Mutations in the gene encoding the gamma2 subunit of AMP-activated protein kinase (PRKAG2) cause familial cardiac hypertrophy and electrophysiological abnormalities, with glycogen accumulation in the heart of affected patients. The authors describe a 38-year-old man with a new heterozygous PRKAG2 mutation (Ser548Pro) manifesting by hypertrophic cardiomyopathy, severe conduction system abnormalities, and skeletal muscle glycogenosis. Considering those results, PRKAG2 gene could be a potential candidate for unexplained muscle glycogenosis associated with cardiac abnormalities.