Down Syndrome: Causes, Symptoms, Types, Diagnosis & Support

Key Takeaways

• Down syndrome is a condition caused by having an extra copy of chromosome 21. It exists in several genetic types.
• Physical characteristics and development are diverse; there is no one checklist that covers all the symptoms of Down syndrome for everyone.
• It is possible to screen for its occurrence during pregnancy, as well as to diagnose it prenatally or postnatally.

Down syndrome is a genetic disorder that occurs due to an additional copy of chromosome 21. The condition can have an impact on development, learning, communication, and some health-related issues; however, its characteristics differ in different patients. Knowledge of Down syndrome will provide you with an opportunity to understand what it means, how it is diagnosed, and what kind of assistance is available.

This guide describes Down syndrome, its characteristics, causes, testing, and health concerns throughout pregnancy and childhood.

What is Down Syndrome?

It is a genetically based disorder that involves having an extra copy of chromosome 21 in either all the body’s cells or only some of them. Typically, people have 46 chromosomes in 23 pairs, while those with the disorder have 47 chromosomes owing to the extra chromosome.

This additional genetic material affects the body's and brain's development. It can cause unusual physical features, developmental delays, and various health problems. But it should be mentioned that such effects differ widely from one individual to another.

What Causes Down Syndrome?

The presence of a third copy of chromosome 21 causes Down syndrome. This third copy often comes about due to an unexpected mistake in cell division known as nondisjunction. The cause of such chromosome changes is still unknown.

In general, Down syndrome is not hereditary. However, translocation Down syndrome is an exception to this statement because a rearrangement of the chromosomes can be hereditary from one of the parents with a balanced translocation and no symptoms. An individual's age at the time of conception does play a role in having a child with Down syndrome; however, children with Down syndrome can be born to parents of any age.

Importantly, nothing a parent did before or during pregnancy causes the chromosome change.

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Symptoms of Down Syndrome

Down syndrome symptoms can include physical traits, developmental delays, and various health issues; however, not all people with Down syndrome will exhibit the same or all symptoms.

Some of the physical traits could include a flatter facial appearance and nose bridge, up-slanted eyes, smaller ears and mouth, a shorter neck, smaller hands and feet, weak muscles, and a single palmar crease. However, such symptoms do not suffice to establish the presence of the condition alone.

Development can also take place at its own pace, where one might have slower development in terms of speech, motor skills, feeding, or other areas. They can also face some challenges with paying attention and communicating.

Some of the health issues that occur in children with Down syndrome are congenital heart defects, hearing or vision issues, thyroid problems, digestive issues, and obstructive sleep apnea.

Down Syndrome Symptoms in Babies

Some of the symptoms in newborn babies include reduced muscle tone, some specific facial characteristics, a short neck, small ears and hands, and slanting eyes. In some babies, there may be problems with feeding or other general functions.

One can never diagnose just by physical features alone. Chromosomal analysis is suggested for some babies suspected of having Down syndrome after birth.

Down Syndrome Symptoms in Children

The symptoms of Down syndrome in a child may be noticeable during development. Developmental problems may lead to problems in movement, communication, learning, and performing various activities. Some children may also suffer from hearing, visual, thyroid, sleep, or cardiac problems.

It is natural for developmental variations to exist; hence, the assessment should take into account the capabilities and needs of the particular child.

Types of Down Syndrome

Three types of genetic Down syndrome are listed below:

Trisomy 21

It is the most frequent type of the disorder and makes up 95% of cases. Each cell has three copies of chromosome 21 instead of two. Trisomy 21 is usually caused by nondisjunction during cell division.

Translocation

When it comes to translocation Down syndrome, an additional chromosome 21 is attached to another chromosome. This kind of genetic mutation occurs in 3% of cases. Sometimes it may be passed from one of the parents having balanced chromosomal translocation.

Mosaicism

The type of Down syndrome called mosaic happens when there is an extra chromosome 21 only in some cells. Such a type comprises 2% of all cases.

Down Syndrome During Pregnancy

The possibility of Down syndrome during pregnancy can be investigated through prenatal screenings and prenatal diagnostic tests. The former gives an estimation of the probability of Down syndrome in the fetus, while it does not give a diagnosis. 

Some of the screening tests that might be used include ultrasound screening, including the thickness of the nuchal translucency, a blood test for the mother, and a cell-free DNA test or NIPT. NIPT can be done starting from 10 weeks, but it should be noted that it is still a screening test.

To determine if the fetus has the chromosomal abnormality, a diagnostic test should be carried out. One of these procedures is CVS, which is usually done at 10-13 weeks of pregnancy, and amniocentesis, which is usually done at 15 weeks.

How is Down Syndrome Diagnosed?

Screening during pregnancy could identify that there is a higher possibility of trisomy 21. A positive result from a screening test does not necessarily mean that the child will have Down syndrome. Diagnosis through either CVS or amniocentesis can be used to determine this.

In the postnatal period, the physical signs may attract the attention of health care personnel who can suggest a blood test. Chromosome analysis, also known as karyotyping, can then be done to determine whether the child has an extra chromosome 21.

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Bottom line: Support and Medical Care

There is no treatment that eliminates the extra chromosome, but assistance at an early age may help individuals develop skills and cope with related medical issues. The treatment can be physical, occupational, and speech therapy; developmental interventions at an early age; educational intervention; hearing and vision care; and treatment of certain medical problems.

Healthcare requirements might vary during a lifetime, and regular check-ups may reveal problems connected to the heart, hearing, vision, thyroid functioning, sleep, or digestion. A healthcare team can provide a treatment plan depending on the person's age and medical problems.

Frequently Asked Questions

Can Down syndrome be detected before birth?

Yes. Prenatal screening will determine the risk for Down syndrome, but diagnostic tests will be able to establish whether there is an extra chromosome 21 in the fetus. Both procedures differ from one another, and specialists will explain their results to families before any further steps are undertaken.

Is it possible to recognize Down syndrome immediately after birth?

Not always. While some newborns show distinctive signs that make the clinician suspicious about Down syndrome right away, others may not show as many. When Down syndrome is suspected, chromosome analysis will be used to diagnose the child. Differences in development may appear later on in life.

Does Down syndrome impact the ability to learn and develop?

Sometimes it does. Children with Down syndrome usually experience certain levels of developmental delays and require more attention in terms of speech therapy, physical activity, and learning and daily activities.

What health problems are associated with Down syndrome?

People with Down syndrome have an increased likelihood of certain health conditions, including congenital heart defects, hearing and vision problems, thyroid disorders, sleep apnea, and digestive issues. Not every person develops these conditions, which is why ongoing preventive care and age-appropriate screening are important.

Can parents pass down Down syndrome to their children?

Most cases are not inherited and occur because of a random chromosome-separation error. Translocation Down syndrome can sometimes be inherited when a parent carries a balanced chromosome rearrangement. Genetic counseling and chromosome testing can help clarify recurrence risk for families with a translocation.

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