DHCR7 and Smith-Lemli-Opitz syndrome: Mutation of 7-dehydrocholesterol reductase gene that encodes an enzyme involved in cholesterol metabolism, is the cause of Smith-Lemli-Opitz syndrome (SLOS), a DD with multiple congenital anomalies including cleft palate and holoprosencephaly (Kelley and Hennekam, 2000).