The basics of lysosomal storage diseases Abstract. Lysosomal storage diseases are comprised of a group of more than 50 genetic disorders which are characterized by a defective lysosomal function. The lysosome is the recycling plant of the cell. Most of the lysosomal storage diseases are caused by a deficient hydrolase. The disturbed metabolism leads to accumulation of complex molecules. The classic classification is by the main storage molecule: Sphingolipidoses, Mucopolysaccharidoses and Glycoproteinosis. The modern classification stretches the definition and includes every disease that has a defect in a lysosomal component, which is needed for the normal function of the lysosome. That component includes lysosomal membrane proteins, activa...