A-312 Segregation in Two Families of the PCDH19Gene Deletion Associated With Infantile Epileptic Encephalopathy of X-Linked Inheritance and Expression in Female Carriers

Abstract

Abstract Background Developmental and epileptic encephalopathy-9 (DEE9) is an X-linked disorder characterized by seizure onset in infancy and mild to severe intellectual impairment. Autistic and psychiatric features have been reported in some individuals. The disorder affects heterozygous females only; transmitting males are unaffected. We described the segregation in two unrelated families where the proband was clinically affected as a female and another family where the proband was clinically unaffected as a male. Methods Array-CGH analysis was performed by a CGXTM HD v1,1 4-plex array 180 k (PerkinElmer), with an average resolution of 40 kb in the backbone and 20 kb in the regions of interest. Results In the first family a deletion of 809.93 Kilobases was detected in the chromosomal region Xq22.1, which includes the PCDH19 gene, in a 1 year old patient with very early onset seizures, 8 months old, inherited from an asymptomatic father. In the second family, a deletion that includes the entire PCDH19 gene was detected in a 5-year-old male patient referred to genetics for autism spectrum disorder (ASD) and not symptomatic for epilepsy; this deletion was inherited from a mother who had episodes of epilepsy in childhood. Conclusion The aCGH technique is currently the technique of choice to determine the presence of deletions/duplications in genes of interest with high reliability in patients with neurodevelopmental disorders such as epilepsy or ASD. The probands of these two families have been studied for different clinical pathology and in both the deletion of the complete PCDH19 gene has been detected. The PCDH19 gene is expressed in developing human and mouse central nervous system, including the hippocampus and cortex, suggesting a role in cognitive function. Malfunction of the protocadherin19 protein is the cause of epileptic seizures in early childhood, the seizures are mostly focal and cause serial seizures (many seizures that cluster together over a few days). It is a type of epilepsy that usually begins in early childhood. Onset may occur spontaneously or in association with fever. Mutations/deletions of the PCDH19 gene are described to cause Early Childhood Epileptic Encephalopathy, with high but incomplete penetrance. DEE9 affects only females heterozygous for the deletion and is characterised by childhood onset of seizures/epilepsy, usually with mild/severe intellectual disability, with males being healthy carriers. Although the cause is not known specifically, it is thought to be related to X-chromosome silencing that occurs in females heterozygous for this mutation. It causes an autosomal dominant X-linked disorder. Some cases of males with a mosaic PCDH19 mutation/deletion have been found to be affected and it has been suggested that the presence of both the normal gene and the mutated/deleted gene is necessary to develop for this epileptic encephalopathy.