KCNJ2 and familial long QT syndrome: The loss-of-function (LoF) mutations of the KCNJ2 gene are known to be causative for LQTS with variable skeletal and muscular phenotype and catecholaminergic polymorphic ventricular tachycardia [24], and gain-of-function (GoF) mutations can cause atrial fibrillation and Short QT syndrome [1,9,24].