Down syndrome (DS) is a condition in which the person has an extra chromosome. Check out this list of 10 facts to learn more about Down syndrome.
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What is Down Syndrome?
DS is the most common chromosomal condition diagnosed in the United States.
People with DS are born with an extra copy of chromosome 21, which gives them a total of 47 chromosomes. Nobody knows for sure why it happens, but we know that the extra chromosome is usually present in every one of the trillions of cells in their bodies. For that reason, DS is often referred to as “trisomy 21,” meaning three copies of chromosome 21.
Down syndrome is an autosomal recessive condition, meaning it is passed down by the mother and/or father but is not shown in the parents.
Facts About Down Syndrome
Down syndrome occurs in approximately one in 700 births.
DS is the most common chromosomal condition diagnosed in the United States. Around 6,000 babies — or one in 700 — are born with DS every year.
There are three types of Down syndrome.
- Trisomy 21: In 95% of cases, babies born with DS have one extra copy of chromosome 21, giving them three total.
- Translocation: In 3% of cases, a partial or whole chromosome is attached (translocated) to a different chromosome rather than being a separate chromosome 21.
- Mosaic: In about 2% of cases, some of the person’s cells have three copies of chromosome 21, but other cells have two copies. Children with mosaic Down syndrome have fewer characteristics of Down syndrome.
Down syndrome has been depicted in historical paintings as far back as the 15th and 16th centuries.
Down syndrome is not new — in fact, the first evidence of its existence dates back 2,500 years. The facial features of DS are found in some ancient pottery and paintings. The syndrome is named after John Langdon Down, an English doctor who published a clinical description in 1866.
Prenatal screening for Down syndrome is available.
Doctors use maternal blood samples and ultrasounds to detect DS in the early stages of pregnancy. Since the condition is more likely in pregnant women age 35 and older, screening tests are commonly recommended for that age group. If a screening test shows signs of possible Down syndrome, more invasive prenatal diagnostic tools — such as amniocentesis and chorionic villus sampling — can diagnose or confirm DS.
Babies also can be diagnosed with DS after birth. A health care provider performs a physical exam that looks for common physical characteristics of the condition. To confirm diagnosis, a sample of the baby’s blood will be sent to a lab for testing.
Other health problems can occur with Down syndrome.
While Down syndrome affects every person differently, people with DS are at a higher risk for certain health issues, such as:
- Hearing problems: Conductive hearing loss is the most common, which can be caused by an inner ear infection and be treated with ear tubes. Sensorineural Hearing Loss is less common and usually permanent.
- Eye issues: Such as cataracts and other vision problems.
- Ear infections: Upper repertory tract infections, which predisposes chronic ear infections are more likely in children with DS. The facial anatomy of DS also predisposes chronic ear disease.
- Congenital heart defects: Three of the most common heart conditions seen in children with DS are atrioventricular septal defect, patent ductus arteriosus, and tetralogy of Fallot.
In adulthood, potential health problems include:
- Sleep apnea: People with DS are more likely to have sleep apnea due to their facial structure, narrow airways to the nose and throat, and low muscle tone.
- Thyroid disease: Between 39-61% of all adults with DS are thought to have thyroid disease, the most common being hypothyroidism which can lead to slow thinking, irritability, changing weight, and tiredness.
- Earlier onset of Alzheimer’s disease: According to the National Down Syndrome Society, around 30% of adults with DS 50+ have Alzheimer’s disease.
While every person with Down syndrome is different, some characteristics are common.
People with Down syndrome have similar physical features and characteristics because of the extra genetic material that affects growth of the skull, bone, cartilage, and connective tissue in the head and face. Some of these characteristics include:
- Delays in development.
- Hypotonia (low muscle tone).
- Almond-shaped eyes.
- A flat nasal bridge.
- A short neck.
- Small ears.
- A small chin.
- Small feet and hands with short fingers.
- Shorter height.
There are health care guidelines in place to guide primary care providers to effectively care for people with DS.
The American Academy of Pediatrics has developed health care guidelines to help health care professionals and families provide proper preventive care. By following these guidelines, many medical conditions can be treated early or even prevented. Health care guidelines for adults with Down syndrome will be available soon.
The family and personal impact of having a child with Down syndrome is overwhelmingly positive.
Studies on the impact of DS on families show that 96% of parents did not regret having a child with Down syndrome, while 96% of siblings wouldn’t trade their sibling with Down syndrome for a sibling without it. And 99% of people with Down syndrome say that they are happy with their lives.
The life expectancy for people living with Down syndrome continues to increase.
In the 1960s, the average down syndrome life expectancy for children was age 10. Today, that number is age 60 and higher, thanks to new therapies and medical care that improve quality of life for people with DS.
People with DS are living higher quality lives than ever before, thanks to appropriate medical care, supportive therapies, and educational options.
People with DS benefit from medical care options that were not available years ago. From speech therapy, physical therapy, and occupational therapy to inclusive educational environments, people with DS have more opportunities than ever before.
Thanks to proper medical support and care, teenagers with Down syndrome are now more likely to:
- Have their own bedroom.
- Dress and undress independently.
- Bathe and dry themselves.
- Eat and drink independently, including some meal preparation.
Adults with Down syndrome have also been able to:
- Live independently.
- Get married.
- Maintain a job.
- Drive a car.
Some adults with DS have broken barriers and achieved many milestones never thought possible before, such as:
- Owning and operating their own restaurant.
- Modeling professionally.
- Acting in movies.
- Receiving a university degree.
- Playing an instrument at Carnegie Hall.
- Designing a line for London Fashion Week.
Editor's Note: This article was originally published on , and was last reviewed on .
1Having a son or daughter with Down Syndrome: Perspectives from mothers and fathers. Skotko BG, Levine SP, Goldstein R.Am J Med Genet A. 2011 Oct;155A(10):2335-47. doi: 10.1002/ajmg.a.34293. Epub 2011 Sep 13.PMID: 21915989
2Having a brother or sister with Down syndrome: Perspectives from siblings. Skotko BG, Levine SP, Goldstein R.Am J Med Genet A. 2011 Oct;155A(10):2348-59. doi: 10.1002/ajmg.a.34228. Epub 2011 Sep 9.PMID: 21910244
3Self-perceptions from people with Down syndrome. Skotko BG, Levine SP, Goldstein R.Am J Med Genet A. 2011 Oct;155A(10):2360-9. doi: 10.1002/ajmg.a.34235. Epub 2011 Sep 9.PMID: 21910246
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