ObjectiveTo explore the genotype and phenotype of PCDH19 gene related epilepsy.Methods41 probands, including 39 girls and 2 boys collected from pediatric department of the Peking University and Neurology Department of Wuhan Children's Hospital from February 2005 to April 2017, were diagnosed as PCDH19 gene related epilepsy. The clinical features of the probands and affected relatives were retrospectively analyzed. PCDH19 mutations were detected by Sanger sequencing or targeted next generation sequencing (NGS) and multiple ligation-dependent probe amplification (MLPA).Results40 in 41 probands with PCDH19 mutations were detected by sequencing and one was detected by MLPA.Two male epilepsy patients with mosaic PCDH19 mutations were detected by NGS with the mutant allele fraction of 85% and 33%. Among 39 female probands, 19 were with inherited mutations and 20 were de novo mutations. The penetrance of females with PCDH19 mutation was estimated as 90% (53/59). Twelve hemizygous fathers and one mosaic father were asymptomatic.The clinical phenotypes of female mutation carriers included epilepsy with mental retardation, Dravet syndrome, febrile seizures, or even asymptomatic. The phenotypic heterogeneity was noticed in females with identical mutations even in members from the same family. The median seizure onset age of 46 patients (including 41 probands and 5 affected relatives) were 11 months (range 4~42months).During the course, 87% (40/46) patients experienced generalized tonic clonic seizures (GTCSs) and 69.6% (32/46) experienced focal seizures. Other rare seizures types included myoclonic seizures (6/46), absence seizures (3/46) and atonic seizures (1/46). Seizures in clusters were observed in all patients, fever sensitivity in 80.4% (37/46), and status epilepticusin only three, cognitive impairment in 76% (35/46) and 7 with autistic features.ConclusionMutations in PCDH19 can be inherited or de novo. Most patients are females, rare mosaic males can be affected or asymptomatic. PCDH19 gene related epilepsy shows incomplete penetrance and variable expressivity.Seizures occurring in clusters and sensitive to fever are the major features.