A rare syndrome characterized by low birth weight, delayed growth, intellectual disabillity, behavioral problems, and a distinctive facial appearance (thin, arched eyebrows, low set ears, small teeth, and small nose). The majority of cases are caused by mutations in the NIPBL gene. Less severe forms of the syndrome are caused by mutations in the SMC1A and SMC3 genes. The disease is Monarch Disease Ontology term MONDO_0016033 (Cornelia de Lange syndrome). Also known as: Brachmann de Lange syndrome, Brachmann-de Lange syndrome, De Lange syndrome.