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Objective: To characterize the features associated with PCDH19-related epilepsy, also known as "female-limited epilepsy.", Methods: We analyzed data from participants enrolled in the PCDH19 Registry, focusing on the seizure-related, developmental, neurobehavioral, and sleep-related features. We evaluated variants for pathogenicity based on previous reports, population databases, and in silico predictions, and included individuals with pathogenic or potentially pathogenic variants. We performed a retrospective analysis of medical records and administered a targeted questionnaire to characterize current or past features in probands and genotype-positive family members., Results: We included 38 individuals with pathogenic or potentially pathogenic variants in PCDH19: 21 de novo, 5 maternally inherited, 7 paternally inherited, and 5 unknown. All 38 had epilepsy; seizure burden varied, but typical features of clustering of seizures and association with fever were present. Thirty individuals had intellectual disability (ID), with a wide range of severity reported; notably, 8/38 (22%) had average intellect. Behavioral and sleep dysregulation were prominent, in 29/38 (76%) and 20/38 (53%), respectively. Autistic features were present in 22/38 (58%), of whom 12 had a formal diagnosis of autism spectrum disorder. We had additional data from 5 genotype-positive mothers, all with average intellect and 3 with epilepsy, and from 1 genotype-positive father., Significance: Our series represents a robust cohort with carefully curated PCDH19 variants. We observed seizures as a core feature with a range of seizure types and severity. Whereas the majority of individuals had ID, we highlight the possibility of average intellect in the setting of PCDH19-related epilepsy. We also note the high prevalence and severity of neurobehavioral phenotypes associated with likely pathogenic variants in PCDH19. Sleep dysregulation was also a major area of concern. Our data emphasize the importance of appropriate referrals for formal neuropsychological evaluations as well as the need for formal prospective studies to characterize the PCDH19-related neurodevelopmental syndrome in children and their genotype-positive parents., (Wiley Periodicals, Inc. © 2018 International League Against Epilepsy.)

Recent technological advances in gene sequencing have led to a rapid increase in gene discovery in epilepsy. However, the ability to assess pathogenicity of variants, provide functional analysis, and develop targeted therapies has not kept pace with rapid advances in sequencing technology. Thus, although clinical genetic testing may lead to a specific molecular diagnosis for some patients, test results often lead to more questions than answers. As the field begins to focus on therapeutic applications of genetic diagnoses using precision medicine, developing processes that offer more than equivocal test results is essential. The success of precision medicine in epilepsy relies on establishing a correct genetic diagnosis, analyzing functional consequences of genetic variants, screening potential therapeutics in the preclinical laboratory setting, and initiating targeted therapy trials for patients. The authors describe the structure of a comprehensive, pediatric Epilepsy Genetics Program that can serve as a model for translational medicine in epilepsy.