Normal electrocardiography at presentation masks SCN5A-related long QT syndrome: the importance of Holter monitoring in children with a family history of Brugada syndrome.

A 10-year-old girl who showed no abnormalities on resting or exercising stress electrocardiograms underwent Holter monitoring because of a family history of Brugada syndrome, which revealed marked QT prolongation during sleep. SCN5A-related inherited arrhythmia was suspected, and genetic testing confirmed the p.Glu1783Lys variant in SCN5A. Children with a family history of Brugada syndrome should undergo Holter monitoring proactively, suspecting the possibility of SCN5A-related inherited arrhythmia, even if 12-lead electrocardiograms show no abnormalities.