Ankylosing spondylitis is a chronic inflammatory disease of the attachment points between tendons, ligaments, or capsule and bone. It causes arthritis of the joints, mainly the spine and pelvis (sacroiliac joints). Ankylosing spondylitis can also cause inflammation of the eyes, lungs, or heart valves.

In severe cases, new bone may develop between the spinal bones. This can cause some areas of the spine to fuse. This fusion will decrease the flexibility and movement of the spine.

Ankylosing Spondylitis
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The cause of ankylosing spondylitis is not known. Some cases may be associated with a problem in a specific gene.