MTHFR and Dravet syndrome: In summary, all the three genetic polymorphisms (MTHFR 677C>T, MTRR 66A>G, and RFC1 80G>A) which have been linked to the maternal risk for the birth of a child with DS by literature meta-analyses (Table 2), and other polymorphisms in the same genes (MTHFR 1298A>C and MTRR 524C>T), have been associated with hematochemical markers of one-carbon metabolism (Table 3).