SLC2A1 and Intellectual disability: SCL2A1 gene encodes glucose transporter type 1 (GLUT1), a glucose transporter across the blood-brain barrier; SCL2A1 is responsible for the GLUT1 deficiency syndrome (infantile-onset epilepsy with heterogeneous type of seizures, complex movement disorders, ataxia, intellectual disability, macrocephaly, and hypoglycorrhachia) [66], and a large phenotypic spectrum characterized by normal glycorrhachia, movement disorders, often normal mental capacities, and seizures, in particular absence seizures [67].