How is Smith-Lemli-Opitz syndrome (SLOS) diagnosed prenatally?

Updated: Jan 27, 2021
  • Author: Robert D Steiner, MD; Chief Editor: Luis O Rohena, MD, MS, FAAP, FACMG  more...
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Fetal ultrasonography may reveal anomalies suggestive of Smith-Lemli-Opitz syndrome (SLOS). When clinical suspicion arises, or if Smith-Lemli-Opitz syndrome was present in a previous pregnancy, confirmation of diagnosis is available with measurements of amniotic fluid or chorionic villous 7DHC content. In addition, enzyme activity can be measured in chorionic villi. Mutation analysis for prenatal diagnosis could also be considered, but this is most likely to be helpful if a proband in the family has had previously identified DHCR7 gene mutations.

Confirmatory prenatal diagnostic testing is currently available by genetic mutation analysis.

Low maternal serum unconjugated estriol levels or a pattern of maternal serum triple or quadruple screen markers suggestive of trisomy but with normal karyotype is a marker for Smith-Lemli-Opitz syndrome or steroid sulfatase deficiency. Shackleton reported the unique presence of equine estriols in the maternal urine during pregnancy of a fetus affected by Smith-Lemli-Opitz syndrome, potentially allowing noninvasive prenatal screening for Smith-Lemli-Opitz syndrome. [29]

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