Among the genetic syndromes that have been characterized are: Dravet syndrome (DS), also called severe myoclonic epilepsy of infancy (SMEI, MIM# 607208) [1], CDKL5/STK9 Rett-like epileptic encephalopathy [2],[3], ARX-related epileptic encephalopathies [4], SRPX2-related rolandic epilepsy associated with oral and speech dyspraxia and mental retardation [5], and very recently, female-limited epilepsy and cognitive impairment (EFMR) associated with mutations in PCDH19, the gene encoding the protocadherin 19 on the X chromosome [6]. This evidence concerns the gene PCDH19 and Cognitive impairment.