The Norwich case-control study was the first trial concerning the possible correlation between MTHFR C677 mutation and PAD: the study concluded that the MTHFR C677T allele has a potential role in the risk of developing atherosclerosis, since the mutation in homozygosity (TT) was found to have a higher prevalence in PAD patients (with an odds ratio of 1.99) than in the control group, emphasizing, therefore, the strong association between PAD and the TT genotype [168]. This evidence concerns the gene MTHFR and atherosclerosis.