Prader-Willi Syndrome (PWS)

Prader-Willi syndrome is a rare neurobehavioral genetic disorder that affects both males and females.

Prader-Willi syndrome (PWS) is a rare neurobehavioral genetic disorder that affects both males and females. PWS is a life-threatening medical disorder caused by loss of active genetic material on chromosome 15.

Prevalence estimates range from 1 in 15,000 to 1 in 25,000 live births worldwide translating to an estimated 8,000 to 10,000 patients in the United States.

PWS affects the functioning of the hypothalamus and other aspects of the brain with symptoms varying by individuals. The most common symptom is hyperphagia, which is an unrelenting lack of satiety, to which a deficiency in oxytocin is believed to be contributory. Oxytocin is a natural hormone that regulates several functions in the body, including hunger, anxiety, social behavior, and bonding. Individuals living with PWS have fewer oxytocin-producing neurons in the brain.

Hyperphagia in PWS is associated with the lack of a normal satiety response, in addition to a low basal metabolic rate. Despite adequate energy reserves, these patients are subjected to a false state of starvation. If left unsupervised, patients with hyperphagia are known to eat to the point of gastric rupture. Due to irregular swallowing and rapid food consumption, patients with PWS also have a greater propensity to choke while eating. Thus, hyperphagic patients require constant supervision.

Other defining features of the syndrome may include altered metabolism, developmental delays, behavioral challenges and moderate cognitive deficits. Patients may also experience high pain tolerance, sleep disturbances, gastrointestinal issues, respiratory and temperature regulation abnormalities.

There is no FDA approved treatment for the hyperphagia associated with PWS.


Prader-Willi syndrome occurs worldwide in approximately one of every 15,000 to 25,000 births.


Common symptoms of PWS often include growth hormone deficiency, abnormal growth and body composition, hypotonia (weak muscles), extreme obesity, and hyperphagia (an insatiable appetite and lack of satiety).

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