SCN1A and Dravet syndrome: DS is genetically one of the most homogeneous DEEs, with more than 80% of people shown to carry a de novo SCN1A variant.3 Large-scale international research efforts such as Epi25 <http://epi-25.org/>, the Deciphering Developmental Disorders (DDD) study4 and the UK 100,000 Genomes Project5 are now concentrating on diagnosing people and identifying genes involved in rare disorders including DEE, using chromosomal microarrays, whole exome sequencing (WES) and whole genome sequencing (WGS).