Cri du chat syndrome is caused by a missing (deleted) piece of genetic material on the short arm of chromosome 5, known as a 5p deletion.

What actually causes Cri du chat syndrome?

  • It is a genetic condition, not caused by anything a parent did during pregnancy.
  • A section at the end of the short arm of chromosome 5 (region 5p) is missing.
  • Two key regions are involved:
    • 5p15.3: strongly linked to the characteristic high‑pitched “cat‑like” cry in infancy.
* 5p15.2: associated with most of the other clinical features (developmental delay, facial features, etc.).

In plain terms: one copy of chromosome 5 is “shorter than it should be” because a chunk has been deleted, and losing those genes leads to the signs of the syndrome.

How and when does this deletion happen?

  • In most cases , the deletion happens randomly very early in development when the egg or sperm is formed, or just after fertilization (a de novo error).
  • In a minority of cases , a parent carries a balanced rearrangement of chromosomes (such as a balanced translocation) that does not affect their own health, but increases the risk of a child inheriting an unbalanced form with a deletion of 5p.

So the usual “cause” is a random genetic change; only occasionally is it inherited from a parent with a balanced chromosomal change.

Is anything known to trigger it?

  • No specific environmental factor (like medications, infections, or lifestyle) has been proven to cause the 5p deletion.
  • The condition is considered rare and mostly sporadic, with an estimated frequency around 1 in 20,000–50,000 live births.

Because it is usually random, there is often nothing that could have been done to prevent it in a given pregnancy.

Genetics overview (table)

[9][1][7][3] [7][9] [1][7] [9][5][7] [5][7][9] [3][7][5]
Aspect Details (Cri du chat syndrome cause)
Chromosome involved Chromosome 5, short arm (5p) deleted.
Type of change Partial monosomy (loss of part of one chromosome), sometimes terminal, sometimes interstitial.
Key regions 5p15.3 (cat‑like cry), 5p15.2 (main syndrome features).
How often random About 85–90% de novo (new/random event).
Familial cases About 10–15% from a parent with a balanced translocation or other rearrangement.
Parental actions No evidence that parental behavior, diet, or activities cause the deletion.

Why different children are affected differently

Even though the underlying cause is the same kind of event (a deletion on 5p), the exact size and position of the missing segment can vary between individuals. Because different genes may be lost, the severity of developmental delay, medical complications, and characteristic features can differ from one child to another.

Quick example story (to make it concrete)

A baby is born with a very high‑pitched cry and feeding difficulties. Genetic testing (karyotype and microarray) shows that one copy of chromosome 5 is missing a section at 5p15.2–5p15.3. The parents’ chromosomes are tested and found to be normal, so doctors explain that this was a random genetic event , not inherited, and that future recurrence risk is low but not zero.

TL;DR

  • What causes cri du chat syndrome? A deletion of part of the short arm of chromosome 5 (5p).
  • Usually happens randomly during egg/sperm formation or early embryo development.
  • A small percentage of cases are due to a parent’s balanced chromosomal rearrangement.
  • It is not caused by anything the parents did or did not do in pregnancy.

Information gathered from public forums or data available on the internet and portrayed here.