Individuals carrying MTHFR C677T TT genotype have been reported to have lower levels of 5-MTHF, probably resulting in lower cell methionine and S-adenosylmethionine (SAM) levels, thereby potentially leading to aberrant DNA methylation [22, 23], which, we hypothesized, may explain the increased NBUD frequencies in BD-exposed workers in the present study. The gene discussed is MTHFR; the disease is Behcet disease.