Any glycogen storage disease in which the cause of the disease is a mutation in the PRKAG2 gene. The disease is Monarch Disease Ontology id MONDO_0009867 (lethal congenital glycogen storage disease of heart). Also known as: PRKAG2 glycogen storage disease, fatal congenital hypertrophic cardiomyopathy due to GSD, fatal congenital hypertrophic cardiomyopathy due to glycogenosis, fatal congenital nonlysosomal cardiac glycogenosis, glycogen storage disease caused by mutation in PRKAG2, phosphorylase kinase deficiency of heart.