Prader-Willi syndrome
<p ><b>Prader–Willi syndrome</b> (<img src="/1f4c615a-59a5-5fdc-855d-3db8fbbf8542.png"/> <a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" >ˈprɑːdər</a> <a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" > ˈvɪli</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a>; abbreviated <b>PWS</b>) is a rare <a href="http://en.wikipedia.org/wiki/Genetic_disorder" title="Genetic disorder" >genetic disorder</a> in which seven genes (or some subset thereof) on <a href="http://en.wikipedia.org/wiki/Chromosome_15_(human)" title="Chromosome 15 (human)" >chromosome 15 (q 11–13)</a> are deleted or unexpressed (<a href="http://en.wikipedia.org/wiki/Chromosome_15q_partial_deletion" title="Chromosome 15q partial deletion" >chromosome 15q partial deletion</a>) on the paternal chromosome. It was first described in 1956 by <a href="http://en.wikipedia.org/wiki/Andrea_Prader" title="Andrea Prader" >Andrea Prader</a> (1919–2001), Heinrich Willi (1900–1971), Alexis Labhart (1916), Andrew Ziegler, and <a href="http://en.wikipedia.org/wiki/Guido_Fanconi" title="Guido Fanconi" >Guido Fanconi</a> of <a href="http://en.wikipedia.org/wiki/Switzerland" title="Switzerland" >Switzerland</a>.<sup id="cite_ref-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Prader-Willi_syndrome#cite_note-0" >[1]</a></sup> </p>
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Characteristic of PWS is "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."<sup id="cite_ref-1" class="reference" ><a href="http://en.wikipedia.org/wiki/Prader-Willi_syndrome#cite_note-1" >[2]</a></sup> The incidence of PWS is between 1 in 25,000 and 1 in 10,000 live births<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup>. The paternal origin of the genetic material that is affected in the syndrome is important because the particular region of chromosome 15 involved is subject to parent of origin<a href="http://en.wikipedia.org/wiki/Genomic_Imprinting" title="Genomic Imprinting" class="mw-redirect" >imprinting</a>, meaning that for a number of genes in this region only one copy of the gene is expressed while the other is silenced through imprinting. </p>
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For the genes affected in PWS, it is the paternal copy that is usually expressed, while the maternal copy is silenced<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup>. This means that while most people have a single working copy of these genes, people with PWS have a non-working copy and a silenced copy. PWS has the sister syndrome <a href="http://en.wikipedia.org/wiki/Angelman_syndrome" title="Angelman syndrome" >Angelman syndrome</a> in which maternally derived genetic material is affected in the same genetic region.</p>
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Many medical professionals are relying on information about PWS which covers the experiences of those with the syndrome, who may be 65 years old or may be 6 months old. The syndrome can affect each individual differently, depending on many factors. Current clinical and diagnostic descriptions of the syndrome must necessarily cover all of the "symptoms" of all individuals with PWS - However this does not mean that every child diagnosed with PWS will deal with every experience listed. Real experience with Prader-Willi Syndrome is best sourced from parents of children with the syndrome, and from medical professionals whose patient case-load is primarily individuals with PWS. </p>
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Any families who are faced with a diagnosis of Prader-Willi Syndrome are strongly encouraged to contact another family who are managing with the condition.</p>
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With the recent benefits of early diagnosis and ongoing interventions the obesity rate among children with Prader-Willi Syndrome has decreased to be similar to the typical population. With behavioural therapy and other treatments the effects of the syndrome can be reduced.<sup id="cite_ref-2" class="reference" ><a href="http://en.wikipedia.org/wiki/Prader-Willi_syndrome#cite_note-2" >[3]</a></sup></p>