de Kovel CGF, et al. - The clinical spectrum associated with KCNB1 variants and the genotype-phenotype correlations are examined in this study. The authors revealed that de novo KCNB1 missense variants in the ion channel domain and loss-of-function variants in this domain and the C-terminal likely cause neurodevelopmental disorders with or without seizures. Patients with presumed pathogenic variants in KCNB1 have a variable phenotype. However, in the protein, the type and position of the variants are (imperfectly) associated with the severity of the disorder.