Cri du chat is a type of chromosomal abnormality that is also known as chromosome deletion 5p syndrome or even monosomy 5p syndrome. Discovered in 1963 by Lejeune and other doctors, it first was recognized as a defective B group chromosome, and then was later recognized as the fifth chromosome, or 5p. The name, Cri du Chat, is French for "cry of the cat", which describes the characteristic high-pitched cry from the children who have this disorder. This distinctive cry can help doctors make an accurate hypothesis at birth as to if a baby has cri du chat syndrome. Along with this distinguishing cry, there is also an extensive grouping of abnormalities, like dysmorphic facial features, with severe mental retardation being the most important. It is caused by a partial deletion of the short arm of chromosome five. There is an estimated 1 in 50 000 live births in the general United...