Recent evidence has suggested that the C677T polymorphism of MTHFR is associated with AD independently of ApoE ε4 carrier status [46] while Anello et al. [47] reported that the effect of homocysteine as a risk factor for AD was exacerbated when both ApoE ε4 and the MTHFR 677T allele were present. This evidence concerns the gene MTHFR and Alzheimer disease.