Frequency and ethnic distribution of the common DHCR7 mutation in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an inherited multiple malformation syn drome caused by enzymatic deficiency of 3 beta -hydroxysterol-Delta (7)-red uctase (DHCR7). SLOS is thought to be most common among European Caucasians , with an incidence of 1 in 20,000 to 1 in 30,000 births. To define the car rier rate and ethnic distribution of SLOS, we screened DNA samples from 2,9 78 unrelated individuals for the most common SLOS mutation (IVS8-1G-->C). T wenty-four heterozygotes of the IVS8-1G-->C mutation were detected in 2,978 individuals of European Caucasian and Black backgrounds. For European Cauc asians, the carrier rate for SLOS may be as high as 1 in 30, suggesting an incidence of 1 in 1,700 to 1 in 13,400. This high number is supported by th e recent observation of newborn and prenatal incidence of 1 in 22,000 in th e Caucasian population. Ours is the first report of the IVS8-1G-->C mutatio n in persons of African ancestry. Published 2001 Wiley-Liss, Inc.