This website provides clinical and genetic information about patients with disease-causing changes in the PCDH19 gene.

Abnormalities in the PCDH19 gene are usually associated with epilepsy in girls. The seizures often start at 8 months (median onset = 10 months), most girls having seizure onset by 3 years of age. Commonly, girls have clusters of many seizures over several days followed by periods where they are seizure free. This distinctive pattern has led to the disorder being often referred to as PCDH19 Clustering Epilepsy (CE) to assist in earlier recognition of PCDH19 epilepsies. Affected girls often have behavioural difficulties, learning problems or intellectual disability that may not be apparent until after the seizures start.

The PCDH19 gene is located on the X chromosome, and was first implicated in epilepsy in 2008. Changes that affect a gene’s ability to function are referred to as pathogenic variants. Many different pathogenic variants in the PCDH19 gene are associated with CE. The PCDH19 gene is important because it encodes a protein that is involved in how brain cells (neurons) communicate with other cells and move in forming the brain.

CE typically affects females, but not all females with PCDH19 pathogenic variants are affected. The penetrance (the extent to which the condition is present with the pathogenic variant) of CE is estimated to be 90%. Males who inherit a PCDH19 pathogenic variant from their mother are generally not affected; they do not have seizures or learning difficulties.

However, in rare cases, males have a PCDH19 pathogenic variant in some, but not all, of their cells (called mosaicism). These males usually have similar features to females with CE. Mosaicism can result from a pathogenic variant occurring in the male during early development (post fertilization of the sperm and egg).

This website was created to facilitate the collection and sharing of information about PCDH19-associated conditions. Our aim is to enhance the understanding of these disorders and improve treatment of individuals with PCDH19 pathogenic variants through PCDH19 research.

Kristy Kolc, PhD Candidate, Adelaide Medical School, The University of Adelaide, North Adelaide, SA 5005, Adelaide, Australia, kristy.kolc@adelaide.edu.au

Jozef Gecz, PhD, Adelaide Medical School, The Robinson Research Institute, The University of Adelaide, South Australia, Adelaide, Australia, jozef.gecz@adelaide.edu.au

Emma Palmer, MD, Genetics of Learning Disability Service, Hunter Genetics, Waratah, NSW 2298, Sydney, Australia, elizabeth.palmer1@health.nsw.gov.au

Ingrid Scheffer, MBBS PhD FRACP, The University of Melbourne, Victoria, Austin Health and Royal Children’s Hospital Australia, Melbourne, i.scheffer@unimelb.edu.au

Lynette Sadleir, MBChB FRACP MD, Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand, lynette.sadleir@otago.ac.nz