Lower incidence of nonsyndromic cleft lip with or without cleft palate in females: is homocysteine a factor?

In India, as in other parts of the world, nonsyndromic cleft lip with or without cleft palate (NSCL +/- P) is a highly prevalent birth defect, its incidence in males being twice that in females. A case-control association study has been carried out with respect to homocysteine level and MTHFR C677T, A1298C and SLC19A1 (RFC1) G80A genotypes from an eastern Indian cohort to investigate whether Hcy and other Hcy-pathway genes also contribute to the risk level. While MTHFR 677T and SLC19A1 80G are individually and cumulatively risk factors, SLC19A1 80A appears to be protective against MTHFR 677T risk allele. Elevated Hcy associates with NSCL +/- P both in case mothers and cases. Significantly, this difference shows a gender bias: the level of elevation of Hcy in female cases is distinctly higher than in males, and more case females are hyperhomocyteinemic than the case males. It implies that compared with the males, higher level of Hcy is needed for NSCL +/- P to manifest in the females. We consider this as one of the possible factors why the incidence of this disorder in females is much lower than in males.