Associated with HLA-B27. Ankylosing Spondylitis Clinical features. A disease primarily affecting the sacroiliac joints with varying involvement of the spine and less so the appendicular skeleton. Onset is usually insidious, generally between 10 and 40 years of age.
Patients generally present with back pain that is worse after rest and improves with exercise.
By definition, the back is always involved. Proximal, large joints, such as hips, knees, shoulders, and ankles, are preferentially affected. Involvement is usually asymmetric but not always. May have mild systemic manifestations such as fever, malaise, or anorexia. The diagnosis is made according to clinical and radiologic criteria.