Abstract

CARDOSO, Maria Luís et al. Prenatal diagnosis of Smith-Lemli-Opitz Syndrome. Arq Med [online]. 2005, vol.19, n.1-2, pp.23-27. ISSN 2183-2447.

The Smith-Lemli-Opitz syndrome (SLO) is an autosomal recessive polimalformative metabolic syndrome, characterized by a recognizable pattern of minor facial anomalies, congenital anomalies of many organs, failure to thrive, and mental retardation. It is caused by a defect in the enzyme 7-dehydrocholesterol reductase, which is responsible for the last step of cholesterol biosynthesis pathway. The Smith-Lemli-Opitz syndrome is characterized by low plasma cholesterol levels and elevated concentrations of the cholesterol precursor 7-dehydrocholesterol. We report on a pregnancy with a positive integrated prenatal screening test for Down’s syndrome, with unusually low maternal serum levels of unconjugated oestriol (uE3). An increased nuchal translucency was noted in the 11 weeks’ scan. The fetal karyotype revealed a normal 46,XY karyotype. Detailed ultrasound scan at 18 weeks revealed ambiguous genitalia, short femur length, cleft lip heart defect and intrauterine growth retardation. Based on these findings and the maternal serum levels of uE3 prenatal diagnosis, SLO was suspected and later confirmed by the demonstration of low levels of cholesterol and high levels of 7-dehydrocholesterol and 8-dehydrocholesterol in a stored frozen sample of amniotic fluid. Pregnancy was terminated at 20 weeks and the mutational analysis of DHCR7 gene on DNA obtained from foetal tissues revealed homozygosity for the common Caucasian mutation IVS81G>C associated with SLO severe phenotypes. The state of the art on prenatal diagnosis of Smith-Lemli-Opitz syndrome is reviewed.

Keywords : Smith-Lemli-Opitz syndrome; oestriol; 7-dehydrocholesterol; cholesterol; DHCR7; prenatal diagnosis; nuchal translucency; ambiguous genitalia; IVS81G>C.

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