long QT syndrome 3 (MONDO_0011377, a Monarch Disease Ontology identifier) is an autosomal dominant condition caused by mutation(s) in the SCN5A gene, encoding sodium channel protein type 5 subunit alpha. It is characterized by a prolonged QT interval that may result in torsade de pointes, ventricular fibrillation and/or sudden cardiac death. Also known as: LQT3, SCN5A long QT syndrome, long QT syndrome caused by mutation in SCN5A, long QT syndrome type 3.