DOWN SYNDROME (TRISOMY 21)

What is Down syndrome?  Down syndrome (DS) is a chromosome disorder resulting in growth retardation, mental retardation, characteristic facial features, and specific birth defects.

Why is it called Down syndrome?   DS is named for Dr. John Langdon Down, an English physician who first described it in 1866.

How common is DS?   For all races and ethnic backgrounds, about 1 in every 700-800 children is born with DS. The chance to have a baby with this condition increases with maternal age.

How is DS Recognized?   At birth, infants with DS are often identified by:

• a round, flattened facial profile
• extra skin folds at the corner of the eyes
• low muscle tone
• extra skin around the neck
• short 5th fingers
• a single crease across the palm

An analysis of the baby's chromosomes from a blood sample is used to confirm the diagnosis.

What Are the Health Concerns with DS?

• About 45-50% of DS babies have some type of heart defect.
• About 12-15% have some type of  gastrointestinal defect.

Children with DS:

• are more susceptible to infections than other children
• have a 60-70% risk to have vision problems
• have a 60-80% chance to have some degree of hearing loss
• are more likely to have thyroid disorders than other children 

Mental retardation varies greatly in children with DS. IQ's may range from the 20s to about 85. Most children fall into the moderate range, and eventually attain the skills of a 6-8 year old. In infancy, delays may not be obvious, with many babies reaching early milestones approximately on time.  However, developmental delays become more apparent as they get older.

What Causes DS?  Normally, there are a total of 46 chromosomes in every cell of the body. These are found in 23 pairs, and are numbered from 1-22 according to their size and staining pattern in the laboratory. Most individuals with DS have 47 chromosomes, with an extra copy of chromosome 21 (hence the name trisomy 21). For more information about the various chromosome rearrangements which may be involved in trisomy 21, including photographs of the chromosomes, click here .

Can DS Be Diagnosed Prenatally?  DS is diagnosed prenatally by chromosome analysis of tissue from chorionic villus sampling or amniotic fluid cells from amniocentesis. 

Is Treatment Available for DS?  Currently, there is no treatment or cure for DS. Corrective surgery is available for congenital heart and gastrointestinal defects. Early intervention and school programs seem to be of benefit in helping children with DS reach their full potential. Controversial treatments for Down syndrome include vitamin supplements and plastic surgery.

Where can I get more information and support?   Speaking to others in a similar situation helps many families and individuals with Down syndrome. Support organizations can provide general information, as well information about the latest research and treatments. Your physician or genetic counselor can help you contact local support groups. There are also many internet resources available.  The National Down Syndrome Society is an excellent place to start. Maryland residents may wish to start with The Chesapeake Down Syndrome Parent Group, Inc .