Cri du-chat syndrome

cri-du-chat syndromeBalbeer Singh

Biosciences (V)Szabist

Cri du Chat: The Cat’s Cry

Cri du chat syndrome, also known as chromosome 5p deletion syndrome

Its name is a French term cat-cry or call of the cat referring

to the characteristic cat-like cry of affected children.

The characteristic cry of affected infants, which is similar to that of a meowing kitten, due

to problems with the larynx. The larynx is not developed

properly.

SYMPTOMS

Normal brain size

TOP: Normal ear position/sizeBOTTOM: Ear position/size with cri-du-chat

Microcephaly Low-set ears

Brain size with cri-du-chat

SYMPTOMSBabies with cri-du-chat are usually small at

birth, and may have respiratory problems. Often, the larynx doesn’t develop

correctly, which causes the signature catlike cry.

Mental retardationSmall head (microcephaly).Small jaw (micrognathia).

Downward slant of the eyes.Wide-set eyes.Abnormally shaped/positioned ears.Webbed fingers or toes.Single line in the palm of the hand (simian

crease).Hanging skin in front of the ears.Slow or incomplete development of basic

skills.

Cause • Cri-du-chat is caused by a deletion on the

short arm of chromosome 5p – the length of

the deletion may vary.

• Multiple genes are missing as a result of this

deletion, and each may contribute to the

symptoms of the disorder.

• One of the deleted genes known to be involved is HTERT (human telomerase reverse transcriptase).

• HTERT helps to keep the information in DNA functioning properly.

• If HTERT is damaged, mental illnesses such as cri-du-chat occur.

Inheritance of Cri-du-Chat The deletion that causes cri-du-

chat syndrome is caused by a dominant trait.

CTNND2 is an important gene that is lost when a portion of the 5 pair chromosome is deleted.

CTNND2 gene usually makes the delta catenin protein. This protein works in the nervous system and helps with cell movement.

The loss of CTNND2 may cause severe brain damage in some patients.

CTNND2 gene under a microscope.

Delta catenin protein.

Diagnosis Doctors most often identify cri-du-chat by looking

at the patient’s symptoms. Another method of diagnosing cri-du-chat

syndrome takes place while the baby is still in its mother's womb.

Doctors can either test a tiny sample of tissue from outside the sac where the baby develops, or they can test a sample of the amniotic fluid – the protective liquid in the womb from which a baby gets nourishment.

Treatment• There is no specific treatment

available for this disorder so medical care is focused on the symptoms. Physical therapy is recommended to strengthen the muscles. To increase communication skills, a speech therapist can help the child learn to use sign language.

Statistics Approximately 90% of cases of cri-du-chat

syndrome result from a randomly-occurring deletion.

The remaining 10% occurs purely by inheritance. Cri-du-chat syndrome occurs in an estimated 1 in

20,000 to 50,000 newborns. Cri-du-chat can occur in all races and in both

genders, although there is a slight female predominance. The male to female ratio is 3:4.

Approximately 30% of infants with cri-du-chat have heart defects.

About 1/3 of infants lose the catlike cry at age 2.

Interesting Facts The geneticist Jerome Lejeune identified cri-du-

chat syndrome in 1963. He also discovered the genetic abnormality that causes Down syndrome.

In 80% of cri-du-chat cases, the chromosome carrying the deletion comes from the father’s sperm rather than the mother’s eggs.

If pairs of chromosomes don’t line up correctly during metaphase in meiosis, the structure of a chromosome can be changed. When this happens with chromosome 5, it causes cri-du-chat.

Cri-du-chat is the most common syndrome caused by deletion.

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