What is Prader-Willi Syndrome?

What is Prader-Willi Syndrome?

Prader-Willi Syndrome (pronounced as PRAH-dur VIL-e) is a complex and rare genetic disorder that affects many aspects of the body including physical, mental, and behavior.

During infancy, the syndrome is characterized by feeding difficulties and delayed development that causes poor growth and hypotonia—weak muscle tone. Below are the detailed signs and symptoms that your child may shows.


Prader-Willi Syndrome Symptoms

The symptoms of Prader-Willi vary from person to person. But it may start from infancy and childhood.


The following may indicate that an infant has Prader-Willi syndrome:

  • Distinct facial features

Most children, though not all, that is born with the condition has a narrow head along with the temple areas. They have almond-shaped eyes, a thin upper lip, and a turned-down mouth.

  • Generally poor responsiveness

This refers to the child poor responses. For example, the child may have a hard time waking up or is unusually tired. The child may even have a weak cry.

  • Poor muscle tone

Hypotonia or poor muscle tone is usually the first sign of the syndrome in infants. You may notice it when the baby is resting with the knees and elbow loosely extended. The said body parts may seem like rag dolls when held.

  • Poor sucking reflex

The baby may be born with a poor sucking ability and it makes the infant hard to feed. The poor reflex is linked to the poor muscle tone of the infant.

  • Underdeveloped genitals

If an infant is male, you may notice that his penis and scrotum has a small size. The testicles do not come out from the abdomen to the scrotum as well. Meanwhile, if an infant is female, you may notice that her labia and clitoris are small.


Early Childhood to Adulthood

In other cases, the symptoms of the condition will skip infancy and appear in the childhood stage. Sometimes, the symptoms remain throughout the child’s life that it needs cautious supervision. Some of the symptoms include:

  • Food craving and weight gain

Food craving is the typical sign of Prader-Willi syndrome. The child seems to have an endless appetite for food that he/she gain weight rapidly. Watch out if your child eats large portions and hoard food that he/she even eat frozen and garbage food.

  • Behavioral problems

Both children and adults may have odd with their behavior that at times they are manipulative, angry, controlling, and stubborn. Most of the time, if you denied them food, they will throw tantrums. They may also manifest repetitive behaviors, become obsessive-compulsive (OC), start skin picking, and develop anxiety.

  • Cognitive impairment

Intellectual ability gets affected, from mild to moderate. The patient may have issues with problem-solving, reasoning, and thinking. If the patient may not have disabilities with their intellectual, try to check their learning disabilities.

  • Delayed motor development

Most toddlers with the condition have a delayed development for motor skills such as sitting up or walking, compared with normal children.

  • Poor growth and physical development

Insufficient production of growth hormone leads to many disorder including high body fat, low muscle mass, short adult height, and endocrine problems.

When problems in the endocrine system arise, the body may not be able to produce sufficient hormones. This may lead to poor body defense. Thus, during infections and stress, the body does not respond appropriately.

  • Sleep disorders

Include in sleep disorders are sleep apnea or pausing of breathing during sleep. Their normal sleep cycles may also disrupt with unknown reason. Thus, they may sleep too much during the daytime.

  • Speech problems

Speech is also a challenge that up to adulthood, poor articulation may experience.

  • Underdeveloped sex organs

This state is called hypogonadism. It happens when the male and female sex organs produce little hormones or no hormones at all. The testes and ovaries are the most affected part of the sex organs that it delayed the patients’ puberty. It sometimes incomplete the puberty stage and leads to infertility. If there is no action taken, women may have to wait for their 30’s before they start menstruating. Or, they may never experience it in their life. On the other hand, a male may not grow much hair on their faces plus their voices may not be deepened.

  • Other signs and symptoms

Other signs of Prader-Willi syndrome are small features of hands and feet, vision problems including nearsightedness, low saliva flow, hip problems, scoliosis or disorder in the spine curvature, a high pain tolerance, body temperature regulating problems, pale eyes as well as skin, and lack of pigment-causing hair.


What Causes Prader Willi Syndrome?

The cause of Prader-Willi syndrome root in genetic mutation. Meaning, one or more genes have an error. The exact mechanism for causing the disorder is not yet identified, but experts can tell that the problem is located somewhere in chromosome 15.

All genes come in pair except the genes associated with the characteristics of gender. These pairs are inherited just like the following:

  • one copy from the paternal gene (father)
  • one copy from the maternal gene (mother)

The pair of genes that comes along, is expressed in pair as well. For instance, if one copy is expressed, the other will be expressed as well. But acting alone is normal for some gene types.

With the case of Prader-Willi syndrome, certain paternal genes are not expressed because:

  • chromosome 15 are missing some paternal genes
  • the child did not inherit any chromosome 15 from the father, and the child received two chromosomes 15 from the mother; and
  • paternal gene error occur in chromosome 15

With this condition, the hypothalamus—a certain part of the brain that is responsible for hormonal release—is disrupted by the error in chromosome 15. Thus, the malfunction interferes with the normal process of the body and results in problems with mood, sexual development, growth, sleep, and hunger.

The good thing, Prader-Willi syndrome is not inherited but caused by a random genetic mutation. Knowing from which genetic error results the condition is a lot of help for genetic counseling.



If you already have a child with a Prader-Willi syndrome and considering to have another little angel, seek genetic counseling to determine the chance of having another child with the same syndrome.

Mom Pamper

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