HLA gene frequencies in children and adults with systemic onset juvenile rheumatoid arthritis.

The HLA genetic region was studied in 51 patients with systemic onset juvenile rheumatoid arthritis: 35 with childhood onset and 16 with adult onset (adult Still's disease). HLA genotypes were established by including family members, 261 of whom were also typed in the study. The most marked difference between patients and controls involved the HLA-DR4 gene, which occurred with a frequency of 0.348 in the childhood onset patients and 0.170 in the controls (chi 2 = 8.97, P = 0.0028, adjusted P = 0.017). In contrast, the adult onset patients showed a marginal increase in HLA-DR7, but were similar to controls with respect to HLA-DR4. HLA-Bw35 was increased in children with systemic onset disease, in accordance with earlier findings. The results suggest that patients with systemic onset juvenile rheumatoid arthritis have complex HLA associations which are different in childhood onset and adult onset disease.