Cri du chat (cri-du-chat) syndrome (French for "cry of the cat") is a medical condition that occurs when a person is born missing part of chromosome five. The disorder, also called 5p- syndrome, is characterized by a cat-like cry during infancy, intellectual disabilities (formerly called mental retardation), and delayed development.
It is estimated that cri du chat affects one out of 20,000-50,000 people. The disorder is slightly more common in females than males.
Some children with cri du chat syndrome are also born with heart defects, which range from mild to life-threatening. About 10% of infants with cri du chat syndrome die as a result of complications associated with heart defects, decreased muscle tone, and feeding difficulties.
There is currently no cure for cri du chat syndrome, but many treatments and therapies may help patients cope with the disorder. With appropriate therapy, some patients are able to live independently once they become adults, while others may need lifelong support and/or residential care. Adults with profound intellectual disabilities usually require lifelong nursing care.
General: A person's DNA (genetic makeup) is contained inside chromosomes. Nearly every cell in the body has a nucleus, which contains two sets of chromosomes. Each parent provides one set (23) to his or her offspring. Therefore, each person has 23 pairs of chromosomes.
Patients with cri du chat syndrome are missing part of chromosome 5. The size of this deletion varies among patients. Current research suggests that larger deletions result in more severe intellectual and developmental disabilities than smaller deletions.
Catenin (CTNND2) gene: The chromosome 5 region that is deleted in cri du chat normally contains the CTNND2 gene. In healthy people, this gene provides instructions on how to make a protein called delta-catenin. Researchers believe that this protein helps guide nerve cells to their proper positions during human development. It has also been shown to play an important role in the function of synapses, which are the junctions between nerve cells where cell-to-cell communication occurs.
Researchers suspect that when this gene is missing, the nerve cells may not reach their proper positions during development and may cause mental developmental abnormalities. Cri du chat syndrome patients who are not missing the CTNND2 gene tend to have milder intellectual disabilities or normal intelligence.
Other missing genes in this region, such as SEMAf and hERT, have also been associated with cri du chat.
Random deletion: Most cases of cri du chat syndrome are not inherited or passed down among families. Instead, part of chromosome 5 is randomly deleted during the development of a sperm, egg, or embryo.
Inherited deletion: An estimated 10% of cri du chat cases are inherited from an unaffected parent, usually the father. In fact, about 80% of the inherited cases of cri du chat are passed down from the father.
In such cases, the parent does not have the disorder, but he/she has a rearranged chromosome (called a balanced translocation). The parent is not missing any genetic information and does not have any extra genetic information. When the parent has a child, however, there is a chance that this balanced translocation may become unbalanced in his/her child. Unbalanced translocations may lead to extra or missing genetic material. In cases of cri du chat, the child is missing part of chromosome 5.
SIGNS AND SYMPTOMS
Cat-like cry: Infants with cri du chat syndrome make high-pitched noises when they cry that sound similar to a cat. This is because they are born with abnormal voice boxes (larynxes). In general, the cat-like cry becomes less apparent over time.
Intellectual disabilities: Intellectual disabilities (formerly called mental retardation) typically range from mild to profound. A small number of people, particularly those who are not missing the CTNND2 gene, may have normal intelligence. Researchers suspect that this is because the CTNND2 gene is needed to help guide the nerve cells to their proper positions during development.
Researchers typically use intelligence quotient (IQ) tests to measure the severity of a person's intellectual disabilities. Individuals who have IQs of 85-115 are considered to have average intelligence.
Patients with mild intellectual disabilities have IQs of 52-69. From birth to age six, patients are able to develop normal social and communication skills, but motor coordination is slightly impaired. By late adolescence, patients are able to learn up to about a sixth-grade level. They are generally able to learn appropriate social skills. Adults with mild intellectual disabilities are usually able to work and support themselves, although some patients may need help during times of social or financial stress.
Patients with moderate intellectual disabilities have IQs of 36-51. Children younger than six years of age are able to talk or communicate with others, but social awareness is generally poor. Motor coordination is typically fair. Adolescents are able to learn some occupational and social skills. For instance, they may be able to learn how to travel alone in familiar places. Adults may be able to support themselves with a job. They usually require guidance and assistance during mild social or financial stress.
Patients with severe intellectual disabilities have IQs of 20-35. Young children can say a few words, but their speech is limited. Motor coordination is generally poor. Adolescents can usually talk or communicate with others. They are able to learn simple tasks. Adults typically require lifelong assistance and guidance with daily activities.
Patients with profound intellectual disabilities have IQs of 19 or lower. Children younger than six years old have very little motor coordination and may require nursing care. Adolescents typically have limited motor and communication skills. Adults usually require lifelong nursing care.
Physical characteristics: Several physical features, including a small head (called microcephaly), low birth weight, and weak muscle tone, are common among people with cri du chat syndrome.
