Sudden Death in a 1-Year-Old Japanese Girl: A Phe110Ile Missense Mutation in the Cardiac Troponin T2 Gene Possibly Associated with Low Activity of the Cardiac Mitochondrial Respiratory Chain Complex I

Abstract

A 1-year-old Japanese girl with an eight-hour history of diaphoresis and emesis, died on arrival at our hospital. Investigations could not determine the cause of death. Imaging findings were consistent with postmortem changes. There were no pathological findings of virus-induced changes, fulminant myocarditis, myocyte disarray, or myocardial hypertrophy. The activity of the cardiac mitochondrial respiratory transport chain complex (MRTCC) I was reduced. Analysis of target resequencing by use of a genetic testing panel for mitochondrial diseases showed the patient had a Phe110Ile missense mutation (c.358T>A; p.F110I) in the cardiac Troponin T2 gene (TNNT2 mutation). TNNT2 mutation is one of the causes of familial hypertrophic cardiomyopathy. Our case is the first report of a patient with the TNNT2 mutation and low activity of cardiac MRTCC I.