SLC2A1 and idiopathic generalized epilepsy: The expanded phenotype, combined with reports that SLC2A1 mutations account for approximately 1% of idiopathic generalized epilepsies (5) and approximately 10% of absence epilepsies (6), suggests that the disease is more prevalent than originally thought; it is estimated that there are at least 4500 Glut1 DS patients in the US alone (7).