HLA-DRB1 IN 8 FINNISH MONOZYGOTIC TWIN PAIRS CONCORDANT FOR RHEUMATOID-ARTHRITIS

This study presents the results of HLA-DRB1 typing of the eight monozy gotic twin pairs with both members affected by rheumatoid arthritis (R A), sampled in the nationwide Finnish twin cohort. The shared epitope, associated with RA in case-control studies, was present in all eight twin pairs, being significantly more frequent than among RA patients i n a recent Dutch case-control study. Furthermore, 4 out of 8 twin pair s were homozygous for the shared epitope, while in 73 Dutch healthy co ntrols encoding the shared epitope only 13 (18%) were homozygous; this suggests a gene dose effect in RA susceptibility. Combining these res ults with data from other sources may help to clarify the contribution of HLA alleles in the genetic predisposition to RA.