Pompe disease – or glycogenosis type II – (PD, MIM 232300) is an autosomal recessive lysosomal storage disorder (LSD), caused by the deficient activity of the acid alpha glucosidase (GAA) enzyme due to pathogenic variants in the GAA gene (MIM 606800; NM_000152.5). The gene discussed is GAA; the disease is lysosomal storage disease.