Ankylosing spondylitis can be hard to diagnose because early symptoms mimic other arthritic conditions.
Ankylosing spondylitis is a systemic rheumatic disease characterized by inflammation of the spine and the sacroiliac joints. These joints are located in the lower back where the sacrum (the bone directly above the tailbone of your back) meets the iliac bones (bones on either side of the upper buttocks). Inflammation in these areas (spondylitis) causes pain and stiffness in and around the spine. Eventually, this can lead to a complete fusion of the vertebrae, a process referred to as ankylosis, which in turn leads to loss of spinal mobility. In addition to harming the spine, ankylosing spondylitis can inflame and injure joints in other parts of the body. Ankylosing spondylitis can also damage organs such as the heart and kidneys.
Ankylosing spondylitis is believed to be genetically inherited. The majority of people with this condition (nearly 90%) are born with a gene known as HLA-B27. Not everyone with the HLA-B27 gene gets ankylosing spondylitis, however: 7% of the U.S. population have the HLA-B27 gene, but only 1% of the population actually has ankylosing spondylitis. Researchers believe other conditions, perhaps environmental, are necessary for ankylosing spondylitis to become expressed.
The symptoms of ankylosing spondylitis are caused by inflammation of the spine, joints, and other organs. Symptoms include pain and stiffness in the lower back and the rest of the spine, upper buttocks, and neck. The pain and stiffness usually progress gradually over a matter of months, although onset can be rapid and intense. The pain and stiffness of ankylosing spondylitis are often worse in the morning or after periods of inactivity. These symptoms are sometimes relieved by motion, applied heat, or a warm shower. Other areas of the body affected by inflammation include the kidneys, heart, lungs, and eyes.
In advanced stages, for example, ankylosing spondylitis can lead to deposits of a substance called amyloid in the kidneys, which can cause kidney failure. Dialysis is sometimes needed to clear the kidneys. Rarely, people with ankylosing spondylitis develop scarring of the heart’s electrical system, which causes an abnormally slow heart rate. This requires correction with implantation of a pacemaker.
