MTHFR and Behcet disease: In further haplotype analysis of MTHFR gene, the individuals in BD-exposed group carrying diplotype 677C-1298A/ 677C-1298A had significantly lower MN frequencies than those carrying diplotype 677 T -1298A/ 677 T-1298C, which indicates that MTHFR C677T T variant contributes mainly to the interactions between MTHFR haplotypes and chromosomal damage.