Previous work with the SCN1B‐p.Cys121Trp variant, linked to GEFS+, showed normal cell surface expression in heterologous cells, but LOF in terms of INa modulation.7, 20 A biallelic Scn1b‐p.Cys121Trp mouse model showed a phenotype that is similar to DS.21 In contrast, heterologous expression experiments with the variant, SCN1B‐p.Arg125Cys, linked to a diagnosis of DS, showed that the mutant β1 protein was retained inside the cell and subsequently unavailable at the plasma membrane to modulate INa. Here, SCN1B is linked to Dravet syndrome.