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Smith-Lemli-Opitz Syndrome 

Smith-Lemli-Opitz Syndrome
Chapter:
Smith-Lemli-Opitz Syndrome
Author(s):

Wen-Hann Tan

and Mira B. Irons

DOI:
10.1093/med/9780199934522.003.0028
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date: 27 February 2021

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple congenital anomaly and neurodevelopmental syndrome caused by a deficiency in the 7-dehydrocholesterol reductase enzyme encoded by DHCR7. The DHCR7 enzyme catalyzes the reduction of the C7-C8 double bond in 7-dehydrocholesterol and in 7-dehydrodesmosterol in the biosynthesis of cholesterol and desmosterol respectively. Deficiency of DHCR7 results in an elevation in plasma 7-dehydrocholesterol (7-DHC) and 8-dehydrocholesterol (8-DHC), as well as a reduction in total cholesterol, all of which contribute to the pathogenesis of SLOS. The clinical manifestations include global developmental delay, small stature, microcephaly, brain malformations, sleep disturbances, anteverted nares, ptosis, genitalia abnormalities, and syndactyly of the second and third toes. Elevation in serum 7-DHC is diagnostic for SLOS. Treatment includes use of cholesterol supplementation, statins, and more recently, antioxidants, but improvements in neurodevelopmental outcomes have not been demonstrated.

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