Developmental epileptic encephalopathy (DEE) is used as a term to describe conditions where the epileptic activity contributes to the severe cognitive and behavioural impairments that are beyond those expected to result from the underlying brain pathology alone.1 The severity of these impairments is variable, and can occur at any age, not just epilepsies with an onset during infancy and childhood.1 Many DEEs have a genetic aetiology.1