The association of HLA-DM genes with rheumatoid arthritis in Eastern France.

In this study, the polymorphisms of the HLA DMA and DMB genes in patients with rheumatoid arthritis (RA) were examined.DMA and DMB typing was performed in 120 white RA patients from eastern France and 100 healthy controls, using PCR-SSO (sequence specific oligonucleotide probes) method for DMA determination and PCR-RFLP (restriction fragment length polymorphism) method for DMB typing. All patients and controls had been HLA DRB1* genotyped.DMA*0103 was found significantly increased in RA patients (RA vs. controls: 18.3% vs. 4%) (p(corr) = 0.004; OR: 5.39; CI: 1.67-19.23). A decreased frequency of DMA*0102 was also observed in the RA group (RA vs. controls: 18.3% vs. 31%), but not significantly. There were no differences in the prevalence of DMB alleles between RA and controls. The patients and the controls were then stratified according to the expression of the HLA DRB1* RA-linked alleles (DRB1*01 and *04) and this allowed us to find no linkage disequilibrium between DMA*0103 and DRB1*01 or *04 alleles. Finally, most DMA*0103 patients were positive for rheumatoid factors and had extraarticular involvement such as subcutaneous nodules. Thus, our results suggest that DMA*0103 could be an additional genetic factor for RA susceptibility in French whites.