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 1:20000-40000 live births. Prevalence may be greater in Nordic countries.

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 build up of potentially toxic by-products of cholesterol production which accumulate in the blood and other tissues. It was traditionally classified into 2 types although they are not considered to represent the spectrum differing severity.

Genetics

It carries an autosomal recessive inheritance 5.

Associations
Markers
  • low maternal low oestriol 4: although nonspecific

There are many which include:

Antenatal ultrasound

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 soon after birth.

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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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