Individuals with Down syndrome in developed parts of the world are becoming increasingly integrated into society and community organizations, such as school, health care systems, work forces, and social and recreational activities. That cannot be said of developing regions faced with the stigma and myths spread about individuals with Down syndrome and their relatives.
Individuals with Down syndrome possess varying degrees of cognitive delays, from very mild to severe.
Due to advances in medical technology, individuals with Down syndrome are living longer than ever before. In 1910, children with Down syndrome were expected to survive to age nine. With the discovery of antibiotics, the average survival age increased to 19 or 20. Now, with recent advancements in clinical treatment, most particularly corrective heart surgeries, as many as 80% of adults with Down syndrome reach age 60, and many live even longer.
Down syndrome is one of the most common chromosome abnormalities in humans. It occurs in about one per 1000 babies born each year.
What is Down Syndrome?
Down syndrome (DS or DNS) also known as Down’s syndrome is a genetic condition. It is not an illness or a disease. It is a set of physical and mental traits caused by a gene problem that happens before birth. It is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.
It is typically associated with physical growth delays, characteristic facial features. Children who have Down syndrome tend to have certain features, such as a flat face and a short neck. They also have some degree of intellectual disability. This varies from person to person. But in most cases it is mild to moderate. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental ability of an 8- or 9-year-old child, but this can vary widely.
The parents of the affected individual are typically genetically normal. The extra chromosome occurs by chance. The possibility increases from less than 0.1% in 20-year-old mothers to 3% in those age 45. There is no known behavioural activity or environmental factor that changes the possibility.
Down syndrome is a lifelong condition. But with care and support, children who have Down syndrome can grow up to have healthy, happy, productive lives.
In 2013, Down syndrome was present in 8.5 million individuals and resulted in 36,000 deaths down from 43,000 deaths in 1990. It is named after John Langdon Down, the British doctor who fully described the syndrome in 1866. Some aspects of the condition were described earlier by Jean-Étienne Dominique Esquirol in 1838 and Édouard Séguin in 1844. In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.
How Down Syndrome Affects Kids
Kids with Down syndrome tend to share certain physical features such as a flat facial profile, an upward slant to the eyes, small ears, and a protruding tongue.
Low muscle tone (called hypotonia) is also characteristic of children with DS, and babies in particular may seem especially "floppy." Though this can and often does improve over time, most children with DS typically reach developmental milestones — like sitting up, crawling, and walking — later than other kids.
At birth, kids with DS are usually of average size, but they tend to grow at a slower rate and remain smaller than their peers. For infants, low muscle tone may contribute to sucking and feeding problems, as well as constipation and other digestive issues. Toddlers and older kids may have delays in speech and self-care skills like feeding, dressing, and toilet teaching.
Down syndrome affects kids' ability to learn in different ways, but most have mild to moderate intellectual impairment. Kids with DS can and do learn, and are capable of developing skills throughout their lives. They simply reach goals at a different pace — which is why it's important not to compare a child with DS against typically developing siblings or even other children with the condition.
Even though people with Down syndrome might act and look similar, each person has different abilities. They are always slower to speak than other children.
Some common physical features of Down syndrome include:
A flattened face, especially the bridge of the nose
Almond-shaped eyes that slant up
A short neck
A tongue that tends to stick out of the mouth
Tiny white spots on the iris (colored part) of the eye
Small hands and feet
A single line across the palm of the hand (palmar crease)
Small pinky fingers that sometimes curve toward the thumb
Poor muscle tone or loose joints
Shorter in height as children and adults
Kids with DS have a wide range of abilities, and there's no way to tell at birth what they will be capable of as they grow up.
Medical Problems Associated With DS
While some kids with DS have no significant health problems, others may experience a host of medical issues that require extra care. For example, almost half of all children born with DS will have a congenital heart defect.
Kids with Down syndrome are also at an increased risk of developing pulmonary hypertension, a serious condition that can lead to irreversible damage to the lungs. All infants with Down syndrome should be evaluated by a pediatric cardiologist.
Approximately half of all kids with DS also have problems with hearing and vision. Hearing loss can be related to fluid buildup in the inner ear or to structural problems of the ear itself. Vision problems commonly include strabismus (cross-eyed), near- or farsightedness, and an increased risk of cataracts.
Regular evaluations by an otolaryngologist (ear, nose, and throat doctor), audiologist, and an ophthalmologist are necessary to detect and correct any problems before they affect language and learning skills.
Other medical conditions that may happen more frequently in kids with DS include thyroid problems, stomach and intestinal problems, seizure disorders, breathing problems, including sleep apnoea and asthma, obesity, an increased chance of infections, and a higher risk of childhood leukemia. People with Down syndrome sometimes have an unstable upper spine and should be evaluated by a doctor before participating in physical activities. Fortunately, many of these conditions are treatable.
Today, many kids with Down syndrome go to school and enjoy many of the same activities as other kids their age. A few go on to college. Many transition to semi-independent living. Still others continue to live at home but are able to hold jobs, thus finding their own success in the community.
How is Down Syndrome Diagnosed?
Your doctor may suggest that you have tests during pregnancy to find out if your baby has Down syndrome. You may decide to have:
Screening tests, such as an ultrasound or a blood test during your first or second trimester. These can help show if the developing baby (fetus) is at risk for Down syndrome. But these tests sometimes give false-positive or false-negative results.
