Cri du chat syndrome is a group of symptoms that result from missing a piece of chromosome number 5. The syndrome’s name is based on the infant’s cry, which is high-pitched and sounds like a cat.

Cri du chat syndrome is rare. It occurs when a piece of information on chromosome 5 is missing. It is likely that multiple genes on chromosome 5 are deleted. One deleted gene, called TERT (telomerase reverse transcriptase) is involved in control of cell growth, and may play a role in how some of the features of this syndrome develop.

Most cases are believed occur during the development of an egg or sperm. A minority of cases result from one parent carrying a rearrangement of chromosome 5 called a translocation.

Between 1 in 20,000 - 50,000 babies are affected. This disease may account for up to 1% of individuals with severe mental retardation.

• Cry that is high-pitched and sounds like a cat
• Downward slant to the eyes
• Low birth weight and slow growth
• Low-set or abnormally shaped ears
• Mental retardation
• Partial webbing or fusing of fingers or toes
• Single line in the palm of the hand (simian crease)
• Skin tags just in front of the ear
• Slow or incomplete development of motor skills
• Small head (microcephaly)
• Small jaw (micrognathia)
• Wide-set eyes

In addition to symptoms, the physical examination may show:

• Inguinal hernia
• Diastasis recti (separated abdominal muscles)
• Low muscle tone
• Epicanthal folds, an extra fold of skin over the inner corner of the eye
• Incompletely or abnormally folded external ears

Genetic tests can show a missing part of chromosome 5. Skull x-ray may reveal an abnormal angle to the base of the skull.