Long QT syndrome with a de novo CALM2 mutation in a 4-year-old boy.

BACKGROUND

Human calmodulin (CALM) gene mutation has been reported to be related to inherited arrhythmia syndromes, but the genotype-phenotype relationship remains unclear.

METHODS AND RESULTS

We report here a 4-year-old boy who had cardiac arrest while playing in a kindergarten playground. Cardiopulmonary resuscitation was initiated immediately. Eleven minutes after the cardiac arrest, ambulance crews arrived and an automated external defibrillator was attached. His heart rhythm, which was ventricular fibrillation (VF), was returned to sinus rhythm after only one shock delivery. The boy was brought to hospital by air ambulance. During transfer, electrocardiogram (ECG) showed transient VF. On arrival, chest radiograph showed a cardiothoracic ratio of 55% without pulmonary congestion. A 12-lead ECG showed a normal sinus rhythm, biphasic T wave, and prolongation of the corrected QT interval. On ECG, VF was preceded by torsade de pointes or frequent polymorphic premature ventricular contractions (PVC). Echocardiography showed a normal heart structure with decreased cardiac function. On the second day of hospitalization, ECG showed remarkable QT prolongation, T-wave alternans, and frequent PVC. Thereafter, propranolol was started. The ECG showed rapid improvement of QT prolongation and T-wave abnormality. Genetic test indicated a CALM2 mutation, and he was diagnosed with long QT syndrome-15 (LQT15).

CONCLUSIONS

CALM mutations cause long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT) and idiopathic VF. This patient with a CALM2 p.N98S mutation had both phenotypes of LQTS and CPVT.