Q: What is Prader-Willi syndrome (PWS)?
A: PWS is a complex genetic disorder that typically causes low muscle tone,
short stature, incomplete sexual development, cognitive disabilities, problem behaviors,
and a chronic feeling of hunger that can lead to excessive eating and life-threatening
obesity.
Q: Is PWS inherited?
A: Most cases of PWS are attributed to a spontaneous genetic error that
occurs at or near the time of conception for unknown reasons. In a very small percentage
of cases (2 percent or less), a genetic mutation that does not affect the parent is passed
on to the child, and in these families more than one child may be affected. A
PWS-like
disorder can also be acquired after birth if the hypothalamus portion of the brain is
damaged through injury or surgery.
Q: How common is PWS?
A: It is estimated that one in 12,000 to 15,000 people has PWS. Although
considered a "rare" disorder, Prader-Willi syndrome is one of the most common
conditions seen in genetics clinics and is the most common genetic cause of
obesity that has been identified. PWS is found in people of both sexes and all races.
Q: How is PWS diagnosed?
A: Suspicion of the diagnosis is first assessed clinically, then confirmed
by specialized genetic testing on a blood sample. Formal diagnostic criteria for the
clinical recognition of PWS have been published (Holm et al, 1993), as have laboratory
testing guidelines for PWS (ASHG, 1996).
Q: What is known about the genetic abnormality?
A: Basically, the occurrence of PWS is due to lack of several genes on one
of an individual’s two chromosome 15s¾ the one normally
contributed by the father. In the majority of cases, there is a deletion—the
critical genes are somehow lost from the chromosome. In most of the remaining cases, the
entire chromosome from the father is missing and there are instead two chromosome 15s from
the mother (uniparental disomy). The critical paternal genes lacking in people with
PWS have a role in the regulation of appetite. This is an area of active research in a
number of laboratories around the world, since understanding this defect may be very
helpful not only to those with PWS but to understanding obesity in otherwise normal
people.
Q: What causes the appetite and obesity problems in PWS?
A: People with PWS have a flaw in the hypothalamus part of their brain,
which normally registers feelings of hunger and satiety. While the problem is not yet
fully understood, it is apparent that people with this flaw never feel full; they have a
continuous urge to eat that they cannot learn to control. To compound this problem, people
with PWS need less food than their peers without the syndrome because their bodies have
less muscle and tend to burn fewer calories.
Q: Does the overeating associated with PWS begin at birth?
A: No. In fact, newborns with PWS often cannot get enough nourishment
because low muscle tone impairs their sucking ability. Many require special feeding
techniques or tube feeding for several months after birth, until muscle control improves.
Sometime in the following years, usually before school age, children with PWS develop an
intense interest in food and can quickly gain excess weight if calories are not
restricted.
Q: Do diet medications work for the appetite problem in PWS?
A: Unfortunately, no appetite suppressant has worked consistently for people
with PWS. Most require an extremely low-calorie diet all their lives and must have their
environment designed so that they have very limited access to food. For example, many
families have to lock the kitchen or the cabinets and refrigerator. As adults, most
affected individuals can control their weight best in a group home designed specifically
for people with PWS, where food access can be restricted without interfering with the
rights of those who don't need such restriction.
Q: What kinds of behavior problems do people with PWS have?
A: In addition to their involuntary focus on food, people with PWS tend to
have obsessive/compulsive behaviors that are not related to food, such as repetitive
thoughts and verbalizations, collecting and hoarding of possessions, picking at skin
irritations, and a strong need for routine and predictability. Frustration or changes in
plans can easily set off a loss of emotional control in someone with PWS, ranging from
tears to temper tantrums to physical aggression. While psychotropic medications can help
some individuals, the essential strategies for minimizing difficult behaviors in PWS are
careful structuring of the person's environment and consistent use of positive behavior
management and supports.
Q: Does early diagnosis help?
A: While there is no medical prevention or cure, early diagnosis of
Prader-Willi syndrome gives parents time to learn about and prepare for the challenges
that lie ahead and to establish family routines that will support their child's diet and
behavior needs from the start. Knowing the cause of their child’s developmental
delays can facilitate a family's access to important early intervention services and may
help program staff identify areas of specific need or risk. Additionally, a diagnosis of
PWS opens the doors to a network of information and support from professionals and other
families who are dealing with the syndrome.
Q: What does the future hold for people with PWS?
A: With help, people with PWS can expect to accomplish many of the things
their "normal" peers do—complete school, achieve in their outside areas of
interest, be successfully employed, even move away from their family home. They do,
however, need a significant amount of support from their families and from school, work,
and residential service providers to both achieve these goals and avoid obesity and the
serious health consequences that accompany it. Even those with IQs in the normal range
need lifelong diet supervision and protection from food availability.
Although in the past many people with PWS died in adolescence or young adulthood,
prevention of obesity can enable those with the syndrome to live a normal lifespan. New
medications, including psychotropic drugs and synthetic growth hormone, are already
improving the quality of life for some people with PWS. Ongoing research offers the hope
of new discoveries that will enable people affected by this unusual condition to live more
independent lives.
Q: How can I get more information about PWS?
A: Contact the Prader-Willi Syndrome Association (USA) at 1-800-926-4797.
A strong national organization of families and professionals, PWSA (USA) offers a
toll-free helpline, a bimonthly member newsletter and numerous publications about PWS, a
World Wide Web page (www.pwsausa.org), an annual family conference and scientific meeting,
and chapters throughout the country to provide local family support and advocacy.
The Prader-Willi Syndrome Association (USA) was formed in 1975 in order to provide a
vehicle of communication for parents, professionals and other interested citizens. It is
an organization dedicated to the sharing of experiences in how to cope with the syndrome.
Chapters of PWSA(USA) are located in most states and are available for support, education
and advocacy.
An annual national conference, a bi-monthly newsletter entitled The Gathered View,
which incorporates contributions from members as well as professional advice and a wealth
of other written materials and publications on Prader-Willi Syndrome, are all part of
PWSA's effort to carry out its mission.
Supported solely by membership fees and donations, Prader-Willi Syndrome Association
(USA) has made a difference in the lives of many affected by this unique syndrome. YOU,
TOO, CAN HELP. Donations and membership applications may be sent to the address below.
