Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) also known as 7-dehydrocholesterol reductase deficiency, is an inborn error of cholesterol synthesis. 

The estimated incidence is at 1:20,000-40,000 live births. Prevalence may be greater in Nordic countries.

There are many symptoms and signs which include:

The condition often results from a mutation in the DHCR7 gene on chromosome 11q12-13 which reduces the activity of 7-dehydrocholesterol reductase. Rarely there may be a mutation in chromosome 7q32.1. There is then a lack of cholesterol production as well as a build-up of potentially toxic byproducts of cholesterol production which accumulate in the blood and other tissues. It was traditionally classified into two types although they are not considered to represent the spectrum differing severity.

It carries an autosomal recessive inheritance 5.

  • low maternal low estriol is non-specific 4

There may be increased nuchal translucency in 1st trimester as an early feature 3. Antenatal ultrasound may also be able to detect some of the above clinical features.

The syndrome carries a poor prognosis with most infants not surviving long after birth.

Article information

rID: 12335
System: Obstetrics
Section: Syndromes
Synonyms or Alternate Spellings:
  • 7-dehydrocholesterol reductase deficiency
  • Smith Lemli Opitz syndrome (SLOS)
  • Smith-Lemli-Opitz syndrome
  • SLO syndrome
  • RSH syndrome
  • RSH-SLO syndrome

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