Cri Du Chat Syndrome Support Group

What is Cri du Chat Syndrome and how is it diagnosed?

Cri-du-chat syndrome (CDCS) is a relatively rare chromosome disorder affecting approximately 1 in 37,000-50,000 live births. The exact sex ratio is not known although reports indicate that females outnumber males by 2 to 1. The syndrome is known to result from a deletion from the short arm of chromosome 5 and represents one of most common deletion syndromes in humans. A deletion occurs when there is a loss of material from one chromosome because of either one break (a terminal deletion) or two breaks (an interstitial deletion). Recent molecular research has further highlighted a ‘critical region’ on chromosome 5 (5p15.2) that appears to be specifically involved in displaying the classical features of cri-du-chat syndrome. If the deletion breakpoint includes this ‘critical region’ the characteristic features diagnostic of the syndrome will be present. Usually the loss from the short arm of chromosome 5 is purely accidental and thus the risk of recurrence is very low, no greater than the original risk of 1 in 37,000-50,000. In 80-95% of cases, the genetic material is lost from the end of chromosome 5 (terminal deletion). When the parental chromosomes of the children with terminal deletions are found to be normal, the deletions are referred to as ‘sporadic’. However, in 10-15% of cases this deleted chromosome is inherited from a parent. When this occurs the risk of having another affected child is much greater than when the syndrome results from a sporadic deletion. A Genetic Counsellor or GP is the most appropriate person to provide professional advice on risk in future pregnancies.

It is also important to note that a growing number of studies have described individuals with 5p deletions outside the critical region. Most often these individuals present with the cat-like cry from which the syndrome derives its name but not severe learning disability or significant developmental delay. These studies highlight the importance of careful and accurate differentiation between deletions that result in the typical CDCS profile and those that result in an atypical, milder profile.

At birth, the main clinical diagnostic feature of the syndrome is a high pitched, monochromatic ‘cat-like’ cry that is always present in the new-born but may disappear with age. Other features include a round, full face (“moon face”), widely spread eyes (hypertelorism), an extra fold of skin at the inner corners of the eyes (epicanthal folds), a flattened and widened nasal bridge and ears that are positioned low on the head. Most children with CDCS will have feeding problems from birth including failure to thrive, poor sucking and slow weight gain. They may also be some medical complications but these will not affect every child and are not frequent.