In LKS, the onset ranges from 3 to 7 years [50], while in CDKL5-deficiency disorder (OMIM #300203) and FOXG1 disorder (OMIM #164874), the median onset of regression was 6.5 and 12 months, respectively [40]. The gene discussed is CDKL5; the disease is developmental and/or epileptic encephalopathy with spike-wave activation in sleep.