PCDH19 and epilepsy: Protocadherin 19 (PCDH19) pathogenic variants cause the infantile encephalopathy Clustering Epilepsy (CE, previously known as Girls Clustering Epilepsy; GCE, Female-Limited Epilepsy; FE and Epilepsy and Mental Retardation Limited to Females; EFMR: OMIM #300088) [1].