Thus, patients lacking GM3 synthase activity exhibited severe neurological disorders such as infantile epilepsy, mental retardation, visual disorders, and also skin pigmentation abnormalities, while no definite abnormal phenotypes were found in KO mice of the GM3 synthase gene (St3gal5) in any sites of the body except for the auditory system [110]. The gene discussed is ST3GAL5; the disease is infantile epilepsy syndrome.