Modulating phenotypic expression of the PRKAG2 cardiac syndrome.

The PRKAG2 cardiac syndrome is a rare, autosomaldominant genetic disease of the heart. Genetic defects in the Prkag2 gene, encoding the regulatory subunit of AMPactivated protein kinase (AMPK), lead to a diverse cardiac phenotype of variable clinical expressivity.1 Typically, affected patients present in late adolescence with frequent paroxysms of supraventricular arrhythmias, demonstrate ventricular preexcitation on 12-lead ECG, and commonly progress to high-grade conduction system disease requiring a permanent pacemaker by their fourth or fifth decade of life. A significant proportion of patients develop mild to severe cardiac hypertrophy with progression to dilated cardiomyopathy. Phenotypic variability within a family is common, suggesting an influence of genetic modifiers. In addition, specific mutations of the Prkag2 gene may predict clinical expression. Mutations giving rise to atrial fibrillation and conduction disease only, severe neonatal cardiomyopathy with death, or skeletal myopathy with a cardiac phenotype have all been described.2–4