Prader-Willi Syndrome: A Complete Guide

When it is time to have a child, no parent expects their baby to be born ill. Yet, that is the reality of Prader-Willi Syndrome. It is a genetic condition with symptoms obvious as a newborn. Muscle weakness, obesity, diabetes, slow development—read further to delve deeper into the signs of the complex, life-altering condition known as Prader-Willi Syndrome.

Prader-Willi Syndrome
Prader-Willi Syndrome Begins at Birth

What is Prader-Will Syndrome?

Prader-Willi Syndrome is a genetic neurodegenerative disorder arising from a loss of function of a set of genes. Although life expectancy is typically normal, manifestations such as low muscle tone, impaired metabolism, delayed growth, and poor cognitive function begin at birth and progress with age.

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According to the Prader-Willi Syndrome Association, an estimated 12,000 to 15, 000 people are diagnosed with the condition worldwide. It affects both genders and all ethnicities equally.

Early Signs of Prader-Willi Syndrome

Since it is genetic, symptoms start at birth. Newborns with Prader-Willi Syndrome are often born breech. Babies are generally fussy and lethargic. They are described as “floppy” due to low muscle tone. Muscle tone involvement causes problems suckling. Feeding problems requiring the use of feeding tubes are common.

A variety of physical features may also be present early on in the disease process:

  • Downturned mouth
  • Almond shaped eyes
  • Thin upper lip
  • High, narrow forehead
  • Excess fat
  • Soft Skin
  • Small hands and feet
  • Tapered fingers
  • Prominent nasal bridge

Later Symptoms of Prader-Willi Syndrome

Symptoms of Prader-Willi Syndrome continue past infancy. However, the mechanism behind the symptoms is not fully understood. Abnormalities of the chromosome are thought to interfere with hypothalamic function. The hypothalamus is the section of the brain which regulates hormones. It sends signals to the endocrine organs (adrenal glands, pituitary gland, and thyroid gland) for metabolism. It is responsible for hunger cues and many other bodily processes Prader-Willi syndrome impairs.

Morbid Obesity and Prader-Willi Syndrome

Prader-Willi syndrome gives “always hungry” an entirely new meaning. By toddler years (2+), excessive food cravings are a prominent symptom. Patients describe excessive eating dominated by incessant sensations of hunger and food cravings. Overeating contributes to rapid weight gain and morbid obesity. Specialist state that “without intervention, adolescents with PWS may weigh 250 to 300 pounds by their late teens” (Butler, 2011).

Complications of overeating and obesity secondary to Prader-Willi syndrome include:

  • Diabetes mellitus
  • Congestive heart failure
  • Choking
  • Food poisoning
  • Stomach rupture
  • Vomiting
  • Tantrums for food
  • Hiding or stealing food
  • Eating inappropriate items (i.e. uncooked food, frozen food, non-food items)

Growth Hormone Deficiency in Prader-Willi Syndrome

There is an underproduction of growth hormones in patients with Prader-Willi Syndrome. A lack of growth hormone leads to abnormally short stature and low muscle tone. This is also why sex organs remain underdeveloped throughout puberty and adulthood. While deficits in growth hormones limit growth, most have a high amount of body fat. Thyroid problems like hypothyroidism and adrenal insufficiency have been reported because the body does not produce other endocrine hormones.

Prader-Willi Syndrome and the Brain: Cognitive Deficits

Cognitive or behavioral problems are always present to some extent in Prader-Willi syndrome. In fact, they are hallmark signs of the disorder. The various cognitive behavioral problems are related to developmental delays.

Intellectual Disability in Prader-Willi Syndrome

Intellectual disability refers to difficulties in cognitive functioning during the prime development stage—childhood and adolescence. Functions such as reasoning, attention, learning, and problem solving are limited. Learning disability is a comparable term for intellectual disability. 60% of patients with Prader-Willi syndrome have mild to moderate intellectual disability. Outcomes of intellectual disabilities associated with this syndrome are short term memory impairment, language formation, and low IQ. Mainstream schooling becomes increasingly difficult as the condition progresses. Assistance in practical skills is typically needed.

Anxiety and Behavioral Problems 

While intellectual symptoms are mild to moderate, behavioral issues stemming from psychiatric illness are more profound. Levels of anxiety in those with this syndrome exceed that of the healthy population. Disruptions in hypothalamus function, as well as the adrenal glands that oversee stress responses, create a mental space of anxiety. Maladaptive behaviors are a way to suppress anxious feelings.

