Down Syndrome

What is Down syndrome?

From: MedlinePlus, National Library of Medicine

Down syndrome is a condition in which a person has an extra chromosome or an extra piece of a chromosome. This extra copy changes how a baby's body and brain develop. It can cause both mental and physical challenges during their lifetime. Even though people with Down syndrome might act and look similar, each person has different abilities.

What causes Down syndrome?

From: MedlinePlus, National Library of Medicine

Chromosomes are tiny "packages" in your cells that contain your genes. Genes carry information, called DNA, that controls what you look like and how your body works. People with Down syndrome have an extra copy of chromosome 21. In some cases, they may have an extra copy of part of the chromosome. Having an extra copy of a chromosome is called trisomy. So sometimes Down syndrome is also called trisomy 21.

Down syndrome is usually not inherited. It happens by chance, as an error when cells are dividing during early development of the fetus. It is not known for sure why Down syndrome occurs or how many different factors play a role.

One factor that increases the risk of having a baby with Down syndrome is the age of the mother. Women ages 35 and older are more likely to have a baby with Down syndrome.

What are the symptoms of Down syndrome?

From: MedlinePlus, National Library of Medicine

The symptoms of Down syndrome are different in each person. And people with Down syndrome may have different problems at different times of their lives. They usually have mild to moderate intellectual disabilities. Their development is often delayed. For example, they may start talking later than other children.

Some of the common physical signs of Down syndrome include:

• A flat face
• Eyes that slant up
• A short neck
• Small hands and feet
• Poor muscle tone
• Loose joints

What other problems does Down syndrome cause?

From: MedlinePlus, National Library of Medicine

Many people with Down syndrome have the common physical signs and have healthy lives. But some people with Down syndrome might have one or more birth defects or other health problems. Some of the more common ones include:

• Hearing loss
• Sleep apnea (a disorder that causes you to repeatedly stop breathing during sleep)
• Ear infections
• Eye diseases
• Congenital heart defects (heart defects that are present at birth)
• Digestive problems
• Problems with the upper part of the spine
• Obesity

How is Down syndrome diagnosed?

From: MedlinePlus, National Library of Medicine

Health care providers can check for Down syndrome during pregnancy or after a child is born.

There are two basic types of tests that help find Down syndrome during pregnancy:

• Prenatal screening tests can show whether your unborn baby has a higher or lower chance of having Down syndrome. If a screening test shows that your baby could have Down syndrome, you'll need another test to find out for sure.
• Prenatal diagnostic tests can diagnose or rule out Down syndrome by checking the chromosomes in a sample of cells. These tests have a small risk of causing a miscarriage, so they're often done after a screening test shows that an unborn baby could have Down syndrome.

After a baby is born, the provider may make an initial diagnosis of Down syndrome based on the physical signs of the syndrome. The provider can use a karyotype genetic test to confirm the diagnosis. The test can check for extra chromosomes in a sample of the baby's blood.

What are the treatments for Down syndrome?

From: MedlinePlus, National Library of Medicine

There is no single, standard treatment for Down syndrome. Treatments are based on each person's physical and intellectual needs, strengths, and limitations.

Services early in life focus on helping children with Down syndrome develop to their full potential. These services include speech, occupational, and physical therapies. They are typically offered through early intervention programs in each state. Children with Down syndrome may also need extra help or attention in school, although many children are included in regular classes.

Since people with Down syndrome can have birth defects and other health problems, they will need regular medical care. They may need to have certain extra health screenings to check for problems that happen more often in people with Down syndrome.

Genetic causes described in the linked summary

From: MedlinePlus Genetics

Most cases of Down syndrome result from trisomy 21, which means each cell in the body has three copies of chromosome 21 instead of the usual two copies.

Less commonly, Down syndrome occurs when part of chromosome 21 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) in a parent or very early in fetal development. Affected people have two normal copies of chromosome 21 plus extra material from chromosome 21 attached to another chromosome, resulting in three copies of genetic material from chromosome 21. Affected individuals with this genetic change are said to have translocation Down syndrome.

A very small percentage of people with Down syndrome have an extra copy of chromosome 21 in only some of the body's cells. In these people, the condition is called mosaic Down syndrome.

Researchers believe that having extra copies of genes on chromosome 21 disrupts the course of normal development, causing the characteristic features of Down syndrome and the increased risk of health problems associated with this condition.

Inheritance described in the linked summary

From: MedlinePlus Genetics

Most cases of Down syndrome are not inherited. When the condition is caused by trisomy 21, the chromosomal abnormality occurs as a random event during the formation of reproductive cells in a parent. The abnormality usually occurs in egg cells, but it occasionally occurs in sperm cells. An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 21. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 21 in each of the body's cells.

People with translocation Down syndrome can inherit the condition from an unaffected parent. The parent carries a rearrangement of genetic material between chromosome 21 and another chromosome. This rearrangement is called a balanced translocation. No genetic material is gained or lost in a balanced translocation, so these chromosomal changes usually do not cause any health problems. However, as this translocation is passed to the next generation, it can become unbalanced. People who inherit an unbalanced translocation involving chromosome 21 may have extra genetic material from chromosome 21, which causes Down syndrome.

Like trisomy 21, mosaic Down syndrome is not inherited. It occurs as a random event during cell division early in fetal development. As a result, some of the body's cells have the usual two copies of chromosome 21, and other cells have three copies of this chromosome.

Which doctor should you see?

The suggested department for discussing Down Syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.