Cri du chat syndrome Health Article

Definition

Cri du chat syndrome occurs when a piece of chromosomal material is missing from a particular region on chromosome 5. 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.

Description

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 "cry of the cat" 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 minus 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.

Genetic profile

Cri du chat is the result of a chromosome abnormality. Human beings have 46 chromosomes in the cells of the their body. Chromosomes contain genes, which regulate the function and development of the body. An individual's chromosomes are inherited from their parents, 23 chromosomes from the egg and 23 chromosomes from the sperm. The 46 chromosomes in the human body are divided into pairs based on their physical characteristics. Chromosomes can only be seen when viewed under a microscope and appear identical because they contain the same genes.

Most chromosomes have a constriction near the center called the centromere. The centromere separates the chromosome into long and short arms. The short arm of a chromosome is called the "p arm". The long arm of a chromosome is called the "q arm".

Individuals should have two copies of chromosome 5. Cri du chat is caused when a piece of material is deleted, or erased, from the "p" arm of one chromosome 5. The piece of chromosomal material deleted contains many genes necessary for normal development. When these genes are missing, the larynx, brain, and other parts of the body do not develop as expected. This is what causes the symptoms associated with cri du chat.

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%.