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.

Symptoms of Prader-Willi syndrome, which can vary, slowly change over time from childhood to adulthood.

Infants

Symptoms that may be present from birth include:

• Poor muscle tone. A main sign during infancy is poor muscle tone, also known as hypotonia. Babies may rest with their elbows and knees loosely extended instead of fixed. They also may feel floppy or like rag dolls when they're held.
• Distinct facial features. Babies may be born with almond-shaped eyes, a narrowing of the head at the temples, a turned-down mouth and a thin upper lip.
• Poor sucking reflex. Infants may have a poor sucking reflex because they have less muscle tone. Poor sucking makes feeding hard and can make it less likely they'll gain weight at the expected rate.
• Generally poor responsiveness. A baby may seem very tired, respond poorly to stimulation, have a hard time waking up or weakly cry.
• Underdeveloped genitals. Males may have a small penis and scrotum. The testicles may be small or not descend from the abdomen into the scrotum. This is known as cryptorchidism. In females, the clitoris and labia may be small.

Early childhood to adulthood

Other features of Prader-Willi syndrome appear when a child is very young and continue for life, including:

• Food craving and weight gain. A classic sign of Prader-Willi syndrome is a craving for food all the time, starting in early childhood. Being hungry all the time leads to eating often and eating large portions. This leads to quick weight gain. Unusual food-seeking behaviors, such as hoarding food, or eating frozen food or garbage, may occur.
• Underdeveloped sex organs. A condition called hypogonadism occurs when sex organs — testes in males and ovaries in females — produce little or no sex hormones. This leads to sex organs that don't develop fully and incomplete or delayed puberty. Nearly all people with Prader-Willi syndrome aren't able to get pregnant. Without treatment, females may not start their menstrual period until their 30s, or they may never have a period. Males may not have much facial hair, and their voices may never fully deepen.
• Poor growth and physical development. Not making enough growth hormone can shorten adult height and lead to low muscle mass and high body fat. Other endocrine problems may include not making enough thyroid hormone, also known as hypothyroidism. Another endocrine problem is central adrenal insufficiency, which keeps the body from responding properly to stress or infections.
• Having a hard time thinking, solving problems and learning. A common feature of Prader-Willi syndrome is having mild to moderate problems thinking, reasoning and problem-solving. This is called cognitive impairment. Even children and adults without cognitive impairment may have learning disabilities.
• Delayed motor skills. Toddlers with Prader-Willi syndrome often reach milestones in physical movement, such as sitting up or walking, later than other children.
• Speech problems. Speech often is delayed. Having a hard time choosing words and speaking clearly may continue as an adult.
• Behavioral problems. At times, children and adults may be very stubborn, angry, controlling or manipulative. They may throw temper tantrums, especially when denied food. They may not accept changes in routine. Also, they may start to show obsessive-compulsive or repetitive behaviors, or both. Other mental health conditions, such as anxiety and skin picking, may occur.
• Sleep conditions. Children and adults with Prader-Willi syndrome may have sleep conditions, including disruptions of the typical sleep cycle. They also may have sleep apnea, which is when breathing pauses during sleep. These conditions can make them very sleepy during the day and worsen behavior problems.
• Other symptoms. These symptoms may include small hands and feet, and curvature of the spine, also known as scoliosis. They also may have hip problems, less saliva flow, dental problems, and nearsightedness and other vision problems. Other symptoms include a lack of pigment, also known as hypopigmentation, which causes hair, eyes and skin to be pale. They also may have problems controlling their body temperature. They may be able to handle more pain than the average person.

When to see a doctor

Regularly scheduled well-baby visits can help find early signs of poor growth and development that can be signs of Prader-Willi syndrome or other conditions. If you have concerns about your baby's health between well-baby visits, schedule an appointment with your child's healthcare professional.

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.

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.

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.

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.

Typically, healthcare professionals suspect Prader-Willi syndrome based on symptoms. A diagnosis can be made through genetic testing nearly all the time. This blood test can find problems in your child's chromosomes that suggest Prader-Willi syndrome.

Early diagnosis and treatment can make quality of life better for people with Prader-Willi syndrome. A team of health professionals likely will manage the condition.

Your child's team may include a doctor who treats hormonal conditions, also known as an endocrinologist, as well as a behavior specialist, a dietitian, physical and occupational therapists, a speech and language therapist, a mental health professional, a geneticist, and other specialists.

