GAA and Glycogen storage disease due to acid maltase deficiency: Pompe disease, or glycogen storage disease type II (GSDII; OMIM #232300), is a rare autosomal recessive disorder caused by biallelic mutations in the acid α-glucosidase (GAA) gene (MIM 606800) that encodes the lysosomal enzyme acid α-1,4-glucosidase (GAA; EC 3.2.1.20), formerly known as acid maltase [1].