Smith-Lemli-Opitz

• 11q 12-13; autosomal recessive
• Due to a defect in cholesterol biosynthesis
  • The enzyme that is defective reduces the c-7,8 bond of  7-dehydrocholesterol
  • plasma cholesterol is low
  • 7-dehydrocholesterol is high
• General: mental retardation
• Head/Facies: microcephaly, bitemporal narrowing and prominent occiput (squeezed head), eyelid ptosis, anteverted nostrils and broad nasal tip, micrognathia w/ cleft palate
• Extr: syndactyly of 2nd/3rd toes, small thumbs
• GU: cryptorchidism, hypospadias
• Other internal abnormalities: pyloric stenosis, cleft palate, pancreatic anomalies, lung segmentation defects

At term, these should suggest the diagnosis of Type I SLO: microcephaly, 2-3 syndactyly of toes, small proximally placed thumbs, cataracts. Males have hypospadias and a hypoplastic scrotum

Type II SLO is a severe lethal form. In males, the external genitalia can be ambiguous or female. Multiple skeletal anomalies, GU, GI, CNS, endocrine abnormalities as well.

CHLA board review course 2005
Baraitser and Winter, 1996. Color Atlas of Congenital Malformation Syndromes