Prader-Willi syndrome (PWS) is a rare disorder that is present at birth and results in a number of physical, mental and behavioral problems, with the key characteristic being a constant sense of hunger that generally begins after the first year of life.
While it is a rare disorder, PWS is the most common known genetic cause of life-threatening obesity in children. Approximately 1 in 10,000 to 1 in 25,000 suffer from PWS with prevalence estimates ranging from 1:10,000 to 1:27,000. It occurs equally in males and females and in all races.
People with PWS have the desire to eat constantly and usually have trouble controlling their weight. Many complications of the syndrome are due to obesity.
The signs and symptoms of Prader-Willi syndrome generally occur in two stages: one stage occurs from birth to the first year of life and the second stage occurs from age one to age four.
Signs of the disorder that may appear in the first year of life include:
Poor muscle tone: This is a primary sign during infancy. Babies may rest with their elbows and knees loosely extended instead of fixed, and may feel floppy when they're held.
Distinct facial features: Children with PWS may be born with almond-shaped eyes, a narrowing of the head at the temples, a turned-down mouth and a thin upper lip.
Failure to thrive: During the first year of life, children may have a poor sucking reflex due to decreased muscle tone. Because of this, feeding is difficult and they tend to gain weight slowly.
Lack of eye coordination: The eyes of a child with PWS may not move together, thus causing them to cross or wander to the side.
Generally poor responsiveness: Babies with PWS may seem unusually tired, respond poorly to stimulation, wake with difficulty, or have a weak cry.
From about the ages of 1 to 4, other signs of Prader-Willi appear, which will remain present throughout life. These signs may include:
Food craving and weight gain: These are the classic signs of the syndrome. A child with PWS is always hungry, eating frequently, and consuming large portions.
Underdeveloped sex organs: A condition called hypogonadism occurs when sex organs produce little or no sex hormones. This results in underdeveloped sex organs, incomplete development at puberty, and in nearly all cases infertility.
Poor growth and physical development: Children with Prader-Willi syndrome have low muscle mass. They may have short hands and feet.
Learning disabilities: Mild to moderate cognitive impairment is a common feature of the disorder. Essentially all people with PWS have some learning disabilities. The average IQ of a person with PWS is 70.
Other signs include: delayed motor development, speech problems , behavioral problems, sleep disorders, scoliosis, nearsightedness, light skin compared with other family members, and high pain tolerance.
Prader-Willi syndrome is a genetic disorder, a condition caused by a missing gene or a defect on a region of chromosome 15.
This genetic defect disrupts the normal roles of a portion of the brain called the hypothalamus. Among its many functions, the hypothalamus controls hunger and thirst, and releases hormones that trigger the release of other substances responsible for growth and sexual development. A malfunctioning hypothalamus interferes with each of these processes, resulting in uncontrollable hunger, stunted growth, sexual underdevelopment, and the other characteristics of PWS.
Many complications of Prader-Willi syndrome result from obesity. In addition to having constant hunger, people with the disorder have low muscle mass, which means they need less calories than the average person. This combination of factors makes a person subject to obesity and the medical problems related to obesity.
Possible complications include: Type 2 diabetes, heart disease and stroke, and sleep apnea.
Other complications arise from hypogonadism, a condition in which the sex organs do not secrete adequate amounts of the sex hormones. These may include sterility and osteoporosis.
Tests and diagnosis
When signs of the syndrome appear, a doctor can request a blood test for PWS. A conclusive diagnosis can almost always be made with a laboratory test. There are also special genetic tests which can identify abnormalities in a child's chromosomes.
Treatments and drugs
Most children with PWS will need a variety of care and treatments including: good infant nutrition, growth hormone treatment, sex hormone treatment, a healthy diet, and a range of therapies from physical to speech to occupational.
Transition to adulthood
Most people with PWS will need specialized care and supervision throughout their entire lives. Many adults with the disorder live in residential care facilities that enable them to eat healthy diets, live safely, work and enjoy leisure activities.
For more insight into this rare disorder, check out the following video links: Kids Who Can't Stop Eating; Living With Prader-Willi.
Defective or missing portions of the genes responsible for Prader-Willi syndrome usually occur randomly. This means that in most instances, PWS syndrome cannot be prevented. Note, however, in a small number of cases, a genetic mutation inherited from the father may cause Prader-Willi syndrome.
If you have a child with Prader-Willi syndrome and would like to have another baby, consider seeking genetic counseling. A genetic counselor may help determine your risk of having another child with Prader-Willi syndrome.
For more information, check out the following websites:
Prader-Willi Syndrome Association
International Prader-Willi Syndrome Organization