How is Prader-Willi Syndrome Diagnosed?

A suspected diagnosis of Prader-Willi syndrome (PWS) is usually made by a physician based on clinical symptoms. PWS should be suspected in any infant born with significant hypotonia (muscle weakness or “floppiness”). The diagnosis is confirmed by a blood test. The preferred method of testing is a “methylation analysis,” which detects >99% of cases, including all of the major genetic subtypes of PWS (deletion, uniparental disomy, or imprinting mutation). A “FISH” (fluorescent in-situ hybridization) test will identify those patients with PWS due to a deletion, but it will not identify those who have Prader-Willi syndrome by “UPD” (uniparental disomy) or an imprinting error.

Almost all cases of PWS can be confirmed by one of the above tests. However, in the rare event that laboratory tests do not confirm PWS, a clinical diagnosis can be helpful for the development of a management plan.

Is Prader-Willi syndrome curable?

Currently, there is no cure for PWS. The lives individuals with PWS can be improved with an early diagnosis and careful management of symptoms (see below), but more effective therapies are needed. Our work to accelerate PWS research offers hope for the development of more effective treatments and an eventual cure. A working list of therapies in development for PWS can be found here.

Are any treatments available for Prader-Willi syndrome?

The treatment of PWS is currently based on treating the symptoms of the disorder as they arise. General guidelines for the care of those with PWS have been published and are available here and here. These are good to keep on hand and share with your general health care provider.

Growth hormone deficiency is present in almost all children and many adults with PWS. In multiple studies, human growth hormone (HGH) has been found to be beneficial for those with Prader-Willi syndrome. In June of 2000, HGH was officially approved by the Federal Drug Administration (FDA) in the United States for use in patients with Prader-Willi syndrome. HGH is effective not only in increasing height, but also in decreasing body fat, increasing muscle mass, improving weight distribution, increasing stamina, and increasing bone mineral density. In addition, studies suggest its positive effects on development and behavior. In 2013, guidelines for the use of HGH in PWS were developed as part of an international meeting of experts – these guidelines are available here and provide an excellent overview of GH use in PWS. Summaries of the use of growth hormone in PWS can be found on this page and in our Growth Hormone Therapy for PWS Fact Sheet.

Despite HGH treatment, many challenging symptoms associated with PWS remain difficult to treat. The inability to control food intake is often the biggest obstacle keeping those with PWS from living independently. To date, no medications have proven effective in normalizing hunger and satiety in PWS, and therefore, strict environmental control and constant supervision are the only ways to prevent life-threatening overeating and extreme obesity at present. However, there are a number of novel anti-obesity drugs in clinical development, some of which might benefit the PWS population, and evaluation of these drugs in clinical trials is an important priority for FPWR. In the meantime, a well-balanced diet is recommended, along with careful control of the environment to minimize uncontrolled access to food.

Additional challenges in PWS include sleep disorders, hormone abnormalities, scoliosis, dental issues, and skin picking. Breathing issues during sleep are common and periodic sleep studies are suggested for all ages, including infants. Excessive daytime sleepiness may be improved by approved wake-promoting medications (including modafinil) with new clinical trials ongoing. Hormone abnormalities common in PWS (low hormones, including thyroid, testosterone, and estrogen) may be treated by an endocrinologist with standard medications. An overview of endocrine issues for health care providers can be accessed here as well as further information on hypogonadism diagnosis and treatment in PWS. Scoliosis is also very common in PWS and should be treated by an orthopedic physician familiar with PWS. Dental problems also occur frequently in PWS, probably in part due to thicker saliva that is common. You can read about tooth wear and PWS here or learn more by reading our research blog post on oral health. Skin picking is common in those with PWS, and may be helped by the use of N-acetylcysteine, you can read more about skin picking in our research blog post: Skin Picking In PWS.

Finally, management and treatment of the psychiatric and behavioral issues associated with PWS also can be very challenging. A combination of behavioral therapy, environmental control, and medication may be needed. Consultation with mental health professionals familiar with PWS is recommended. The Pittsburgh Partnership offers resources for behavioral and psychiatric concerns in PWS that can be downloaded here.

Additional Resources

Additional resources, including information about educational and support services, are available through the PWS Medical Home Portal and National PWSA-USA websites. For those living outside the USA, FPWR Canada, PWSA (UK) and the IPWSO websites provide additional information for parents, caregivers, and others interested in learning more about PWS.

Downloadable Resources:

First Steps: A Parent’s Guide to Prader-Willi Syndrome
What Is PWS — fact sheet
Growth Hormone and PWS — fact sheet
Understanding PWS — slide deck
An Open Label Pilot Study of N-Acetylcysteine for Skin-Picking in Prader-Willi Syndrome download
Efficacy of Modafinil on Excessive Daytime Sleepiness in Prader-Willi Syndrome download
A Reduced-Energy Intake, Well-Balanced Diet Improves Weight Control in Children With Prader-Willi Syndrome download
Clinical Report – Health Supervision for Children with Prader-Willi Syndrome download
Recommendations for the Diagnosis and Management of Prader-Willi Syndrome download
Endocrine Manifestations and Management of Prader-Willi Syndrome download
Severe Tooth Wear in Prader-Willi Syndrome download
Growth hormone consensus guidelines download
Sleep disorders in PWS and sleep study recommendations download
Parenting and managing behavior for a child with Prader-Willi Syndrome, video

Frequently Asked Questions

How do these genetic defects cause the symptoms seen in Prader-Willi syndrome?

The PWS region of chromosome 15 is one of the most complex regions of the human genome. Although there have been signficant advances in understanding and characterizing the genetic changes associated with PWS, the exact mechanism by which lack of functional genetic material in this region leads to the symptoms associated with PWS is not understood. Scientists are actively studying the normal role of the genetic sequences in the PWS region and how their loss affects the hypothalamus and other systems in the body.

Is Prader-Willi syndrome hereditary?

Deletion and UPD are random occurrences and generally are not associated with an increased risk of recurrence in future pregnancies. In the case of an imprinting mutation, Prader-Willi syndrome can reoccur within a family. Families with concerns about their risk for PWS should speak to a genetic counselor.

Diagnosis & Treatment