Association of Major Histocompatibility Complex Class I Chain-Related Gene A and HLA-B Alleles with Behçet's Disease in Turkey.

PURPOSE

Behçet's disease (BD) is known to be associated with HLA-B51 in many different ethnic groups. Recently, the major histocompatibility complex class I chain-related gene A (MICA), located near the HLA-B gene, has been proposed as a candidate gene for BD susceptibility in several ethnic groups. To compare the relative contribution of MICA polymorphisms and HLA-B51 to BD in different ethnic groups, we studied MICA polymorphisms in Turkish BD patients.

METHODS

Thirty-three Turkish BD patients and 65 healthy controls were enrolled for analysis of polymorphisms in the extracellular domains of MICA.

RESULTS

The phenotype frequencies of MICA009 were significantly higher in BD patients (75.8%) than in controls (29.2%) (P = 0.000015). HLA-B51 was also significantly more frequent in BD patients (81.8%) than in controls (29.2%) (P = 0.0000007). A strong association existed between MICA009 and HLA-B51. To assess the confounding effect of MICA009 on HLA-B51, we performed a stratification analysis that showed that BD was distinctly associated only with HLA-B*51.

CONCLUSION

Our results indicate that the major susceptibility gene for BD is HLA-B51 and that the association between MICA009 and BD arises from a strong linkage disequilibrium with HLA-B51. However, we suggest that MICA009 likely elicits an immune effect secondary to BD.