What is Prader-Willi syndrome?

Prader-Willi syndrome
Classification and external resources
Patient with the syndrome showing characteristic facial appearance, with elongated face, prominent nose, and smooth philtrum
ICD-10	Q87.1
ICD-9	759.81
OMIM	176270
DiseasesDB	10481
eMedicine	ped/1880
MeSH	D011218

Prader–Willi syndrome (abbreviated PWS) is a rare genetic disorder in which seven genes (or some subset thereof) on chromosome 15 (q 11-13) are deleted or unexpressed (chromosome 15q partial deletion) on the paternal chromosome. It was first described in 1956 by Andrea Prader, Heinrich Willi, Alexis Labhart, Andrew Ziegler, and Guido Fanconi of Switzerland.^[1] The incidence of PWS is between 1 in 10,000 and 1 in 25,000 live births. The paternal gene origin is lost due to deletion and the maternal genes are silenced due to imprinting. PWS has the sister syndrome Angelman syndrome that includes maternally deleted and paternally imprinted genes in the same genetic region.

 patient with the syndrome, showing characteristic facial appearance, with elongated face, prominent nose

What is Prader-Willi syndrome?
Prader-Willi Syndrome is an uncommon genetic disorder that causes poor muscle tone, low levels of sex hormones and a constant feeling of hunger among other things. People with this disorder have a problem with their hypothalamus, part of the brain that controls feelings of fullness or hunger. Thus, these people never feel full and have a constant urge to eat, ultimately leading to life-threatening obesity.
Prader-Willi syndrome in most cases result from a spontaneous genetic mutation in genes on chromosome 15 that occurs at conception.  In rare cases, the mutation is inherited.
What are the symptoms of Prader-Willi syndrome?
Often people with this disorder experience symptoms in two stages.
Stage 1 - Infants with Prader-willi syndrome can have low muscle tone affecting their ability to such properly. Because of this, they need special feeding assistance to help them eat and they may have problems gaining weight.  The situation gets better as they grow older.
Stage 2--Between the ages of 1 and 6 years, the children with the disorder may feel constant hunger, have an insatiable appetite, meaning they never feel full.
Although they eat more, but because they have less muscle mass,  they do not burn as many calories as the normal peers leading to the development of life-threatening obesity if the diet is not kept under strict control.
Other symptoms that may affect people with Prader-Willi syndrome include
Behavioral problems such as stubbornness or temper tantrums
Delayed motor skills and speech due to low muscle tone
Cognitive problems, ranging from near normal intelligence to mild intellectual and developmental disabilities; learning disabilities are common
Repetitive thoughts and verbalizations
Collecting and hoarding of possessions
Picking at skin
Low sex hormone levels
Prader-Willi syndrome is considered a spectrum disorder, meaning that not all symptoms are expected to occur in everyone with the disorder and the symptoms may range from mild to severe.
People with Prader-Willi syndrome often have some special mental strengths as well, such as skills in jigsaw puzzles.  If obesity can be prevented, people with the syndrome can live a normal lifespan.
What are the treatments for Prader-Willi syndrome?
There is no cure for Prader-Willi syndrome. But, early intervention can help people with the disorder build skills for living a better life.  Early diagnosis is essential and luckily a health care provider can simply do a blood test to check for Prader-Willi syndrome.
Exercise and physical activity can help control weight gain and develop motor skills.  Speech therapy may also help with oral skills.
Human growth hormone can help increase height, decrease body fat, and increase muscle mass.  However, nothing can help control appetite in those with Prader-Willi syndrome.