Mutations in the GAA gene cause glycogen-storage disease type II (GSDII; Pompe disease, acid maltase deficiency, MIM 232300), a neuromuscular LSD characterized by the deficit of α-glucosidase activity, resulting in the lack of glycogen degradation and its progressive accumulation within the lysosomes [24]. The gene discussed is GAA; the disease is Glycogen storage disease due to acid maltase deficiency.