Glycogen storage disease type Ⅲ (GSD-Ⅲ) is an autosomal recessive inherited metabolic disorder caused by a deficiency in the glycogen debranching enzyme (amylo-l,6-glucosidase).1 The disease is characterized by hepatomegaly,fasting hypoglycemia,growth retardation,and progressive myopathy.1 It can also cause cardiomyopathy.1-5 We report a rare case of GSD-Ⅲ with metabolic cardiomyopathy mimicking obstructive hypertrophic cardiomyopathy, a sarcomere-protein gene disorder.