Developmental and Epileptic Encephalopathies (DEEs) are a group of rare and severe epilepsies which are characterized by seizures and significant developmental delays. Most DEEs begin in early life, often in infancy, with children experiencing frequent and severe seizures, which can be of multiple types. This generates a complex clinical picture in which both developmental abnormalities and severe epilepsy contribute to the functional impairment of these children which continues into adulthood.