QUESTIONS AND ANSWERS ON PRADER-WILLI SYNDROME
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
hypothalamic portion
of the brain is damaged through injury or surgery. All families with a child
diagnosed with PWS should see a geneticist for genetic counseling in
order to fully understand their chances of having another child with
PWS.
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 15s— 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 or email pwsaweb@gmail.com
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.
Last Edited:
02/09/2012
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