Although the mechanism remains poorly understood, the sodium channel‐dependent cardiac current is increased in SCN1A‐R1407X knock‐in mice,39 and autonomic dysfunctions such as abnormalities in heart rate variability, QT and P wave dispersion are observed in patients with Dravet syndrome,40 suggesting that some SCN1A variants might cause sudden death or lethal arrhythmia through neurocardiac or solely cardiac mechanisms. The gene discussed is SCN1A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.