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A syndrome associated with a high-pitched, cat-like cry in the newborn period, severe mental retardation, facial anomalies, scoliosis, muscular hypotonia and congenital cardiac defects.

Cri-du-Chat Syndrome; Lejeune Syndrome, Deletion of Short Arm of Chromosome 5; Monosomy 5p.

First described in 1963 by the French pediatrician Jérôme Jean L.M. Lejeune.

Appears to be the most common human deletion syndrome, with an incidence of 1 in 15,000 to 1 in 50,000 live births. The frequency in patients with profound mental retardation (IQ<20) may be as high as 0.3%. A slight female predominance has been reported.

The syndrome arises from a partial or total deletion of the short arm of chromosome 5. A loss of the critical 5p15.2 region gives rise to most of the clinical features. The vast majority of cases are sporadic resulting from new mutations. Some arise from unbalanced translocations or parental chromosomal rearrangements. The severity of the syndrome is related to the extent of the chromosome deletion.


Based on the clinical picture plus molecular cytogenetic confirmation of 5p deletion with fluorescent in situ hybridization (FISH), which is considered the gold standard.

The name of the syndrome derives from the characteristic, high-pitched cry in infancy, which sounds similar to the mewing of a cat and is considered diagnostic for this disorder. The abnormal cry is mainly caused by anatomical anomalies of the larynx (long, curved and floppy epiglottis, laryngeal hypoplasia, laryngomalacia, asymmetric vocal cords, anterior approximation of the vocal cords with a large posterior commissure), however, in some patients the larynx was found to be structurally normal, which explains why some researchers believe that there may also be a neurological component involved in the abnormal cry. Mental retardation is most often severe. Central nervous findings include marked brainstem atrophy (mainly at the level of the pons) and cerebellar hypoplasia also involving the middle cerebellar peduncles. Generalized muscular hypotonia, poor sucking reflex, and respiratory distress may result in failure to thrive, which in combination with the commonly present intrauterine growth retardation results in postnatal growth retardation. The head usually is microcephalic with a round face due to full cheeks, downward slanting of the palpebral fissures, hypertelorism, low-set ears, depressed nasal bridge, microand/or retrognathia with a high-arched, narrow palate (cleft palate has also been described), and macrostomia. Up to 30% of these patients have congenital cardiac defects (most commonly atrial and/or ventricular septal defects, tetralogy of Fallot, pulmonary stenosis, and patent ductus arteriosus). Abdominal findings may include malrotation, megacolon, and inguinal hernias. The urogenital system may also be affected and findings include renal anomalies (e.g., renal agenesis, horsehoe kidney, hydronephrosis), hypospadias, cryptorchidism and testicular atrophy (although spermiogenesis is most often with intact). Skeletal features that have been reported are scoliosis, clubfoot, clinodactyly, and syndactyly of fingers and toes. Abnormal dermatoglyphics (e.g., simian crease) and premature graying of the hair may be present. Severely destructive behavioral problems (agression, ...

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