Diseases & Conditions


Down Syndrome

Synonyms of Down Syndrome
  • Chromosome 21, Mosaic 21 Syndrome
  • Chromosome 21, Translocation 21 Syndrome
  • Trisomy 21 Syndrome
  • Trisomy G Syndrome

Disorder Subdivisions

    General Discussion
    Down syndrome is a chromosomal condition in which all or a portion of chromosome 21 appears three times (trisomy) rather than twice in cells of the body. In some affected individuals, only a percentage of cells may contain the chromosomal condition (mosaicism).

    Symptoms and findings may vary greatly in range and degree, depending on the specific length and location of the duplicated (trisomic) portion of chromosome 21 as well as the percentage of cells containing the condition. However, in many affected individuals, such characteristics may include low muscle tone (hypotonia); a tendency to keep the mouth open with protrusion of the tongue; and distinctive facial characteristics including a short, small head (microbrachycephaly), upwardly slanting eyelid folds (palpebral fissures), a depressed nasal bridge, a small nose, and a relatively flat facial profile. Individuals with Down syndrome may also have unusually small, misshapen (dysplastic) ears; a narrow roof of the mouth (palate); vertical skin folds covering the inner corners of the eyes (epicanthal folds); dental abnormalities; and excessive skin on the back of the neck. Other characteristics include unusually short arms and legs; short fingers; and unusual skin ridge patterns (dermatoglyphics) on the fingers, palms, and toes. Individuals with Down syndrome may also have short stature, poor coordination, mild to severe intellectual disability, and hearing impairment.

    In some cases, Down syndrome may also be characterized by structural malformations of the heart at birth (congenital heart defects). In addition, those with the condition may have an increased susceptibility to respiratory disease (e.g., pneumonia), other infectious diseases, and malignancies in which there is an increased proliferation of certain white blood cells (leukemia). Rarely do these conditions lead to potentially life-threatening complications.

    Organizations related to Down Syndrome
    • ANDO (Apoyo al Nino Down)
      Dept. of Medical Genetics, Children's Hospital
      Washington DC 20010
      Phone #: 202-884-2187
      800 #: N/A
      e-mail: [email protected]
      Home page: N/A
    • Association for Children with Down Syndrome, Inc.
      4 Fern Place
      Plainview NY 11803
      Phone #: 516-933-4700
      800 #: --
      e-mail: [email protected]
      Home page: http://www.acds.org
    • Birth Defect Research for Children
      930 Woodcock Rd
      Orlando FL 32803
      Phone #: 407-895-0802
      800 #: --
      e-mail: [email protected]
      Home page: http://www.birthdefects.org
    • International Mosaic Down Syndrome Association
      P.O. Box 1052
      Franklin TX 77856
      Phone #: 979-828-4177
      800 #: 888-637-5465
      e-mail: [email protected]
      Home page: http://www.imdsa.com
    • MUMS (Mothers United for Moral Support, Inc) National Parent-to-Parent Network
      150 Custer Court
      Green Bay WI 54301-1243
      Phone #: 920-336-5333
      800 #: 877-336-5333
      e-mail: [email protected]
      Home page: http://www.netnet.net/mums/
    • Madisons Foundation
      PO Box 241956
      Los Angeles CA 90024
      Phone #: 310-264-0826
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.madisonsfoundation.org
    • March of Dimes Birth Defects Foundation
      1275 Mamaroneck Avenue
      White Plains NY 10605
      Phone #: 914-428-7100
      800 #: 888-663-4637
      e-mail: [email protected]
      Home page: http://www.marchofdimes.com
    • NIH/National Institute of Child Health and Human Development
      31 Center Dr
      Bethesda MD 20892
      Phone #: 301-496-5133
      800 #: --
      e-mail: N/A
      Home page: http://www.nichd.nih.gov/
    • National Center for Down's Syndrome
      9 Westbourne Road
      Birmingham None B-15
      Phone #: 021-454-3126
      800 #: --
      e-mail: N/A
      Home page: N/A
    • National Consortium on Deaf-Blindness (NCDB)
      The Teaching Research Institute
      Monmouth OR 97361
      Phone #: 800-438-9376
      800 #: 800-438-9376
      e-mail: [email protected]
      Home page: http://www.nationaldb.org
    • National Down Syndrome Congress
      1370 Center Drive
      Atlanta GA 30338
      Phone #: 770-604-9500
      800 #: 800-232-6372
      e-mail: [email protected]
      Home page: http://www.ndsccenter.org
    • National Down Syndrome Society
      666 Broadway
      New York NY 10012-2317
      Phone #: 212-460-9330
      800 #: 800-221-4602
      e-mail: [email protected]
      Home page: http://www.ndss.org/
    • National Foundation for Celiac Awareness
      P.O. Box 544 or 224 South Maple Street
      Ambler PA 19002
      Phone #: 215-325-1306
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.CeliacCentral.org
    • National Institute of Mental Retardation
      York University
      Ontario None M3J 1P3
      Phone #: 416-661-9611
      800 #: --
      e-mail: N/A
      Home page: N/A
    • New Horizons Un-Limited, Inc.
      811 East Wisconsin Ave
      Milwaukee WI 53202
      Phone #: 414-299-0124
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.new-horizons.org
    • PHP - Parents Helping Parents, Inc.
      3041 Olcott Street
      Santa Clara CA 95054-3222
      Phone #: 408-727-5775
      800 #: 866-747-4040
      e-mail: [email protected]
      Home page: http://www.php.com
    • PLAN Institute for Caring Citizenship
      260-3665 Kingsway
      British Columbia None V5R 5W2
      Phone #: 604--43-9-9566
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.planinstitute.ca/?q=learnfromus/library
    • Perkins School for the Blind
      175 North Beacon St.
      Watertown MA 02472
      Phone #: 617-924-3434
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.Perkins.org
    • R.O.C.K. (Raising Our Celiac Kids)
      3527 Fortuna Ranch Rd
      Encinitas CA 92024
      Phone #: 858-395-5421
      800 #: N/A
      e-mail: [email protected]
      Home page: http://www.celiackids.com
    • The Arc (a national organization on mental retardation)
      1010 Wayne Ave
      Silver Spring MD 20910
      Phone #: 301-565-3842
      800 #: 800-433-5255
      e-mail: [email protected]
      Home page: http://www.thearc.org/

    For a Complete Report

    This is an abstract of a report from the National Organization for Rare Disorders, Inc. ? (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html