Article: Cri du chat

Cri du chat syndrome, also called deletion 5p syndrome, or 5p minus, is a rare genetic disorder due to a missing portion of chromosome 5. It was first described by Jérôme Lejeune in 1963. The condition affects an estimated 1 in 20,000 to 50,000 live births. The disorder is found in people of all ethnic backgrounds and is slightly more common in females.

Signs and symptoms

Its name, meaning cry of the cat in French, is from the distinctive mewing sound made by infants with the disorder. As babies, patients tend to be squirmy with a mewing cry, ascribed to abnormal laryngeal development. The cry becomes less distinctive with age. Individuals with cri du chat syndrome are often underweight at birth. The disorder is characterized by distinctive facial features, small head size (microcephaly), low birth weight, weak muscle tone (hypotonia), a round face, epicanthal folds, low set ears, strabismus, facial asymmetry and downward slanting palpebral fissures. Cardiac malformations may occur and affect the vital prognosis. The importance of the whole syndrome seems to vary depending on the amount of lost DNA material.

In terms of development and behaviour, severe mental retardation is typical. Expressive language is an area of weakness, and signing is often used. Hypersensitivity to noise is common. Also, some have autistic traits such as repetitive behaviors and obsessions with certain objects. Apparently, many enjoy pulling hair. They are often happy children, and are described as "loving" and sociable.

Genetics

Cri du chat syndrome is due to to a partial deletion of the short arm of chromosome number 5. Approximately 85% of cases results from a sporadic de novo deletion, while about 15% are due to unequal segregation of a parental chromosome translocation. Although the size of the deletion varies, a deletion at region at 5p15.3 is responsible for the unique cry and the critical region of 5p15.2 is responsible for the other features. The deletion is of paternal origin in about 80% of cases in which the syndrome is de novo. Genetic counseling and genetic testing may be offered to families with cri du chat syndrome.