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How many people are affected/at risk for Prader-Willi syndrome (PWS)?

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Prader-Willi syndrome, which occurs in about one in every 15,000 to 25,000 live births, is the most common genetic disorder that can lead to life-threatening obesity in children. Boys and girls are equally affected.1

Scientists do not know what increases the risk for Prader-Willi syndrome. The genetic error that leads to Prader-Willi syndrome occurs at random, usually around the time of conception or during early fetal development. The syndrome is usually not hereditary.2

Genetic testing can identify the chance that a second sibling will develop Prader-Willi syndrome, a possibility that is usually less than 1%.


  1. Scheimann, A. (2011, June 8). Prader-Willi Syndrome. Medscape Reference. Retrieved July 17, 2012, from http://emedicine.medscape.com/article/947954-overview#a0199 External Web Site Policy [top]
  2. McCandless, S. E.; Committee on Genetics. (2010). Clinical report-health supervision for children with Prader-Willi syndrome. Pediatrics, 127, 195-204. [top]

Last Updated Date: 11/30/2012
Last Reviewed Date: 11/30/2012
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