HLA DR4 and rheumatoid arthritis in Japanese people.

Eighty-eight Japanese patients with rheumatoid arthritis and 104 normal Japanese persons were typed for HLA A, B, C, and DR antigens. The frequency of HLA DR4 was 70.5% in patients compared with 46.1% in normal controls (P less than 0.001). However, a sex difference in the frequency of HLA DR4 in patients was noted. HLA DR4 was found in 80.6% of male patients, which was highly significant compared with controls (P less than 0.0005), while only a borderline increase of 60.5% was found in female patients (P less than 0.05). In addition, the frequency of HLA DR2 was remarkably low in male patients. These suggest the possible heterogeneity of rheumatoid arthritis in Japanese.