STXBP1 and neurodevelopmental disorder: STXBP1 encephalopathy, caused by heterozygous pathogenic variants in syntaxin-binding protein 1 (STXBP1, also known as MUNC18-1), is among the most frequent developmental and epileptic encephalopathies (Symonds and McTague, 2020; Verhage and Sørensen, 2020) and neurodevelopmental disorders (Deciphering Developmental Disorders Study, 2015; Kaplanis et al., 2020).