Prader-Willi (PRAH-dur VIL-e) syndrome is a rare disorder present at birth that results in a number of physical, mental and behavioral problems. A key feature of Prader-Willi syndrome is a constant sense of hunger that usually begins at about 2 years of age.

People with Prader-Willi syndrome want to eat constantly because they never feel full (hyperphagia) and usually have trouble controlling their weight. Many complications of Prader-Willi syndrome are due to obesity.

If you or your child has Prader-Willi syndrome, a team of specialists can work with you to manage symptoms, reduce the risk of developing complications and improve quality of life.

Infants with Prader-Willi syndrome

Signs and symptoms of Prader-Willi syndrome generally occur in multiple phases. Signs that may be present from birth include:

  • Poor muscle tone. A primary sign during infancy is poor muscle tone (hypotonia). Babies may rest with their elbows and knees loosely extended instead of fixed, and they may feel floppy or like rag dolls when they're held.
  • Distinct facial features. Children 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. Infants may have a poor sucking reflex due to decreased muscle tone. Because poor sucking makes feeding difficult, they tend to gain weight slowly.
  • Lack of eye coordination (strabismus). The child's eyes may not move together — they may cross or wander to the side.
  • Generally poor responsiveness. A baby may seem unusually tired, respond poorly to stimulation, have a hard time waking up or have a weak cry.

Early childhood to adulthood

Other features of Prader-Willi syndrome appear during early childhood and remain throughout life, requiring careful management or treatment. These features may include:

  • Food craving and weight gain. Classic signs and symptoms include constant craving for food and rapid weight gain. Because a child with Prader-Willi syndrome may always be hungry, he or she eats frequently and consumes large portions. A child may develop unusual food-seeking behaviors, such as hoarding food or eating things such as garbage or frozen food.
  • Underdeveloped sex organs. A condition called hypogonadism occurs when sex organs — testes in men and ovaries in women — produce little or no sex hormones. This results in underdeveloped sex organs, incomplete development at puberty and, in nearly all cases, infertility. Without treatment, women may not start menstruating until their 30s, or they may never menstruate, and men may not have much facial hair, and their voices may never fully deepen.
  • Poor growth and physical development. Children with Prader-Willi syndrome have low muscle mass and high body fat. They may have small hands and feet. When a person with the disorder reaches full adult stature, he or she is usually shorter than other family members.
  • Intellectual disability. Mild to moderate impairment in intellectual functioning, such as thinking, reasoning and problem-solving (intellectual disability), is a common feature of the disorder. Even those without significant intellectual disability have some learning disabilities.
  • Delayed motor development. Toddlers with Prader-Willi syndrome often reach milestones in physical movement — for example, sitting up or walking — later than other children do.
  • Speech problems. Speech is often delayed. Poor articulation of words may be an ongoing problem into adulthood.
  • Behavioral problems. Children and adults may at times be stubborn, angry, controlling or manipulative. They may throw temper tantrums, especially when denied food. They may not tolerate changes in their routine. They may also develop obsessive-compulsive or repetitive behaviors, or both. Other mental health disorders, such as skin picking, may develop.
  • Sleep disorders. Adults and children with Prader-Willi syndrome may have sleep disorders, including disruptions of the normal sleep cycle and sleep apnea, a condition in which breathing pauses during sleep. These disorders can result in excessive daytime sleepiness and worsen behavior problems. Obesity may worsen sleep disorders.
  • Scoliosis. A number of children with Prader-Willi syndrome develop abnormal curvature of the spine (scoliosis).
  • Other endocrine problems. These may include insufficient production of thyroid hormone (hypothyroidism), growth hormone deficiency or central adrenal insufficiency, which prevents the body from responding appropriately during stress or infections.

Other signs and symptoms of Prader-Willi syndrome may include:

  • Nearsightedness (myopia) and other vision problems
  • Light skin and hair compared with other family members
  • High pain tolerance, making it difficult to identify injury or illness
  • Problems regulating body temperatures during fever or in hot and cold places

When to see a doctor

A number of conditions can cause some of the early signs of Prader-Willi, such as a failure to thrive, poor muscle tone and poor sucking. So it's important to get a prompt and accurate diagnosis. See your health care provider if your child shows any signs or symptoms listed above.

Prader-Willi syndrome is a genetic disorder, a condition caused by an error in one or more genes. Although the exact genes responsible for Prader-Willi syndrome haven't been identified, the problem lies in a particular region of chromosome 15.

With the exception of genes related to sex characteristics, all genes come in pairs — one copy inherited from your father (paternal gene) and one copy inherited from your mother (maternal gene). For most types of genes, if one copy is "active," or expressed, then the other copy also is expressed.

However, some types of genes act alone. For example, with certain genes it's normal for the paternal gene to be expressed and the maternal gene to be "silent," or repressed.

