Ankylosing spondylitis: Chinese perspective, clinical phenotypes, and associated extra-articular systemic features.

Ankylosing spondylitis (AS) is a common rheumatic disease in the Chinese population, which is the largest population in the world associated with the global burden of health care. Herein we review and report the epidemiology and specific clinical characteristics of Chinese AS. More than 90 % of Chinese AS patients are HLA-B27 positive with the predominant HLA-B*2704 subtype; the incidence of HLA-B27 positivity ranges from 4 to 8 % in the general Chinese population. The first-degree relatives of AS probands often develop atypical AS with relatively mild disease and particularly undifferentiated spondyloarthropathy in females. Chinese AS patients have higher frequencies of juvenile-onset AS and peripheral arthritis. Of extra-articular manifestations, AS patients have earlier onset and more recurrent attacks of HLA-B27-related acute anterior uveitis. Cardiac arrhythmias or other cardiovascular disorders and metabolic syndrome are not infrequently found. Importantly, apical lung diseases in Chinese AS patients are also frequently associated with tuberculosis infection.