A previous study by Arad et al. suggested that Danon disease is distinguishable from cardiomyopathy due to PRKAG2 or sarcomere‐protein defects by male sex, early onset of symptoms, massive concentric LVH, asymptomatic elevations of serum‐chemistry values, and electrocardiographic abnormalities, particularly ventricular preexcitation (Arad et al., 2005). Here, PRKAG2 is linked to Danon disease.