Although CDD is rare, it was recently discovered that CDKL5 is one of the most commonly mutated genes in childhood epilepsy, and CDKL5 mutations have also been associated with milder syndromes typified by intellectual disability and behavioural defects (Krishnaraj et al, 2017; MacKay et al, 2020). This evidence concerns the gene CDKL5 and Intellectual disability.