Neurodevelopmental disorders (NDDs) encompass multiple disease phenotypes that are linked to a highly heterogenous genetic architecture.1 Mutations in the SYNGAP1 gene account for as many as 1% of NDD cases, with patients often presenting with intellectual disability and autism spectrum disorder.2–6 Most patients with SYNGAP1 pathogenic variants display some form of epilepsy with a high prevalence of absence seizures and a behavioural developmental delay occurring upon seizure onset. Here, SYNGAP1 is linked to neurodevelopmental disorder.