Smith-Lemli-Opitz syndrome (SLOS; MIM 270400) is an autosomal recessive disorder characterized by multiple congenital anomalies and intellectual deficit. The severity and the symptoms can vary from minor physical and learning problems to major physical abnormalities and severe intellectual disability. Patients with SLOS can have microcephaly, intellectual disability, behavioral problems, hypotonia, syndactyly of the 2nd and 3rd toes, malformations of various organs including brain, gastrointestinal track, genitalia, heart, kidneys, and lung. Common craniofacial features include anteverted nares, broad, flat nasal bridge, cleft palate, micrognathia, and ptosis. SLOS is caused by mutations in the DHCR7 gene, which codes for 7-dehydrocholesterol reductase.