CDKL5 and Intellectual disability: CDKL5 (cyclin-dependent kinase-like 5) deficiency disorder (CDD) is a severe X-linked neurodevelopmental disease characterized by early-onset infantile developmental and epileptic encephalopathy (DEE) syndrome, intellectual disability, motor abnormalities, and cortical visual impairments along with sleep disturbances and gastrointestinal dysfunction [1,2,3].