Atypical clinical presentation of ankylosing spondylitis

To describe a subgroup of patients with ankylosing spondylitis (AS), whose disease evolved without the characteristic inflammatory back pain or significant disability.

Three patients who were diagnosed in their late 5th decade of life as having AS are described. Information about asymptomatic cases of AS or patients who were unaware of their disease was gathered from case reports and from studies involving HLA-B27-positive individuals. Another source of information derived from studies that investigated conditions known to be a complication of AS, such as heart block or aortic regurgitation.

The data collected from the literature suggest that 1.5% to 10% of the patients with AS are asymptomatic or have very mild disease. These patients are diagnosed late in the course of the disease.

Because of the mild nature of the symptoms, the real prevalence of atypical AS is unknown. The information gathered from the literature allows to delineate 4 subgroups of patients with AS: (1) Classic AS with characteristic clinical and radiographic manifestations; (2) Asymptomatic AS with characteristic radiographic findings; (3) Asymptomatic AS with extra-articular features as the presenting manifestations; (4) Symptomatic AS without radiographic supporting evidence. Patients with asymptomatic or mild symptoms deserve more attention, because a better understanding of the factors that affect the expression of pain in different individuals may generate better pain control therapies.