Cri du Chat syndrome is a rare genetic condition arising from a specific chromosomal abnormality. Named for the characteristic high-pitched cry of affected infants, which resembles a cat’s meow, it was first described in 1963 by Jérôme Lejeune, a French pediatrician and geneticist. This syndrome, also known as 5p- syndrome, involves a missing segment of genetic material on chromosome 5.
Understanding Its Occurrence
Cri du Chat syndrome is considered a rare disorder, affecting an estimated 1 in 15,000 to 1 in 50,000 live births globally. While uncommon, it stands as one of the more frequently observed chromosomal anomalies. It is found across all ethnic backgrounds, without a predisposition to any particular group. Females are diagnosed slightly more often than males, with a ratio of approximately 4 females to every 3 males.
Its rarity is largely attributed to its spontaneous nature. In most cases, the genetic change occurs randomly during the formation of reproductive cells or in early fetal development. This means there is typically no family history of the disorder, making it an unpredictable event.
The Underlying Genetic Change
Cri du Chat syndrome results from a partial deletion of the short arm of chromosome 5. This deletion is often referred to as 5p monosomy or 5p- syndrome, indicating the missing piece on the “p” (short) arm of chromosome 5. The size and exact location of this missing segment can vary, influencing the range and severity of the syndrome’s characteristics.
Most cases (80% to 90%) arise from a de novo deletion. This means the genetic change is a new mutation that occurs without being inherited from either parent. In about 80% of these de novo cases, the deleted chromosome 5 originates from the paternal side. The remaining 10% to 15% of cases are linked to an unbalanced parental translocation, where a parent carries a chromosomal rearrangement without symptoms but passes an unbalanced version to their child.
Identifying Features
Newborns with Cri du Chat syndrome often have a distinctive cry, resembling a cat’s meow, which typically prompts diagnosis. This unique cry is believed to stem from anatomical alterations in the larynx and nervous system. While prominent in infancy, this characteristic cry can become less noticeable as the child grows older.
Affected individuals also exhibit recognizable physical and developmental characteristics. Common facial features include:
- Small head (microcephaly)
- Rounded face
- Widely spaced eyes (hypertelorism)
- Broad nasal bridge
- Low-set ears
- Small jaw (micrognathia)
- Downward-slanting eyelid folds
Beyond these physical indicators, individuals with Cri du Chat syndrome often experience intellectual disability and delayed development, affecting motor skills, speech, and overall growth.