The most prominent HCM phenocopies in adults include [3] Fabry disease, caused by mutations in the galactosidase-α gene (GLA); Danon disease, a lysosomal storage disease caused by mutations in the lysosomal-associated membrane protein 2 gene (LAMP2); and LVH associated with Wolff-Parkinson-White syndrome, caused by mutations in the regulatory subunit of adenosine monophosphate-activated protein kinase gene (PRKAG2) (Table 1). Here, LAMP2 is linked to Danon disease.