CALM2 and catecholaminergic polymorphic ventricular tachycardia: Apart from this case, Makita et al described four other children with de novo CALM2 mutations associated with arrhythmia susceptibility in association with LQTS and exertion-induced fatal arrhythmias; in one of these cases there was an overlap diagnosis between LQTS and CPVT, with no definitive phenotypical features.