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.
It carries an autosomal recessive inheritance 5.
- low maternal low oestriol 4: although nonspecific
There are many which include:
- mental retardation
- congenital cardiac anomalies
- congenital urogenital anomalies
- intra-uterine growth restriction (IUGR)
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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- 2. Caruso PA, Poussaint TY, Tzika AA et-al. MRI and 1H MRS findings in Smith-Lemli-Opitz syndrome. Neuroradiology. 2004;46 (1): 3-14. doi:10.1007/s00234-003-1110-1 - Pubmed citation
- 3. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 4. Bick DP, Mccorkle D, Stanley WS et-al. Prenatal diagnosis of Smith-Lemli-Opitz syndrome in a pregnancy with low maternal serum oestriol and a sex-reversed fetus. Prenat. Diagn. 1999;19 (1): 68-71. Prenat. Diagn. (link) - Pubmed citation
- 5. Shinawi M, Szabo S, Popek E et-al. Recognition of Smith-Lemli-Opitz syndrome (RSH) in the fetus: utility of ultrasonography and biochemical analysis in pregnancies with low maternal serum estriol. Am. J. Med. Genet. A. 2005;138 (1): 56-60. doi:10.1002/ajmg.a.30898 - Pubmed citation
- 6. Waye JS, Eng B, Nowaczyk MJ. Prenatal diagnosis of Smith-Lemli-Opitz syndrome (SLOS) by DHCR7 mutation analysis. Prenat. Diagn. 2007;27 (7): 638-40. doi:10.1002/pd.1735 - Pubmed citation