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Down Syndrome - Types , Causes, Symptoms, and Diagnosis

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Down Syndrome - Types , Causes, Symptoms, and Diagnosis

5 min read


Down syndrome is a genetic disorder. Read this article to learn more about the symptoms, causes, and treatment.

Written by

Dr. Lochana .k

Medically reviewed by

Dr. Faisal Abdul Karim Malim

Published At February 1, 2022
Reviewed AtMay 2, 2024


The human body comprises cells, and genetic material is stored as genes in each cell. These genes carry the codes responsible for all the inherited traits and are grouped with rod-like structures known as chromosomes. Generally, there are 23 pairs of chromosomes in a cell nucleus, half of which are inherited from each parent. When there is a partial or full extra copy of chromosome 21 in an individual, it is called Down syndrome. It is also called 'trisomy-21 syndrome' or 'mongolism'. It is caused by advanced maternal age, uterine and placental abnormalities, and chromosomal aberrations.

What Are the Researches Done for Down Syndrome?

For many centuries, people with Down syndrome have been mentioned in art, literature, and science. In the nineteenth century, in 1866, John Langdon Down, an English physician, published an article on a precise or accurate description of a person with Down syndrome. He was recognized as the "father" of this syndrome. Although many people described this syndrome, he was the first to describe the condition as a distinct and separate entity.

Recently, advances in medicine and science have made it easier for researchers to investigate further the characteristics of people with Down syndrome. In 1959, Jerome Lejeune, a French physician, identified Down syndrome as a chromosomal condition. Lejeune observed 47 chromosomes instead of 46 in the cells of individuals with Down syndrome. Later, it was determined that an extra partial or whole copy of chromosome 21 results in the characteristics associated with Down syndrome. In 2000, scientists identified and cataloged each of approximately 329 genes on chromosome 21. This advancement leads to significant accomplishments and advances in Down syndrome research.

What Are the Types of Down Syndrome?

1) Trisomy 21 (Nondisjunction):

In Down syndrome, there is usually an error in cell division called nondisjunction. This results in the embryo having three copies of chromosome 21 instead of two. Before or during conception, a pair of 21st chromosomes in the sperm or the egg fails to separate. As a result, when the embryo grows, the extra chromosome is replicated in every cell of the body. This type accounts for about 95 % of all cases.

2) Mosaicism:

Mosaicism (or mosaic Down syndrome) results from a mixture of two types of cells. Some have the usual 46 chromosomes, and some have 47. Those cells with 47 chromosomes contain an extra chromosome 21.

In Down syndrome, mosaicism is the least common type and accounts for only about one percent of all cases. According to research, individuals with mosaic Down syndrome have fewer Down syndrome characteristics than those with other types of Down syndrome. However, with a wide range of abilities, broad generalization is not possible for people with Down syndrome.

3) Translocation:

This accounts for about 4% of cases of Down syndrome. Here, the total number of chromosomes remains 46. However, an additional partial or full copy of chromosome 21 attaches to another chromosome, usually chromosome 14. The presence of extra full or partial chromosome 21 causes the characteristics of Down syndrome.

What Are the Causes of Down Syndrome?

The exact cause of the extra full or partial chromosome is still unknown. The only factor might be maternal age, which might be the chance of having a baby with Down syndrome resulting from nondisjunction or mosaicism. There is no definite evidence indicating that parents' environmental factors or activities cause Down syndrome before or during pregnancy.

What Are the Risk Factors of Down Syndrome?

The likelihood of having a child with Down syndrome is higher for some parents. Among the risk factors are:

  • Increasing mother's age. The likelihood that an older egg will result in incorrect chromosomal division increases with age, increasing the likelihood that a mother will give birth to a kid with Down syndrome. The probability of a mother carrying a child with Down syndrome rises beyond the age of thirty-five. But because younger women give birth to many more children than older ones, the majority of Down syndrome children are delivered to women under 35.

  • Parents who have had a translocation and have one child with Down syndrome are more likely to get another Down syndrome child in the future.

What Are the Symptoms Seen in Down Syndrome?

