Jerome Lejeune, a geneticist, identified Cri du chat syndrome in the year 1963; he is also the person who discovered the genetic abnormality which causes Down syndrome. They syndrome's name is French for, 'cry of the cat,' and refers to the distinctive cry children with the disorder have. The cry is caused by an abnormal development of a child's larynx when they have the syndrome, that commonly becomes noticeable as they become older, which can make it more difficult for a doctor to diagnose Cri du chat past the age of two.
Cri du chat syndrome, also known as chromosome 5p deletion syndrome, 5p- (said minus) syndrome or Lejeune's syndrome, is a rare genetic disorder due to a missing part (deletion) of chromosome 5. Its name is a French term (cat-cry or call of the cat) referring to the characteristic cat-like cry of affected children. Most cases are believed to occur during the development of the egg or sperm. A small number of cases occur when a parent passes a different, rearranged form of the chromosome to their child.
The syndrome is caused by a deletion on the short arm of chromosome five. A number of genes are missing due to the deletion, and each can contribute to the symptoms the child experiences. One of the deleted genes that is known to be involved is referred to as, 'TERT,' or telomerase reverse transcriptase,' which is important during cell division because it assists in keeping the tips of chromosomes in tact. Additional names Cri du chat is referred to by include, 'Chromosome 5p deletion syndrome,' '5p minus syndrome,' and, 'Cat cry syndrome.'
Cri du chat is one of the most common syndromes caused by chromosomal deletion, affecting between one in twenty-thousand and one in fifty-thousand children. Eighty-percent of children affected by the syndrome experience chromosome deletion that comes from their father's sperm, rather than their mother's egg. When these deletions in the child's chromosomes occur during the formation of sperm or an egg, it is caused by an unequal recombination during meiosis. Recombination usually happens between pairs of chromosomes during meiosis while there are lined up at the metaphase plate. If the pairs of chromosomes do not line up as they should, or if the chromosome breaks are not repaired appropriately, the structure of the chromosome may be altered. When unequal recombination happens at this location on chromosome five - the result is Cri du chat syndrome.
Deletions are caused by a break in the person's DNA molecule that makes up a chromosome. In the majority of instances, the chromosome breaks happen while the sperm or egg cell, also referred to as the, 'male or female gamete, is still developing. When the gamete becomes fertilized, the child will develop Cri du chat syndrome. The parent themselves; however, does not have the break in any other cells in their body; they do not have the syndrome themselves. The break is usually so rare an event that it is even unlikely to happen again, should the same parent have another child. It is possible though, for a child to inherit a broken chromosome from a parent who also had Cri du chat syndrome.
Children born with Cri du chat syndrome are commonly small at the time of their birth. They may also experience respiratory difficulties, as well as a larynx which does not develop as it should, leading to the characteristic cat-like cry associated with the syndrome. People with Cri du chat syndrome present with very distinctive features, such as a small head or, 'microcephaly,' a small chin, an unusually round face, a small bridge of the nose, and folds of skin over their eyes.
People with the syndrome can experience a number of problems inside their bodies as well. Some children with Cri du chat syndrome have skeletal problems, heart defects, poor muscle tone, or hearing and vision difficulties. As children with the syndrome grow, they often experience difficulties with talking or walking, and can have behavioral difficulties such as hyperactivity or aggression, as well as severe mental retardation. If a child with Cri du chat syndrome does not experience defects with major organs or other critical medical conditions, their life expectancy is average. The population of people with Cri du Chat syndrome might account for approximately one-percent of persons with severe mental retardation.
The symptoms of Cri du chat syndrome can include:
The majority of the time, a doctor is able to identify Cri du chat syndrome by an infant's cat-like cry, which is distinctive. Additional signs include microcephaly, mental retardation, and poor muscle tone. Chromosomal testing, while a child is still in the mother's womb, is another means of testing for the syndrome. An expert can either test a small sample of tissue from outside the sac where the child develops, referred to as, 'chorionic villus sampling or CVS,' or they may test a sample of amniotic fluid known as, 'amniocentesis.'
A physical examination of the child can also reveal some different things. The child may experience an inguinal hernia, separated abdominal muscles or, 'diastasis recti,' incompletely or abnormally folded ears, or an extra fold of skin over the inner corner of their eye, referred to as, 'epicanthal folds.' A skull X-ray can also show an abnormal angle at the base of the child's skull.
Medical science has not created a form of treatment for Cri du chat syndrome at this time. Children with the syndrome may; however, pursue therapy with the goals of improving their motor and language skills, as well as to assist them with development. Mental retardation can also be addressed through a variety of means. There is no known way to prevent Cri du chat syndrome at this time. People with a family history of the syndrome who wish to become pregnant might consider genetic counseling.