Cornelia de Lange syndrome is a developmental disorder that affects many parts of the body. The condition is characterized by distinctive facial features (including thin, arched eyebrows), slow growth before and after birth, mental retardation, abnormalities involving the arms and hands, excessive body hair (hirsutism), heart defects, and problems with the gastrointestinal tract. Other common signs and symptoms include an opening in the roof of the mouth (a cleft palate), deafness, eye problems, and skeletal abnormalities. The features of Cornelia de Lange syndrome vary widely among affected individuals.