The Cri du Chat syndrome (CdCS) is a genetic disease resulting from a deletion 
of variable size occurring on the short arm of chromosome 5 (5p-). The incidence 
ranges from 1:15,000 to 1:50,000 live-born infants. The main clinical features 
are a high-pitched monochromatic cry, microcephaly, broad nasal bridge, 
epicanthal folds, micrognathia, abnormal dermatoglyphics, and severe psychomotor 
and mental retardation. Malformations, although not very frequent, may be 
present: cardiac, neurological and renal abnormalities, preauricular tags, 
syndactyly, hypospadias, and cryptorchidism. Molecular cytogenetic analysis has 
allowed a cytogenetic and phenotypic map of 5p to be defined, even if results 
from the studies reported up to now are not completely in agreement. 
Genotype-phenotype correlation studies showed a clinical and cytogenetic 
variability. The identification of phenotypic subsets associated with a specific 
size and type of deletion is of diagnostic and prognostic relevance. Specific 
growth and psychomotor development charts have been established. Two genes, 
Semaphorin F (SEMAF) and delta-catenin (CTNND2), which have been mapped to the 
"critical regions", are potentially involved in cerebral development and their 
deletion may be associated with mental retardation in CdCS patients. Deletion of 
the telomerase reverse transcriptase (hTERT) gene, localised to 5p15.33, could 
contribute to the phenotypic changes in CdCS. The critical regions were recently 
refined by using array comparative genomic hybridisation. The cat-like cry 
critical region was further narrowed using quantitative polymerase chain 
reaction (PCR) and three candidate genes were characterised in this region. The 
diagnosis is based on typical clinical manifestations. Karyotype analysis and, 
in doubtful cases, FISH analysis will confirm the diagnosis. There is no 
specific therapy for CdCS but early rehabilitative and educational interventions 
improve the prognosis and considerable progress has been made in the social 
adjustment of CdCS patients.