Definition

Prader-Willi syndrome is a disease that is present from birth (congenital). It affects many parts of the body. People with this condition feel hungry all the time and become obese. They also have poor muscle tone, reduced mental ability, and underdeveloped sex organs.

Causes

Prader-Willi syndrome is caused by a missing gene on chromosome 15. Normally, parents each pass down a copy of this chromosome. The syndrome can occur in a couple of ways:

• The father's genes are missing on chromosome 15
• There are variations with the father's genes on chromosome 15
• There are two copies of the mother's chromosome 15 and none from the father

These genetic changes occur randomly. People who have this syndrome usually do not have a family history of the condition.

Symptoms

Signs of Prader-Willi syndrome may be seen at birth.

• Newborns are often small and floppy with reduced muscle tone
• Male infants may have undescended testicles

Other symptoms may include:

• Trouble feeding as an infant, with poor weight gain
• Almond-shaped eyes
• Delayed muscle and motor function development
• Narrowed head at the temples
• Rapid weight gain
• Short stature
• Slow mental development
• Very small hands and feet in comparison to the child's body

Children have an intense craving for food. They will do almost anything to get food, including hoarding. This can result in rapid weight gain and morbid obesity. Morbid obesity may lead to:

• Type 2 diabetes
• High blood pressure
• Joint and lung problems

Exams and Tests

Genetic testing is available to test children for Prader-Willi syndrome.

As the child grows older, lab tests may show signs of morbid obesity, such as:

• Abnormal glucose tolerance
• High insulin level in the blood
• Low oxygen level in the blood

Children with this syndrome may not respond to luteinizing hormone-releasing factor. This is a sign that their sex organs are not producing hormones. There also may be signs of right-sided heart failure and knee and hip problems.

Treatment

Obesity is the greatest threat to health. Limiting calories will control weight gain. It is also important to control your child's environment to prevent access to food. Your child's family, neighbors, and school must work together, because your child will try to get food wherever possible. Exercise can help a child with Prader-Willi syndrome gain muscle.

Growth hormone is used to treat Prader-Willi syndrome. It can help:

• Build strength and agility
• Improve height
• Increase muscle mass and decrease body fat
• Improve weight distribution
• Increase stamina
• Increase bone density

Taking growth hormone therapy may lead to sleep apnea. A child who takes hormone therapy needs to be monitored for sleep apnea.

Low levels of sex hormones may be corrected at puberty with hormone replacement.

Mental health and behavioral counseling are also important. This can help with common problems such as skin picking and compulsive behaviors. Sometimes, medicine to treat mental health conditions may be needed.

Support Groups

The following organizations can provide resources and support:

• Prader-Willi Syndrome Association -- www.pwsausa.org
• Foundation for Prader-Willi Research -- www.fpwr.org

Outlook (Prognosis)

The child will need the right education for their IQ level. The child will also need speech, physical, and occupational therapy as early as possible. Controlling weight will allow for a much more comfortable and healthy life.

Possible Complications

Complications of Prader-Willi can include:

• Type 2 diabetes
• Right-sided heart failure
• Bone (orthopedic) problems

When to Contact a Medical Professional

Contact your health care provider if your child has symptoms of this condition. The disorder is frequently suspected at birth.

References

Cooke DW, DiVall SA, Radovick S. Normal and aberrant growth in children. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 25.

Escobar O, Gurunca N, Viswanathan P, Witchel SF. Pediatric endocrinology. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2023:chap 9.

Kumar V, Abbas AK, Aster JC, Deyrup AT, Das A. Genetic and pediatric diseases. In: Kumar V, Abbas AK, Aster JC, Deyrup AT, Das A, eds. Robbins and Kumar Basic Pathology. 11th ed. Philadelphia, PA: Elsevier; 2023:chap 4.