HLA-DRB1 alleles associated with rheumatoid arthritis in southern France. Absence of extraarticular disease despite expression of the shared epitope.

Abstract

Extraarticular rheumatoid arthritis (RA) is almost unknown in Marseille in southern France. We investigated whether this was due to rare expression of the HLA-DRB1 shared epitope. HLA-DRB1 alleles were characterized in 73 patients with RA and 108 controls by polymerase chain reaction amplification and oligonucleotide hybridization. In patients with RA, 76% expressed the shared epitope (46% DR1, 45% DR4). Four HLA-DRB1 alleles were positively associated with disease: DRB1*0101, DRB1*0401, DRB1*0404, DRB1*0405. Patients with double dose shared epitope had the most severe articular damage, but no extraarticular disease. In Marseille, 76% of patients with RA are shared epitope positive. Still, most do not develop extraarticular RA. This may be caused by the low frequency of HLA-DRB1*0401 in this population.