[Ankylosing Spondylitis].

Ankylosing Spondylitis (AS) is one of the rheumatoid diseases, however its clinical features are different. The diagnosis of AS and clinical features are shown, especially the diagnosis is very important. The new modified criteria for diagnosis is detailed here. In addition, the differential diagnosis is exhibited which is significantly useful for the diagnosis of AS. Recently As has been included in the group of seronegative spondylarthropathy (SPA). Now AS is thought to be the central position among SPA which has a lot of similar symptoms. The characteristic symptoms of SPA or AS are spinal, eye, skin, sytemic lesions and enthesopathy. These clinical features are also critical in the diagnosis of AS as well. Finally, what is the most important factor in AS? The answer is an early treatment by a correct diagnosis.