In addition, Smith-Lemli-Opitz syndrome, a rare human condition caused by a defect in 7-dehydrocholesterol reductase, is associated with dysmorphic features affecting the head (eg, microcephaly), face (eg, cleft palate), and extremities (eg, poly- or syndactyly) as well as cardiac and intestinal (aganglionosis) defects that may in part reflect impaired NCC function53. This evidence concerns the gene DHCR7 and microcephaly.