Down Syndrome

Overview

Down syndrome is a genetic condition that occurs when a person has an extra full or partial copy of chromosome 21. This is why it is also called trisomy 21. The extra genetic material changes how the body and brain develop, leading to a recognizable set of physical features, varying degrees of intellectual disability, and a higher chance of certain health conditions.

Down syndrome is one of the most common chromosomal conditions. People with Down syndrome have a wide range of abilities, and with good health care, early support, and inclusive education, many lead full, active, and meaningful lives. The condition is lifelong but not a disease that can be "cured"; care focuses on supporting health and development.

Features and Symptoms

Down syndrome is associated with a combination of physical and developmental features, though their presence and degree vary from person to person:

• Distinct facial features, such as a flattened face, almond-shaped eyes that slant upward, and a small nose
• Low muscle tone, especially in infancy
• Short stature and a single deep crease across the palm in some individuals
• Mild to moderate intellectual disability and developmental delays
• Delayed speech and motor milestones

Many associated health conditions, such as heart defects, are detected and managed through routine monitoring rather than causing obvious symptoms at first.

Causes

Down syndrome is caused by an extra copy of chromosome 21. There are three forms:

• Trisomy 21: The most common form, where every cell has three copies of chromosome 21 instead of two, usually from an error in cell division.
• Translocation: Extra chromosome 21 material is attached to another chromosome.
• Mosaic: Only some cells have the extra chromosome.

In most cases it happens by chance and is not caused by anything the parents did before or during pregnancy.

Risk Factors

• Advancing maternal age, which increases the chance of trisomy 21
• Having previously had a child with Down syndrome
• Being a carrier of a chromosome 21 translocation, which can be inherited

Down syndrome occurs in families of all backgrounds, and most children with the condition are born to parents without these specific risk factors.

Diagnosis

Down syndrome can be identified before or after birth:

• Prenatal screening: Blood tests and ultrasound during pregnancy estimate the chance of Down syndrome.
• Prenatal diagnostic tests: Procedures such as amniocentesis or chorionic villus sampling can confirm the diagnosis during pregnancy.
• After birth: A diagnosis may be suspected from physical features and confirmed with a chromosome test (karyotype).

Screening choices are personal, and counseling helps families understand their options.

Care and Management

There is no cure for Down syndrome, and care centers on supporting health, development, and quality of life.

• Regular health monitoring: For heart conditions, hearing and vision, thyroid function, and other concerns that are more common with Down syndrome.
• Early intervention: Physical, occupational, and speech therapy from infancy to support development.
• Inclusive education and support services tailored to each person's abilities.
• Treating specific conditions, such as surgery for a heart defect, as needed.
• Lifelong, coordinated care involving the family and a team of professionals.

With these supports, many people with Down syndrome attend school, work, build relationships, and live independently or with some assistance.

When to See a Doctor

Children and adults with Down syndrome benefit from regular medical checkups to monitor for and manage associated conditions early. Seek prompt care for signs of a heart or breathing problem, such as poor feeding, breathlessness, or bluish color in an infant, or for new symptoms like changes in hearing, vision, energy, or behavior. Families considering prenatal screening or who have questions about inheritance can ask their provider for genetic counseling.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Facts about Down Syndrome.
2. MedlinePlus, U.S. National Library of Medicine. Down syndrome.
3. National Institute of Child Health and Human Development (NICHD). Down Syndrome.
4. National Down Syndrome Society (NDSS).