Glycogen storage disease type II (GSDII; Online Mendelian Inheritance in Man (OMIM) 232300; Pompe disease or acid maltase deficiency) is an autosomal recessive disorder caused by mutations in the acid alpha-glucosidase (GAA) gene encoding a lysosome enzyme that hydrolyses glycogen to glucose [1]. The gene discussed is GAA; the disease is Glycogen storage disease due to acid maltase deficiency.