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 Behcet'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.