PCDH19 and epilepsy: The majority of diagnoses feature rare, highly deleterious variants concentrated in a small number of recurrently implicated genes (i.e. PRRT2, SCN1A, KCNQ2, CDKL5, SCN2A, STXBP1, SLC2A1, and PCDH19), with the 10 most represented genes accounting for ~ 80% of cases of monogenic epilepsy [8, 9].