In the second group, epilepsy associated with intellectual disability can be caused by late-onset presentations of disorders of creatine metabolism, mitochondrial disorders, GLUT-1 deficiency, urea cycle defects, organic acidemias, succinic semi-aldehyde dehydrogenase deficiency (SSADH), and lysosomal storage disorders such as juvenile Niemann–Pick disease Type C [74]. This evidence concerns the gene SLC2A1 and hyperinsulinemic hypoglycemia, familial, 4.