Prenatal diagnosis of the Hurler syndrome: report on 40 pregnancies at risk.

In 40 pregnancies at risk for the Hurler syndrome 13 affected fetuses were detected by the demonstration of an alpha-L-iduronidase deficiency and an increased level of 35S-sulphate incorporation. The diagnosis were confirmed by the analysis of fetal tissues and/or cultured fetal skin fibroblasts. Microassays for alpha-L-iduronidase, using phenyl alpha-L-iduronide and more recently 4-methyl-umbelliferyl alpha-L-iduronide, enabled a reliable diagnosis to be made within 15 to 18 days after amniocentesis. 35S-sulphate incorporation has been a valuable adjunct in cases with a low (heterozygote) enzyme activity.