The behavioral symptoms surface between 3 and 5 years of age. Temper tantrums, stubbornness, and anger are the first behavioral traits exhibited in 70 to 90 percent of patients. Insatiable hunger exacerbates many of the behavioral problems. Examples are outbursts if denied food, angry behavior to get food, and stealing food.

Obsessive Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a mental disorder characterized by reoccurring, intrusive thoughts and compulsive behavior. Someone with OCD feels they have to repeatedly partake in compulsive behaviors to relieve the undesired thoughts. Studies of those with Prader-Willi syndrome are found to have compulsive behaviors like skin picking, hoarding, and excessive questioning.

Limited Social Skills and Depression

With cognitive delays, social skills remain undeveloped. Those with Prader-Willi syndrome do not reach cognitive maturity. They do not tolerate disruption in their routine. Poor peer interactions are the result, as they cannot differentiate appropriate social behavior.

Lack of peer acceptance, in combination with a deficiency of endocrine hormones, can cause depression. Depression is a mental disorder depicted by unexplained sadness for longer than two weeks. Thus, a loss in interest in activities, a melancholy mood, and social isolation are not rare in Prader-Willi Syndrome.

Other Symptoms of Prader Willi Syndrome

  • Underdeveloped sex organs—Testicles in males are often undescended, and penis and scrotum are small. The labia in clitoris is small in females with Prader-Willi Syndrome.
  • Hypogonadism—Sex organs in both males and females do produce little to no sex hormones. Hypogonadism delays puberty. Boys do not develop facial hair and their voices do not deepen. Girls begin menstruation late in life, like in their 30s, or not at all.  
  • Hypopigmentation—Hair, skin, and eyes are pale.  
  • Delayed motor development—Motor skill milestones (i.e. sitting up, crawling, walking) do not develop at the same rate of children without the syndrome.
  • Spinal deformity—Scoliosis is curvature of the spine worsened by obesity in Prader-Willi patients.
  • Sleep disordersChildren and adults experience disruptions in the sleep cycle. They remain awake at night with insomnia, but have excessive daytime sleepiness and might sleep the day away. Sleep-apnea, common in those who are obese, contributes to sleep disorders.
  •  Reduced saliva—Mouth secretions are under produced and may be thick and sticky.
  • High pain tolerance—Alterations in brain function causes people with Prader-Willi syndrome to have an extremely high pain threshold. They must be monitored closely to avoid severe injury.
  • Vision problems—Nearsightedness (myopia) and misaligned eyes are from muscle weakness.

Causes of Prader-Willi Syndrome

The majority of Prader-Willi syndrome cases have a genetic basis with a loss of function of the genes on chromosome 15. Under normal circumstances, each parent passes down a copy of the chromosome. About three-fourths of Prader-Willi syndrome cases occur from a deletion, meaning the paternal segment of the chromosome is missing genes. The remaining cases are caused by receiving two copies of the chromosome from the mother, or through the translocation phenomena when a defect turns off certain genes on chromosome 15.

Hypothalamus Damage 

Damage to the hypothalamus can mimic the symptoms of Prader-Willi syndrome without the presence of a genetic mutation. Trauma to the hypothalamus resulting in damage may take the form of a tumor, surgery to remove a tumor, or a head injury. Behavioral problems and insatiable appetite are two symptoms depicted in this subset of patients.

Diagnosing Prader-Willi Syndrome

The diagnostic process is straight forward. A medical professional completes a thorough exam of the physical signs and symptoms. If Prader-Willi syndrome is suspected, genetic sequencing can locate the genetic markers in a blood sample.

Treating Prader-Willi Syndrome

Consistent with other genetic conditions, Prader-Willi syndrome has no cure. Patients with Prader-Willi syndrome rely on multiple specialists for early intervention strategies and lifelong management of symptoms.

Diet for Prader-Willi Syndrome

Feeding difficulties during infancy are prevalent in Prader-Willi Syndrome. Infants struggling with feeding typically require a feeding tube until they are able to feed normally.

Prader-Willi Syndrome: A Complete Guide
Controlling Portion Sizes for Prader-Willi Syndrome Patients

As appetite and cravings increase in childhood, strict diet changes are imperative to managing the condition. Dietary managements should begin with controlling food.  

