Two of the most commonly identified synaptopathies, Phelan–McDermid syndrome (PMD) and SYNGAP1-related intellectual disability (SYNGAP1-ID) have characteristic neurodevelopmental deficits including intellectual disability, global developmental delay, autism and epilepsy [8,9,10,11,12]. This evidence concerns the gene SYNGAP1 and Pelizeaus-Merzbacher spectrum disorder.