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Prader-Willi syndrome


Other Names for this Disease

  • Prader-Labhart-Willi syndrome
  • PWS
  • Willi-Prader 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.

Overview

What is Prader-Willi syndrome?

What are the signs and symptoms of Prader-Willi syndrome?

What causes Prader-Willi syndrome?

Is Prader-Willi syndrome inherited?

How is Prader-Willi syndrome diagnosed?

How might Prader-Willi syndrome be treated?

What is the long-term outlook for people with Prader-Willi syndrome?

What is Prader-Willi syndrome?

Prader-Willi syndrome (PWS) is a genetic condition that affects many parts of the body. Infants with PWS have severe hypotonia (low muscle tone), feeding difficulties, and slow growth. In later infancy or early childhood, affected children typically begin to eat excessively and become obese. Other signs and symptoms often include short stature, hypogonadism, developmental delays, cognitive impairment, and distinctive behavioral characteristics such as temper tantrums, stubbornness, and obsessive-compulsive tendencies. PWS is caused by missing or non-working genes on chromosome 15. Most cases are not inherited and occur randomly. Rarely, a genetic change responsible for PWS can be inherited.[1][2]
Last updated: 1/5/2015

What are the signs and symptoms of Prader-Willi syndrome?

In infancy, Prader-Willi syndrome (PWS) is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. In later infancy or early childhood, affected children develop an extreme appetite, which leads to overeating and obesity.[2][1]

Other signs and symptoms of PWS may include:[2][1]
  • mild to moderate intellectual disability
  • sleep abnormalities
  • unusually fair skin
  • underdeveloped genitals
  • delayed or incomplete puberty
  • short stature
  • strabismus
  • scoliosis
  • small hands and feet
  • distinctive facial features such as a narrow forehead, almond-shaped eyes, and a triangular mouth

Behavioral problems are common and often include temper tantrums, stubbornness, and obsessive-compulsive tendencies.[2][1]

Last updated: 1/5/2015

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.[1]

About 70% of cases of PWS occur when a person is missing specific genes on the paternal copy of chromosome 15. In about 25% of cases, PWS is due to a person inheriting 2 maternal copies of chromosome 15, instead of one copy from each parent. This is called maternal uniparental disomy. Rarely, 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. Each of these genetic changes results in a loss of gene function on part of chromosome 15, which is what causes the characteristic features of PWS.[1]
Last updated: 1/5/2015

Is Prader-Willi syndrome inherited?

Most cases of Prader-Willi syndrome (PWS) are not inherited. The genetic causes in these cases occur as random events during the formation of egg or sperm cells, or in early fetal development. In rare cases, the genetic change responsible for PWS can be inherited.[1]

The vast majority of families have a recurrence risk for PWS of less than 1%. However, certain causes of the condition have a recurrence risk as high as 50%, and a scenario with a risk of 100% (though extremely unlikely) is theoretically possible.[2]

The various genetic causes of PWS are very complex. People seeking detailed information about the genetics of PWS and the genetic risks to family members should speak with a genetics professional.
Last updated: 1/5/2015

How is Prader-Willi syndrome diagnosed?

There are clinical diagnostic criteria for Prader-Willi syndrome (PWS) that were developed in the past that continue to be useful; however, the current mainstay of a diagnosis of PWS is DNA methylation testing when PWS is suspected. This type of testing can detect abnormal, parent-specific imprinting on the region of chromosome 15 that is responsible for PWS. It determines whether the region is maternally inherited only (i.e., the paternally contributed region is absent) and detects more than 99% of affected people. DNA methylation testing is especially important in those who have non-classic features or are too young to show enough features to make the diagnosis based on signs and symptoms alone.[2]

You can view detailed information about the clinical diagnostic criteria for PWS on the NICHD Web site by the National Institutes of Health.
Last updated: 1/6/2015

How might Prader-Willi syndrome be treated?

