Prader-Willi syndrome is an uncommon disorder that causes physical, mental, and behavioral problems, and especially an unrelenting feeling of hunger.
People PWS always feel hungry.
A person with Prader-Willi Syndrome (PWS) has serious problems controlling their body weight, because they spend a long time eating, and there is a very strong food compulsion. PWS is the most common genetic cause of morbid obesity in children.
According to the Prader Willi Association in the United States, between 1 in 8,000 and 1 in 25,000 people live with the condition. Other sources suggest it affects between 1 in 10,000 and 1 in 30,000 globally. It affects both sexes equally.
Contents of this article:
What is Prader-Willi syndrome?
PWS is a genetic condition, which means that people are born with it. People with PWS have seven genes on chromosome 15 that are deleted or unexpressed.
Patients with PWS often have low muscle tone, incomplete sexual development, and chronic hunger. Their metabolism tends to utilize fewer calories, compared with other people. Many individuals with PWS have short stature if they do not receive growth hormone therapy.
A newborn with PWS tends to weigh less than normal, has weak muscles, known as hypotonia, and they may find sucking difficult.
Between the ages of 2 and 5 years, but sometimes later, individuals start developing a strong appetite, called hyperphagia. This is due to a significantly decreased feeling of fullness. Once hyperphagia begins, it tends to persist for life.
Signs and symptoms of Prader-Willi syndrome
Symptoms have traditionally been described in two stages. The first symptoms normally emerge during the first year of life, and others appear between the ages of 1 and 6 years.
Symptoms in the first year
From 0 to 12 months, the infant is likely to have the following symptoms:
- Hypotonia, or poor muscle tone, means that the child feels floppy when held. The elbows and knees may be loosely extended instead of firmly in position. Hypotonia improves with age.
- Specific facial features may include almond-shaped eyes and a head that narrows at the temples. The mouth appears to be small, and it may be turned down, with a thin upper lip.
- Reduced physical development, as poor muscle tone can undermine the ability to suck properly, making feeding difficult. The infant may gain weight more slowly than their peers.
- Strabismus, in which the eyes do not move in unison. One eye may appear to wander, or the eyes may cross.
The infant may also have an unusually weak cry, they may not respond fully to stimulation, and they may appear tired.
Genitals may be underdeveloped, and depigmentation of the skin and eyes is common.
Symptoms from age 1 to 6 years
Between 1 and 6 years of age, there may be:
- Food craving and gain in body weight, as the child craves food constantly, eating a lot and often. They may hoard food or eat items that most people would not, such as frozen food before it is thawed or cooked, or food that has gone bad.
- Hypogonadism, in which the testes or ovaries do not produce enough sex hormones, resulting in underdeveloped sex organs. There is poor sexual development during puberty, and most adults with PWS cannot reproduce. The testes of males may not descend, and in females, menstruation may be scant or nonexistent.
- Limited growth and strength, poor muscle mass, and small hands and feet. People with PWS may not reach full adult height due to a deficiency in the growth hormone.
- Limited cognitive development, leading to mild to moderate learning disabilities.
- Delayed motor skills, with coordination milestones, such as sitting up or walking being reached later than usual. The infant may not walk until 24 months.
- Delayed verbal skills, so that speech begins late. Oral expression may remain challenging.
- Behavior and mental disorders, including temper tantrums, especially relating to food. The child may be argumentative, oppositional, rigid, manipulative, possessive, and stubborn. Some children may experience obsessive-compulsive disorder (OCD), repetitive behaviors, recurring thoughts, and other mental disorders. Excessive skin picking and nail biting may occur.
- Sleep disorders, such as sleep apnea, possibly due to obesity. There may be disturbances of the normal sleep cycle.
- Scoliosis, or curvature of the spine.
- Depigmentation, so that skin and hair may be fairer than that of parents and siblings.
There may be a high tolerance for pain. Myopia, or short-sightedness, is also common.
According to the Prader-Willi Syndrome Association, PWS is increasingly seen as a multistage syndrome.
In Phase 2, at 18 to 36 months, the child's weight crosses over from lower to higher than average, without any additional interest in food or calorific intake. Phase 3 starts on average at the age of 8 years, and it has the classic feature of relentless food-seeking.
What are the warning signs for parents?
Parents should consult a physician if an infant has difficulty feeding, does not wake up easily, does not respond to normal stimulation, such as touch, and feels floppy when held. Other warning signs are if the child is always hungry, constantly looks for food, or gains weight rapidly.
Causes of Prader-Willi syndrome
PWS stems from a faulty gene, or genes. It remains unclear which genes are involved, but the abnormality is found on chromosome 15.
PWS happens when genes are missing on chromosome 15.
All human genes come in pairs, except for those related to sex characteristics. One copy is from the father, called the paternal gene, and one copy is from the mother, the maternal gene.
In PWS, it is thought that the paternal genes on chromosome 15 are either missing or faulty.
This genetic fault affects how the hypothalamus works. The hypothalamus is a part of the brain which controls thirst and hunger. It also releases hormones involved in sexual development and growth.
If a person's hypothalamus is damaged at some time, for example, through a head injury, tumor, or surgery to remove a tumor, PWS-like signs and symptoms may develop.
Despite not having the genetic faults or physical characteristics of PWS, the person may acquire some of the behavioral problems, such as a constant craving for food.
Treatment used for patients born with PWS can help those with acquired PWS.
Diagnosing Prader-Willi syndrome
A number of tests are available for PWS, but according to the Prader Willi Research Association, methylation, a form of genetic testing, can detect 99 percent of cases.
Early testing is important, because an early diagnosis makes early intervention possible.
Some people with PWS remain without a diagnosis, or they are misdiagnosed as having Down syndrome or autism spectrum disorder, as these different conditions have overlapping features.
Treatment options for Prader-Willi syndrome?
There is no cure, but ongoing therapy can help to reduce symptoms by focusing on related deficiencies. Approaches include nutrition, growth, and sex hormone therapy, physical, speech, occupational, and developmental therapy.
Nutrition therapy can supply an infant with feeding difficulties with a high-calorie formula. Weight and growth are monitored, and a nutritionist may assist in developing a healthy, low-calorie, weight-control diet. People with PWS must follow a very strict diet with lower calorie goals than usual for the age group. Physical barriers to obtaining food may be necessary, such as locking food away.
Growth hormone treatment can help increase growth and reduce body fat, but the long-term effects 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, and speech therapy.
Mental health problems such as OCD, mood disorders, or behavioral problems may need the help of a psychologist or psychiatrist.
Most people with PWS will need supervision and specialized care throughout their lives.
Constant restriction of food and behavior management can be difficult and stressful for family members. Family support and counseling groups can help.
Further complications of Prader-Willi syndrome
Other problems include unusual reactions to medications, especially sedatives, and complications with anesthesia.
The high pain threshold may mean that an infection or illness goes unnoticed until it is severe. Vomiting is also rare, unless a problem is already serious.
People with PWS have a higher rate of tooth erosion. Osteoarthritis and osteoporosis may occur.
If obesity can be prevented and complications controlled, the life expectancy for a person with PWS is thought to be normal or near-normal. However, special medical supervision is advised after the age of 40 years.