Prader-Willi Syndrome (PWS)
is a relatively rare genetically determined neurodevelopmental disorder. People
with the syndrome have their own individual characteristics but share in common
particular physical features, specific cognitive strengths and weaknesses, and
a propensity to particular behaviors and mental health problems that change with
age and together make up the early and later physical and behavioral phenotypes
of the syndrome.
Prader-Willi is caused by
the deletion of a gene on chromosome 15. The majority of patients have a
deletion of the father's DNA in this region. The remaining patients frequently
have two copies of the mother's chromosome 15. The maternal copy of this gene
is turned off in all people. When there is a deletion of the father's DNA
(approximately 70% of patients), the disease occurs. This is because the
patient is left with only the inactive, maternal copy.
manifestations of PWS are generally evident at birth. Babies
with the condition are often small and very floppy (hypotonic). Males may have undescended
testicles. The growing child exhibits slow mental and delayed motor
development, increasing obesity, and characteristically small hands and feet.
Mental development is slow, and the IQ seldom exceeds 80.
After an initial unwillingness to feed, children with PWS develop
an intense craving for food, which leads to morbid obesity. This is a life-long
problem that, without intervention, results in uncontrollable weight gain.
Morbid obesity (the degree of obesity that seriously affects health) may lead
to respiratory failure with hypoxia (low blood oxygen levels), cor pulmonale
(right-sided heart failure), and death. Appetite suppressants are shown not to
work, and stomach stapling is ineffective. While people with PWS can
demonstrate will power in other areas of their life, food seeking and eating
(even out of waste receptacles) cannot be controlled. Sufferers will go to
great lengths to obtain anything even vaguely edible. Unless their diet is
carefully controlled (locks on cupboards and the fridge, and even the doors to
the house, for example) weight gain can be very rapid. Coupled with an
inability to recognize when they are full, PWS sufferers have a greatly reduced
capacity to feel pain. People with the syndrome have been known to walk around
with a broken arm hanging limply by their side without any recognition that it
disorders are common in people with PWS, with obsessive behaviors most evident.
A propensity for affective disorders (e.g., rage, anxiety and panic attacks)
appears to be higher in PWS sufferers than in the normal population.
This book, Prader-Willi Syndrome follows a process of
discovery that included getting to know many people with PWS and their families
through the undertaking of a population-based study of children and adults with
PWS living in the then Anglia and Oxford Health Region of the United Kingdom.
The aims of this study were to systematically investigate many aspects of the
syndrome free from the selection biases that may have influenced previous
clinic and volunteer-based studies. The in-depth knowledge gained from this
Cambridge study through direct contact with people with PWS, their families and
other carers, and the integration of this knowledge with that in the
literature, has led in turn to new hypotheses and new interpretations of some
aspects of PWS.
authors of this book, both Cambridge University scholars, were motivated to do
this study because they recognized that to understand
PWS fully there is the need to integrate research from the diverse fields of
genetics and the behavioral, medical and neurosciences. The integration of
these scattered and still incomplete areas of knowledge is the central aim of
this book. By doing this the pathophysiological mechanisms linking the observed
genetic abnormality (genotype) to the physical, behavioral, and psychiatric
manifestations (phenotype) of the syndrome are well elucidated (though personal
accounts of PWS sufferers would have supplied yet another valuable dimension to
the study). The study, as is, enables the development of interventions to
modify aspects of the phenotype and thereby increase the possibility of a good
quality of life for those with the syndrome and their families. Highly
© 2005 Elizabeth McCardell
McCardell, PhD, Independent scholar, Australia.