Here, we report 11 affected individuals from six unrelated families, with a severe neurodevelopmental phenotype consisting of early-onset epilepsy, intellectual disability, cleft palate and a variable association of pes equinovarus, arthrogryposis multiplex congenita, scoliosis and omphalocele due to bi-allelic loss-of-function variants in GAD1. This evidence concerns the gene GAD1 and cleft palate.