Recent progress of lysosomal diseases.

The majority of lysosomal storage diseases results from genetic inability to express one or another of the many activities of the lysosomal hydrolases. A few lysosomal diseases are caused by a defective transport of certain metabolites across the lysosomal membrane. The recognition of the specific lysosomal defects led to diagnostic tests also for first trimester prenatal diagnosis. The availability of cloned genes for a number of lysosomal enzymes marks the beginning of an understanding of the precise defects responsible for lysosomal storage diseases.