Cri du chat syndrome, which we prefer to call today “5p deletion” is a rare genetic disease which results from an anomaly on chromosome 5.
Definition: what is cri du chat syndrome?
Cri du chat syndrome, or 5p deletiondesignates a rare genetic disease which results from the loss of a more or less large part of the short arm of chromosome 5. Discovered by Professor Jérôme Lejeune in 1963, this chromosomal anomaly was described as “cat cry” because Newborns affected by it emit sounds similar to the meows of a small cat. It is estimated that approximately one in 50,000 newborns are affected.
What are the symptoms of cri du chat syndrome?
Symptoms evolve with age. At birth, the 5p deletion is characterized by a small baby, with a small round head, often associated with hypertelorism (widespread eyes). The newborn utters a very unusual cry that resembles the meow of a cat. “This disappears with growth but children still keep a very particular voice, a little high. This specificity would be due to a slightly different arrangement of the larynx, which is also accompanied by Eating disorders: false routes, difficulty breastfeeding. Children with cri du chat syndrome also have hypotonia and psychomotor delay“, indicates Dr Aimé Ravel, pediatric geneticist. Gastroesophageal reflux disease, congenital heart disease and kidney abnormalities can manifest. Growing up, the face becomes longer (dolichocephaly) and divergent strabismus often appears, that is, the eyes look outward. “The subjects remain small in size, and often suffer hyperlaxity (very soft ligaments)which leads to the appearance of a scoliosis. Myopia, cataracts and hearing problems linked to serous otitis are often observed“, he continues.
What causes cri du chat syndrome?
The 5p deletion is a pathology detected at birth. In 77% of cases, it is linked to the deletion, that is to say the lack of the end of the short arm of chromosome 5. “In 9% of cases, there may be a interstitial deletion : a piece of the short arm is missing but the distal end remains in place. It can then be a translocation, i.e. an exchange of chromosomal material with a chromosome from another pair. In 4% of cases, the syndrome results from de novo translocations, meaning only the child carries it, not their parents. In 4% of cases, there is a family translocation, which means that the child’s abnormality arises from an abnormality in one of the parents but which is balanced in the latter. It is at the time of fertilization and the first divisions that a chromosomal accident occurs leading to the loss of a small piece of the short arm of chromosome 5. In 1% of cases, the anomaly results from a inversion in one of the parents : a piece of chromosome 5 has broken and turned upside down, which leads to the loss of a fragment when the baby is conceived“, explains the pediatric geneticist. As in any genetic disease, there are large disparities from one patient to another depending on genetic variations and possible associated diseases.
Cri du chat syndrome is a rare genetic disease, the prevalence of which varies depending on the country. Overall, it concerns between 1/15,000 to 1/50,000 births and affects both girls and boys. It is most often a non-hereditary genetic accident.
How does cri du chat syndrome progress?
This disorder is responsible for a psychomotor delay often important. Children walk on average at 3 years old and have a marked language delay. Some people manage to make small sentences around the age of 6, but more often around 10 years old. They also suffer from lack of autonomy : only half of patients can eat from a spoon alone at 3 and a half years old. Hyperactivity, stereotypies (repeated gestures) and self-offensive behaviors (banging your head against the wall, biting your fingers) may be present and last into adulthood.
The diagnosis is based on the karyotypeto know standard chromosome examination, which allows us to see that the short arm of chromosome 5 is shorter. In case of doubt, a FISH (fluorescence in situ hybridization) can be carried out: by doing the karyotype, the geneticist introduces into the preparation a fluorescent product which specifically marks the short arm of chromosome 5.However, the karyotype tends to be replaced by a computerized exam called the ACPA (chromosomal analysis by DNA chip), in which the device cuts the patient’s DNA into small pieces and migrates it onto a plate where it is compared with DNA considered normal, which automatically gives an indication of the pieces which are more or less“, the specialist would like to point out.
What is the treatment for cri du chat syndrome?
Due to their difficulty in eating, their low birth weight and sometimes even difficulty breathing, patients often have stay in neonatology where they are fed by nasogastric tube. Of oxygen is sometimes needed if they have difficulty breathing. As soon as they are independent in eating and breathing, they return home. “In case of eating and swallowing disorders, speech therapy sessions can be proposed. Physiotherapy helps strengthen the child’s tone because it is hypotonic. As we grow up, we see a hypertonic tendency appear in some people, in which case it is necessary to work on flexibility and relaxation. There psychomotor skills aims, through often fun activities, to encourage the child’s awakening. In the presence of visual disturbances, corrective lenses can be recommended, as can occlusion of one eye in order to develop bilateral vision and, if the child is capable, orthoptic rehabilitation“, explains Dr Aimé Ravel.
What is the life expectancy?
Life expectancy has increased significantly. She is now over 50 years old, we do not have enough perspective to know how far it will extend.
Thanks to Dr Aimé Ravel, pediatric geneticist at the Jérôme Lejeune Foundation which works for people with intellectual disabilities of genetic origin.