Cri du Chat Syndrome (5p– Syndrome)

Cri du chat (French: "cat's cry") syndrome is a chromosomal deletion disorder caused by loss of material from the short arm of chromosome 5. It is one of the most recognizable contiguous gene deletion syndromes.

Genetics

Deletion: Terminal or interstitial deletion of chromosome 5p — the critical region is band 5p15
Karyotype notation: 46,XX or XY, del(5p)
Incidence: ~1 in 15,000–50,000 live births
Most cases are sporadic (de novo); only 10–15% result from a parent carrying a balanced translocation
The degree of intellectual impairment generally correlates with deletion size; haploinsufficiency of regions within 5p14–p15 contributes disproportionately to severe intellectual disability
Detected by routine karyotype (large deletions) or chromosomal microarray (CMA) for smaller ones

Clinical Features

Domain	Features
Pathognomonic	High-pitched, cat-like cry in infancy (due to laryngeal underdevelopment)
Craniofacial	Microcephaly, hypertelorism, epicanthal folds, low-set ears, micrognathia, round/moon face, brachycephaly, antimongoloid palpebral slant
Neurological	Severe intellectual disability, hypotonia, developmental delay
Cardiac	Congenital heart disease: VSD, ASD, PDA
Growth	Low birth weight, failure to thrive
Other	Strabismus, preauricular tags (occasional)

The Characteristic Cry

The syndrome's name derives from the cat-like mewing cry of affected neonates — a consequence of underdevelopment (hypoplasia) of the larynx. This is the most distinctive early feature and typically diminishes with age.

Diagnosis

Prenatal: Can be detected on non-invasive prenatal testing (NIPT) for fetal microdeletion/duplication syndromes; also by conventional karyotyping of chorionic villus or amniocentesis samples
Postnatal: Karyotype or chromosomal microarray (CMA detects all cases, including those with cytogenetically invisible deletions)

Clinical photograph and karyotype

Male child with cri du chat syndrome showing microcephaly and hypertelorism, alongside partial karyotype showing terminal deletion of chromosome 5p

Child with cri du chat syndrome (A) showing microcephaly and hypertelorism; (B) partial karyotype with the arrow indicating the terminal deletion of chromosome 5p short arm. — The Developing Human: Clinically Oriented Embryology

Key Points for Exam/Clinical Practice

5p deletion → cri du chat (compare: 4p deletion → Wolf-Hirschhorn syndrome)
Critical deleted band: 5p15
Cry is due to laryngeal hypoplasia, NOT a neurological cause
Intellectual disability is severe; degree correlates with deletion size
Sporadic in ~85–90% of cases; recurrence risk low unless a parent carries a translocation
Diagnosed postnatally by CMA; prenatally by NIPT or amniocentesis karyotype

Sources: Thompson & Thompson Genetics and Genomics in Medicine (9th ed.), Emery's Elements of Medical Genetics and Genomics, The Developing Human: Clinically Oriented Embryology, Adams and Victor's Principles of Neurology (12th ed.), Harriet Lane Handbook (23rd ed.)

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