Genetic association studies revealed associations of this polymorphism with maternal risk of DS birth either alone (Zampieri et al., 2012b), or in combination with MTR (combined TCN2 776CC/MTR 2756AG genotype) (Fintelman-Rodrigues et al., 2009) or MTHFR (combined TCN2 776CG/MTHFR 677TT genotype) (Liao et al., 2014) polymorphisms. The gene discussed is MTHFR; the disease is Dravet syndrome.