The authors describe the important progress in the therapy of hereditary metabolic disorders at the lysosome level and specifically the possibilities of causal therapy in some of them. They analyze in detail their longest practical experience with causal therapy of mucopolysaccharidosis type I (MPS I). A female patient with neuropathic form of MPS I has been treated since her ten years of age for three years with the enzyme substitution therapy with laronidase (preparation Aldurazyme). Effects of this therapy have been regularly evaluated by objective tests in the course of treatment. In spite of positive results of these tests a relatively significant somatic stigmatization is still present. The self-service of the patient is the most prominent feature of improvement.

        Key words: lysosomal diseases, mucopolysaccharidosis type I and type VI, Gaucher diseases, Fabry disease, Pompe disease, enzyme substitution therapy