Smith–Lemli–Opitz syndrome
an autosomal recessive disorder marked by the inability to produce cholesterol and by microcephaly. Other features may include a broad, short nose; syndactyly (fused digits) or polydactyly (extra digits); and intellectual disability. Nearly all affected males have urethral or other genital anomalies, whereas females have no obvious abnormalities of the external genitalia, a factor that led early investigators to believe erroneously that the syndrome affected only males. This disorder is caused by mutations of the DHCR7 gene. Also called RSH syndrome (from the names of the three affected families originally reported); Smith syndrome. [reported in 1964 by David W. Smith (1926–1981), U.S. pediatrician; Luc Lemli (1935– ), Belgian pediatrician; and John M. Opitz (1935– ), U.S. geneticist]