HLA extended haplotypes in childhood and adult onset HLA-DR4-associated arthropathies.

Alpha HLA-DR4 extended haplotypes have been established by family studies in children and adults with chronic arthritis, the children having polyarticular juvenile rheumatoid arthritis and the adults rheumatoid arthritis. These diseases are probably the same disorder presenting at different ages. The results demonstrate age-related differences in the frequency of HLA-DR4 extended haplotypes between the two groups of patients. The childhood onset was associated with the presence of the HLA-B44, SC30, DR4 extended haplotype, whereas the adult form was more strongly associated with the HLA-Bw62, SC33, DR4 haplotype. These results suggest that differences in the age at onset are influenced by the MHC in addition to the presence of the HLA DR4 gene itself.