SEIZURE-EUROPEAN JOURNAL OF EPILEPSY, cilt.139, ss.101-109, 2026 (SCI-Expanded, Scopus)
Purpose: Neonatal-onset genetic epilepsies are clinically heterogeneous and are increasingly diagnosed through genomic testing. We aimed to describe the phenotypes and neurodevelopmental outcomes of infants with neonatal-onset genetic epilepsy from eighteen tertiary centres and to explore subgroup differences across functional gene categories. Methods: This retrospective multicentre study included 144 infants with seizure onset within the neonatal period and a genetically supported etiology. Clinical, electroencephalographic, neuroimaging, and genetic data were obtained from participating centres and re-evaluated. Functional gene categories were predefined, and comparative analyses were performed. A sensitivity analysis was conducted in the pathogenic/likely pathogenic subset. Results: We identified 107 variants across 76 genes; whole-exome sequencing was the most common diagnostic method (64.6%). Variants mapped most frequently to genes related to cell metabolism/functioning/signalling (58.3%), followed by ion channels/neurotransmitter receptors (29.2%) and synaptic vesicle docking/release (12.5%). Mean postnatal age at seizure onset was 11.9 +/- 12.4 days (range 1-45), and median follow-up was 24 months (range 3-84). Across functional gene groups, seizure onset occurred earliest in the ion channel/neurotransmitter receptor group (p = 0.038), and dysmorphic features were more frequent in the cell metabolism/ functioning/signalling group (p = 0.002). These findings remained consistent in sensitivity analyses restricted to pathogenic/likely pathogenic cases (onset: p = 0.046; dysmorphia: p = 0.007). Comparative analyses showed no significant differences between VUS and pathogenic/likely pathogenic groups in evaluated clinical and outcome variables. Conclusion: This large multicentre cohort delineates the phenotypic and molecular spectrum of neonatal-onset genetic epilepsies and highlights patterns across functional gene groups that warrant validation in prospective studies.