SCN1A and Delayed speech and language development: Proband MC-17-3 carries a de novo frameshift deletion in SCN1A, in line with his epilepsy phenotype, and proband JC-57-3 carries a de novo nonsense variant in the syndromic ASD gene ZNF292. This mutation (p.R454X) has previously been reported in a patient with mild developmental and speech delays but not with ASD79.