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Prader-Willi syndrome (PWS) is a rare genetic disorder due to an abnormality on the 15th chromosome resulting in an excessive preoccupation with food and constant hunger, which in turn can lead to obesity and obesity–related health problems. Hypotonia (sometimes called “floppy baby syndrome”), small stature, cognitive delays, and other developmental disabilities are also associated with PWS. There are three ways chromosome 15 is affected: as a paternal deletion, a maternal disomy (UPD), or through an imprinting error. Sixty to seventy percent of people with PWS have a section of their chromosome 15 that is deleted or missing on the chromosome contributed by the father (hence the name paternal deletion.) Recent research has indicated two different subtypes of paternal deletion that are characterized by whether a long (Type I) or short (Type II) section of the chromosome is missing. PWS is caused by a maternal disomy in about 25% of individuals with PWS. This occurs when the fetus receives two chromosomes 15s from the mother, and none from the father. Hence, there are still missing genes from the father, which are essential for normal development. Imprinting is the least common form of PWS and occurs when the father’s chromosome 15 exists, but is not working properly.


Ironically, during the first two years of life, children with Prader-Willi syndrome are often considered failure to thrive due to poor muscle tone and poor sucking ability. During the toddler and adult years, children with PWS develop hyperphagia (excessive over-eating). The culmination of failure to thrive, hypotonia, and certain facial features such as almond-shaped eyes, may cue the physician for further genetic testing which is vital for diagnosis.


It is not uncommon for individuals with PWS to have sleep apnea, respiratory problems, high blood pressure, and/or diabetes. Anesthesia during surgery proves to be more complicated in people with Prader-Willi Syndrome than for the general population. Some of the complications noted are different responses to medications, high pain threshold, temperature instability, and thick saliva.Various behavioral problems arise in individuals with PWS.  Such issues may be compulsivity, temper tantrums, and skin picking. Family members may go to great lengths to ensure proper supervision so that overeating and food stealing won’t occur.


Overall, individuals with PWS are happy, healthy and fun to be around. Although they have many health concerns, they often lead very full and productive lives.

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