Cat cry syndrome: A disorder caused by the loss of part of the short (p) arm from chromosome 5. Also called the cri du chat (or cri-du-chat) syndrome.

The cat cry syndrome is one of the most common human deletion syndromes with an incidence varying between 1 in 20,000 to 1 in 50,000 births. The frequency of the syndrome among profoundly retarded patients (with an IQ less than 20) is approximately 1 in 100.

The syndrome was discovered in France in 1963 by a team headed by the late Jerome Lejeune. The peculiar cry of affected infants sounded to Lejeune like the meowing of a Parisian cat. The syndrome involves severe developmental and mental retardation and a characteristic constellation of congenital malformations which include microcephaly (small head), round face, hypertelorism (wide-spread eyes), micrognathia (small chin), epicanthal folds (inner eye folds), low-set ears, hypotonia (poor muscle tone), and motor and mental retardation. Although the majority of patients die in early childhood, some survive into adulthood and exhibit an IQ below 20, a loss of hypertelorism and epicanthic folds and development of a thin narrow face with prominent nasal bridge.