PRENATAL-DIAGNOSIS OF LYSOSOMAL STORAGE DISEASES

The prenatal diagnosis of lysosomal storage disorders can be achieved, once the diagnosis is confirmed in the index case, by a variety of te chniques including analysis of amniotic fluid, asay of enzymic activit y in cultured amniotic fluid cells, cultured chorionic villus cells an d by direct assay of activity in chorionic villus samples, These studi es can be accompanied by ultrastructural observations which give an in dependent means of diagnosis, In some instances molecular genetic stud ies for mutation detection or linkage analysis are appropriate for pre natal diagnosis, Pseudodeficiencies of some of the lysosomal enzymes, which cause no clinical problems, can complicate the initial diagnosis particularly in metachromatic leucodystrophy where the pseudodeficien cy is more common than the disease itself. Mutation analysis as well a s enzyme assay is necessary not only in the index case but also in the parents before the same techniques are applied to a sample for prenat al diagnosis, A large number of lysosomal storage disorders may presen t as fetal hydrops and the diagnosis can be established at this late s tage by fetal blood sampling and examination by microscopy as well as by biochemical assay of the appropriate enzyme or metabolite in amniot ic fluid, All prenatal diagnoses in which an affected fetus is indicat ed should have confirmation of the diagnosis as soon as possible to re assure anxious parents, and to act as audit of the laboratory's compet ence to undertake prenatal diagnosis, A combined approach to prenatal diagnosis involving biochemical, molecular genetic and morphological s tudies is recommended.