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Key Features

  • Elevated 7- and 8-dehydrocholesterol in serum is diagnostic in Smith-Lemli-Opitz (SLO) syndrome, which presents with developmental delay and malformations

  • Chondrodysplasia punctata, skin defects, and neurologic symptoms can indicate other cholesterol synthetic defects

  • An autosomal recessive disorder caused by a deficiency of the enzyme 7-dehydrocholesterol Δ7-reductase

Clinical Findings

  • Microcephaly

  • Poor growth

  • Mental retardation

  • Typical dysmorphic features of face and extremities (particularly two- to three-toe syndactyly)

  • Malformations of the heart and genitourinary system


  • Elevated 7- and 8-dehydrocholesterol in serum or amniotic fluid is diagnostic

  • Serum cholesterol levels may be low or in the normal range

  • Enzymes of cholesterol synthesis may be assayed in cultured fibroblasts or amniocytes, and mutation analysis is possible


  • Although postnatal treatment does not resolve prenatal injury, supplementation with cholesterol in SLO improves growth and behavior

  • The role of supplemental bile acids is controversial

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