Diagnostic tests, such as chorionic villus sampling or amniocentesis. These can show if a baby has Down syndrome. You may want to have these tests if you have abnormal results from a screening test or if you are worried about Down syndrome.
Sometimes a baby is diagnosed after birth. A doctor may have a good idea that a baby has Down syndrome based on the way the baby looks and the results of a physical exam. To make sure, the baby's blood will be tested. It may take 2 to 3 weeks to get the test results.
Are There Different Types Of Down Syndrome?
Yes there are. Three types of Down syndrome exist, namely: trisomy 21 (nondisjunction), translocation and mosaicism.
Trisomy 21 (Nondisjunction)
Down syndrome is usually caused by an error in cell division called "nondisjunction." Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This type of Down syndrome, which accounts for 95% of cases, is called trisomy 21.
Mosaicism (or mosaic Down syndrome) is diagnosed when there is a mixture of two types of cells, some containing the usual 46 chromosomes and some containing 47. Those cells with 47 chromosomes contain an extra chromosome 21.
Mosaicism is the least common form of Down syndrome and accounts for only about 1% of all cases of Down syndrome. Research has indicated that individuals with mosaic Down syndrome may have fewer characteristics of Down syndrome than those with other types of Down syndrome. However, broad generalizations are not possible due to the wide range of abilities people with Down syndrome possess.
In translocation, which accounts for about 4% of cases of Down syndrome, the total number of chromosomes in the cells remains 46; however, an additional full or partial copy of chromosome 21 attaches to another chromosome, usually chromosome 14. The presence of the extra full or partial chromosome 21 causes the characteristics of Down syndrome.
What Causes Down Syndrome?
Regardless of the type of Down syndrome a person may have, all people with Down syndrome have an extra, critical portion of chromosome 21 present in all or some of their cells. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome.
Down syndrome is caused by having three copies of the genes on chromosome 21, rather than the usual two. The parents of the affected individual are typically genetically normal.
In every cell in the human body there is a nucleus, where genetic material is stored in genes. Genes carry the codes responsible for all of our inherited traits and are grouped along rod-like structures called chromosomes. Typically, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Normally, a person has 46 chromosomes. But most people with Down syndrome have 47 chromosomes. Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21.
This additional genetic material changes the way the brain and body develop thereby, altering the course of development and causes the characteristics associated with Down syndrome. A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the centre of the palm.
The cause of the extra full or partial chromosome is still unknown. Maternal age is the only factor that has been linked to an increased chance of having a baby with Down syndrome resulting from nondisjunction or mosaicism. Scientists do know that women age 35 and older have a significantly higher risk of having a child with the condition. At age 30, for example, a woman has about a 1 in 1,000 chance of conceiving a child with DS. Those odds increase to about 1 in 400 by age 35. By 40 the risk rises to about 1 in 100.
There is no definitive scientific research that indicates that Down syndrome is caused by environmental factors or the parents' activities before or during pregnancy.
The additional partial or full copy of the 21st chromosome which causes Down syndrome can originate from either the father or the mother.
Is Down Syndrome Hereditary?
All 3 types of Down syndrome are genetic conditions (relating to the genes), but only 1% of all cases of Down syndrome have a hereditary component (passed from parent to child through the genes). Heredity is not a factor in trisomy 21 (nondisjunction) and mosaicism. However, in one third of cases of Down syndrome resulting from translocation there is a hereditary compontent - accounting for about 1% of all cases of Down syndrome.
The age of the mother does not seem to be linked to the risk of translocation. Most cases are sporadic - chance - events. However, in about one third of cases, one parent is a carrier of a translocated chromosome.
What is the Likelihood of Having a Second Child with Down Syndrome?
Once a woman has given birth to a baby with trisomy 21 (nondisjunction) or translocation, it is estimated that her chances of having another baby with trisomy 21 is 1 in 100 up until age 40.
The risk of recurrence of translocation is about 3% if the father is the carrier and 10-15% if the mother is the carrier. Genetic counselling can determine the origin of translocation.
What Kind of Care Will a Child with Down Syndrome Need?
Starting soon after birth, a baby with Down syndrome will be tested for health problems, such as eye, ear, or thyroid problems. The sooner these problems are found, the better they can be managed. Regular doctor visits can help your child stay in good health.
Your doctor will make a treatment plan that meets your growing child's needs. For example, most children with Down syndrome need speech therapy and physical therapy. Teens and adults with Down syndrome may need occupational therapy to learn job skills and learn how to live on their own. Counselling may help with social skills and emotional issues.
Many professionals will help you and your child through life. But you are vital to your child's success. To help your child:
Learn all you can about Down syndrome. This can help you know what to expect and how you can help your child.
Find out what type of financial help you can get by contacting your state's Department of Developmental Disabilities.
Check into resources in your area. For example, many states provide free early-intervention programs for children with Down syndrome up to age 3 to help them get off to a good start.
Look into school options for your child.
Raising a child with Down syndrome has both challenges and rewards. Remember to take time for yourself. And ask for help when you need it. Talking to other parents who are raising children with Down syndrome can be a big help. Ask your doctor or hospital about parent support groups.
If you've had a baby with Down syndrome and are planning another pregnancy, you may want to talk to your doctor about genetic counselling.