What happens in Prader-Willi syndrome

Prader-Willi syndrome occurs because certain paternal genes that should be expressed are not for one of these reasons:

  • 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 error or defect in paternal genes on chromosome 15.

Prader-Willi syndrome disrupts the normal functions of a portion of the brain called the hypothalamus. The hypothalamus controls hunger and thirst and releases hormones that prompt the release of other substances responsible for growth and sexual development. A hypothalamus that isn't functioning properly — caused by the defect on chromosome 15 — interferes with each of these processes, resulting in uncontrollable hunger, stunted growth, sexual underdevelopment and other characteristics of Prader-Willi syndrome.

Obesity-related complications

Many of the possible complications of Prader-Willi syndrome result from obesity. In addition to having constant hunger, people with the disorder have low muscle mass, so they require fewer than average calories. This combination of factors makes a person prone to obesity and the medical problems related to obesity, such as:

  • Type 2 diabetes. Type 2 diabetes affects the way your body metabolizes blood sugar (glucose), due to your body's inability to use insulin efficiently. Insulin plays a vital role in making blood sugar (your body's fuel) available to your cells. Obesity significantly increases the risk of diabetes.
  • Heart disease and stroke. People who are obese are more likely to have high blood pressure, hardened arteries, high cholesterol, and other factors that can lead to heart disease and stroke.
  • Sleep apnea. This sleep disorder is characterized by pauses in breathing during sleep. The disorder can cause daytime fatigue, high blood pressure and, rarely, sudden death. People with Prader-Willi syndrome may have sleep apnea or other sleep disorders even if they aren't obese, but obesity can worsen sleep problems.
  • Other complications. Obese people, including those with Prader-Willi syndrome, are at increased risk of liver disease and can have pain in their joints due to excessive wear and tear.

Complications of hypogonadism

Complications may also arise from hypogonadism, a condition in which your sex organs don't secrete sufficient amounts of the sex hormones testosterone (males) and estrogen and progesterone (females). These may include:

  • Sterility. Although there have been a few reports of women with Prader-Willi syndrome becoming pregnant, most people with this disorder are unable to have children.
  • Osteoporosis. Osteoporosis is a condition characterized by weak and brittle bones, which can break easily. People with Prader-Willi syndrome are at an increased risk of developing osteoporosis because they have low levels of sex hormones and may also have low levels of growth hormone — both hormones help maintain strong bones.

Other complications

Other complications can arise from the complex nature of Prader-Willi syndrome:

  • Effects of binge eating. Eating large amounts of food quickly, called binge eating, can cause your child's stomach to become abnormally distended (gastric dilatation). Individuals with Prader-Willi syndrome may not report pain and they rarely vomit. Binge eating can also cause choking and any of the other complications associated with obesity. Rarely, a person with Prader-Willi syndrome may eat so much that it causes stomach rupture.
  • Significant behavior problems. Behavioral problems can interfere with family functioning and successful education and social participation. They can also reduce the quality of life for children, teenagers and adults with Prader-Willi syndrome.

Well-baby visits

If you have a newborn infant, it's important to go to all regularly scheduled well-baby visits. These checkups can help identify early signs of poor growth and development, which can be signs of Prader-Willi syndrome or other disorders.

At each visit, your child's health care provider measures your baby's height, weight and head circumference. This enables your provider to track changes and identify problems. The provider also tests your child's muscle tone by seeing how your child responds to having his or her legs and arms moved. The complete physical exam includes checking the genitals for abnormalities.

Be prepared to answer questions that your baby's provider is likely to ask, such as:

  • How often and how much does your baby eat?
  • Does your baby have any problems sucking?
  • How well does your baby wake up?
  • Does your baby seem listless, weak or sick?

If you have any concerns about your baby's health between well-baby visits, schedule an appointment.

Visits during childhood

If you have concerns about your older child's weight gain, eating habits or other behaviors, schedule an appointment with your child's health care provider. Your provider may ask you questions such as:

  • How much does your child eat?
  • Does he or she constantly look for food?
  • Does your child eat any unusual items or steal or sneak food?
  • Does your child eat to the point of vomiting?
  • Does your child show extreme stubbornness or throw tantrums?
  • Does your child show any other troubling behaviors?

If your provider believes that your child shows signs of Prader-Willi syndrome or suggests diagnostic tests, consider asking these questions:

  • When will we know the results of the tests?
  • How often should we schedule follow-up visits?
  • What treatments and care strategies do you recommend?
  • How will we know whether the treatment is helping?
  • What kind of diet should be followed?
  • How many daily calories are appropriate for my child?
  • Can you suggest educational materials and local support services?
  • What services are available for early childhood development?

