Cri du chat syndrome
Newborns with cri du chat (cat's cry) syndrome have a characteristic mewing cry believed caused by abnormal development of the larynx (the organ containing the vocal chords). The syndrome arises from what is known as a deletion--the absence of genetic material from a missing portion of a chromosome. In cridu chat syndrome, the deletion is in chromosome 5. The disorder is also called 5p- (5 p minus) syndrome, in reference to the area where the deletion occurs. Children with this syndrome have physical abnormalities, language and motor skill difficulties, and varying degrees of mental retardation.
Although all individuals have two copies of chromosome 5, the normal chromosome does not compensate for the genetic material missing from the flawed chromosome in cri du chat syndrome. The deletion can be inherited through generations of a family or may appear at random. It is estimated that the syndrome occurs in 1 in 50,000 births. According to the 5p- Society, approximately 50-60children are born with cri du chat syndrome each year in the United States.
The deletion on chromosome 5 has several indicators. The primary sign is theunusual high-pitched mewing cry during the first weeks of life. This is accompanied by low birth weight, slow growth, and a small head (microcephaly). Muscle tone is poor (hypotonia) and possible medical problems include heart disease and scoliosis (curvature of the spine). Children with cri du chat syndrome have language difficulties, delayed motor skill development, and mental deficiencies that vary in severity. Behavioral problems, such as hyperactivity,may become apparent as the child matures.
As the child matures, the cat-like cry is lost. A definitive diagnosis is based on karyotyping--a laboratory procedure that separates chromosomes from theinfant's cells and demonstrates that genetic material is missing. Cri du chat syndrome can be detected before birth if the mother undergoes amniocentesistesting or chorionic villus sampling. Samples of cells are collected from the fluid surrounding the fetus and are analyzed for genetic defects (amniocentesis) or from the outer membrane (chorion) of the sac that holds both the fetus and the fluid (chorionic villus sampling).
Cri du chat syndrome is a very rare disorder with no cure or known prevention. Treatment consists of supportive care and developmental therapy.
The extent of mental retardation and other symptoms depends on the size of the chromosomal deletion--larger deletions generally translate into more serious symptoms. With intensive early intervention and special schooling, many cridu chat children can develop adequate social, motor, and language skills. Most individuals with cri du chat syndrome have a normal lifespan.