Pompe disease (glycogen storage disease type II, OMIM 232300) is a lysosomal storage disorder caused by a deficiency of lysosomal enzyme acid-α-glucosidase (GAA; acid maltase; EC 3.2.1.20), and characterized by progressive structural disruption and cell dysfunction of muscle tissues due to lysosomal accumulation of glycogen [1]. The gene discussed is GAA; the disease is lysosomal storage disease.