Ankylosing spondylitis.

Ankylosing Spondylitis (AS) is an autoimmune disease of unknown cause belonging to the group of spondyloarthritides associated with HLA B27. This disease affects the spine and sacroiliac joints, but may also concern peripheral joints and different organs. Symptoms include morning stiffness and dull low back pain, both improving by exercise. AS causes reduction in life expectancy due to subsequent manifestation in different organs, so early diagnosis and treatment are of great importance.