Cri-du-chat syndrome, also known as cat cry syndrome or 5p- syndrome, is a rare genetic disorder caused by a deletion of genetic material on part of chromosome 5. The impact of this can vary from one child to the next, but most will have delayed development and some degree of intellectual disability. The most common symptom of the disorder is a distinct high-pitched, shrill cry that sounds like a cat cry and may be present during the first few weeks of life. The cry becomes less noticeable as the baby grows older. Other symptoms of the disorder include small head size (microcephaly), low birth weight, weak muscle tone (hypotonia) in infancy, and distinctive facial features such as widely set eyes (hypertelorism), low-set ears, a small jaw, and a rounded face. Some children with cri-du-chat syndrome are born with a heart defect. The disorder occurs in 1 in 15,000 to 1 in 50,000 live births in the U.S. .