Down syndrome (also called Down’s Syndrome or trisomy 21) is a genetic disorder affecting infants who have a defect in chromosome 21. Instead of the normal two copies of the chromosome, Down Syndrome people have three copies of the chromosome. Thirty years ago, mothers of Down Syndrome babies did not know their child had trisomy 21 until they were born. Today, Down Syndrome can be detected in the fifth month of a pregnancy by amniocentesis, a prenatal screening procedure that tests for chromosomal deformities in the fetus. This ability to detect Down Syndrome early in a pregnancy helps parents adjust to the idea of having a Down Syndrome child and better prepare to take care of a special needs person.
What Causes Down Syndrome?
Down Syndrome affects about one out of every 1000 babies born every year, making it the most common type of chromosome defect in humans. The reason for the syndrome, i.e., three copies of chromosome 21, was discovered in 1959, although the condition was originally described in the 1860s by British physician John Langdon Down.
Normally, each human has two copies of genes on chromosome 21. When a child is born with three copies of genes on chromosome 21, they exhibit signs of having Down Syndrome. Parents of a Down Syndrome child rarely have Down Syndrome themselves and parents who already have one child with the syndrome will have a one percent risk of having another child with trisomy 21.
When the 21st chromosome fails to separate during sperm or egg development, trisomy 21 inevitably occurs, resulting in a Down Syndrome child having 47 normal chromosomes and three copies of chromosome 21. Nearly 90 percent of all cases of trisomy 21 stem from nonseparation of the mother’s chromosomes and eight percent of nonseparation of the father’s chromosomes. Three percent of trisomy 21 cases happen after the sperm and egg have merged. The creation of an extra chromosome results from the overexpression of some of the 310 genes comprising chromosome 21.
Geneticists recently discovered that the neurofibrillary tangles and senile plagues indicating early onset dementia commonly affect Down Syndrome individuals by the age of 35. Resulting from excess amyloid beta peptide in the brain, this condition is one of the primary reasons for the development of Alzheimer’s disease. Although DS people over 30 may not present signs of dementia, they almost always have the beginnings of “plaques and tangles” emerging in their brain indicative of Alzheimer’s.
Symptoms of Down Syndrome
Down Syndrome significantly impairs intelligence (>70 IQ) as well as physical ability. Adults with Down Syndrome generally have the mental capacity of a nine year old, suffer compromised immune systems and experience a variety of other health conditions ranging from heart problems and hypothyroid disorder to chronic eczema and hair loss.
Typical symptoms include:
- Abnormally slanted eyes
- Dental malformations/protruding or overly large tongue
- Stunted growth (average height of five feet for men, four feet, eight inches for women)
- Shortened neck and hands
- Excess skin at the back of the neck
- Decreased muscle tone
- Narrow palate (roof of the mouth)
- Flattened skull
- Strabismus and nearsightedness
- Undescended testicles in boys
- Congenital heart disease
- Irregular or stuttering speech patterns
The majority of Down Syndrome people test at IQ levels between 50 and 70; some may test as low as 30 in some cases and require 24-hour care. Developmental milestones such as crawling, walking and talking are significantly delayed, necessitating the need for physical and speech therapy.
Because Down Syndrome is considered an intellectual disability, they often do as well as expected socially and rarely exhibit behavorial issues unless they have been diagnosed with a co-morbid disorder, such as autism, bipolar disorder or schizophrenia. About 10 percent of children with DS experience epileptic seizures and nearly half of all adults with DS may suffer at least one seizure in their 30s and 40s.
Down Syndrome Facts
The National Down Syndrome Society provides the following facts about the causes of Down Syndrome, types of treatment methods and other information helpful to parents or caregivers of DS individuals.
- One in every 690 children in the United States is born with DS.
- Down Syndrome is found at all social levels and in all races.
- The risk of having a baby with DS increases in women over 35.
- A unique sign of Down’s Syndrome is the presence of one, deep crease across the palm.
- The life expectancy of someone with DS in 1983 was 25; today it is 60.
- Older individuals with DS often suffer from cataracts which should be removed through laser surgery.
- The majority of Down Syndrome cases are not inherited. Instead, it is a random chromosomal abnormality emerging when the reproductive cells unite and begin forming.
- In addition to an amniocentesis, diagnostic tests for determining whether an unborn child has Down Syndrome include chorionic villus sampling (tests placental material) and percutaneous umbilical blood sampling (tests blood found in the umbilical cord).
- People with DS can attend school, support themselves in low-skill jobs and can make certain decisions that affect their lives. Providing a stimulating physical, social and intellectual environment will greatly enhance the ability of those with Down Syndrome to lead independent and productive lives.
About 15 percent of Down Syndrome babies die before they reach one year of age. Reasons for shortened life expectancy include severe heart disorders, a condition called esophageal atresia (failure of the esophagus to connect to the stomach), transesophageal fistula, where the esophagus has somehow connected itself to the lungs and duodenal atresia, or congenital blockages in the small bowel.
Hirschsprung disease is often diagnosed in DS babies as well as babies without DS. It is a birth defect that impairs functioning of large intestine nerve cells responsible for pushing waste and food through the large intestine. Symptoms of Hirschsprung’s disease include swollen stomach, infection, pain, vomiting and failure to thrive. If not detected and treated early, Hirschsprung’s could be life-threatening, especially to DS babies who are already vulnerable to a variety of health problems.
Down Syndrome children over the age of one year tend to experience the following conditions that may lead to a shorter than normal life expectancy:
- Worsening of congenital heart disease
- Undetected infections/sepsis
Life expectancy for people with Down Syndrome is also associated with IQ level. Those having mild to moderate deficits in intelligence (45 to 70) often live 20 or more years longer than those with more severe cognitive and/or physical impairments.
Caring for Down Syndrome Children
Breast milk is not only easier for DS babies to digest but may also help reduce incidences of atopic dermatitis, respiratory and ear infections. Breast feeding also promotes oral motor development and enhances the bond between infant and mother.
If breast feeding is not viable due to a DS baby suffering a heart defect or hypotonia (poor muscle control), mothers can express their milk manually and bottle-feed their baby. When breast-fed, DS babies do not gain sufficient weight in the first few months of life, pediatricians will prescribe a high-calorie, formula supplement in addition to breast milk,
The diet of a DS baby should progress normally, with the introduction of infant-specific foods taking place at seven to eight months. If eruption of teeth is significantly delayed, parents may need to wait until the child is older before introducing solid foods.
Down Syndrome children especially need to receive immunizations on schedule because of their susceptibility to ear, nose and throat infections. All infants, toddlers and school-age DS children should get their diptheria, tetanus, pertussis, polio, hepatitis B and MMR vaccinations at the appropriate ages. Pediatricians specializing in Down Syndrome health care also recommend yearly flu vaccinations to help reduce ear infections.
The NADS offers an exhaustive resource for parents or caregivers of Down Syndrome individuals that can help them find the assistance or information they need to improve all aspects of their lives and the overall quality of life of their child. AT the NADS website, you will find an e-booklet about understanding the implications of a Down Syndrome diagnosis; how aging affects those with it; where to find online support organizations; where to purchase educational DVDs and legal information regarding the ability of DS people to receive government assistance and/or disability social security payments.