Genetic testing: If cri du chat syndrome is suspected, a cytogenetic test may be performed to confirm a diagnosis. A sample of the patient's blood is taken and analyzed in a laboratory for the absence of part of chromosome 5. If a translocation is present, a positive diagnosis is made.
Prenatal DNA testing: If a parent has a balanced translocation associated with cri du chat syndrome, prenatal testing may be performed to determine if the fetus has the disorder. Amniocentesis and chorionic villus sampling (CVS) can diagnose cri du chat syndrome with 98-99% accuracy. However, because there are serious risks associated with these tests, patients should discuss the potential health benefits and risks associated with these procedures with a medical professional.
During amniocentesis, a long, thin needle is inserted through the abdominal wall and into the uterus and a small amount of amniotic fluid is removed from the sac surrounding the fetus. Cells in the fluid are then analyzed for normal and abnormal chromosomes. Patients with cri du chat are missing part of chromosome 5. This test is performed after 15 weeks of pregnancy. The risk of miscarriage is about one in 200-400 patients. Some patients may experience minor complications, such as cramping, leaking fluid, or irritation where the needle was inserted.
During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta between the ninth and 14th week of pregnancy. CVS may be performed through the cervix or through the abdomen. The cells in the tissue sample are then analyzed for absence of part of chromosome 5. Miscarriage occurs in about 0.5-1% of women who undergo this procedure.
Heart defects: About 30% of people with cri du chat syndrome are born with heart defects, which range from mild to life-threatening. Examples of heart defects or heart abnormalities include endocardial cushion defect, ventricular septal defect, secundum atrial septal defect, tetralogy of Fallot, and isolated patent ductus arteriosus (when the vessel that connects the aorta to the pulmonary artery fails to close after birth). These abnormalities occur when the structures of the heart, including the chambers, valves, or blood vessels, do not develop properly.
General: There is currently no cure for cri du chat syndrome, but many treatments and therapies may help patients cope with the disorder. With appropriate therapy, some patients are able to live independently once they become adults, while others may need lifelong support and/or residential care. Adults with profound intellectual disabilities usually require lifelong nursing care.
Occupational therapy: Patients may benefit from occupational therapy. During sessions, a therapist helps the child learn skills needed to perform basic daily tasks, such as feeding, dressing, and communicating with others. Some patients work with therapists who specialize in disorders and disabilities, including cri du chat syndrome. Parents and caregivers can ask their children's pediatricians for recommended therapists.
Education: Patients with cri du chat syndrome must have access to education that is tailored to their specific strengths and weaknesses. According to the Individuals with Disabilities Education Act, all children with disabilities, including cri du chat syndrome, must receive free and appropriate education. According to the law, members of the patient's school should consult with the patient's parents or caregivers to design and write an individualized education plan. The school faculty should document the child's progress in order to ensure that the child's needs are being met.
Educational programs vary among patients. In general, most experts believe that children with disabilities, including cri du chat syndrome, should be educated alongside their non-disabled peers. The idea is that non-disabled students will help the patient learn appropriate behavioral, social, and language skills. Therefore, some cri du chat syndrome patients are educated in mainstream classrooms. Other cri du chat syndrome patients attend public schools but take special education classes. Others attend specialized schools that are designed to teach children with disabilities.
Behavioral therapy: Behavioral therapy may also be beneficial. Several different types of behavioral therapy are available to help cri du chat syndrome patients improve their communication and social skills, as well as their learning abilities and adaptive behaviors. Evidence suggests that behavioral therapy is most effective if it is started in early childhood.
Speech-language therapy: Some patients with cri du chat syndrome may benefit from speech-language therapy because these individuals often develop communication skills slower than normal. During speech-language therapy, a qualified speech-language professional (SLP) works with the patient on a one-on-one basis, in a small group, or in a classroom, to help the patient improve speech, language, and communication skills. Programs are tailored to the patient's individual needs.
Speech pathologists use a variety of exercises to improve the patient's communication skills. Exercises typically start simple and become more complex as therapy continues. For instance, the therapist may ask the patient to name objects, tell stories, or explain the purpose of an object.
On average, patients receive five or more hours of therapy per week for three months to several years. Doctors typically recommend that treatment is started early to ensure the best possible prognosis for the child. About half of patients with cri du chat syndrome are able to develop sufficient verbal skills to communicate with others.
Currently, there is a lack of scientific data on the use of integrative therapies for the treatment or prevention of cri du chat.
There is currently no known method of prevention for cri du chat syndrome. Most cases occur randomly and are not inherited.
If a parent has a balanced translocation associated with cri du chat syndrome, genetic counselors can help patients understand the risks of having a child with the condition. Genetic counselors can explain the different types of genetic tests, including prenatal tests, and can help patients understand the potential risks, benefits, and results of these tests.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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