Ankylosing Spondylitis

What Causes Ankylosing Spondylitis?

The specific cause of ankylosing spondylitis is unknown, but genetic factors seem to play a role.

  • About 95% of people who have ankylosing spondylitis also have a genetic marker known as human leukocyte antigen-B27 (HLA-B27).
  • About eight people in 100 among American Caucasians are born with the HLA-B27 gene. The gene is much less common among African Americans.

Genetic markers are protein molecules found on the surfaces of cells. The HLA markers enable the body’s immune system to distinguish between “self” and “other.”

Ankylosing spondylitis may be triggered by certain types of bacterial or viral infections that activate an immune response that does not shut off after the infection is healed. The immune system then attacks the body’s own tissue. A disorder caused by the body’s own immune system is called an autoimmune disease.

Is Ankylosing Spondylitis Inherited?

If one parent has HLA-B27 and ankylosing spondylitis, there clearly is some increased risk that the B27 gene and disease will be passed on to a child. However, only about 2% of people with HLA-B27 develop ankylosing spondylitis.

Ankylosing spondylitis occurs more frequently in some ethnic groups. In the United States, it occurs most frequently among Native Americans and is almost never found among African Americans. Chinese individuals have the gene much more often than Japanese individuals.

Is Ankylosing Spondylitis Different In Men And Women?

Men develop ankylosing spondylitis about three times more often than women do. The disorder affects men and women differently.

  • Men are more likely to have the inflammation of the spine, pelvis, chest wall, and shoulders
  • Women are more likely to have inflammation of the pelvis, hips, knees, and wrists.

A diagnosis of ankylosing spondylitis may sometimes be missed in women because the disease affects them somewhat differently and has been considered less severe.

Do Children Get Ankylosing Spondylitis?

It is rare, but possible, for ankylosing spondylitis to develop in childhood. It usually does not strike until adolescence, and it is unusual for a child under 11 years old to develop the disease.

When symptoms begin before the age of 17, the condition is called juvenile ankylosing spondylitis. According to the Spondylitis Association of America, one child in a thousand may develop juvenile ankylosing spondylitis.

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