Associations of vitamin D receptor gene polymorphisms FokI and BsmI with susceptibility to rheumatoid arthritis and Behçet's disease in Tunisians.

ABSTRACT

OBJECTIVES: Reports of immunomodulating effects of vitamin D suggest a need for examining allele and genotype frequencies of the vitamin D nuclear receptor gene (VDR) in patients with autoimmune diseases. T-helper-1 (Th1) counts in peripheral blood are increased in both rheumatoid arthritis (RA) and Behçet's disease (BD). We studied VDR polymorphisms in patients with these two diseases in Tunisia. METHODS: In 108 patients with RA, 131 patients with BD, and 152 controls, we studied FokI and BsmI VDR polymorphisms, using the restriction fragment length polymorphism technique. RESULTS: The FokI polymorphism alleles and genotype were significantly more common in the RA group than in the controls (P=0.001 and P=0.005, respectively). The FokI F allele and F/F genotype were significantly associated with BD (P=0.0003 and P=0.002, respectively). Furthermore, in the group with BD, the FokI polymorphism was significantly associated with the presence of vascular manifestations (P=0.006). In patients with RA, the FokI polymorphism was significantly associated with female gender (P=0.003). No significant associations were found between the Bsm1 polymorphism and RA or BD. CONCLUSION: The VDR F allele is associated with RA and BD in Tunisians.