  • Skull: There is a flat face, large anterior frontally, and open sutures. There is also the presence of a brachycephalic skull that is shaped with prominence and occipital flattening.

  • Palpebral Fissures: These are almond-shaped with superior lateral or Mongolian obliquity.

  • Eyes: Slight slanting of eyes with epicanthic folds. The eyes are widely spaced. There is also the presence of ocular hypertelorism.

  • Nose: There is a flattened nasal bridge.

  • Tongue: Increase in the size of the tongue with protrusion.

  • Maxillary Sinus: The presence of hypoplasia or aplasia of the maxillary sinus.

  • Teeth: The teeth are malformed; hypoplasia and microdontia are present.

  • Malocclusion: A small maxillary arch relative to the mandibular arch.

  • Periodontal Disease: A severe, destructive periodontal disease with no other local cause in origin.

  • Others: There is sexual underdevelopment, cardiac abnormalities, and hypermobility of the joints. There is also an open mouth, frequent prognathism, and a high-arched palate.

What Other Issues Are Brought on by Down Syndrome?

Many individuals with Down syndrome lead healthy lives and exhibit the typical physical symptoms. However, some individuals with Down syndrome may also have other health issues or one or more birth abnormalities. Among the more prevalent ones are:

  • Loss of hearing.

  • The condition known as sleep apnea causes you to cease breathing while asleep periodically.

  • Infections of the ears.

  • Disorders of the eyes.

  • Congenital cardiac defects are those that exist at birth.

  • Digestive issues.

  • Issues with the cervical region of the spine.

  • Being overweight.

How Is Down Syndrome Diagnosed?


Two kinds of tests can be performed before a baby is born; screening and diagnostic tests.

  • Screening Tests: These tests do not reveal whether the fetus has Down syndrome; they only provide a probability. These tests involve a blood test and an ultrasound (sonogram).

  • Diagnostic Tests: These tests provide a definitive diagnosis with almost 100 percent accuracy. This involves chorionic villus sampling (CVS) and amniocentesis. These procedures carry up to a one percent risk of causing a spontaneous termination, that is, miscarriage. Amniocentesis is generally performed in the second trimester of pregnancy between 15 and 20 weeks of gestation, and CVS is performed in the first trimester between 9 and 14 weeks.

At Birth:

It is identified by the presence of certain physical traits: an upward slant of the eyes, a single deep crease around the palm, a slightly flattened facial profile, and low muscle tone since these features may be present in babies without Down syndrome, a chromosomal analysis known as karyotype is done to confirm the diagnosis.

How Is Down Syndrome Managed?

As of now, there is no specific treatment for this syndrome, and many of the patients die during the first year of life.

What Are the Complications?

  • Heart Abnormalities: Approximately 50 percent of infants born with Down syndrome have a congenital cardiac condition. These cardiac issues may need surgery in the early stages of infancy and pose a life-threatening risk.

  • GI (Gastrointestinal) Abnormalities: Some children with Down syndrome have GI abnormalities, which can include problems with the intestines, esophagus, trachea, and anus. There may be a higher chance of having digestive issues, including celiac disease, GI obstruction, or heartburn (gastroesophageal reflux).

  • Immune Conditions: People with Down syndrome are more susceptible to autoimmune illnesses, some types of cancer, and infectious diseases such as pneumonia due to immune system abnormalities.

  • Leukemia: Young children diagnosed with leukemia are more likely to have Down syndrome.

  • Dementia: Dementia is a serious risk factor for people with Down syndrome; symptoms and signs may appear around age 50. The chance of Alzheimer's disease also rises in people with Down syndrome.

What Is the Impact of Down Syndrome on Society?

Individuals with Down syndrome are becoming more integrated into communities and organizations such as schools, health care systems, workforces, and social and recreational activities. With recent advances in medical technology, individuals with Down syndrome are living longer than ever before. More and more people are interacting with individuals with Down syndrome, increasing the need for widespread public education and acceptance.


More than ever, individuals with this syndrome live longer, richer lives. Even though they may encounter a distinct set of difficulties, they can also overcome them and flourish. To help them succeed, individuals with the condition and their families need an understanding of family and friends as well as a strong network of skilled professionals.

