Cytogenetic basis of the disease
The cause of Syndromum cri-du-chat is a structural chromosomal aberration — deletion. This means there is a physical loss of a specific DNA segment.
In this case, a fragment of the short arm of the fifth chromosome is lost. At the cytogenetic level (when studying the cariogram), this is designated by the symbol "5p-", where "5" is the chromosome number, "p" is the short arm, and the minus sign indicates the loss of genetic material.
As a classic clinical example, we can examine the karyotype of a male patient with this syndrome:
- 46 — the normal total number of chromosomes in the cell.
- XY — male sex chromosomes.
- (5p-) — indication of the specific deletion.
On a visual karyogram, this defect is often indicated by an arrow to clearly demonstrate the difference between the normal and the damaged chromosome from the fifth pair.
Clinical presentation and phenotype
The loss of genetic material on the fifth chromosome leads to severe systemic disorders in the child's body. The clinical picture is characterized by multiple developmental abnormalities.
Main targets of the syndrome:
- Nervous system: patients exhibit pronounced intellectual disability.
- Cardiovascular system: development of various heart and vascular lesions is typical.
- Digestive tract: lesions of the gastrointestinal tract, particularly the stomach, are recorded.
In addition, patients are characterized by a specific phenotype — recognizable facial features that, together with other anomalies, make it possible to suspect the syndrome even during an external examination of the newborn.
Pathognomonic feature
The most striking symptom, which gave the entire pathology its name, is the specific sound emitted by the infant when crying.
This sound is strikingly similar to a cat's meow. It is not accidental, but has a clear anatomical basis: an anomaly in the development of the larynx and vocal cords. It is precisely this structural impairment of the vocal apparatus that physically causes such an unusual acoustic effect. This sign is considered pathognomonic (unique and unequivocally pointing to a specific disease) for cri-du-chat syndrome.
To remember the affected chromosome, imagine that the number "5" visually resembles a cat with an arched back. The loss of part of this "cat" (5p deletion) leads to cri-du-chat syndrome.
Class and exam questions
In what year and by whom was cri-du-chat syndrome discovered?
The pathology was first described in 1963 by the French geneticist Jérôme Lejeune.
What does the designation 46, XY(5p-) mean?
This is the karyotype of a boy (46 chromosomes, XY sex chromosomes) who lacks a segment of the short arm of the fifth chromosome (5p-).
Why do children with this syndrome cry like kittens?
The cause of the specific cry is a congenital anatomical anomaly in the development of the larynx and vocal cords.
What else to study on this topic
- Detailed analysis of facial phenotypic features in cri-du-chat syndrome
- Types and severity of cardiovascular lesions in 5p- deletion
- Specific anomalies of the gastrointestinal tract and stomach
- Degree of severity of intellectual disability in patients with Lejeune syndrome
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