Down syndrome (DS) is a condition caused by a chromosome abnormality. DS was named after English doctor John Langdon Down, who brought recognition of the defect in 1866 with his research. Down syndrome leads to both physical disabilities and intellectual disabilities; however many people learn to live happy and productive lives.
Definition & Facts
Down syndrome is the most common chromosomal condition. Three types include trisomy 21, mosaic Down syndrome, and translocation Down syndrome. Most people carry a total of 46 chromosomes. Both the mother and father provide 23 each. But those with Down syndrome have an extra one totaling 47, which then changes the development of the body and the brain.
Physical delays and intellectual delays can range from moderate to severe. For every 691 births, one child is born will Down syndrome. Currently over 400,000 people in the United States have the condition. Some with DS will require life-long medical care while others can learn to live a fairly independent life.
Symptoms & Complaints
- Health problems – such as heart defects, respiratory infections, vision problems, hearing problems, and dental problems. Also childhood leukemia, Alzheimer’s disease, hypothyroidism or celiac disease have been documented as well.
- Mental disabilities – range from mild to moderate cognitive deficits, behavior problems such as ADHD or autism and depression.
- Distinct body features – may include shorter than average stature, short and stocky neck, arms and legs or hypotonia (low muscle tone) which will make the stomach protrude out.
- Distinct facial features – may include upward slanted eyes, with or without spots on the iris. Also a flattened nasal bridge between the eyes and nose, abnormally shaped mouth and a protruding tongue, small ears or crooked teeth.
Doctor’s don’t know why cells divide abnormally causing Down syndrome. They do know abnormal cell division occurs in the early embryo development stage, deriving from either the male or the female. Trisomy 21, the most common form of DS occurs during egg fertilization. Either the sperm or egg passes down three, instead of the normal two, chromosome 21. During cell division, the extra chromosome repeats in every cell.
Mosaic is similar to Trisomy 21 but extremely rare. In this kind of DS, the extra chromosome 21 is not in every cell and the abnormality occurs during and/or after fertilization. Translocation refers to a portion of chromosome 21 attaching to another chromosome, either at or before conception. The resulting child may be a genetic carrier but not exhibit any Down syndrome symptoms. Risk factors that may also contribute include:
- Conceiving later in life – Women have a significantly higher chance of having a child with Down syndrome the older they are during conception. At 30 years of age chances are 1 in 1,000 of conceiving a DS baby. By age 35 chances are 1 in 400 and by age 40 they become 1 in 100.
- Translocation type – Research shows that translocation Down syndrome may be genetically inherited by family members. Those with a family history or parents who have had a previous pregnancy resulting in a child with Down syndrome are at a greater risk.
Diagnosis & Tests
Doctors can determine if a baby has Down syndrome through tests both during pregnancy and after the birth. The American College of Obstetrics and Gynecology (ACOG) recommends all women be given the option of testing.
During pregnancy, screening tests may be undertaken that, while highly accurate and non-invasive, are not a definitive diagnosis of Down syndrome. A doctor will look for markers in the blood or common fetal traits during a sonogram to estimate the chances of the baby having Down syndrome. A positive result may indicate the likelihood of Down syndrome. The doctor will then recommend diagnostic testing to confirm the diagnosis.
A chorionic villus sampling (CVS) or amniocentesis is usually performed during the first or second trimester of pregnancy. With CVS a sample of the placenta is taken, and with amniocentesis a small amount of amniotic fluid is removed. Both tests carry a very small risk of inducing miscarriage or premature birth. The benefits outweigh the risk, as these tests are 100% accurate.
After birth, doctors may observe the physical characteristics of the child. To diagnose Down syndrome a doctor will look for low muscle tone, upward slanted eyes, a deep crease along the palm of the hand or a flattened facial profile. While some babies without Down syndrome can have these features, an analysis of the chromosomes will also be performed.
Chromosomal analysis may also be performed. Genetic testing such as Karyotype testing or fluorescence in situ hybridization (FISH) studies determine the chromosomal make-up of the baby and will confirm the diagnosis.
Treatment & Therapy
Maintaining regular doctor visits will increase the child’s chances of staying healthy and mastering skills. The doctor will monitor or manage the many diseases or health concerns that can occur to those with Down syndrome. A doctor will also advise on stages of development and types of support that may be needed, such as:
- Emotional support for parents and caring for a Down syndrome newborn
- Therapies an infant may need for physical and verbal development
- Teaching the child healthy behaviors
- Educational services available under the Individuals with Disabilities Education Act (IDEA)
- Supporting the growing young adult through puberty and adolescence
While it may take a little longer than normal, a Down syndrome child can learn to walk and talk and develop good social skills. A teen or adult can learn useful educational skills, training to get a job and perhaps how to live independently.
Prevention & Prophylaxis