A multidisciplinary team approach is ideal for the treatment of people with Prader-Willi syndrome (PWS). Early diagnosis, early multidisciplinary care, and growth hormone treatment have greatly improved the quality of life of many affected children. In general, management of this condition depends on the affected person's age and symptoms.[2]

When a diagnosis of PWS is made, several evaluations are needed to assess the extent of the condition. For example, newborns should be assessed for sucking problems; infants should be assessed for development; and young children should have a vision exam. All males should be evaluated for the presence of cryptorchidism. Other associated conditions for which evaluations may be recommended include hypothyroidism, scoliosis, behavioral problems, psychosis, and respiratory problems and sleep issues.[2]

In infants, special feeding techniques may be needed. Young children often need early intervention, including physical therapy for muscle strength and reaching physical milestones, and speech therapy for language issues. Cryptorchidism may resolve on its own but usually requires hormonal and/or surgical treatment. When excessive eating begins and weight centiles increase, affected children should be on a program of a well-balanced diet, exercise, and close supervision with food. A consultation with a dietitian is recommended. Behavioral problems may be addressed with special behavioral management programs. Serotonin uptake inhibitors have helped many affected teenagers and adults, particularly those with obsessive-compulsive symptoms.[2]

Growth hormone treatment can normalize height, increase lean body bass, and increase motility. Controlled trials of growth hormone therapies have shown significant benefit from infancy through adulthood. Benefits may include an increase in language and cognitive skills, and better motor performance. Sex hormone replacement helps to produce secondary sex characteristics (those that develop during puberty) but is somewhat controversial due to possible behavior problems in males, risk of stroke, and hygiene concerns related to menstruation in females.[2]

Clinical trials investigating potential treatment options for people with PWS are ongoing. ClinicalTrials.gov provides patients, family members, and members of the public with current information on clinical research studies. People interested in participating in clinical trials are encouraged to visit this site to determine if any trials would be helpful. Use each study's contact information to learn more. You can view a list of clinical trials for PWS here.
 
To learn more about how to find and participate in a research study, clinical trial, or patient registry, view our Get Involved in Research page.
 
You may also visit the Foundation for Prader-Willi Research's Diagnosis & Treatment page for additional information and links to a variety of valuable resources. Additional information about the management of PWS can also be viewed on the GeneReviews Web site and on Medscape's Web site
Last updated: 1/9/2015

What is the long-term outlook for people with Prader-Willi syndrome?

Children with Prader-Willi syndrome (PWS) can be mainstreamed into the classroom environment, although they need additional speech therapy and should have additional physical activity periods in place of rest periods. They generally need a structured environment and may need a smaller classroom size for individual attention.[3]

People with PWS usually reach adulthood and are able to function in a group home setting, performing vocational work, or attending community college classes.[3] According to the Prader-Willi Syndrome Association, people with PWS can expect to accomplish many of the things their peers do. However, they do need a significant amount of support from their families and from school, work, and residential service providers. Even those with IQs in the normal range need lifelong diet supervision and protection from food availability.[4]

Complications that could affect the quality of life and potentially shorten life expectancy include those relating to hypogonadism, behavioral or psychological issues, and morbid obesity.[3]
Last updated: 1/6/2015

References
  1. Prader-Willi syndrome. Genetics Home Reference. June, 2014; http://ghr.nlm.nih.gov/condition/prader-willi-syndrome. Accessed 1/5/2015.
  2. Driscoll DJ, Miller JL, Schwartz S, and Cassidy SB. Prader-Willi Syndrome. GeneReviews. January 23, 2014; http://www.ncbi.nlm.nih.gov/books/NBK1330/.
  3. Ann Scheimann. Prader-Willi Syndrome. Medscape. March 18, 2014; http://emedicine.medscape.com/article/947954-overview. Accessed 1/6/2015.
  4. FAQ. Prader-Willi Syndrome Association. March 2010; http://www.pwsausa.org/about-pws/faq.


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