SYNGAP1 and Neurodevelopmental delay: The genetic basis of MRD5 has been attributed to the loss-of-function mutation of the SYNGAP1 gene, which is ranked the fourth most common NDD-related gene among a large spectrum of genes sharing overlapping phenotypes, accounting for ∼0.75% of all NDD patients (Berryer et al., 2013; Deciphering Developmental Disorders Study, 2015; Kilinc et al., 2022).