Height is less affected than weight from birth up to 2 years of age in both sexes. For all ages, median head circumference and weight are near or below the 2 nd and 5 th percentile, respectively. Specific growth charts for CdCS, based on a multicentre study carried out on 374 patients from the United States, Italy, the United Kingdom and Australia, confirmed the existence of prenatal and postnatal growth retardation. Malformations of the cranial base suggest associated anomalies of the brain (rhombencephalic region) and larynx during embryonal development. The characteristic cat-like cry is probably due to anomalies of the larynx (small, narrow, diamond-shaped) and of the epiglottis (flabby, small, hypotonic), as well as to neurological, structural and functional alterations. 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. Karyotype analysis and, in doubtful cases, FISH analysis will confirm the diagnosis. The diagnosis is based on typical clinical manifestations. 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 critical regions were recently refined by using array comparative genomic hybridisation. Deletion of the telomerase reverse transcriptase ( hTERT) gene, localised to 5p15.33, could contribute to the phenotypic changes in CdCS. Two genes, Semaphorin F ( SEMAF) and δ-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. Specific growth and psychomotor development charts have been established. The identification of phenotypic subsets associated with a specific size and type of deletion is of diagnostic and prognostic relevance. Genotype-phenotype correlation studies showed a clinical and cytogenetic variability. 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. Malformations, although not very frequent, may be present: cardiac, neurological and renal abnormalities, preauricular tags, syndactyly, hypospadias, and cryptorchidism. 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. The incidence ranges from 1:15,000 to 1:50,000 live-born infants. 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-).
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