In infants, signs that may prompt your health care provider to request a blood test for Prader-Willi syndrome include:

  • Poor muscle tone and a weak cry
  • Poor sucking and feeding problems
  • Almond-shaped eyes and narrowing of the head at the temples
  • Problems with growth and development

In older children, your child's health care provider may suspect Prader-Willi syndrome if your child exhibits:

  • Excessive eating and weight gain
  • Underdeveloped sex organs
  • Short height and small hands and feet
  • Developmental delays
  • Intellectual disability
  • Thick and sticky saliva

A definitive diagnosis can almost always be made with a lab test. Special genetic tests can identify abnormalities in your child's chromosomes that indicate Prader-Willi syndrome.

Early diagnosis and treatment can improve quality of life for a person with Prader-Willi syndrome. A team of health professionals will likely work with you to manage the condition.

Most children with Prader-Willi syndrome will need the following care and treatments:

  • Good nutrition for infants. Many infants with Prader-Willi syndrome have difficulty feeding due to decreased muscle tone. Your child's health care provider may recommend a high-calorie formula or special feeding methods to help your baby gain weight and will monitor your child's growth.
  • Human growth hormone treatment. Human growth hormone (HGH) stimulates growth and influences the body's conversion of food into energy (metabolism). Growth hormone treatment in children with Prader-Willi syndrome helps increase growth, and likely improves muscle tone and decreases body fat. Long-term effects of HGH treatment aren't known. A doctor who treats hormonal disorders (endocrinologist) can help determine whether your child would benefit from growth hormone treatment.
  • Sex hormone treatment. Your endocrinologist may suggest that your child take hormone replacement therapy (testosterone for males or estrogen and progesterone for females) to replenish low levels of sex hormones. Hormone replacement therapy usually starts when your child reaches the normal age for puberty and can help reduce your child's risk of developing thinning of the bones (osteoporosis).
  • Healthy diet. As your child gets older, a dietitian may help you develop a healthy, reduced-calorie diet to keep your child's weight under control while ensuring proper nutrition. Restricted access to food and strict supervision of food intake may be required.
  • Treatment of sleep disturbances. Treating sleep apnea and other sleep problems can improve daytime sleepiness and behavioral issues. A sleep evaluation should be done before starting growth hormone treatment.
  • Overall development. Your child will likely benefit from a range of therapies, including physical therapy to improve movement skills and strength, speech therapy to improve verbal skills, and occupational therapy to learn everyday skills. Developmental therapy to learn age-appropriate behaviors, social skills and interpersonal skills also may help. In the United States, early intervention programs providing these types of therapy are usually available for infants and toddlers through a state's health department.
  • Mental health care. A mental health professional, such as a psychologist or a psychiatrist, may help address psychological problems your child may have — for example, obsessive-compulsive behaviors or a mood disorder. Some children may need medication to control behavioral problems.

Other treatments may be necessary, depending on the specific symptoms your child has or complications that develop.

Transition to adult care

Most people with Prader-Willi syndrome will need specialized care and supervision throughout their 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.

As your child approaches adulthood, consider these strategies:

  • Find local resources and services through organizations such as the Prader-Willi Syndrome Association
  • Investigate guardianship issues and wills regarding future care and supervision for your child
  • Talk to your child's health care provider for suggestions about making the transition to adult medical care

Tips to help you take care of your loved one with Prader-Willi syndrome include the following:

  • Pick up your child carefully. Babies and children with Prader-Willi syndrome have poor muscle tone, which increases their risk of slipping between your hands when you lift them under their armpits.
  • Stick to a strict meal plan. Eating a low-calorie diet is essential to keep your child from becoming overweight. Structure meal times and the type of food provided to help develop routines and to help your child understand expectations.
  • Take steps to help prevent binge eating. Avoid buying high-calorie snacks. Store food out of your child's reach. Lock pantries, refrigerators and cupboards. Use small dishes for serving meals.
  • Ask about supplements for your child's diet. If your child is on a restricted-calorie diet, ask your health care provider if supplemental vitamins or minerals are necessary to ensure balanced nutrition.
  • Encourage regular daily activity. Increasing physical activity and exercise can help manage weight and improve physical functioning.
  • Set limits. Create a firm schedule and work on behavioral problems. If needed, seek help to address problems.
  • Schedule appropriate screening tests. Talk with your health care provider about how often screening is needed for complications of Prader-Willi syndrome, such as diabetes, osteoporosis or an abnormally curved spine (scoliosis).

Having a child with Prader-Willi syndrome and related behavioral problems is challenging and can take a lot of patience. Managing eating problems, behaviors and medical issues can impact the whole family.

Some people find it helpful to talk with others who share similar experiences. Ask your health care provider about family support groups in your area. Organizations such as the Prader-Willi Syndrome Association provide resources, support groups and educational materials. You can reach the Prader-Willi Syndrome Association at 800-926-4797.

Defective or missing portions of paternal genes responsible for Prader-Willi syndrome usually occur randomly. This means that in most instances, Prader-Willi syndrome can't be prevented. 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.

Apr. 17, 2014