Abnormal interaction between CaM and RyR2 due to mutations in the CaMBD of RyR2 or in CaM itself can cause severe cardiac complications, including cardiac hypertrophy, heart failure and arrhythmias, such as CPVT (Balshaw et al., 2001; Yamaguchi et al., 2013, 2007). The gene discussed is CALM1; the disease is catecholaminergic polymorphic ventricular tachycardia.