Features of Japanese juvenile spondyloarthritis patients in our hospital.

Spondyloarthritis (SpA) is thought to be very rare in Japan, because possession rate of HLA-B27 in healthy people is 0.4% and it is significantly lower than that of other countries (5%). This makes it difficult for Japanese physicians to diagnose SpA early. Since 10-20% of SpA patients experience symptoms in their childhood, it is very important to distinguish them from other chronic arthritis patients for pediatric rheumatologists.