Patients have greater developmental impairments than DS, are nonambulatory, and the majority require feeding tubes.40 Heterologous expression of the mutant Nav1.1‐p.Thr226Met protein showed negative shifts in the voltage dependence of both activation and inactivation of INa compared to WT Nav1.1, which can be interpreted as both gain‐ and loss‐of‐function.41 The gene discussed is SCN1A; the disease is Dravet syndrome.