cri du chat syndrome
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Cri Du Chat Syndrome
Cri du chat syndrome occurs when a piece of chromosomal material is missing from a particular region on chromosome 5. The disorder is also called cat cry syndrome or chromosome deletion 5p syndrome. Individuals with this syndrome have unusual facial features, poor muscle tone (hypotonia), small head size (microcephaly), and mental retardation. A classic feature of the syndrome is the cat-like cry made by infants with this disorder.
Dr. Jerome Lejeune first described cri du chat syndrome in 1963. The syndrome is named for the cat-like cry made by infants with this genetic disorder. Cri du chat means "cat's cry" in French. This unusual cry is caused by abnormal development of the larynx (organ in the throat responsible for voice production). Cri du chat syndrome is also called 5p deletion syndrome because it is caused by a deletion, or removal, of genetic material from chromosome 5. The deletion that causes cri du chat syndrome occurs on the short or "p" arm of chromosome 5. This deleted genetic material is vital for normal development. Absence of this material results in the features associated with cri du chat syndrome.
A high-pitched mewing cry during infancy is a classic feature of cri du chat. Infants with cri du chat also typically have low birth weight, slow growth, a small head (microcephaly) and poor muscle tone (hypotonia). Infants with cri du chat may have congenital heart defects. Individuals with cri du chat syndrome have language difficulties, delayed motor skill development, and mental retardation. Behavioral problems may also develop as the child matures.
It has been estimated that cri du chat syndrome occurs in one of every 50,000 live births. It accounts for 1 in every 500 cases of mental retardation. According to the 5p minus Society, approximately 50-60 children are born with cri du chat syndrome in the United States each year. It can occur in all races and in both sexes, although there is a slight female predominance. The male:female ratio is 3:4.
Causes and symptoms
Cri du chat is the result of a chromosome abnormality—a deleted piece of chromosomal material on chromosome 5. In about 80% of patients, the defective chromosome comes from the father. In 90% of patients with cri du chat syndrome, the deletion is sporadic. This means that it happens randomly and is not hereditary. If a child has cri du chat due to a sporadic deletion, the chance the parents could have another child with cri du chat is 1%. In approximately 10% of patients with cri du chat, there is a hereditary chromosomal rearrangement that causes the deletion. If a parent has this rearrangement, the risk for them to have a child with cri du chat is greater than 1%.
The severity of mental retardation in cri du chat syndrome is correlated with the extent of deletion of delta-catenin, a protein with an important role in brain functioning. The more extensive the deletion, the more profound the mental dysfunction.
An abnormal larynx causes the unusual cat-like cry made by infants that is a hallmark of the syndrome. As children with cri du chat get older, the cat-like cry becomes less noticeable. This feature can make the diagnosis more difficult in older patients. In addition to the cat-like cry, individuals with cri du chat also have unusual facial features. These facial differences can be very subtle or more obvious. Microcephaly (small head size) is common. During infancy many patients with cri du chat do not gain weight or grow normally. Approximately 30% of infants with cri du chat have a congenital heart defect. Hypotonia (poor muscle tone) is also common, leading to problems with eating and slow, but normal development. Mental retardation is present in all patients with cri du chat, but the degree of mental retardation varies among patients.
During infancy, the diagnosis of cri du chat syndrome is strongly suspected if the characteristic catlike cry is heard. If a child has this unusual cry or other features seen in cri du chat syndrome, chromosome testing should be performed. Chromosome analysis provides the definitive diagnosis of cri du chat syndrome and can be performed from a blood test. Chromosome analysis, also called karyotyping, involves staining the chromosomes and examining them under a microscope. In some cases the deletion of material from chromosome 5 can be easily seen. In other cases, further testing must be performed. FISH (fluorescence in-situ hybridization) is a special technique that detects very small deletions. The majority of the deletions that cause cri du chat syndrome can be identified using the FISH technique.
Cri du chat syndrome can be detected before birth if the mother undergoes amniocentesis testing or chorionic villus sampling (CVS). This testing would only be recommended if the mother or father is known to have a chromosome rearrangement, or if they already have a child with cri du chat syndrome.
