Cardiac disease is a leading cause of morbidity and early death across several lysosomal storage disorders (LSDs); however, the cardiomyopathies of Fabry, Pompe, and Danon disease are still largely treated as separate, substrate-specific disorders. We argue that they are better understood as variations on a single theme: the breakdown of the autophagy-lysosome system within cardiomyocytes. In the healthy heart, this system clears damaged proteins and organelles and is regulated by mTORC1 and the master regulator TFEB. Once lysosomal degradation or autophagosome-lysosome fusion fails, undegraded substrates and defective mitochondria accumulate, driving hypertrophy, interstitial fibrosis, and conduction disease. Danon disease, resulting from the loss of LAMP2, is the clearest example of a primary defect in autophagic flux, whereas the glycogen storage of Pompe disease and the globotriaosylceramide accumulation of Fabry disease impair flux through different upstream mechanisms that converge on the same downstream injury. The same framework extends to other storage disorders with cardiac involvement, such as mucopolysaccharidosis (MPS). We trace this shared pathobiology from molecule to bedside, examine biomarkers that reflect lysosomal and autophagic dysfunction rather than storage alone, and re-examine treatment in that light: why enzyme replacement therapy corrects substrate accumulation but leaves much of the autophagic and mitochondrial damage unresolved, and why gene therapy-particularly AAV9-LAMP2B for Danon disease-together with autophagy- and TFEB-directed strategies may help close that gap. Viewing these disorders through a single mechanistic lens reshapes how we monitor them and where future therapies should be directed.