Genetic deficiency of sialyltransferase ST3GAL3 (OMIM#611090) (17–22) and ST3GAL5 (OMIM#609056) (23, 24), two enzymes that add sialic acid residues to glycoproteins and glycolipids, leads to infantile epilepsy and developmental delay. Here, ST3GAL3 is linked to infantile epilepsy syndrome.