Cri du chat syndrome
Cri du chat (a French phrase that means "cry of the cat") syndrome is a group of symptoms that result when a piece of chromosomal material is missing (deleted) from a particular region on chromosome 5. Children born with this chromosomal deletion have a characteristic mewing cat-like cry as infants that is thought to be caused by abnormal development of the larynx (organ in the throat responsible for voice production). They also have unusual facial features, poor muscle tone ( hypotonia ), small head size (microcephaly), and mental retardation .
Jerome Lejeune first described cri du chat syndrome in 1963. Cri du chat syndrome is also called 5p minus syndrome or chromosome 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 also have congenital heart defects, language difficulties, delayed motor skill development, scoliosis , and varying degrees of mental retardation. Behavioral problems such as hyperactivity 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. According to the 5p minus Society, approximately 50 to 60 children are born with cri du chat syndrome in the United States each year. The syndrome can occur in all races and in both sexes.
Causes and symptoms
Cri du chat is the result of a chromosome abnormality—a deleted piece of chromosomal material on chromosome 5. In 90 percent of children 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 percent. In approximately 10 percent of children with cri du chat, there is a hereditary chromosomal rearrangement that causes the deletion. If a parent has this rearrangement, the risk for their having a child with cri du chat is greater than 1 percent.
An abnormal larynx causes the unusual cat-like cry made by infants that is a hallmark feature of the syndrome. As children with cri du chat get older, the cat-like cry becomes less noticeable. This can make the diagnosis more difficult in older children. In addition to the catlike 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 children with cri du chat do not gain weight or grow normally. Approximately 30 percent 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 children with cri du chat, but the degree of mental retardation varies between children.
When to call the doctor
A doctor should be consulted if a child exhibits symptoms typical of cri du chat syndrome.
During infancy, the diagnosis of cri du chat syndrome is strongly suspected if the characteristic cat-like 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. Fluorescence in-situ hybridization (FISH) 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.
As of 2004, there is no cure for cri du chat syndrome. Treatment consists of supportive care and developmental therapy.
Individuals with cri du chat have a 10 percent 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 extent of mental retardation and other symptoms depends on the site of the chromosomal deletions, with larger deletions resulting in more serious symptoms. With extensive early intervention and special schooling, many cri du chat children can develop adequate social, motor, and language skills.
As of 2004, cri du chat syndrome had no known prevention.
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.
Families may wish to seek counseling regarding the effects of the syndrome on relationships within the family . Many people respond with guilt, fear , or blame when a genetic disorder is diagnosed in the family, or they may overprotect the affected member. Support groups are often good sources of information about cri du chat syndrome; they can offer helpful suggestions about living with it as well as emotional support.
Key, Doneen. Do You Want to Take Her Home?: Trials and Tribulations of Living Life as a Handicapped Person Due to Multiple Birth Defects. Lancaster, CA: Empire Publishing, 2001.
Moore, Keith L., et al. Before We Are Born: Essentials of Embryology and Birth Defects. Kent, UK: Elsevier—Health Sciences Division, 2002.
5p- Society. 7108 Katella Ave. #502, Stanton, CA 90680. Web Site: http://www.fivepminus.org.
Alliance of Genetic Support Groups. 4301 Connecticut Ave. NW, Suite 404, Washington, DC 20008. Web site: http://www.geneticalliance.org.
Cri du Chat Society. Department of Human Genetics, Box 33, MCV Station, Richmond VA 23298. Telephone: 804/786-9632.
Cri du Chat Syndrome Support Group. Web site: http://www.cridchat.u-net.com.
National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. Web site: http://www.rarediseases.org.
"Cri du chat syndrome." Medline Plus. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/001593.htm (accessed November 16, 2004).
Judith Sims Holly Ann Ishmael, M.S.
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 for analysis. 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.
Chorionic villus sampling —A procedure performed at 10 to 12 weeks of pregnancy in which a needle is inserted either through the mother's vagina or abdominal wall into the placenta to withdraw a small amount of chorionic membrane from around the early embryo. The amniotic fluid can be examined for signs of chromosome abnormalities or other genetic diseases.
Chromosome —A microscopic thread-like structure found within each cell of the human body and consisting of a complex of proteins and DNA. Humans have 46 chromosomes arranged into 23 pairs. Chromosomes contain the genetic information necessary to direct the development and functioning of all cells and systems in the body. They pass on hereditary traits from parents to child (like eye color) and determine whether the child will be male or female.
Congenital —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 —Having reduced or diminished muscle tone or strength.
Karyotyping —A laboratory test used to study an individual's chromosome make-up. Chromosomes are separated from cells, stained, and arranged in order from largest to smallest so that their number and structure can be studied under a microscope.
Microcephaly —An abnormally small head.