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Diseases

Genetic and Rare Diseases Information Center (GARD)

Prader-Willi syndrome


Other Names for this Disease
  • PWS
  • Willi-Prader syndrome
  • Prader-Labhart-Willi syndrome
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Cause

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What causes Prader-Willi syndrome?

Prader-Willi syndrome (PWS) is caused by the loss of active genes in a specific region of chromosome 15. People normally inherit one copy of chromosome 15 from each parent. Some genes on chromosome 15 are only active (or "expressed") on the copy that is inherited from a person's father (the paternal copy). When genes are only active if inherited from a specific parent, it is called genomic imprinting.

About 70% of cases of PWS occur when a person is missing specific genes on the long arm of the paternal copy of chromosome 15. This is called a deletion. While there are copies of these same genes on the maternal copy of chromosome 15, the maternal copies of these genes are not expressed.
 
In about 25% of cases, PWS is due to a person inheriting only 2 maternal copies of chromosome 15, instead of one copy from each parent. This is called maternal uniparental disomy.

Rarely (in about 2% of cases), PWS is caused by a rearrangement of chromosome material called a translocation, or by a change (mutation) or other defect that abnormally inactivates genes on the paternal chromosome 15.[1]

Each of these genetic changes result in a loss of gene function on part of chromosome 15, likely causing the characteristic features of PWS.[1]
Last updated: 12/28/2015

References
  1. Prader-Willi syndrome. Genetics Home Reference. June, 2014; http://ghr.nlm.nih.gov/condition/prader-willi-syndrome. Accessed 1/5/2015.


Other Names for this Disease
  • PWS
  • Willi-Prader syndrome
  • Prader-Labhart-Willi syndrome
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.