Monarch Disease Ontology identifier MONDO_0009532 (Miller-Dieker lissencephaly syndrome) is a rare syndrome caused by deletion of genetic material in the short arm of chromosome 17. It is characterized by an abnormally smooth brain with fewer folds and grooves. It results in intellectual disability, developmental delay, seizures, spasticity, hypotonia, and feeding difficulties. Affected individuals have distinctive facial features that include a prominent forehead, midface hypoplasia, small, upturned nose, low-set ears, small jaw, and thick upper lip. Also known as: Miller-Dieker syndrome, lissencephaly due to 17p13.3 deletion, monosomy 17p13.3, telomeric deletion 17p.