Down Syndrome

Down Syndrome Overview

Reviewed: May 8, 2014

Down syndrome is a condition in which a person is born with an extra copy of chromosome 21. 

This additional genetic material causes the characteristic physical problems, as well as intellectual disabilities, although every person born with Down syndrome is unique.

A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. These common characteristics occur in varying degrees and sometimes not at all.

There are three types of Down syndrome:  trisomy 21 (nondisjunction), translocation and mosaicism.


Down Syndrome Symptoms

There are some facial and other physical features that are typical in people with Down syndrome, although not everyone with the syndrome will have all of these features:

  • A flattened or oval-shaped face
  • Almond-shaped eyes that slant up
  • An extra skin fold on the upper eyelid (epicanthal fold)
  • A small nose with a flat bridge
  • A short neck
  • Small, low-set ears
  • A tongue that tends to stick out of the mouth
  • Tiny white spots on the iris (colored part) of the eye
  • Small hands and feet
  • A single line across the palm of the hand (palmar crease)
  • Small pinky fingers that sometimes curve toward the thumb
  • Poor muscle tone or loose joints
  • Shorter in height as children and adult

Each person with Down Syndrome has different abilities. People with Down syndrome usually have an IQ (a measure of intelligence) in the mildly-to-moderately low range and are slower to speak than other children.

Approximately half of babies with Down syndrome will have a heart problem that they are born with. The most common problem is a hole in the muscle that usually separates the different chambers in the heart, known medically as an atrioventricular septal defect (AVSD). This problem, if detected early, can usually be corrected.

Down Syndrome Causes

Someone with Down syndrome has an extra copy of chromosome number 21 in the cells of their body. This is also known as trisomy 21. Trisomy refers to the fact that there are three copies of chromosome 21. Because there is an extra chromosome 21, there is extra genetic material in the body. This causes the typical features of Down syndrome. There are different ways that trisomy 21 can occur.

Down Syndrome Diagnosis

A diagnosis of Down syndrome after birth is often based initially on physical signs of the syndrome.

But because individuals with Down syndrome may not have these symptoms, and because many of these symptoms are common in the general population, the health care provider will take a sample of the baby's blood to confirm the diagnosis. The blood sample is analyzed to determine the number of the baby's chromosomes.

Living With Down Syndrome

For the more than 400,000 people living with Down syndrome in the U.S., most fully participate in public and private educational programs, although to some extent this may depend on how severely they are affected. They are valued members of their communities, are integrated into regular education, sports, music, and art programs, and are active participants in the educational, vocational, social, and recreational activities of the community. 



Down Syndrome Treatments

While there is no cure for Down syndrome, treatment is aimed at monitoring for any birth defects or complications and treating these where possible. 

Common health problems among children with Down syndrome include:

  • Hearing loss (up to 75% of people with Down syndrome may be affected)
  • Obstructive sleep apnea, which is a condition where the person’s breathing temporarily stops while asleep (between 50 -75%)
  • Ear infections (between 50 -70%)
  • Eye diseases (up to 60%), like cataracts and eye issues requiring glasses
  • Heart defects present at birth (50%)

Other less common health problems among people with Down syndrome include:

  • Intestinal blockage at birth requiring surgery
  • Hip dislocation
  • Thyroid disease
  • Anemia (red blood cells can’t carry enough oxygen to the body) and iron deficiency (anemia where the red blood cells don’t have enough iron)
  • Leukemia in infancy or early childhood
  • Hirschsprung disease

Health care providers routinely monitor children with Down syndrome for these conditions. If they are diagnosed, treatment is offered.

Down Syndrome Prognosis

Life expectancy for those born with Down syndrome is improving due to advancements in medical treatments. 

Good health care, family support, quality education, and a stimulating home and community environment can help people with Down syndrome lead productive and fulfilling lives well into adulthood. At least half of all people with Down syndrome can now live into their 50s and 60s. They can live independently, attend school and work, and get involved in their community.