PRENATAL-DIAGNOSIS OF SMITH-LEMLI-OPITZ SYNDROME IS POSSIBLE BY MEASUREMENT OF 7-DEHYDROCHOLESTEROL IN AMNIOTIC-FLUID

Amniocentesis was performed at 17.3 weeks in a pregnancy with severe intrauterine growth retardation. Cytogenetic studies on amniocytes were normal, 46,XX. and the pregnancy was continued. The diagnosis of Smith-Lemli-Opitz syndrome was suspected in the neonatal period and confirmed by the presence of 7-dehydrocholesterol (7-DHC) in the plasma (0.4 mmol/l, normal=not detectable) associated with a low total cholesterol concentration (0.4 mmol/l, normal=2.56+/-0.23). Retrospective analysis of the amniotic fluid sample revealed an elevated level of 7-DHC (0.022 mmol/l; normal=undetectable). Therefore measurement of 7-DHC levels in amniotic fluid during the second trimester of pregnancy is useful for the prenatal diagnosis of Smith-Lemli-Opitz syndrome in families at risk and should be considered in cases of severe growth retardation of unknown aetiology for which amniotic fluid is available and in which a normal chromosomal pattern in amniocytes is present.