B27-bearing HLA haplotypes in rheumatoid arthritis: characterization in Finnish patients.

The frequency of human leukocyte antigen (HLA)-B27 has been found to be increased in rheumatoid arthritis (RA) in Finland and marginally also in some other populations. In the present study HLA-B27-bearing haplotypes in RA patients were found to carry DR1 and DR4 genes more often than do B27 haplotypes in control population. B27;DR4,DW14;DQw7 was a typical B27-DR4 haplotype whereas DR4 in the majority of other haplotypes occurs with Dw4 and DQw8 genes. The result indicates that the B27 association with RA is not independent of DR1 and DR4, but whether the B27;DR4;DQw7 haplotype subjects a person to a higher disease risk than do other DR4 haplotypes, or is associated with a more severe course of the disease, remains to be investigated.