Down Syndrome
Down syndrome (also called Trisomy 21) is a genetic condition that occurs when a person is born with an extra copy of chromosome 21. This additional genetic material affects development in different ways, often leading to characteristic physical features, slower growth, and mild to moderate intellectual disability.
While there is no cure for Down syndrome, early support, quality education, and proper medical care can greatly enhance a person’s quality of life.
Many children with Down syndrome thrive in mainstream classrooms, some require more specialized support, and some go on to finish high school or even pursue further education.
In adulthood, individuals with Down syndrome often contribute meaningfully through various forms of work, sometimes with additional support in structured environments.
What Are You Looking For?
1. About Down Syndrome
i. Signs and Symptoms
ii. Health Problems
iii. Screening
iv. Diagnosis
v. Management
vi. Prognosis
vii. Epidemiology
viii. Ethics
2. Other Intellectual Disorders
– Learning Disabilities
– Asperger Syndrome
About Down Syndrome
The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age 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 random chance. There is no known behavior or environmental factor that changes the risk. Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing, or after birth by direct observation and genetic testing. Since the introduction of screening, pregnancies with the diagnosis are often terminated. Regular screening for health problems common in Down syndrome is recommended throughout the person’s life.
There is no cure for Down syndrome. Education and proper care have been shown to improve quality of life. Some children with Down syndrome are educated in typical school classes, while others require more specialized education. Some individuals with Down syndrome graduate from high school and a few attend post-secondary education. In adulthood, about few do paid work in some capacity with many requiring a sheltered work environment. Support in financial and legal matters is often needed. Life expectancy is around 50 to 60 years in the developed world with proper health care.
Down syndrome is one of the most common chromosome abnormalities in humans. It occurrs in about one per 1000 babies born each year. In 2013, Down syndrome was present in 8.5 million individuals and resulted in 36,000 deaths down from 43,000 deaths in 1990. The genetic cause of Down syndrome is an extra copy of chromosome 21.
i. Signs and Symptoms
Those with Down syndrome nearly always have physical and intellectual disabilities.
As adults, their mental abilities are typically similar to those of an 8- or 9-year-old.
They also typically have poor immune function and generally reach developmental milestones at a later age. They have an increased risk of a number of other health problems, including congenital heart disease, epilepsy, leukemia, thyroid diseases, and mental disorders, among others.
Health Problems

Heart
The rate of congenital heart disease in newborns with Down syndrome is around 40%. Of those with heart disease, about 80% have an atrioventricular septal defect or ventricular septal defect with the first being more common.
Mitral valve problems become common as people age, even in those without heart problems at birth.
Other problems that may occur include tetralogy of Fallot and patent ductus arteriosus. People with Down syndrome have a lower risk of hardening of the arteries
Cancer
Although the overall risk of cancer is not changed, the risk of leukemia and testicular cancer is increased and risk of solid cancers is reduced.
Solid cancers are believed to be less common due to increased expression of tumor suppressor genes present on chromosome 21.
Cancers of the blood are 10 to 15 times more common in children with Down syndrome. In particular, acute lymphoblastic leukemia is 20 times more common and the megakaryoblastic form of acute myelogenous leukemia is 500 times more common. Transient myeloproliferative disease, a disorder of blood cell production that does not occur outside of Down syndrome, affects 3–10% of infants. The disorder is typically not serious but occasionally can be.
It resolves most times without treatment; however, in those who have had it, a 20 to 30% risk of developing acute lymphoblastic leukemia at a later time exists.
Genetics
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. Those who have one child with Down syndrome have about a 1% risk of having a second child with the syndrome, if both parents are found to have normal karyotypes.
The extra chromosome content can arise through several different ways. The most common cause (about 92–95% of cases) is a complete extra copy of chromosome 21, resulting in trisomy 21. In 1.0 to 2.5% of cases, some of the cells in the body are normal and others have trisomy 21, known as mosaic Down syndrome. The other common mechanisms that can give rise to Down syndrome include: a Robertsonian translocation, isochromosome, or ring chromosome. These contain additional material from chromosome 21 and occur in about 2.5% of cases. An isochromosome results when the two long arms of a chromosome separate together rather than the long and short arm separating together during egg or sperm development.
Screening
Guidelines recommend screening for Down syndrome to be offered to all pregnant women, regardless of age.
A number of tests are used, with varying levels of accuracy. They are typically used in combination to increase the detection rate.
None can be definitive, thus if screening is positive, either amniocentesis or chorionic villous sampling is required to confirm the diagnosis.
Screening in both the first and second trimesters is better than just screening in the first trimester.
