SMN1 and Intellectual disability: Since SMN1 and FMR1 represent the most common recessive severe muscle disorder and intellectual disability disease gene, respectively, we complemented the exome sequencing data of 3045 genes (including FMR1 sequence variants) by targeted testing for these two genes and thus analyzed a total of 3046 AR/XL genes, of which 1009 were annotated as definitive NDD genes in the sysNDD database, which includes genes causing developmental delay, intellectual disability and autism spectrum disorder.