HLA-B27 Gene

A specific gene for the HLA-B27 tissue type is present in many people who have ankylosing spondylitis. Of people with ankylosing spondylitis, 80-95% also have the gene for HLA-B27. This does not mean, however, that a person will automatically get ankylosing spondylitis if he or she has the gene. Although about 8% of Americans have the gene for HLA-B27, only about 1% of them actually has or will develop ankylosing spondylitis. However, if a person is thought to have ankylosing spondylitis, a blood test is useful to determine if that person has the gene for HLA-B27.

In the early stages of ankylosing spondylitis, determining a definite diagnosis is sometimes difficult. If a person has the specific signs and symptoms of ankylosing spondylitis and he or she has the gene for HLA-B27, the diagnosis of ankylosing spondylitis is likely correct.