Prader-Willi syndrome

Overview

Prader-Willi (PRAH-dur VIL-e) syndrome is a rare genetic condition that leads to physical, mental and behavioral problems. A key feature of Prader-Willi syndrome is a sense of being hungry all the time.

People with Prader-Willi syndrome want to eat all the time because they never feel full. This is called hyperphagia. As a result, they usually find it hard to manage their weight. Many complications of Prader-Willi syndrome are due to obesity.

A team of different types of specialists can best manage the symptoms of Prader-Willi syndrome. The team approach to this complex condition makes complications less likely and improves quality of life.

Causes

Prader-Willi syndrome is a genetic condition that is caused by an error in one or more genes. Although it's not known exactly what causes Prader-Willi syndrome, the problem lies in the genes in a region of chromosome 15.

Except for genes related to sex characteristics, all genes come in pairs. One copy is inherited from the father, known as a paternal gene. And one copy is inherited from the mother, known as a maternal gene. For most types of genes, if one copy is active, also known as expressed, then the other copy also is expressed. But it's typical for some types of genes to act alone.

Prader-Willi syndrome occurs because certain paternal genes that should be expressed aren't because:

• Paternal genes on chromosome 15 are missing.
• The child inherited two copies of chromosome 15 from the mother and no chromosome 15 from the father.
• There's some change in paternal genes on chromosome 15.

A missing or changed gene on chromosome 15 disrupts how a portion of the brain called the hypothalamus typically works. This part of the brain controls the release of hormones. A hypothalamus that isn't working properly can affect hunger, growth, sexual development, body temperature, mood and sleep.

In most cases, a random gene change that isn't inherited causes Prader-Willi syndrome. Finding which gene change caused Prader-Willi syndrome can help with genetic counseling.

Risk factors

A child with an error in one or more genes in chromosome 15 is at the highest risk of getting Prader-Willi syndrome. For example, one of the genes might be missing. This error may or may not be inherited.

Those who have a child with Prader-Willi syndrome and would like to have another baby should think about getting genetic counseling. A genetic counselor can help figure out the risk of having another child with Prader-Willi syndrome.

Complications

Obesity-related complications

In addition to being hungry all the time, people with Prader-Willi syndrome have low muscle mass. As a result, they need fewer calories, and they may not be physically active. These factors make them prone to obesity and the medical problems related to obesity, such as:

• Type 2 diabetes.
• High blood pressure.
• High cholesterol.
• Heart disease.
• Sleep apnea.
• Other complications, such as being more likely to have liver disease and gallstones.

Complications of not making enough hormones

Complications that come from not making enough hormones may include:

• Sterility. Although there have been a few reports of females with Prader-Willi syndrome becoming pregnant, most people with this condition can't have children.
• Osteoporosis. Osteoporosis causes bones to break easily. People with Prader-Willi syndrome are more likely to get osteoporosis because they have low levels of sex hormones. They also may have low levels of growth hormone. Both hormones support strong bones.

Other complications

Prader-Willi syndrome can cause other complications, including:

• Choking and stomach rupture. Eating large amounts of food quickly, called binge eating, can cause the stomach to become larger than usual. People with Prader-Willi syndrome may not report pain, and they rarely vomit. Binge eating also can cause choking. Rarely, people may eat so much that it ruptures their stomachs.
• Dental problems. Having less saliva and saliva that is thickened with dry mouth are common in Prader-Willi syndrome, as is poorly developed tooth enamel. These problems, combined with poor dental hygiene, can lead to dental cavities and gum disease.
• Reduced quality of life. Behavioral problems can affect family functioning, getting a good education and taking part in social activities. These issues lower the quality of life.

Prevention

If you have a child with Prader-Willi syndrome and would like to have another baby, think about getting genetic counseling. A genetic counselor can help you figure out the risk of having another child with Prader-Willi syndrome.