SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: Dravet syndrome is the archetypal DEE and amongst the most common of the rare epilepsies.1,4 Understanding of Dravet syndrome pathophysiology is amongst the most advanced for any DEE, reflected in the range of targeted therapies now in development.66–68 The core phenotype is sufficiently distinct that the diagnosis is usually made clinically, followed by genetic testing anticipating a causal SCN1A variant, reflecting the very strong association between phenotype and causal gene.