As mentioned, Pompe disease, Danon disease, Fabry disease, and MPS type I are caused by mutations in the GAA [8], LAMP-2 [9,10], α-galactosidase A (a-Gal A) [11], and the α-L-iduronidase (IDUA) genes [12], respectively. The gene discussed is LAMP2; the disease is Danon disease.