The mucopolysaccharidoses: biochemistry and clinical symptoms.

The mucopolysaccharidoses are a group of genetic diseases which are characterized by an excessive intralysosomal accumulation of partially degraded mucopolysaccharides. This storage is caused by the inactivity of one of eleven enzymes that are required for the degradation of the different types of mucopolysaccharides. There is a rough correlation between phenotype and chemical nature of the storage material. Similar clinical pictures, however, may be caused by an inactivity of different enzymes. Conversely, different clinical expressions of the defect of a single enzyme may be attributed to allelic mutations. The recent development of specific assay procedures for the respective enzymes allows 1. an early genotype-specific diagnosis of affected patients, 2. prenatal diagnosis of the metabolic defect in families at risk, 3. to prognosticate the course of the disease at least in some instances, and 4. genetic counseling for members of affected families. At present, there is no specific therapy. Attempts of enzyme replacement therapy are still at an experimental stage.