The different screening techniques in use are able to pick up 90 to 95% of cases with a false-positive rate of 2 to 5%.
Diagnosis
Before birth
When screening tests predict a high risk of Down syndrome, a more invasive diagnostic test (amniocentesis or chorionic villus sampling) is needed to confirm the diagnosis.
If Down syndrome occurs in one in 500 pregnancies and the test used has a 5% false-positive rate, this means, of 28 women who test positive on screening, only one will have Down syndrome confirmed. If the screening test has a 2% false-positive rate, this means one of 10 who test positive on screening have a fetus with DS. Amniocentesis and chorionic villus sampling are more reliable tests, but they increase the risk of miscarriage between 0.5 and 1%.
The risk of limb problems is increased in the offspring due to the procedure. The risk from the procedure is greater the earlier it is performed, thus amniocentesis is not recommended before 15 weeks gestational age and chorionic villus sampling before 10 weeks gestational age.
After birth
The diagnosis can often be suspected based on the child’s physical appearance at birth.
An analysis of the child’s chromosomes is needed to confirm the diagnosis, and to determine if a translocation is present, as this may help determine the risk of the child’s parents having further children with Down syndrome.
Parents generally wish to know the possible diagnosis once it is suspected and do not wish pity.
The National Down Syndrome Society have developed information regarding the positive aspects of life with Down Syndrome.

Management
Efforts such as early childhood intervention, screening for common problems, medical treatment where indicated, a good family environment, and work-related training can improve the development of children with Down syndrome. Education and proper care can improve quality of life.
Raising a child with Down syndrome is more work for parents than raising an unaffected child. Typical childhood vaccinations are recommended.
Prognosis
Children with Down syndrome sometimes attend regular school and graduate from high school; however, most do not.
Many learn to read and write and some are able to do paid work. Many are able to live semi-independently, but they often require help with financial, medical, and legal matters. Those with mosaic Down syndrome usually have better outcomes.
Individuals with Down syndrome have a higher risk of early death than the general population. This is most often from heart problems or infections.
Following improved medical care, particularly for heart and gastrointestinal problems, the life expectancy has increased to 50 to 60 years in the developed world in the 2000s.
Currently between 4 and 12% die in the first year of life. The probability of long-term survival is partly determined by the presence of heart problems. In those with congenital heart problems 60% survive to 10 years and 50% survive to 30 years of age.
In those without heart problems 85% survive to 10 years and 80% survive to 30 years of age. About 10% live to 70 years of age.
Epidemiology
The risk of having a Down syndrome pregnancy in relation to a mother’s age. Globally, as of 2010, Down syndrome occurs in about 1 per 1000 births and results in about 17,000 deaths. More children are born with Down syndrome in countries where abortion is not allowed and in countries where pregnancy more commonly occurs at a later age.
Maternal age affects the chances of having a pregnancy with Down syndrome.
At age 20, the chance is one in 1441; at age 30, it is one in 959; at age 40, it is one in 84; and at age 50 it is one in 44. Although the probability increases with maternal age, 70% of children with Down syndrome are born to women 35 years of age and younger, because younger people have more children. The father’s older age is also a risk factor in women older than 35, but not in women younger than 35, and may partly explain the increase in risk as women age.
Ethics
Some argue that not to offer screening for Down syndrome is unethical. As it is a medically reasonable procedure, per informed consent, people should at least be given information about it. It will then be the woman’s choice, based on her personal beliefs, how much or how little screening she wishes.
When results from testing become available, it is also considered unethical not to give the results to the person in question.
Some deem it reasonable for parents to select a child who would have the highest well-being. One criticism of this reasoning is it often values those with disabilities less. Others argue that Down syndrome shouldn’t be prevented or cured and that eliminating Down syndrome amounts to genocide.
The disability rights movement does not have a position on screening, although some members consider testing and abortion discriminatory.
Within Christianity, some Protestants denominations see abortion as acceptable when a fetus has Down syndrome, while Orthodox Christians and Roman Catholics often do not. Some of those against screening refer to it as a form of “eugenics”. Disagreement exists within Islam regarding the acceptability of abortion in those carrying a fetus with Down syndrome. Some Islamic countries allow abortion, while others do not. Women may face stigmatization whichever decision they make.
Advocacy groups for Down syndrome formed after the Second World War. These were organizations advocating for the inclusion of people with Down syndrome into the general school system and for a greater understanding of the condition among the general population, as well as groups providing support for families with children with Down syndrome.
The first World Down Syndrome Day was held on 21 March 2006. The day and month were chosen to correspond with 21 and trisomy, respectively. It was recognized by the United Nations General Assembly in 2011.