Ankylosing spondylitis: clinical aspects and diagnosis

Ankylosing spondylitis (AS) is an inflammatory autoimmune disorder that predominantly affects the spine. If untreated it may cause significant morbidity.The primary site of inflammation in AS is the entheses, the sites of insertion of tendons and ligaments into bone. If the inflammation remains untreated, there is resultant fibrosis and ultimately ossification at the entheseal sites. AS should be suspected in patients who report back pain and stiffness with rest, especially in the morning, which improves with exercise. Although the condition affects both the sacroiliac joints, a proportion of patients report pain radiating into the buttocks which may be unilateral or alternate, particularly in the early stages. In addition to the spine, large joint synovitis may develop as well as features of entheseal involvemen