As of 2004 there is no cure for cri du chat syndrome. Treatment consists of supportive care and developmental therapy. Behavioral modification therapy has been found to be useful to control head-banging, hyperactivity, and other behavioral problems that emerge during later childhood.
Amniocentesis — A procedure performed at 16-18 weeks of pregnancy in which a needle is inserted through a woman's abdomen into her uterus to draw out a small sample of the amniotic fluid from around the baby. Either the fluid itself or cells from the fluid can be used for a variety of tests to obtain information about genetic disorders and other medical conditions in the fetus.
Centromere — The centromere is the constricted region of a chromosome. It performs certain functions during cell division.
Chorionic villus sampling (CVS) — A procedure used for prenatal diagnosis at 10-12 weeks gestation. Under ultrasound guidance a needle is inserted either through the mother's vagina or abdominal wall and a sample of cells is collected from around the early embryo. These cells are then tested for chromosome abnormalities or other genetic diseases.
Chromosome — A microscopic thread-like structure found within each cell of the body and consists of a complex of proteins and DNA. Humans have 46 chromosomes arranged into 23 pairs. Changes in either the total number of chromosomes or their shape and size (structure) may lead to physical or mental abnormalities.
Congenital — Refers to a disorder that is present at birth.
Deletion — The absence of genetic material that is normally found in a chromosome. Often, the genetic material is missing due to an error in replication of an egg or sperm cell.
Hypotonia — Reduced or diminished muscle tone.
Karyotyping — A laboratory procedure in which chromosomes are separated from cells, stained and arranged so that their structure can be studied under the microscope.
Microcephaly — An abnormally small head.
Individuals with cri du chat have a 10% mortality during infancy due to complications associated with congenital heart defects, hypotonia, and feeding difficulties. Once these problems are controlled, most individuals with cri du chat syndrome have a normal lifespan. The degree of mental retardation can be severe. However, a recent study suggested that the severity is somewhat affected by the amount of therapy received.
Beers, Mark H., MD, and Robert Berkow, MD, editors. "Chromosomal Abnormalities." Section 19, Chapter 261 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Beers, Mark H., MD, and Robert Berkow, MD., editors. "Developmental Problems." Section 19, Chapter 262 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Chen, Harold, MD. "Cri-du-chat Syndrome." eMedicine November 21, 2002. http://emedicine.com/ped/topic504.htm.
Israely, I., R. M. Costa, C. W. Xie, et al. "Deletion of the Neuron-Specific Protein Delta-Catenin Leads to Severe Cognitive and Synaptic Dysfunction." Current Biology 14 (September 21, 2004): 1657-1663.
Van Buggenhout, G. J. C. M., et al. "Cri du Chat Syndrome: Changing Phenotype in Older Patients." American Journal of Medical Genetics 90 (2000): 203-215.
5pSociety. 7108 Katella Ave. #502, Stanton, CA 90680. (888) 970-0777. http://www.fivepminus.org.
Alliance of Genetic Support Groups. 4301 Connecticut Ave. NW, Suite 404, Washington, DC 20008. (202) 966-5557. Fax: (202) 966-8553. http://www.geneticalliance.org.
Cri du Chat Society. Dept. of Human Genetics, Box 33, MCV Station, Richmond VA 23298. (804) 786-9632.
Cri du Chat Syndrome Support Group. http://www.cridchat.u-net.com.
National Organization for Rare Disorders (NORD). 55 Kenosia Avenue, P. O. Box 1968, Danbury, CT 06813-1968. (203) 744-0100. Fax: (203) 798-2291. http://www.rarediseases.org.
OMIM—Online Mendelian Inheritance in Man. http://www.ncbi.nlm.nih.gov/Omim/.
cri du chat syndrome[kre-du-shah] (Fr.)
a hereditary congenital syndrome characterized by a wide space between the eyes, microcephaly, severe mental deficiency, and a plaintive catlike cry caused by laryngeal abnormalities, due to deletion of part of the short arm of chromosome 5.
cri du chat syndrome(krī dĕ shah)
A sporadically inherited congenital anomaly in which affected infants have mental retardation, microcephaly, dwarfism, and a laryngeal defect that results in unusual vocalizations.. An affected infant is said to cry like a cat (cri du chat in French). It results from a deletion of the short arm of chromosome 5.