A 6 month old baby brought to emergency depament with features of cardiac failure. On examination, she found to have developmental delay and a large tongue. Echocardiography shows severe concentric LVH. The most probable diagnosis is:

The type of glycogen storage disease that primarily involves the hea is Pompe disease (GSD IIa) in which acid maltase, necessary for hydrolysis of the outer branches of glycogen, is absent. There is marked deposition of glycogen within the myocardium. Affected infants are well at bih, but symptoms of growth and developmental delay, feeding problems, and cardiac failure occur by the sixth month of life. Physical examination reveals generalized muscular weakness, a large tongue, and cardiomegaly without significant hea murmurs. Chest radiographs reveal cardiomegaly with or without pulmonary venous congestion. The ECG shows a sho PR interval and LVH with ST depression and T-wave inversion over the left precordial leads. Echocardiography shows severe concentric LVH. Children with Pompe disease usually die before age 1 year. Death may be sudden or result from progressive HF. Ref: Darst J.R., Collins K.K., Miyamoto S.D. (2012). Chapter 20. Cardiovascular Diseases. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.