People with Prader-Willi syndrome typically have mild to moderate intellectual impairment and learning disabilities. Behavioral problems are common, including temper outbursts, stubbornness, and compulsive behavior such as picking at the skin. Sleep abnormalities can also occur. Additional features of this condition include distinctive facial features such as a narrow forehead
Frequency
Prader-Willi syndrome affects an estimated 1 in 10,000 to 30,000 people worldwide.
Causes
Prader-Willi syndrome is caused by the loss of function of genes in a particular region of chromosome 15
Most cases of Prader-Willi syndrome (about 70 percent) occur when a segment of the paternal chromosome 15 is deleted
It appears likely that the characteristic features of Prader-Willi syndrome result from the loss of function of several genes on chromosome 15. Among these are genes that provide instructions for making molecules called small nucleolar RNAs (snoRNAs). These molecules have a variety of functions, including helping to regulate other types of RNA molecules. (RNA molecules play essential roles in producing proteins and in other cell activities.) Studies suggest that the loss of a particular group of snoRNA genes, known as the SNORD116 cluster, may play a major role in causing the signs and symptoms of Prader-Willi syndrome. However, it is unknown how a missing SNORD116 cluster could contribute to intellectual disability, behavioral problems, and the physical features of the disorder.
In some people with Prader-Willi syndrome, the loss of a gene called OCA2 is associated with unusually fair skin and light-colored hair
Researchers are studying other genes on chromosome 15 that may also be related to the major signs and symptoms of this condition.
Inheritance
Most cases of Prader-Willi syndrome are not inherited, particularly those caused by a deletion
Rarely, a genetic change responsible for Prader-Willi syndrome can be inherited. For example, it is possible for a genetic change that abnormally turns off genes on the paternal chromosome 15 to be passed from one generation to the next.
Other Names for This Condition
- Prader-Labhart-Willi syndrome
- PWS
- Willi-Prader syndrome
References
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