Smith-Lemli-Opitz syndrome (SLOS; OMIM #270400) is an autosomal recessive human disease caused by mutations in the DHCR7 gene, which encodes the enzyme 7-dehydrocholesterol reductase (DHCR7, EC1.3.1.21), the last enzyme in the cholesterol biosynthetic pathway [1,2]. This evidence concerns the gene DHCR7 and Smith-Lemli-Opitz syndrome.