Prader-Willi syndrome is a congenital (present from birth) disease. It affects many parts of the body. People with this condition are obese, have reduced muscle tone and mental ability, and have sex glands that produce little or no hormones.
Causes, incidence, and risk factors
Prader-Willi syndrome is caused by a gene missing on part of chromosome 15. Normally, your parents each pass down a copy of this chromosome. Most patients with Prader-Willi syndrome are missing the genetic material on part of the father's chromosome. The rest of patients with this condition often have two copies of the mother's chromosome 15.
The genetic changes occur randomly. Patients usually do not have a family history of the condition.
Signs of Prader-Willi syndrome may be seen at birth.
Newborns are often small and floppy.
Male infants may have undescended testicles.
Other symptoms may include:
Trouble eating as an infant, with poor weight gain
Delayed motor development
Narrow bifrontal skull
Rapid weight gain
Slow mental development
Very small hands and feet in comparison to the child's body
Children have an intense craving for food and will do almost anything to get it. This can result in uncontrollable weight gain and morbid obesity. Morbid obesity may lead to type 2 diabetes, high blood pressure, and joint and lung problems.
Signs and tests
Genetic testing is available to test children for Prader-Willi syndrome.
As the child grows older, laboratory tests may show signs of morbid obesity, such as:
Abnormal glucose tolerance
Above normal level of the hormone insulin in the blood
Decreased level of oxygen in the blood
Failure to respond to luteinizing hormone releasing factor
There may also be signs of right-sided heart failure and knee and hip problems.
Obesity is the greatest threat to health. Limiting calories will control the obesity, but the family, neighbors, and school must work together closely because the child will try to get food wherever possible. Exercise can increase lean body mass in children with Prader-Willi syndrome.
Growth hormone is approved by the Food and Drug Administration for the treatment of Prader-Willi syndrome. It can help:
Improve physical strength and agility
Increase lean muscle mass and decrease body fat
Improve weight distribution
Increase bone mineral density
There have been some concerns that taking growth hormone therapy may lead to sleep apnea. A child who takes hormone therapy needs to have annual sleep studies to monitor for sleep apnea.
Low levels of sex hormones may be corrected at puberty with hormone replacement.
The child will need the right education for his or her 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.
Type 2 diabetes
Right-sided heart failure
Bone (orthopedic) problems
Calling your health care provider
Call your health care provider if your child has symptoms of this condition. The disorder is frequently suspected at birth.
Cooke DW, Divall SA, Radovick S. Normal and aberrant growth. In: Melmed S, ed. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 24.
A.D.A.M.Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine (5/1/2011).