Prader-Willi syndrome is a chromosomal deletion syndrome in which part of chromosome 15 is missing or malfunctioning.
(See also Overview of Chromosome and Gene Disorders.)
About 70% of people who have Prader-Willi syndrome are missing part of chromosome 15. About 25% of people who have this syndrome have problems with the function of chromosome 15.
Symptoms of Prader-Willi Syndrome
Many symptoms of Prader-Willi syndrome vary according to the child's age.
Newborns with the syndrome feel limp, feed poorly, and gain weight slowly. Eventually these symptoms resolve.
Then, between the ages of 1 and 6, appetite increases, often becoming insatiable. Children can rapidly gain weight if their food intake is not strictly controlled. They may develop behaviors similar to a compulsion in obsessive-compulsive disorder, such as having an intense preoccupation with food, and constantly seek food.
The hands and feet are small, and children remain short. Abnormalities of the face include almond-shaped eyes and a mouth with a thin upper lip and down-turned corners. Children have bone disorders (such as scoliosis and kyphosis).
Intellectual disability is common.
Hormonal problems are common, and the function of the reproductive organs is abnormally decreased in both boys and girls, which limits growth and sexual development. Boys have undescended testes (cryptorchidism) and an underdeveloped penis and scrotum. Girls also have underdeveloped genitals.
Weight gain often continues into adulthood and is excessive, which can lead to other health problems, such as obesity. Obesity can be severe enough to justify gastric bypass surgery.
Diagnosis of Prader-Willi Syndrome
Before birth, ultrasound of the fetus and sometimes noninvasive prenatal screening or amniocentesis or chorionic villus sampling
After birth, the appearance of the infant and advanced chromosomal testing
Before birth, Prader-Willi syndrome may be suspected based on findings detected during an ultrasound of the fetus. Doctors also can do a test to find deoxyribonucleic acid (DNA) from the fetus in the mother's blood and use this DNA to determine an increased risk of Prader-Willi syndrome. This test is called noninvasive prenatal screening (NIPS) or cell-free fetal DNA analysis. Doctors may also do chorionic villus sampling to obtain and test a small sample of the placenta or amniocentesis to obtain and test a sample of the fluid that surrounds the fetus (amniotic fluid). These tests can confirm the diagnosis.
After birth, doctors may diagnose Prader-Willi syndrome based on the newborn's physical appearance. Doctors can confirm the diagnosis by doing advanced chromosomal testing for imprinting (marking) of DNA. (See also Next-generation sequencing technologies.)
Treatment of Prader-Willi Syndrome
Growth hormone
Replacement of sex hormones
Obesity control
There is no cure for Prader-Willi syndrome, but some specific symptoms and problems associated with the syndrome can be treated. For example, doctors can surgically repair bone disorders if needed.
People who have Prader-Willi syndrome may be given human growth hormone to improve height, increase muscle size, and build strength.
Adolescents who have low levels of sex hormones may be given hormone replacement therapy. At puberty, boys may be given testosterone and girls may be given estrogen. This therapy helps children develop secondary sex characteristics, such facial hair and a deeper voice in boys and breasts in girls.Adolescents who have low levels of sex hormones may be given hormone replacement therapy. At puberty, boys may be given testosterone and girls may be given estrogen. This therapy helps children develop secondary sex characteristics, such facial hair and a deeper voice in boys and breasts in girls.
Lifestyle and behavioral interventions are the foundations of obesity management in people with Prader-Willi syndrome. Strict supervision of food intake, structured meal plans, locking refrigerators and food storage cabinets, and regular exercise are important to control obesity.
Care for people with Prader-Willi syndrome should also include genetic counseling for the family, social support, and educational programming appropriate for the level of intellectual functioning (see Treatment of Intellectual Disability). Early intervention (for example, physical, speech, and behavioral therapies) improves the functioning and quality of life of young children with Prader-Willi syndrome.
Ongoing research is being done to find treatments that help improve the prognosis for children and adults who have Prader-Willi syndrome.
