Molecular analysis of HLA-DR polymorphism in polymyalgia rheumatica. Swiss Group for Research on HLA in Polymyalgia Rheumatica.

Objective: To analyze by molecular typing possible associations of HLA-DRB1 alleles with polymyalgia rheumatica (PMR) compared to controls and patients with rheumatoid arthritis (RA) in Switzerland.

Methods: In a multicenter survey, we recruited 100 patients with PMR with and without signs of giant cell arteritis (GCA), 198 with RA, and 200 controls (volunteer bone marrow donors). HLA-DR generic typing was performed by microtiter plate oligotyping and DR4 subtypes analyzed by dot blot hybridization with sequence specific oligonucleotides or by polymerase chain reaction sequence specific primers.

Results: DR4 and DR1 tended to be increased in PMR, compared to controls (36 vs 30%, p = 0.30; and 19 vs 12%, p = 0.16, respectively). Frequencies of all RA associated DR4 and DR1 subtypes tended to be increased in PMR as well. Frequency of the HLA-DR beta 1 70-74 shared motif (QK/RRAA) was significantly higher in PMR than in controls [50 vs 36%, odds ratio (OR) = 1.8, p = 0.018], although lower than in RA (77 vs 36%, OR = 6.0, p < 0.0001), and slightly out of the range of significance if a Bonferroni correction was applied (p = 0.1). At double dose, this epitope was also increased in PMR, but not significantly (5 vs 2%, OR = 2.6, p = 0.17), while it was markedly augmented in RA (22 vs 2%, OR = 14, p = < 0.0001). In patients with the shared epitope, the frequency of clinical signs of GCA tended to be increased (19 vs 10%, p = 0.25). Frequency of the HLA-DR beta 1 DRYF 28-31 motif was identical in PMR (95%) and controls (93%).

Conclusion: PMR may be associated with the HLA-DR beta 1 70-74 shared epitope. This association, however, would be much weaker for PMR than for RA, particularly with the shared epitope at double dose. PMR is clearly not associated with the HLA-DR beta 1 DRYF 28-31 motif.