Down syndrome is caused by an extra copy of chromosome 21, and its occurence is random 95 percent of the time. The condition can be detected during pregnancy, and intervention during infancy can greatly improve outcomes for children with Down syndrome. Learn more about this condition, which affects 350,000 Americans, in the following St. Louis Post-Dispatch article by WUSM pediatrician Kathy Grange.
Early assistance helps kids with Down syndrome
(Republished with permission from the St. Louis Post-Dispatch. This article originally ran in the Health & Fitness section on Monday, February 7, 2005)
By Dr. Kathy Grange
Down syndrome is a common genetic condition associated with developmental disabilities and birth defects. It occurs in about 1 in 800 newborns and affects all racial and ethnic groups.
More than 350,000 people with Down syndrome live in the United States, and about 5,000 babies with Down syndrome are born each year. Here are a few questions and answers to explain the condition:
Q: What causes Down syndrome?
A: It is caused by an abnormality of the chromosomes, the structures inside each cell of the body that contain all of our genetic information. Humans usually have 23 pairs of chromosomes, for a total of 46, but people with Down syndrome have an extra copy of chromosome No. 21.
Q: How is it diagnosed?
A: It is usually suspected soon after birth, because of characteristic physical features including differences in the shape of the head, flat profile of the face, upslanting eyes, small ears and minor changes of the hands and feet, in association with low muscle tone. A blood test is done to examine the chromosomes. Sometimes Down syndrome is diagnosed during pregnancy after an abnormal maternal blood screening test or abnormal fetal ultrasound.
Ninety-five percent of the time, Down syndrome occurs by chance in a family. About 2 percent to 4 percent of cases are caused by a chromosome abnormality called a translocation, which may have been inherited from one of the parents. About 1 percent of cases of Down syndrome are due to mosaicism, which means that some cells of the body have an extra copy of chromosome 21, while other cells have normal chromosomes. Mosaic Down syndrome may be milder.
Q: How does Down syndrome occur?
A: During cell division of the egg or sperm cell, the chromosomes do not separate properly, resulting in an extra chromosome No. 21. The underlying cause for the failure to separate is poorly understood.
Older mothers have a higher risk of having a child with Down syndrome, so aging of the egg cells likely plays a role. However, the extra chromosome No. 21 can come from either the father or the mother.
Eighty percent of babies with Down syndrome are born to women under 35, because the women in this age group are giving birth to more babies overall. Mothers at age 20 have a 1 in 1,400 chance of having a baby with Down syndrome; the risk rises to 1 in 350 at age 35, and 1 in 100 at age 40.
Q: What are the developmental concerns in people with Down syndrome?
A: People with Down syndrome typically have developmental delays, but their abilities can vary widely. A few function in the lower range of normal intelligence, but most have mild to moderate mental retardation.
We now realize that developmental intervention beginning early in infancy, including physical, occupational and speech therapy, can greatly improve the long-term outcome for people with Down syndrome. Special-education programs are extremely important in helping people with Down syndrome achieve their fullest potential.
Many children with Down syndrome can be in regular classrooms, with differing levels of educational support. Most graduate from high school, and some may enroll in vocational programs.
Often, people with Down syndrome can live semi-independently in apartments or group homes; others may live with parents or siblings. Many adults have jobs in the community or in sheltered workshops.
Q: What are the health concerns in people with Down syndrome?
A: About 50 percent of babies with Down syndrome have a congenital heart defect. All newborns with Down syndrome need to have an echocardiogram (an ultrasound of the heart) and may need to be evaluated by a pediatric cardiologist.
About 10 percent of infants have a birth defect involving the gastrointestinal tract; these defects can include a blockage in the upper intestine or colon. Fortunately, almost all of these defects can be detected early and repaired surgically.
Every child with Down syndrome needs the same medical care as other children, including regular check-ups and vaccinations. However, there are some additional medical concerns that may require special attention:
Many children with Down syndrome have narrow ear passages and have recurrent ear infections, which can lead to hearing loss.
Eye problems also are common; most people with Down syndrome will need glasses.
About 15 percent of people with Down syndrome develop hypothyroidism (low thyroid gland function).
With proper medical care, the life expectancy for people with Down syndrome has increased; many live into their 50s and 60s, and sometimes longer.
Q: Where can families find help?
A: Go online to the National Down Syndrome Society (www.ndss.org) and the National Down Syndrome Congress (www.ndsccenter.org). Locally, the Down Syndrome Association of Greater St. Louis (www.stlouisdsa.org, 314-961-2504) provides support and advocacy for families.
The new Down Syndrome Center at St. Louis Children’s Hospital offers comprehensive medical care for those with Down syndrome from infancy to age 21. For more information, call 314-454-6093, go online to stlouischildrens.org, or e-mail downsyndromecenter@kids.wustl.edu.
With a supportive family, appropriate medical care and special educational services, people with Down syndrome can lead full and healthy lives.
Dr. Kathy Grange is the division director of the Down Syndrome Center at St. Louis Children’s Hospital and an associate professor of pediatrics at Washington University School of Medicine.
Copyright 20045 St. Louis Post-Dispatch, Inc.