Cri du Chat results from a very rare mutation caused by the loss or deletion of a significant portion of the genetic material from chromosome number five which is vital to cell growth. In most cases, this disorder occurs during egg and sperm development. However, it can be passed down from parent to offspring.
Symptoms of Cri du Chat commonly include a cry that is high-pitched and sounds like a cat, a downward slant to the eyes, a low birth weight and slow growth, low-set or abnormally shaped ears, mental retardation, partial webbing or fusing of fingers or toes, a single line in the palm of the hand, skin tags just in front of the ear, slow or incomplete development of motor skills, a small head, a small jaw, and wide-set eyes. Babies with this syndrome may experience difficulty breathing and swallowing. They may also show poor growth and development. A few children with the disorder may even lose the cry after the age of two, but will still have trouble with speech and movement.
Test and ExaminationsEditPhysical tests may show inguinal hernia, which is the formation of a sac (usually appears like a bulge), and diastasis recti, which is the separation of abdominal muscles caused by poor muscle tone. Some patients with this disorder have an extra skin fold near the eye or have abnormally formed ears. Genetic tests are available to detect the missing part of the chromosome. A prenatal detection is possible by examining uncultured amniocyte interphase cells. These cells can be analyzed to detect any unbalanced chromosome abnormality. There is also a procedure called Chorionic villus sampling (CVS). This procedure involves taking a very small sample of the chorionic sac followed by karyotyping, looking at the chromosomes. Though these tests do determine whether the baby has the syndrome or not, they can also be risky. Researchers have stated that if a child was tested for the syndrome using one of these methods, there would be more of a risk for a miscarriage to occur even if the baby is healthy.
Cri du Chat is very hard to treat medically. However, there are programs that help children overcome some of their difficulties. Some of these programs include therapy for speech and behavioral issues. People affected by the disorder should attend physical therapy, occupational therapy and speech therapy to achieve their fullest potential. Surgery can be used to correct any deformed organs. There are no drugs that are currently administered to Cri du Chat patients.
Life Expectancy and Quality of LifeEdit
Most people with this disorder can have a normal life expectancy, unless they have deformed organs or severe retardation.
Those with the disorder may experience a tough life because Cri du Chat can cause mental retardation and a characteristic physical appearance. These combined make school a very tough place for affected children who will need to cope with bullies and the frustrations caused by struggling with school work.
A person with the disorder will require speech therapy, occupational therapy, and physical therapy and help from teachers and family to achieve his or her full potential. Many people with the disorder struggle with language and basic movement. Many will only be able to form basic sentences and have a very simple vocabulary. Some require sign language and hand gestures to communicate.
People with the disorder, adults and children alike, are generally happy and extremely social. However, some people affected by the disorder may never be able to function independently. There are support groups for those affected by the disorder that help the families cope with the hardships associated with disorder. The 5P- Society aids families and children affected by Cri du Chat syndrome, helping the children maximize their capabilities.
Cri du Chat Syndrome is usually not inherited. Children born with Cri du Chat generally have no family history of the disorder. This is because the deletion usually occurs in gamete, or sex cell, formation in the parent’s reproductive organs during meiosis. The deletion will normally occur during crossing over during Prophase I and Metaphase I as the chromosomes line up at the metaphase plate. If the chromosome is damaged at this time and not repaired, Cri du Chat will result. Many researchers believe that the size of the deletion on the short arm of chromosome five directly correlates to the severity of the disorder. Thus, the larger the deletion, the worse the condition of the person affected.
Approximately one in ten Cri du Chat births is inherited from a parent who demonstrates no symptoms of Cri du Chat and has a certain chromosomal abnormality. The chromosome abnormality is called a balanced translocation which is a rearrangement of genetic material that has no loss or gain of genetic material. When those with balanced translocations reproduce, it is highly likely that that translocation becomes unbalanced resulting in either excess or reduced genetic material. Those who inherit Cri du Chat from their parent’s translocation will have an unbalanced translocation on chromosome five.
Mental retardation of those with Cri du Chat has been linked to the “catenin (cadherin-associated protein), delta 2 (neural plakophilin-related arm-repeat protein)” or CTNND2 gene located on the short arm of chromosome five. This gene carries the instructions to make the delta-catenin protein which is responsible for intracellular attachment of neurons and cellular movement. The protein plays a crucial role in the synaptic cleft where dendrites from one neuron attach to the axon terminal of another neuron. When deleted, the affected individual will have severe mental retardation and poor motor skills because their cell to cell communication within the nervous system is not as efficient as those with the gene. People with Cri du Chat Syndrome who still have this gene intact will experience a milder mental retardation, or even demonstrate normal intelligence.
The disorder is extremely rare because the deletion must occur on the short arm of chromosome five. The body has various checkpoints throughout meiosis that work to correct any mistakes made in the process of generating gametes. Approximately 1 in 50,000 births results in Cri du Chat Syndrome. The disorder is more common in females than in males However, about eighty percent of the time; it is the male’s sperm that causes the disorder.
80% of the time, the chromosome with the deletion is from the father’s sperm
5P- stands for a deletion (-) of the sort (P) arm of chromosome five (5).
Not all deletions are the same size; they just need to be from the sort arm of chromosome five.
Jerome Lejeune also was the person who discovered Trisomy 21, the chromosome abnormality that causes Down Syndrome.
By Nicholas Chen and Toral Patel