SCN1A and Dravet syndrome: Individual examples of composite phenotypes related to oligogenic causation have been published, for example, the variation in DEPDC5 seen in a patient with Dravet syndrome because of a pathogenic variant in SCN1A, who also has epileptogenic focal cortical dysplasia,14 or a pathogenic variant in ALPL in a patient with Unverricht–Lundborg disease caused by biallelic variants in CSTB.15