MTHFR and systemic lupus erythematosus: It is tempting to believe that NTDs have reached a high prevalence in Mexico because the Amerindian heritage of alleles provides a survival advantage, similar to those reported for other alleles like the SLE risk haplotype in IRF5. Further detailed genetic and environmental analysis should be performed in order to elucidate the impact of the MTHFR polymorphisms on the high incidence of severe pathologies like NTDs.