Abstracts

Four individuals who had epileptic seizures and carried PCDH19 pathogenic variants were enrolled. The age at seizure onset ranged from 8 months to 20 months of age following an upper respiratory tract infection or a fever after immunization. All individuals had cluster seizures during an illness.
Individual 1 primarily presented with myoclonic seizures and automatism, and her interictal EEG showed generalized background slowing and focal spikes. Individual 2 initially showed febrile and afebrile seizures, subsequently developed cluster attacks with pleomorphic seizure types, followed by acute encephalopathy after an episode of SARS-CoV-2 virus infection; and ictal EEG revealed multifocal spikes, ictal shifts, and a burst suppression pattern, mimicking the ictal EEG feature of febrile-infection related epileptic syndrome (FIRES). Individual 3 had focal tonic seizures with impaired awareness or automatism, while interictal EEG showed a normal result. Individual 4 exhibited generalized tonic, tonic-clonic seizures, or automatism, and the interictal EEG demonstrated generalized background slowing and focal spikes. Brain magnetic resonance imaging features were unremarkable in individuals 1, 3, and 4, while individual 2 had T2-weighted hyperintensity in the bilateral parietal-temporal regions. The identified PCDH19 causative variants were p.Phe206Cys in individual 1, p.Ile178GlnfsTer47 in individual 2, and p.Pro561Arg in individuals 3 and 4, who are siblings.
During a follow-up period ranged from 1 year and 2 months to 4 years and 2 months, the clinical outcomes varied: individual 1 had profound psychomotor impairment, individual 2 was mild developmental delay, and individuals 3 and 4 achieved normal developmental milestones.