Human lymphocyte antigen, HL-A27, in Japanese patients with ankylosing spondylitis.

A high association of HL-A27 specificity with ankylosing spondylitis was found in Japanese patients in spite of a very low frequency of this specificity in a normal Japanese population. These findings coincide well with those in Caucasian patients, and indicate the strong relationship between the susceptibility to ankylosing spondylitis and HL-A27 specificity beyond racial differences. No particular HL-A patterns were noted in patients with the ossification of the posterior longitudinal ligament of the cervical vertebrae. This observation provides an evidence that this disease is etiologically different from ankylosing spondylitis.