STXBP1 and Intellectual disability: STXBP1-DEE is now recognized as one of the more frequent monogenic DEEs, with a predicted incidence of 3.30–3.81 per 100,000 births.18 In addition to intellectual disability and epilepsy, movement disorders such as tremor and ataxia are frequent.12,19, -, 22 Extrapyramidal features have been described in a few adolescents and adults with STXBP1-DEE, although information on the prevalence of this clinical symptomatology at adult age is missing.12,23