DRB1 alleles in polymyalgia rheumatica and rheumatoid arthritis in southern France.

To investigate the association of HLA-DRB1 alleles with polymyalgia rheumatica (PMR) and rheumatoid arthritis (RA), 55 patients with PMR without giant cell arteritis, 203 patients with RA and 230 controls, all from the European population of Marseille, were HLA-DRB1 genotyped by PCR-SSO. HLA-DRB1*01 was significantly increased in both the PMR and RA groups compared to controls (35% versus 17%, P(c) < 0.05, and 41% versus 17%, P(c) < 0.001, respectively). HLA-DRB1*04 was significantly increased in the RA group compared to controls (48% versus 23%, P(c) < 0.001) but not in the PMR group. HLA-DRB1*04 subtype frequencies were significantly different between PMR patients and RA patients. Shared epitope-positive HLA-DRB1*04 alleles (DRB1*0401, 0404, 0405, 0408) were significantly overrepresented in RA patients compared to PMR patients and shared epitope-negative HLA-DRB1*04 alleles were overrepresented in PMR patients compared to RA patients. In conclusion, in the Mediterranean population studied, HLA-DRB1*01 is associated with RA and PMR whereas HLA-DRB1*04 is associated with RA only.