Prader Willi Syndrome

National Organization for Rare Disorders, Inc.

It is possible that the main title of the report Prader Willi Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Cryptorchidism-Dwarfism-Subnormal Mentality
  • HHHO
  • Hypogenital Dystrophy with Diabetic Tendency
  • Hypotonia-Hypomentia-Hypogonadism-Obesity Syndrome
  • Labhart-Willi Syndrome
  • Prader-Labhart-Willi Fancone Syndrome
  • Willi-Prader Syndrome

Disorder Subdivisions

  • None

General Discussion

Prader-Willi syndrome (PWS) is a genetic disorder characterized by low muscle tone, short stature if not treated with growth hormone, incomplete sexual development, and a chronic feeling of hunger that, coupled with a metabolism that utilizes drastically fewer calories than normal, can lead to excessive eating and life-threatening obesity. The food compulsion makes constant supervision necessary. Average IQ is 70, but even those with normal IQs almost all have learning issues. Social and motor deficits also exist. At birth the infant typically has low birth weight for gestation, hypotonia (weak muscles), and difficulty sucking due to the hypotonia which can lead to a diagnosis of failure to thrive. The second stage ("thriving too well"), has a typical onset between the ages of two and five, but can be later. The hyperphagia (extreme unsatisfied drive to consume food) lasts throughout the lifetime. Children with PWS have sweet and loving personalities, but this phase is also characterized by increased appetite, weight control issues, and motor development delays along with some behavior problems and unique medical issues.


Prader-Willi Syndrome Association (USA)
8588 Potter Park Drive
Suite 500
Sarasota, FL 34238
Tel: (941)487-6729
Fax: (941)312-0142
Tel: (800)926-4797

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)997-4488
Fax: (914)997-4763
Tel: (888)663-4637

Prader-Willi Syndrome Association (UK)
125A London Rd
Derby, Intl DE1 2QQ
United Kingdom
Tel: 01 332 365676
Fax: 01 332 360401

Cassidy, Suzanne, M.D.
University of Arizona
Department of Pediatrics
Tucson, AZ

Erickson, Robert, M.D.
University of Arizona
Department of Pediatrics
1501 North Campbell Ave
Tucson, AZ 85724

NIH/National Institute of Child Health and Human Development
31 Center Dr
Building 31, Room 2A32
Bethesda, MD 20892
Tel: (301)496-5133
Fax: (301)496-7101

Prader-Willi France
10 Rue Charles Clement
Mondrepuis, Intl F02500
Tel: 33 323 98 79 04
Fax: 33 323 98 79 04

MUMS National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
Tel: (920)336-5333
Fax: (920)339-0995
Tel: (877)336-5333

Sjældne Diagnoser / Rare Disorders Denmark
Frederiksholms Kanal 2, 3rd Floor
Copenhagen K, 1220
Tel: 45 33 14 00 10
Fax: 45 33 14 55 09
Email: mail@sjaeldnediagnoser

Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311
TDD: (888)205-3223

Madisons Foundation
PO Box 241956
Los Angeles, CA 90024
Tel: (310)264-0826
Fax: (310)264-4766

Foundation for Prader-Willi Research
104 Hume Avenue
Alexandria, VA 22301
Tel: (703)683-7500
Fax: (703)683-4482

International Prader Willi Syndrome Organization (IPWSO)
c/o Baschirotto Institute for Rare Diseases (BIRD)
Via Bartolomeo Bizio, 1
36023 Costozza (VI),
Tel: +39 0444 555557
Fax: +39 0444 555557

For a Complete Report

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

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