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Topic Resources Down syndrome is a genetic disorder in which a person has an extra copy of a chromosome called chromosome 21. This extra chromosome causes many health problems.
Down syndrome is caused by abnormalities in one of the chromosomes. People with Down syndrome have an extra 21st chromosome. Instead of having 2 of these chromosomes, people with Down syndrome have 3. (Down syndrome is also called trisomy 21, and the word "trisomy" means having 3 of one kind of chromosome.) About 1 in 700 babies has Down syndrome. You have a higher chance of having a baby with Down syndrome if:
Down syndrome affects both physical and mental development. Some children have mild symptoms. Others can have more severe symptoms. Physical characteristics of babies with Down syndrome can include:
Mental, developmental, and learning characteristics can include:
Children and adults with Down syndrome are more likely to be overweight and to have:
Before your baby is born: After your baby is born:
Down syndrome can’t be cured. But doctors and other members of the health care team will treat any health problems related to Down syndrome, including:
CLICK HERE FOR THE PROFESSIONAL VERSION Copyright © 2022 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved. OverviewDown syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It's the most common genetic chromosomal disorder and cause of learning disabilities in children. It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders. Better understanding of Down syndrome and early interventions can greatly increase the quality of life for children and adults with this disorder and help them live fulfilling lives. SymptomsEach person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe. Some people are healthy while others have significant health problems such as serious heart defects. Children and adults with Down syndrome have distinct facial features. Though not all people with Down syndrome have the same features, some of the more common features include:
Infants with Down syndrome may be average size, but typically they grow slowly and remain shorter than other children the same age. Intellectual disabilitiesMost children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected. When to see a doctorChildren with Down syndrome usually are diagnosed before or at birth. However, if you have any questions regarding your pregnancy or your child's growth and development, talk with your doctor. Sign
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health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail. CausesHuman cells normally contain 23 pairs of chromosomes. One chromosome in each pair comes from your father, the other from your mother. Down syndrome results when abnormal cell division involving chromosome 21 occurs. These cell division abnormalities result in an extra partial or full chromosome 21. This extra genetic material is responsible for the characteristic features and developmental problems of Down syndrome. Any one of three genetic variations can cause Down syndrome:
There are no known behavioral or environmental factors that cause Down syndrome. Is it inherited?Most of the time, Down syndrome isn't inherited. It's caused by a mistake in cell division during early development of the fetus. Translocation Down syndrome can be passed from parent to child. However, only about 3 to 4 percent of children with Down syndrome have translocation and only some of them inherited it from one of their parents. When balanced translocations are inherited, the mother or father has some rearranged genetic material from chromosome 21 on another chromosome, but no extra genetic material. This means he or she has no signs or symptoms of Down syndrome, but can pass an unbalanced translocation on to children, causing Down syndrome in the children. Risk factorsSome parents have a greater risk of having a baby with Down syndrome. Risk factors include:
ComplicationsPeople with Down syndrome can have a variety of complications, some of which become more prominent as they get older. These complications can include:
For people with Down syndrome, getting routine medical care and treating issues when needed can help with maintaining a healthy lifestyle. Life expectancyLife spans have increased dramatically for people with Down syndrome. Today, someone with Down syndrome can expect to live more than 60 years, depending on the severity of health problems. PreventionThere's no way to prevent Down syndrome. If you're at high risk of having a child with Down syndrome or you already have one child with Down syndrome, you may want to consult a genetic counselor before becoming pregnant. A genetic counselor can help you understand your chances of having a child with Down syndrome. He or she can also explain the prenatal tests that are available and help explain the pros and cons of testing. Which describes the condition in which a child is born with an extra 21st chromosome?Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is 'trisomy. ' Down syndrome is also referred to as Trisomy 21.
What does an extra 21 chromosome do?Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome.
Why is it called trisomy 21?An egg or sperm cell may keep both copies of chromosome number 21, instead of just 1 copy. If this egg or sperm is fertilized, then the baby will have 3 copies of chromosome number 21. This is called trisomy 21.
What is the source of the extra chromosome 21 in an individual with Down syndrome?To date, no behavioral activity of the parents or environmental factor is known to cause Down syndrome. After much research on these cell division errors, researchers know that: In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
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