SCN2A and neurodevelopmental disorder: Surprisingly, none of the major recurrent variants in STXBP1 showed significant phenotypic similarity, in contrast to the main recurrent variants in other neurodevelopmental disorders such as SCN2A-related disorders.32 This lack of phenotypic similarity for recurrent variants indicates that when compared to the phenotypes of STXBP1-disorders as a whole, the baseline variability of phenotypic features is too high for single-phenotype associations to result in overall phenotypic similarity.