Variations in 10 genes that relate to ID/GDD including CACNA1A, CACNA1C, CACNA1I, CACNA1H, CACNA1D, CACNA2D1, CACNA2D2, CACNA1E, CACNA1F, and CACNA1G were found, and most variants exhibited gain-of-function effect. Here, CACNA2D2 is linked to Global developmental delay.