Down Syndrome Symptoms

What Is Down Syndrome?

Down syndrome is a genetic disorder that is caused by mistakes in cell division during development of the human egg, sperm, or embryo. Over 90% of Down syndrome individuals have three copies of chromosome 21 instead of the normal two in all of their body cells. The other individuals that are diagnosed with Down syndrome also have cells that possess either extra copies of chromosome 21 in some body cells (mosaic Down syndrome) or have extra pieces or parts of chromosome 21 in their cells (termed translocation Down syndrome). There are no known factors that cause Down syndrome; only the relatively infrequent (about 4% of all Down syndrome individuals) inherit translocation Down syndrome from a parent with risk varying from 3% (for fathers) and about 10% to 15% for mothers. Major risk factors include maternal advancing age, having one child with Down syndrome, and being a male or female with the translocation Down syndrome gene.

What Are the Symptoms of Down Syndrome?

Most children (and adults) have distinct facial features, but not all individuals have all of the features. The most common features are as follows:

  • Small head
  • Flattened facial features
  • Short neck
  • Odd shaped ear
  • Upward slant to the eyes
  • Protruding tongue
  • Small nose

Other fairly common features include dental abnormalities, short fingers on broad short hands, and poor muscle tone with increased flexibility in some joints and heart defects.

Although Down syndrome infants are usually average size at birth, as babies they grow slowly and often may remain shorter than other children. Unfortunately, infants and children with Down syndrome may often show development delays in sitting, crawling and walking, and talking. Some degree of mental retardation occurs in all Down syndrome individuals, but the extent of mild-to-moderate dysfunction is highly variable in individuals with Down syndrome. In addition, although most develop slowly, the patients usually prematurely age.

Who Is at Risk for Down Syndrome

The risk of your baby having Down syndrome can be investigated during pregnancy; it is usually not done as a screening test unless there are risk factors (see above). The tests may include blood analysis, ultrasound, and/or more invasive tests such as amniocentesis and other tests that eventually result in examination of collected cells for chromosome 21 defects (partial or complete copies).

Symptoms, both physical and mental, vary widely among Down syndrome patients. It is difficult to predict the functional level the Down syndrome patient can achieve. However, there are several national organizations that can provide details about the care and developmental levels Down syndrome patients can, with help, achieve (see last two references). Finally, people should be reminded that many parents of Down syndrome patients have found great happiness in raising their children who provide them with numerous occasions that are filled with love and joy.


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Medically reviewed by Margaret Walsh, MD; American Board of Pediatrics


National Association for Down Syndrome.

National Down Syndrome Society.