Prader-Willi syndrome is a rare condition that causes physical, mental, and behavioral problems. An unrelenting feeling of hunger is common.

A person with has extreme difficulty controlling their body weight, as they spend a long time eating and have a powerful compulsion to eat as much food as possible. PWS is the most common genetic cause of morbid obesity in children.

According to the Prader-Willi Syndrome Association in the United States, between people live with the condition.

Other suggest the syndrome occurs in between 1 in 10,000 and 1 in 30,000 people globally. It affects both sexes equally.

PWS occurs when genes are missing on chromosome 15.

PWS is a genetic condition, which means that people inherit it from their parents.

It is present from birth, although a diagnosis often does not occur until later in life.

People with PWS have seven genes on chromosome 15 that are either deleted or inactive.

They will often have low muscle tone, incomplete sexual development, and chronic hunger.

Their metabolism tends to burn fewer calories when compared to people who do not have the condition. Many individuals with PWS have short stature.

A new-born infant with PWS tends to have a lower-than-usual birth weight, weak muscles, and difficulties with sucking. Muscle weakness is known as hypotonia.

Individuals start developing a strong appetite called hyperphagia between 2 and 5 years of age and sometimes later.

This characteristic occurs due to a significantly decreased feeling of fullness after eating. Once hyperphagia begins, it tends to be a lifelong condition.

Symptoms of PWS typically develop in two stages.

The first symptoms often emerge during the first year of life, and others start to occur between the ages of 1 and 6 years old.

Symptoms in the first year

Between 0 and 12 months of age, an infant is likely to have some or all of the following symptoms:

The infant may also have an unusually weak cry, display incomplete responses to stimulation, and appear tired.

Genitals may not develop correctly, and depigmentation of the skin and eyes sometimes occurs.

Symptoms from age 1 to 6 years

Between 1 and 6 years of age, the following symptoms may occur:

There may be a high tolerance for pain. Short-sightedness is also common.

The Prader-Willi Syndrome Association is now increasingly seeing PWS as a of multiple stages rather than just the two used initially.

In Phase 2, at 18 to 36 months, body weight crosses over from being lower than average to higher without any additional interest in food or calorific intake.

Phase 3 starts around the age of 8 years and can carry on to adulthood. Relentless food-seeking begins and is a key feature of this stage.

Going forward, people with PWS undergo poor sexual development during puberty. Females may experience scant menstruation or none at all, and most adults with PWS may not be able to reproduce.

A nutritional therapist may prescribe high-calorie milk formula for an infant with feeding difficulties.

There is no cure for PWD.

However, ongoing therapies can help reduce symptoms by focusing on related hormone and developmental deficiencies.

Therapies that doctors might use include:

  • nutrition
  • growth
  • sex hormones
  • physical
  • speech
  • occupational
  • developmental

Nutrition therapy can supply an infant who is experiencing feeding difficulties with high-calorie milk formula.

A doctor who is treating PWS will closely monitor weight and growth, while a nutritionist may assist in developing a nutrient-dense, low-calorie diet that promotes weight control.

People with PWS must follow a very strict diet with lower-calorie goals than would be common for the age group. Parents and guardians may have to put physical barriers in place to account for food cravings, such as locking food inside kitchen cabinets.

Growth hormone treatment can help increase growth and reduce body fat, but the long-term effects of these are unclear.

Sex hormone treatment, such as hormone replacement therapy (HRT), can top up testosterone for boys and progesterone for girls. This helps with sexual development and can reduce the risk of osteoporosis.

Other treatments include:

  • developmental therapy to encourage age-appropriate social and interpersonal skills
  • occupational therapy to help with routine tasks
  • physical therapy to manage coordination and movement
  • speech therapy to promote communication ability

A person with PWS may also need to consult a psychologist or psychiatrist for help with the psychological effects of PWS.

Most people with PWS need supervision and specialized care throughout their lives. Continually restricting food and managing behavior can cause stress for family members, and family support and counseling groups can sometimes offer help.