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Cri du chat - a genetic disorder in which a part of chromosome 5 is missing
What is Cri du Chat Syndrome?
Cri du chat is a rare genetic condition discovered by French Geneticist, Jerome Lejeune, in 1963. He named the disorder cri du chat after the distinct feautre patients held, a high-pitched cat like meowing cry. In the French lanuage, cri du chat means "cry of the cat". (International Cri du Chat, 2013.) The syndrome occurs when there is a loss of genetic material in a portion of the short arm in the fifth chromosome. This genetic condition is also known as 5p- syndrome, the "5" meaning the fifth chromosome, the "p" reffering to the p arm (short arm of the chromosome), and the "-" alluding to the deletion that occurs. Witin all affected by cri du chat, deletion size varies. (Haldeman, 2013).
Chromosome 5 contains CTNND2, the catenin gene, which in the unaffected, provides instructions on how to make a protein called delta-catenin. This protein is known to help guide nerve cells to their proper positions during human developement and contribute in the function of synapses, which are the junctions between nerve cells where cell-to-cell communication occurs. When this gene is missing, the nerve cells may not reach their specific positions during development, causing the devlopmental abnormalities profound in cri du chat paients. (Internatinal Cri du Chat, 2013).
In most cases, the specific cause of the deletion can not be identified. However, in majority of individuals affected, the syndrome is not inherited or passed down hereditary. Instead, the deletion during the development of the sperm, egg, or embryo is random. In the unlikely case, 10% of cri du chat cases are inherited from an unaffected parent, predominantly the father. In these cases, the parent contains a rearranged chromosome which may be passed down to their child, leading to missing genetic material in the fifth chromosome. (Mainardi, 2013).
Characteristics
The most distinctive characteristic in cri du chat paients is their high-pitched, cat-like cry, highly significant in infants. The size and location of the deletion correspondingly has correlation with the effects of the syndrome on an individual, those with small deletions in and above band 15.2 in chromosome 5 are midly affected to those with very large deletions. In addition to the cry, common distinguishing physcial characteristics are infants born with a small head, high palate, round face, low broad nasal ridge, widely spaced downward slanted eyes, and low set ears. The gene causing these predominant features are in band 5p15.2 and the gene resulting in the cry is located in band 15.3. Although the cry is predominant in childhood, the characteristic of a high-pitched voice persists into adolescence. In adulthood, the face becomes elongated, the nasal bride rises, and the head remains small. The disorder becomes less noticable as the individual affected ages. (Mainardi, 2013).
Common medical problems caused by cri du chat seen in infants are heart defects, kidney abnormalities, hernias, and swallowing problems. Swallowing difficulties are present in newborns, however rarely presist into adulthood. Common symptoms identified as the child matures are, delayed speech, language acquisition, slow delopment of motor skill, and slight behavioral difficulties. (Interanational Cri du Chat, 2013).
The life expectancy of an individual with cri du chat is unpredictable as the defects range correspondingly to the location and size of deletion on the fifth chromosome. The few affected with serious health issues may have a limited life expectancy, however most will live well to adulthood. The oldest person reported living with cri du chat syndrome was to the age of 60. (Mainardi, 2013).
