Linkage studies of HLA and rheumatoid arthritis in multicase families.

The linkage of rheumatoid arthritis (RA) to the HLA-DR locus was investigated in 17 families with multiple cases of RA. Log odds scores were computed using the Liped program; sibship associations were examined by 2 methods. The results showed a trend toward linkage which was short of significance. The results were similar for patients with classic or definite RA, with or without the inclusion of probable RA patients. The finding of strong association and weak linkage would suggest that it is DR4, itself, that is important in RA.