Health Topics A-Z

What Is Ankylosing Spondylitis?

Ankylosing spondylitis is a form of arthritis that mainly targets the spine. Ankylosing spondylitis over time can cause your spine to become stiffer and eventually the vertebrae (bones in your spine) may fuse together. People have a tendency to develop a stooped-over posture as the disease progresses. It affects 129 out of every 100,000 people in the US.

You may also experience other complications, including arthritis of the hip joints and the joints between the ribs and breastbone, between the ribs and spine, bone spurs and inflammation in the feet, inflammation of the eyes, scarring of the lungs, inflammation of the prostate and inflammation of the aorta and aortic valve. Severe disease may lead to poor posture and deformities.

There is some disagreement over whether men are more likely than women to get ankylosing spondylitis. While some researchers believe this to be the case, others believe that women have the same rate of developing this condition but they develop milder cases that sometimes go undiagnosed. Most symptoms of ankylosing spondylitis crop up in early adulthood, prior to 40 years of age, although young males may have symptoms in early adolescence or, occasionally, even in childhood.

What Causes It?

The cause of ankylosing spondylitis is unknown, although researchers have shown that people with this disorder are more likely to have a certain genetic marker called HLA-B27. If there is a family history of ankylosing spondylitis in parents or siblings and a person is also positive for the HLA-B27 marker there is a 20% chance for that individual to develop ankylosing spondylitis if he or she is less than 40 years old. The odds are much lower in those greater than 40 years of age. Also, some researchers are exploring an association between certain bacteria and ankylosing spondylitis.