Medically reviewed by Daniel Combs, MD
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- Early signs of Prader-Willi syndrome (PWS) in infants often include low muscle tone, feeding difficulties, and distinct facial features like almond-shaped eyes.
- As children grow, signs and symptoms often include constant hunger, rapid weight gain, short stature, and learning or behavioral challenges.
- If you notice your child has signs and symptoms of PWS, talk to their pediatrician early, as the condition can be managed with medications, therapy, and lifestyle changes.
Prader-Willi syndrome (PWS) is a rare genetic condition that affects how the brain controls hunger, growth, and behavior. Signs and symptoms can vary depending on the stage of life.
Symptoms in Infancy
The earliest signs of Prader-Willi syndrome are often noticeable within the first few weeks of life. They’re sometimes referred to as stage 1 symptoms.
1. Decreased Muscle Tone
Babies with PWS often have low muscle tone, called hypotonia. They may feel unusually “floppy” when held and not have as much strength to support their head. Hypotonia can affect the whole body, which is why these babies may have a weak cry, low energy, and seem unusually sleepy or hard to wake up.
2. Feeding Difficulties
Because of their low muscle tone, many babies with PWS have a weak sucking reflex. Nursing or bottle-feeding takes effort, so they may get tired before they’ve had enough to eat. This can lead to poor weight gain, known as failure to thrive. Some babies need extra support, like special nipples or temporary tube feeding.
3. Distinct Physical Features
Babies with PWS are often born with certain physical traits. These include:
- Almond-shaped eyes
- A long, narrow forehead
- A thin upper lip with a downward slanted mouth
Some children develop strabismus, the medical term for crossed eyes, which is usually noticed in the first few years of life.
In baby boys, the testicles may not have fully descended at birth, a condition called cryptorchidism.
On their own, these features might not raise a red flag, but together with other signs and symptoms, they can suggest a potential case of PWS.
Symptoms in Childhood and Adulthood
As children with PWS grow, the symptoms and challenges they face change. Early feeding issues often improve, but new symptoms, sometimes known as stage 2, emerge.
1. Food Cravings and Weight Gain
Somewhere between ages 2-3, most children with PWS develop an intense, constant urge to eat. This is one of the most well-known signs of PWS.
Unlike typical hunger, this craving doesn’t go away after a meal. Because the brain doesn’t signal that the stomach is full, children can develop an obsession with food, known as hyperphagia. They may constantly ask for snacks, hide food, or even try to eat things that aren’t food. Without supervision and a managed diet, this can lead to rapid weight gain and obesity.
2. Poor Growth and Short Stature
Even with weight gain, children with PWS are often shorter than expected for their age. This is partly due to lower levels of growth hormone. You may notice smaller hands and feet, as well as slower height growth and less muscle mass.
Scoliosis, a sideways curve of the spine, is also common and may need treatment and monitoring as people with PWS get older.
3. Underdeveloped Sex Organs
Along with undescended testicles, males may have a smaller penis as they grow, along with an underdeveloped scrotum. In females, the inner labia or clitoris may be smaller than usual or not fully developed.
As children move into their teen years, puberty is often delayed or incomplete, and fertility problems are common in adulthood.
4. Learning and Development Delays
Children with PWS tend to reach milestones slower than their peers. Sitting up and crawling often occur later than expected. Most don’t walk independently until around age 2, and speech and language often develop slowly as well.
By school age, children may show signs of cognitive and learning differences that can affect reading, math, and memory. But many do thrive with early intervention, individualized education plans, and support at home.
5. Behavioral and Emotional Problems
Children with PWS may have frequent temper tantrums, difficulty with changes in routine, or strong emotional reactions. Some may show extreme stubbornness and anxiety.
Obsessive-compulsive tendencies, such as fixating on certain topics and objects, repeating questions, and needing routines, are also common. Some children may pick at their skin, which can lead to wounds or infections if not managed.
Other Signs To Know
Other signs of PWS include:
- Sleep problems, such as sleep apnea, or feeling very sleepy during the day
- Lighter skin, hair, and eyes (iris) than relatives due to reduced pigmentation
- A delayed realization that they’re uncomfortable or sick since many people with PWS have a higher pain tolerance
Not everyone with PWS will experience all of these signs and symptoms, but they’re helpful to keep in mind.
When To Talk To a Healthcare Provider
If you notice signs of PWS in your child, reach out to their pediatrician early. They can help diagnose the cause and, if necessary, refer you to appropriate specialists, such as a geneticist for testing or a pediatric endocrinologist for hormone-related care.
There’s no cure for PWS, but many of its symptoms can be managed with medications, diet, supportive therapies, and lifestyle adjustments.
Going to the appointment with a list of questions can help you get the most out of your child’s medical visit. Consider asking:
- What tests are needed to confirm PWS?
- How can we safely manage feeding issues?
- How can we manage food access at home and school?
- Could my child benefit from growth hormone therapy, and what does that involve?
- What types of supportive therapies should my child start now?
- What information do I need to request support at school for my child right now?
- What signs should I watch for that would need more urgent attention?
- What kinds of support are available for caregivers of people with PWS?
