Population genetics of rheumatoid arthritis.

A major component of genetic susceptibility to rheumatoid arthritis (RA) appears to be explained by inheritance of HLA-DRB1 alleles, which have a conserved sequence of amino acids in the third hyper-variable region of the molecule. This "shared epitope" is found on various DR4, DR1, and DR6 variants, as well as on DR10. The evidence for this "shared epitope" in RA is examined at the population level, including how it fits in with the available epidemiologic data and RA disease severity.