We characterized a family presenting with a history of ventricular fibrillation (VF) and sudden death without ECG or echocardiographic abnormalities at rest. Two siblings died suddenly at the ages of 9 and 10 years, and another two were resuscitated from out-of-hospital cardiac arrest with documented VF at age 10 and 16, respectively. Exome sequencing identified a missense mutation affecting a highly conserved residue (p.Phe90Leu) in the CALM1 gene encoding calmodulin. This mutation was also carried by one of the sibs who died suddenly, for whom DNA was available. The mutation was present in the mother and in an sibling, both asymptomatic but displaying a marginally prolonged QT-interval during exercise. CONCLUSIONS: We identified a mutation in CALM1 underlying IVF manifesting in childhood and adolescence. The causality of the mutation is supported by previous studies demonstrating that Phe90 mediates the direct interaction of CaM with target peptides