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Lysosomes are heterogeneous subcellular organelles containing specific hydrolyses that allow selective processing or degradation of proteins, nucleic acids, carbohydrates, and lipids. There are more than 50 different lysosomal storage diseases (LSDs), classified according to the nature of the stored material (Table 411-1). Several of the most prevalent disorders are reviewed here: Tay-Sachs disease, Fabry disease, Gaucher disease, Niemann-Pick disease, lysosomal acid lipase deficiency (LALD), the mucopolysaccharidoses, and Pompe disease. LSDs should be considered in the differential diagnosis of patients with neurologic, renal, or muscular degeneration and/or unexplained hepatomegaly, splenomegaly, cardiomyopathy, or skeletal dysplasias and deformations. Physical findings are disease specific, and enzyme assays or genetic testing can be used to make a definitive diagnosis. Although the nosology of LSDs segregates the variants into distinct phenotypes, these are heuristic; in the clinic, each disease exhibits—to varying degrees—a continuous spectrum of manifestations, from severe to attenuated variants.
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