Cri-du-chat is a genetic disorder that is caused by a deletion of the short arm of chromosome 5. The name of the syndrome, meaning cat cry, was coined after the main clinical finding of a high-pitched, monochromatic cat-like cry. The clinical picture, severity, and progression of the disease vary depending on the region of the chromosome deleted and whether it is terminal or interstitial. In other words, differences in phenotype are attributable to the differences in genotype. This disorder characteristically presents with distinctive facial features, delayed development, and intellectual disability.
Cri-du chat results from either a partial or complete deletion of chromosome 5p. Most of the deletions occur de novo. The deletions occur as random events during the formation of reproductive cells in early fetal development. Around 80% to 90% are paternal in origin, which can arise from a chromosomal breakage during gamete formation. The remaining 10% to 15% result from unbalanced parental translocation. Moreover, 80% to 90% of cases result from terminal deletions of chromosome 5, while 3% to 5% are due to an interstitial deletion. Mosaicism, inversions, and ring chromosomes are less common mechanisms.
Although Cri du chat is considered a rare disorder, it is one of the most common chromosomal anomalies. The incidence ranges from 1 in 15,000 to 1 in 50,000 liveborn infants. The incidence in females is slightly higher than males. The exact incidence and prevalence worldwide and among races has not been established. Similarly, specific risk factors associated with prenatal events or parental age have are not clear. However, there are occasional reports of parental exposure to radiation, hyperemesis, anorexia, and toxemia.
Patients demonstrate phenotypic and genotypic variability. Research has revealed that partial deletion of the short arm of chromosome 5 to be the cause of the characteristic phenotype. The phenotype being identifiable despite the fact that variations in deletion size have led to a theory that a critical region is responsible for the characteristic feature in hemizygosity. The region identified is 5p15.2, and individuals with a deletion of chromosome 5 that do not include this region do not show a typical phenotype and, in some cases, are even normal.
Cytogenetic studies have helped identify two regions, 5p15.3, which is responsible for the characteristic cry, and 5p15.2, which is responsible for the other significant clinical findings. Similarly, other areas have been identified for additional features such as speech retardation and dysmorphism. Therefore, clinical manifestations depend on the deletion of the critical area. Another crucial factor in the manifestation is the size as well as the type of deletion and whether it is interstitial or terminal.
The most characteristic feature of this disease is high-pitched crying, and the pathogenesis is attributable to the anatomical alteration of the laryngeal morphology, which may be a result of:
However, not all patients with abnormal crying have the above features. Therefore, there may be neurological changes as well.
In the neonatal period, the most characteristic finding is a high-pitched, monotonous cry, which usually disappears within the first few months of life. The cry is not limited to this syndrome alone and is known to accompany a few other neurological disorders. Newborns also exhibit low birthweight and microcephaly as well as asphyxia, muscle hypotonia, and impaired suction. These lead to impaired growth and development during the first few years of life. Reports exist of recurrent respiratory and intestinal infections. 
(a) Craniofacial malformations:
With increasing age, the following features change:
(b) Other anomalies that might be present:
(c) Orofacial abnormalities:
(d) Developmental and behavioral manifestations:
Cri du chat is diagnosable via amniocentesis during the antenatal period, where the deletion of chromosome 5 will be visible. The structural abnormalities are observable sonographically. Also, fetuses who show mosaicism may display fetoplacental and fetoamniotic chromosomal abnormalities along with microcephaly and cerebellar hypoplasia.
A diagnosis can be made based on clinical findings. The occurrence of specific characteristic findings such as microcephaly, low birth weight, moon face, muscle hypotonia, and a cat-like cry together should raise clinical suspicion of the condition. Sometimes this can be difficult because the features may not be obvious as patients show a cytogenetic variation leading to phenotypic variation. The clinical features, as well as the severity and prognosis, can be determined by the size and position of the deletion.
If clinical suspicion is present, one of the first tests that can confirm the diagnosis is a karyotype analysis. However, in cases where the clinical suspicion is high in the presence of a normal karyotype, further specific tests can be carried out, such as FISH, CGH (comparative genomic hybridization), or quantitative PCR (polymerase chain reaction).
FISH has led to an improvement in the diagnosis of genetic disorders caused by chromosome deletion and has provided a phenotypic map and the associated genome of an individual. Newer techniques, such as CGH, have opened up new doors by including the whole genome and the associated markers, which can identify genetic alterations.
There have been very few studies on the MRI findings. However, pontine hypoplasia seems to be the most common feature. This presentation is associated with other findings such as cerebellar hypoplasia and microcephaly as well as corpus callosum anomalies. Supratentorial abnormalities also have been observed.
There is no specific treatment for patients due to the early onset of cerebral damage during embryonal development. However, patients benefit from rehabilitation, especially with early intervention. This approach has demonstrated to improve prognosis as well as social adaptation.
During the neonatal period, physical therapy should be started in the first week of life to help with any difficulty in swallowing and suction. Breastfeeding is still possible, and intensive care is rarely necessary.
Physical therapy, psychomotricity, and speech therapy are suggested interventions for psychomotor and speech retardation. Patients often have sensorineural deafness; therefore, audiometric examinations should take place in all children. Other helpful treatments include surgery, a special diet, and healthy routines.
Families should be involved in the care of the patient. They should receive information about the disease and available support groups.
The differential diagnosis of cri du chat syndrome include the following:
Morbidity and mortality rates decrease after the first few years of life. Reportedly 75% of deaths occur during the first month of life, and about 90% of deaths occur during the first year. It is important to note that the type, size, and location of the deletion(s) significantly influence the prognosis.
One of the most important factors in the prognosis of the disease is an early diagnosis. Early diagnosis allows for the implementation of therapeutic measures early on to improve the outcome of physical as well as psychomotor development and helps with social adaptation.
Cri du chat syndrome is a chromosomal deletion caused by the partial deletion of the p arm of chromosome 5. Complicated may include the following:
Apart from the patients, the families of affected individuals have to deal with increased stress due to the patient's maladaptive behavior. The patients and families require support from healthcare providers, other families, and friends. Families should be educated on the latest information regarding the syndrome and provided with the necessary resources.
Cri du chat is managed by an interprofessional team that includes nurses, therapists, social workers, and dietitians. There is no specific treatment for patients due to the early onset of cerebral damage during embryonal development. However, patients benefit from rehabilitation, but results are better the earlier it starts. This approach to treatment improves prognosis as well as social adaptation. During the neonatal period, physical therapy should be started in the first week of life to help with any difficulty in swallowing and suction. Breastfeeding is still possible, and intensive care is rarely necessary.
Unfortunately, outcomes for infants with this disorder are poor. They face numerous difficulties with feeding, breathing, and development. Most die within the first few months, but those with mild deficits may live longer.
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