Although no clear correlation with variant type (missense vs nonsense) or position within the protein have been observed, authors have reported differences in the severity of phenotype in individuals with different CDKL5 variants, highlighting how variants in close proximity on the CDKL5 gene can result in widely varying clinical phenotypes, mostly evaluated on the basis of achievement of developmental milestones, motor and communication ability and epilepsy burden. This evidence concerns the gene CDKL5 and epilepsy.