Miller-Dieker syndrome: A congenital malformation syndrome characterized by lissencephaly ("smooth brain") and a characteristic facial appearance with a prominent forehead with bitemporal hollowing, short nose with upturned nares, thickened upper lip with a thin vermilion upper border, widely spaced eyes, low ears, and small jaw. Associated features include mental retardation, epilepsy, pre- and postnatal growth retardation, and reduced life span. There may also be multiple abnormalities of the brain, kidneys, heart, and gastrointestinal tract.
MDS is a contiguous gene syndrome. It is due to deletion of several adjacent genes from 17p (the short arm of chromosome 17). The syndrome is named for JQ Miller who described it in 1963 and H Dieker who in 1969 emphasized that it should be termed the lissencephaly syndrome because there are malformations beyond the brain.