STXBP1 and infantile spasms: Overall, some of the genes most frequently associated with IESS include pathogenic variants in TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1, SCN2A and SCN8A, amongst others, although exact incidences of variants fluctuate between individual cohort studies [10,12,13,70,71,72,73,74].