About PWS
What is Prader-Willi Syndrome?
Prader-Willi syndrome (PWS) is the most common known genetic cause of life-threatening obesity in children. PWS is the result of an abnormality on the 15th chromosome. PWS affects approximately 1:15,000 births and occurs equally between males and females and affects all races.
PWS disrupts the normal functions of a portion of the brain called the hypothalamus. The hypothalamus controls the body's ability to regulate temperature, blood pressure, heart rate, and hormone release which affects the body's metabolism, sleep regulation, appetite, learning, memory and social behavior.
Common characteristics of PWS are low muscle tone, motor and developmental delays, short stature, and incomplete sexual development. Most children begin treatment with Human Growth Hormone (HGH) shortly after diagnosis. HGH helps not only with increasing muscle mass and strength, but helps to redistribute fat to appropriate areas of the body and also improves brain development and learning.
Stage One: Infancy
PWS has been historically known as a two stage syndrome. The first stage occurs during infancy. Babies are most often diagnosed as "failure to thrive" due to their poor feeding and hypotonia (low muscle tone). Babies with PWS would often not survive without extreme interventions. Most babies spend the first few weeks of life in Intensive Care Nurseries, cared for around the clock. They are fed via feeding tubes either through the nose or directly into the stomach. During this stage, therapies help to strengthen the baby's weak muscle system, including physical and occupational therapy, are vital. Feeding and/or speech therapy are also valuable in strengthening the oral-motor muscles.
As infants with PWS grow into toddlers and school aged children, therapies continue to be imperative. Birth to 3 services such as continued physical, occupational and speech therapies will help children reach their milestones. Behavioral Therapy can improve anxiety, another hallmark of the disease, and other therapies like Hippotherapy — physical and occupational therapy while horseback riding — are also wonderful resources to help children with PWS reach their potential.
Stage Two: Hyperphagia
The second stage of PWS is characterized by the development of hyperphagia, an uncontrollable drive to eat, combined with weight gain while consuming fewer calories. This is the most common characteristic of PWS — uncontrolled hunger. This has been known to occur in children as early as 3 years old. However, research has shown that children on GH develop an insatiable appetite later in childhood.
More recent research describes that there are more than just two phases of PWS.
PWSA (USA) Five Main Phases of PWS
PWSA (USA) has outlined the breakdown of five main phases and their sub phases:
Phase 0
Occurs in utero and is characterized by decreased fetal movements, birth weight and length.
First Phase
The infant is hypotonic and not obese. Sub-phase 1a (median age range = 0–0.75 years) is characterized by poor appetite, feeding difficulties, and failure to thrive. Sub-phase 1b (median age range = 0.75–2.08 years) occurs when the infant is growing steadily along the normal growth curve which is associated with improved appetite.
Second Phase
Occurs when the weight starts to increase and crosses percentile lines in the normal weight curve, generally beginning between 18–36 months of age. Sub-phase 2a (median age range = 2.08–4.50 years): the child's weight increases above the normal rate without significant increase in calorie intake — no increased appetite or interest in food. Sub-phase 2b (median age range = 4.5–8.0 years): the child has an abnormally increased, but not necessarily insatiable, appetite which leads to overweight/obesity if diet is not appropriately regulated.
Third Phase
Median age of onset is 8.0 years and lasts into adulthood. This is the development of an insatiable appetite and drive to eat, accompanied by intense or relentless food-seeking. This is the classic phase most people associate with PWS, but its onset is variable — it may appear as early as age 3 or as late as age 15. This phase can be managed through appropriate environmental interventions (usually including locked food access) and psychological food security.
Fourth Phase
May occur in later adulthood when an individual who was previously in Phase 3 no longer has an insatiable appetite and can feel full. Families and caretakers note a significant improvement in appetite and weight control. Phase 4 only occurs in a minority of adults with PWS — most will remain in Phase 3.
“I ran and ran and ran every day, and I acquired this sense of determination, this sense of spirit that I would never, never give up, no matter what else happened.”
― Wilma Rudolph
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