  • Limit food exposure—Locks on cabinets, pantries, and refrigerators are sometimes helpful because patients cannot control intake dictated by insatiable hunger cues.    
  • Inform others—Teachers, relatives, and friends should be aware of the child’s problem with food.
  • Scheduled meal times—Permit the child access to food at scheduled mealtimes only.
  •  Limit portion sizes—Do not allow additional portions. Limit portions of fatty foods or foods with excess sugar.
  • Low calorie foods—Increasing low calorie foods like fruits and vegetables is suggested for weight management. The fibrous fruits and vegetables are more filling, so patients with Prader-Willi syndrome can consume more to satiate their appetite.
  • Vitamin supplements—Vitamin deficiencies generate food cravings. Taking a vitamin supplement ensures the body is receiving the vitamins necessary for optimal function.
  • Appetite suppression—Medications that suppress the appetite are prescribed by the specialist in severe cases, but non-medication management techniques are preferred.

Physical Activity for Prader-Willi Syndrome

Physical activity is crucial to treating Willi-Prader syndrome. It is recommended that patients be evaluated by a physical therapist. The physical therapist locates which areas of the body are lacking, and then implements a series of exercises that enhance motor skills and promote muscle strength. Starting in infancy, physical activity is to counteract low muscle tone. As the patient progresses, exercises serve as a weight management tool too. Recommended activities include swimming and walking.

Hormone Treatment for Prader-Willi Syndrome

A doctor specializing in hormones of the endocrine system, also called an endocrinologist, prescribes hormones to treat Prader-Willi Syndrome. Sex hormones are restored with testosterone, estrogen, and progesterone replacement. At the normal age for puberty, males take testosterone replacement and females estrogen and progesterone. The goal of hormone replacement is to decrease the risk of osteoporosis (bone thinning) from insufficient hormone levels.

Human growth hormone (HGH) is another therapy for Prader-Willi syndrome. The artificial growth hormone increases muscle strength, decreases body fat, improves energy, and corrects the physical features of the condition. The length of growth hormone therapy is from early childhood until the end of growth in late adolescence.

Behavioral Interventions

Addressing mental health concerns is an important aspect of Prader-Willi syndrome treatment. This is done through the care of a psychologist. Cognitive behavioral therapy (CBT) is the accepted form of talk therapy used in the treatment of Prader-Willi syndrome. It seeks to correct underlying thoughts that motivate behavior while developing coping skills. Cognitive behavioral therapy especially targets obsessive-compulsive symptoms like skin picking.

Early Intervention for Prader-Willi Syndrome

Early interventions are a group of services that support patients with developmental delays and disabilities. Speech therapy aids in oral motor skills to facilitate sucking as a baby. With age, speech therapy improves verbal skills that arise from intellectual disabilities.

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Occupational and developmental therapy instills skills applicable to day-to-day life. Through specialized therapies, the patient learns tips to succeed in school, relationships, and independent personal care. Therapists assist in:

  • Attention—Attention is an executive function impaired in Prader-Willi syndrome. Activities to assist attention are valuable for school.
  • Participation—Decreased social skills limits participation. Supervised play with peers refines social skills in a clinical setting that are eventually achieved outside of therapy.  
  • Academic intervention—Intellectual disabilities cause difficulties in school for children and adolescents with Prader-Willi syndrome. Therapists turn academics such as reading into games with rewards to encourage the patient.
  • Motor movement—Practicing skills like writing, pinching, grasping, dressing, and using the bathroom are central to occupational therapy.
  • Sensory integrationThose with Prader-Willi syndrome become easily overstimulated. Sensory play activities reduce overstimulation in regular environments.
  • Equipment—Modifications make an environment more conducive for the patient. Whether comfortable chairs or utensils, equipment is to provide the child with enough resources for independence during growth.

Prader-Willi syndrome is a debilitating genetic condition, but with proper interventions and support from family, friends, and medical professionals, patients have a chance at a fulfilling, productive life.


Adams, D. (2015). Intellectual Characteristics. Retrieved from

Butler M. G. (2011). Prader-Willi Syndrome: Obesity due to Genomic Imprinting. Current genomics, 12(3), 204-15.

Prader-Willi Syndrome. (2014). Retrieved from

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