GAA and glycogen storage disease II: Pompe disease (PD), also known as glycogen storage disease type II (GSDII; ORPHA:365; ORPHA:308552; MONDO:0009290; MIM #232300 and MIM#606800) is a rare monogenic, autosomal recessive metabolic disorder caused by mutations in the acid alpha-glucosidase (GAA) gene located at 17q25.2-q25.3 [1,2].