Sinus node dysfunction is a feature seen in several inherited arrhythmic syndromes such as catecholaminergic polymorphic ventricular tachycardia,25 and in particular SCN5A gene-associated diseases such as long QT syndrome26,27 and Brugada syndrome.9,28 These rare inherited syndromes, often underdiagnosed,29 are associated with an increased risk of early sudden death, and it is possible that they contribute to explain the increased mortality in families with early-onset SND. The gene discussed is SCN5A; the disease is Down syndrome.