Ankylosing Spondylitis Causes
Scientists have identified certain genes that increase a person's chances of developing ankylosing spondylitis. For example, variations of the HLA-B gene increase the risk of developing the condition. The HLA-B gene provides instructions for making a protein that plays an important role in the immune system. HLA-B27, one variation, is found in about 95 percent of Caucasians with ankylosing spondylitis. It is also found in about 50 percent of African Americans with the condition.
Although many people with ankylosing spondylitis have the HLA-B27 variation, most people with this version of the 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 disease. 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 causing ankylosing spondylitis.
Age and Gender
Ankylosing spondylitis occurs twice as often in men as in women, and symptoms of the disease tend to be more severe in men. It is typically diagnosed in adolescence or early adulthood. (Most people are diagnosed with the disease between the ages of 17 and 35.)
Researchers think that infections with a virus or bacteria may increase a person's chances of developing ankylosing spondylitis. There also seems to be an increased risk in people who have recurrent urinary tract infections or bowel infections. This does not mean that ankylosing spondylitis is contagious. Researchers think the infection somehow triggers the condition in those people who are already susceptible to it because of their genetics.