First trimester prenatal diagnosis of metachromatic leukodystrophy on chorionic villi by 'immunoprecipitation-electrophoresis'.

Prenatal diagnosis of metachromatic leukodystrophy (MLD) due to arylsulphatase A (ASA) deficiency can be performed by amniocentesis with the disadvantage of a late pregnancy termination. Whether chorionic villi (CV) obtained by trophoblast biopsy during the first trimester of pregnancy can be useful for diagnosis depends on the reliability of results. The complexity of arylsulphatase expression in CV and the existence of several isozymes make diagnosis difficult. However, the use of an anti-ASA antiserum enabled us to discriminate between ASA and a comigrating contaminant isozyme, and the antigen-antibody (Ag-Ab) complex gave better evidence of the presence or absence of ASA after enhancement of activity with 4-methylumbelliferyl sulphate (4-MUS). We propose that immunoprecipitation followed by electrophoresis could be a valuable method of MLD prenatal diagnosis on chorionic villi.