Although specific treatments vary depending on symptoms, most children with Prader-Willi syndrome will need:

• Good nutrition. Many infants with Prader-Willi syndrome have a hard time feeding because they have less muscle tone. Your child's healthcare professional may recommend a high-calorie formula or special feeding methods to help your baby gain weight. They will monitor your child's growth.
• Human growth hormone (HGH) treatment. HGH treatment helps infants and children with Prader-Willi syndrome grow. It also makes muscle tone better and lowers body fat. HGH also may be used in adults. A doctor who treats hormonal conditions, also known as an endocrinologist, can help find out whether your child would benefit from HGH and talk about any risks.
• Sex hormone treatment. Your endocrinologist may suggest that your child take hormone replacement therapy — testosterone for males or estrogen and progesterone for females — because of low levels of sex hormones. Hormone replacement therapy usually starts when your child reaches the usual age for puberty. It can lower the risk of bone thinning, also known as osteoporosis. Your child may need surgery to correct undescended testicles.
• Weight management. A dietitian can help you create a healthy, reduced-calorie diet to help manage your child's weight while ensuring proper nutrition. A restricted-calorie diet may require supplemental vitamins or minerals to ensure balanced nutrition. Being more physically active and exercising can help manage weight and make your child better able to function physically.
• Treatment of sleep disturbances. Treating sleep apnea and other sleep problems can improve daytime sleepiness and behavioral issues.
• Various therapies. Your child likely will benefit from a range of therapies. These include physical therapy to make movement skills and strength better, speech therapy to make verbal skills better, and occupational therapy to learn everyday skills. Developmental therapy to learn age-appropriate behaviors, social skills and interpersonal skills also may help. In the U.S., early intervention programs with these types of therapy usually are available for infants and toddlers through a state's health department. During school years, educational planning and support can improve learning.
• Behavior management. You may need to create schedules for your child and set strict limits on access to food and how much food is eaten. It's important to be clear on what you expect in terms of your child's behavior. Sometimes medicine is needed to manage behavioral problems.
• Mental healthcare. A mental health professional, such as a psychologist or a psychiatrist, may help with mental health problems, such as obsessive-compulsive behaviors, skin picking, anxiety or a mood condition. Medicine may ease mental health symptoms.
• Other treatments. These may include managing specific symptoms or complications. For example, exams for vision issues or scoliosis and tests for hypothyroidism or diabetes may find problems.

Transition to adult care

Many adults with the condition live in residential care facilities that allow them to eat healthy diets, live safely, work and enjoy leisure activities.

As your child approaches adulthood, consider these plans:

• Find local resources and services for adults through your child's school and organizations such as the Prader-Willi Syndrome Association — USA.
• Look into guardianship issues, wills and special needs trusts so your child is cared for and supervised in the future.
• Talk to your child's healthcare professional about ways to switch to adult medical care.

Here are tips to help you take care of your child with Prader-Willi syndrome:

• Learn about Prader-Willi syndrome. Work with your child's healthcare team to learn about the condition and create a care plan to manage symptoms and issues. Managing hormone levels and weight can improve development and behavior and prevent complications.
• Stick to a strict meal plan. To keep from becoming overweight, your child needs a low-calorie diet. Structure mealtimes and the types of food served at meals to create routines and help your child learn expectations. Use small dishes to serve meals and don't buy high-calorie snacks. Store food out of your child's reach. Lock pantries, refrigerators, cupboards and garbage cans.
• Encourage regular daily activity. Being more physically active and exercising can help manage weight and make your child better able to function physically.
• Set limits. Create a firm schedule and set behavioral expectations. If needed, talk to your healthcare team about ways to deal with problems.
• Schedule regular medical care. Talk with your healthcare professional about a regular schedule of health appointments and tests to check for problems or complications.

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

For coping and support, think about taking these steps:

• Talk to a mental health professional. If you're having trouble coping or you feel overwhelmed, talk to a mental health counselor or therapist.
• Join a support group. Some people find it helpful to talk with others who share similar experiences. Ask your healthcare provider about family support groups in your area. Organizations such as the Prader-Willi Syndrome Association — USA provide resources, support groups and educational materials.
• Seek other sources of support. Ask about sources of short-term care and ask for support from family and friends. Also, take time for your own interests and activities.

Your child may first see your family healthcare professional. Your child may need to see a pediatric endocrinologist and other specialists.

Here's some information to help you prepare for your child's appointment. Think about taking a family member or friend along to support you and help you remember information.

What you can do

To prepare for the appointment, make a list of:

• Any symptoms your child has been having and for how long.
• Your child's key medical information, including recent illnesses and medical conditions, as well as the names and doses of any medicines, vitamins, herbs or other supplements.
• Questions you want to ask your child's healthcare professional.

Some basic questions to ask your healthcare professional may include:

• What is likely causing my child's symptoms?
• What kinds of tests does my child need?
• What treatment approach do you recommend?
• What are the expected results of treatment?
• What are the possible side effects of treatment?
• What type of follow-up is needed and how often?
• What is my child's risk of long-term complications?
• Can you suggest educational materials and local support services?
• What services are available for early childhood development?

What to expect from your doctor

Your child's healthcare professional likely will ask you several questions. Be ready to answer them so you have time to go over the points you want to focus on. For example, the healthcare professional may ask different questions depending on your child's age.

Questions about your baby include:

• 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 tired, weak or sick?

Questions about young children include:

• How much does your child eat?
• Does your child look for food all the time?
• Does your child eat any unusual items or steal or sneak food?
• Does your child have tantrums?
• Does your child show any other troubling behaviors?

The healthcare professional will ask more questions based on your responses, as well as your child's symptoms and needs. Being ready for these questions will help you make the most of your time with the healthcare professional.