Down syndrome is a genetic disorder caused when abnormal cell division results in extra genetic material from chromosome 21.
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.
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.
Each 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.
Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.
Children 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.
Human 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.
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.
There are 23 pairs of chromosomes, for a total of 46. Half the chromosomes come from the egg (the mother) and half come from the sperm (the father). This XY chromosome pair includes the X chromosome from the egg and the Y chromosome from the sperm. In Down syndrome, there is an additional copy of chromosome 21, resulting in three copies instead of the normal two copies.
Some parents have a greater risk of having a baby with Down syndrome. Risk factors include:
People 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 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.
There'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.
The American College of Obstetricians and Gynecologists recommends offering the option of screening tests and diagnostic tests for Down syndrome to all pregnant women, regardless of age.
Your health care provider can discuss the types of tests, advantages and disadvantages, benefits and risks, and the meaning of your results. If appropriate, your provider may recommend that you talk to a genetics counselor.
Screening for Down syndrome is offered as a routine part of prenatal care. Although screening tests can only identify your risk of carrying a baby with Down syndrome, they can help you make decisions about more-specific diagnostic tests.
Screening tests include the first trimester combined test and the integrated screening test.
The first trimester combined test, which is done in two steps, includes:
Using your age and the results of the blood test and the ultrasound, your doctor or genetic counselor can estimate your risk of having a baby with Down syndrome.
The integrated screening test is done in two parts during the first and second trimesters of pregnancy. The results are combined to estimate the risk that your baby has Down syndrome.
If your screening test results are positive or worrisome, or you're at high risk of having a baby with Down syndrome, you might consider more testing to confirm the diagnosis. Your health care provider can help you weigh the pros and cons of these tests.
Diagnostic tests that can identify Down syndrome include:
Preimplantation genetic diagnosis is an option for couples undergoing in vitro fertilization who are at increased risk of passing along certain genetic conditions. The embryo is tested for genetic abnormalities before it's implanted in the womb.
After birth, the initial diagnosis of Down syndrome is often based on the baby's appearance. But the features associated with Down syndrome can be found in babies without Down syndrome, so your health care provider will likely order a test called a chromosomal karyotype to confirm diagnosis. Using a sample of blood, this test analyzes your child's chromosomes. If there's an extra chromosome 21 in all or some cells, the diagnosis is Down syndrome.
Early intervention for infants and children with Down syndrome can make a major difference in improving their quality of life. Because each child with Down syndrome is unique, treatment will depend on individual needs. Also, different stages of life may require different services.
If your child has Down syndrome, you'll likely rely on a team of specialists that can provide medical care and help him or her develop skills as fully as possible. Depending on your child's particular needs, your team may include some of these experts:
You'll need to make important decisions about your child's treatment and education. Build a team of health care providers, teachers and therapists you trust. These professionals can help evaluate the resources in your area and explain state and federal programs for children and adults with disabilities.
When you learn your child has Down syndrome, you may experience a range of emotions, including anger, fear, worry and sorrow. You may not know what to expect, and you may worry about your ability to care for a child with a disability. The best antidote for fear and worry is information and support.
Consider these steps to prepare yourself and to care for your child:
Expect a bright future. Most people with Down syndrome live with their families or independently, go to mainstream schools, read and write, participate in the community, and have jobs. People with Down syndrome can live fulfilling lives.