Definition of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome: A multiple congenital malformation syndrome caused by an abnormality in cholesterol metabolism, deficiency of the enzyme 7-dehydrocholesterol reductase (DHCR7), due to mutation of the DHCR7 gene on chromosome 11.

The syndrome is characterized by growth retardation, microcephaly (small head), mental retardation, and malformations that include distinctive facial features, cleft palate, heart defects, underdeveloped external genitalia in males, polydactyly (extra digits), and syndactyly (webbing) of the toes.

The syndrome is inherited in an autosomal recessive manner and, interestingly, is associated with low cholesterol levels in blood.