motion in the low back
  • hip pain and stiffness
  • limited expansion of the chest
  • limited range of motion, especially involving spine and hips
  • joint pain and joint swelling in the shoulders, knees, and ankles
  • neck pain
  • heel pain
  • chronic stooping to relieve symptoms
  • fatigue
  • fever, low grade
  • loss of appetite
  • weight loss
  • eye inflammation
Signs and tests

A physical examination and characteristic symptoms are indicative of limited spine motion or chest expansion.

Tests may include:
  • HLA-B27 antigen test is positive.
  • A spine X-ray or pelvis X-ray shows characteristic findings.
  • ESR may or may not be elevated.
  • CBC may show mild anemia.
Treatment

The goal is to relieve the joint pain and to prevent, delay, or correct deformities.

MEDICATIONS

Nonsteroidal anti-inflammatory medications (NSAIDs) such as aspirin are used to reduce inflammation and pain associated with the condition. They allow patients to exercise, which improves posture and breathing.

DO NOT give aspirin or other NSAIDs to children unless advised to do so by the health care provider!

Corticosteroid therapy or medications to suppress the immune system may be prescribed to control various symptoms. Some health care professionals use cytotoxic drugs (drugs that block cell growth) in people who do not respond well to corticosteroids or who are dependent on high doses of corticosteroids.

Drugs called TNF-inhibitors have been shown to improve the symptoms of ankylosing spondylitis.

SURGERY

Surgery is done if pain or joint damage is severe.

LIFESTYLE CHANGES

Exercises can help improve posture and breathing. Lying flat on the back at night can help maintain normal posture. Use devices to help with activities of daily living.

Expectations (prognosis)

The course of the disease is unpredictable; remissions and relapses may occur at any stage. Most people are able to function unless the hips are severely involved.

Complications
  • heart valve disease, typically aortic valve stenosis
  • aortitis
  • eye inflammation (uveitis)
  • pulmonary fibrosis


Informations obtained from National Institute of Health.
Library | Products | Service | Affiliates | Home