Frequently Asked Questions


Is There a Cure for Down Syndrome?

Down syndrome is known as a chromosome 21 disorder that is characterized by developmental and intellectual delays. There is no cure for down syndrome. Nevertheless, early intervention programs help improve distorted skills. The treatment options include the following:
 - Physical therapy.
 - Occupational therapy.
 - Speech therapy.
 - Educational therapy.


What Is the Survival Rate of a Child With Down Syndrome?

Down syndrome is a genetic disorder in which a child has an additional chromosome obtained from chromosome 21. Though the condition has no cure, a child can live a productive and happy life with appropriate treatment and care. Therefore, the average life expectancy for Down syndrome is about 60 years.


Is an Individual With Down Syndrome Bright?

Down syndrome is a genetic condition associated with developmental delays, mild to moderate intellectual concerns, and specific facial features. Children with down syndrome possess certain disabilities, though,  being similar to the normal ones. So, they have an IQ range of mild to moderate.


Can Down Syndrome People Get Pregnant?

It is a misconception that individuals with Down syndrome cannot give birth to a child. The actual fact is that women with this condition are fertile and can have children. But, they may have certain challenges during the process.


Is Down Syndrome a Harmful Condition?

Down syndrome is a genetic condition affecting development and intelligence. It can cause severe complications that include the following.
 - Heart defects. Nearly half of the children with down syndrome were reported with heart defects. 
 - Immune system concerns.
 - Blood disorders like leukemia.


Can Individuals With Down Syndrome Lead a Normal Life?

A child with down syndrome can be treated through years after birth. Though down syndrome is a condition in which growth, development, and intelligence are affected, the children can grow up leading a normal life with appropriate treatment and care.


How to Prevent Down Syndrome During Pregnancy?

Down syndrome is a genetic condition that cannot be prevented in most instances. However, the parents can indulge in specific ways to reduce the overall risk. One should avoid late reproduction.


Which Gender Is More Prevalent in Cases of Down Syndrome?

Gender predilection has no significant differences with occurring down syndrome. However, the studies and clinical findings reveal that pregnant women aged thirty-five or older have a high proportion of giving birth to children with Down syndrome.


What Is the Reliable Age of the Oldest Person With Down Syndrome?

According to various studies and medical reports, a woman with Down syndrome from the USA died at the age of eighty-three. The woman had certain complications resulting from a broken hip during her death.


Is Down Syndrome Affiliated With the Father’s Age?

The father’s age group is fifty percent attributable to the possibility of a child with down syndrome. Parents over thirty-five years have a higher risk of having a child with down syndrome. The rate of this condition is approximately sixty per 10,000 births with the ages of parents above forty.


Can Down Syndrome Individuals Get Married?

Though Down syndrome is considered a severe condition, children with this condition can lead a normal life with appropriate intervention, hospitality, and care. Individuals having Down syndrome can get married. They are fertile and so can give birth to children.


Who Is at More Risk of Getting Down Syndrome?

Women getting pregnant at thirty-five years or above have a higher risk of having a child with Down syndrome. Nevertheless, these days, women younger than 35 also have Down syndrome children.


Are Down Syndrome People Influenced by Mental Health?

Down syndrome is considered the most common chromosome-associated genetic condition affecting a child’s growth, development, and intelligence in the US. As a result, brain development is influenced, so the child has physical and mental disabilities.


How to Identify Whether the Baby Has Down Syndrome?

Down syndrome can be diagnosed during the times of pregnancy. The doctors will diagnose the condition after birth if not identified during pregnancy. The doctors might recommend blood investigations to assess the chromosomes of the child.


Which Factors Increase the Risk of Down Syndrome?

Down syndrome is a common genetic condition resulting from the presence of extra abnormal chromosomes. Women getting pregnant at the later stages with 35 or above are more likely to give birth to a child with down syndrome. Therefore, the risks of down syndrome increase with late reproduction.
Dr. Lochana .k
Dr. Lochana .k



down syndrome
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