Rare diseases: 5p deletion syndrome ('Cri-du Chat' syndrome)

By Cristiano Antonino On Dec 19, 2022

The 5p deletion syndrome (‘Cri-du Chat’ syndrome) is a rare disease. The name of this genetic disorder originates from the fact that in the first months of life, babies have a very faint cry, similar to a meow

The 5p deletion syndrome, or Cri-du-Chat syndrome, is a genetic disorder linked to the absence (deletion) of a piece of the short arm of a chromosome 5.

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The name Cri-du-Chat derives from the fact that in the first few months of life these children manifest a very faint cry (resembling a meow)

The 5p deletion syndrome has an estimated frequency of 1 in 50,000 births. Both boys and girls can be affected.

A correlation with maternal or paternal age has never been noted.

The 5p deletion is caused by the loss (deletion) of the short arm end of a chromosome 5

The size of the deletion varies greatly between individuals and the manifestations of the deletion are likely to depend on the loss of many genes.

However, the loss of the CTNND2 gene is believed to play a very important role in leading to severe mental retardation.

In 85% of cases, the deletion occurs during sperm or egg formation and the syndrome is therefore not hereditary.

The remaining 15% of subjects with a 5p deletion inherited the deletion from the father or mother carrier (or carrier) of a so-called balanced translocation: a piece of the short arm was lost from a number 5 chromosome but transferred to another chromosome.

Consequently, the person with a balanced translocation has a complete genetic make-up and as a rule has no symptoms.

However, he or she has a non-negligible risk of having a child with the deletion.

The 5p deletion syndrome is characterised by a small head (microcephaly), low birth weight, weak muscle tone (hypotonia) and the presence of cardiac, renal or intestinal malformations.

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A variable degree of delay in psychomotor and cognitive development and peculiar facial features are present:

Eyes widely spaced apart (hypertelorism);
Rounded face;
Skin fold covering the inner corner of the eye (epicanthus);
Mouth with angles directed downwards and outwards;
Narrow palate;
Small jaw (micrognathia);
Low-set ear pinnae.

Children often have difficulty feeding and growth may be slow, both in weight and height.

Rarer abnormalities include skeletal malformations (such as congenital dysplasia of the hips or club-foot), malformations of the lip and/or palate, abnormalities of the genital apparatus (hypospadias or cryptorchidism).

The diagnosis of 5p deletion is based on the presence of characteristic clinical abnormalities and is confirmed by standard karyotype study (observation of chromosomes) on peripheral blood lymphocytes.

With the cytogenetic-molecular technique FISH (fluorescent in situ hybridization) it is possible to directly highlight the 5p deletion

The molecular array-CGH examination allows the extent of the deletion to be characterised.

When the deletion is very small (less than 10 mb) it can only be visualised and diagnosed by array-CGH.

Indeed, the size of the deletion is often different in different patients.

However, it must be taken into account that a specific chromosomal region between 5p14 and 5p15 is considered critical for the main manifestations of the disease.

Treatment of 5p deletion is symptomatic

Monitoring involves checking growth and psychomotor development.

Ultrasound screening for possible associated malformations is indicated.

For malformations, correction surgery may sometimes be necessary, with different timing depending on the severity of the malformation and the child’s clinical situation.

It is important to start physiotherapy and psychomotor rehabilitation treatment as soon as possible.

This is followed by speech and cognitive therapy.

Treatment of malformations is surgical, when indicated.

Feeding support may be necessary, especially in the first year of life.

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