Smith-Lemli-Opitz Syndrome

Excerpt

Smith-Lemli-Opitz syndrome (SLOS) is a rare inherited condition characterized by a defect in cholesterol synthesis, resulting in low plasma cholesterol levels and raised levels of precursor 7-dehydrocholesterol (7-DHC). The clinical manifestations result from a deficiency in 7-dehydrocholesterol reductase (DHCR-7). In 1964, Dr. Smith, Dr. Lemli, and Dr. Opitz first described the condition based on a case series of 3 male pediatric patients who all presented with common abnormal clinical signs.

Genetic studies have shown that SLOS has an autosomal recessive pattern of inheritance and is characterized by several features, including syndactyly, microcephaly, growth restriction, intellectual disability, hypospadias (in males), internal abnormalities affecting most organ systems, and other distinctive phenotypical features. White populations have a carrier frequency of 1% to 2%. Discrepancies between the incidence and number of expected cases are attributed to intrauterine death in severe cases and missed diagnosis in mild cases.