Smith-Lemli-Opitz syndrome (SLOS) is a developmental disorder that affects many parts of the body, and is caused by a homozygous or compound heterozygous mutation in the gene encoding sterol delta-7-reductase (DHCR7) located on chromosome 11q13, with autosomal recessive inheritance (Tint et al., 1995). The gene discussed is DHCR7; the disease is Smith-Lemli-Opitz syndrome.