PRKAG2 and cardiomyopathy: PRKAG2 (Protein Kinase Adenosine monophosphate activated Gamma 2 non-catalytic subunit 2) cardiomyopathy, an important HCM phenocopy, is a rare autosomal dominant, non-lysosomal glycogen storage disease characterized by ventricular pre-excitation, supra-ventricular arrhythmias and cardiac hypertrophy.