PRADER-WILLI Syndrome
Definition: Prader-Willi Syndrome is a complex genetic condition that affects many parts of the body. It is estimated that Prader-Willi Syndrome affects between 1 in 10,000 to 25,000 people. In infancy, this condition is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. Beginning in childhood, affected individuals develop an insatiable appetite and chronic overeating (hyperphagia). As a result, most experience rapid weight gain leading to obesity. People with Prader-Willi Syndrome typically have intellectual impairment or learning disabilities and behavioral problems. Many people with this disorder also have distinctive facial features and short stature. The genitals in both males and females are underdeveloped, and most affected individuals are unable to conceive children (infertile). Additionally, some people with Prader-Willi Syndrome have unusually fair skin and light-colored hair.
Cause: Prader-Willi Syndrome is caused by the loss of active genes in a specific region of chromosome 15. People normally inherit one copy of this chromosome from each parent. Some genes are active only on the copy that is inherited from a person's father (the paternal copy). This parent-specific gene activation is called genomic imprinting. Prader-Willi Syndrome occurs when the region of the paternal chromosome 15 containing these genes is missing. Most cases of Prader-Willi Syndrome are not inherited, particularly those caused by a deletion in the paternal chromosome 15 or by maternal uniparental disomy. These genetic changes occur as random events during the formation of reproductive cells or in early fetal development. Affected people typically have no history of the disorder in their family. Researchers have determined, however, that a deletion of the OCA2 gene on chromosome 15 is associated with unusually fair skin and light-colored hair in some affected individuals.
Symptoms may include:
Treatment: Obesity represents the greatest problem to health. Limiting caloric intake will control the obesity but the family, neighbors, school, and other institutions must cooperate closely as the child will attempt to obtain food wherever possible. Exercise can increase lean body mass in children with Prader-Willi Syndrome.
Growth hormone has also been shown to improve physical strength and agility in patients with Prader-Willi Syndrome. There have been some concerns regarding the effect of GH on lung function in children with this condition. Parents should discuss the possible side effects with the child's doctor.
A very small penis in the male infant may be corrected with testosterone.
Low levels of sex hormones may be corrected at puberty with hormone replacement.
Support Groups: For additional resources and support, see:
Possible Complications
Definition: Prader-Willi Syndrome is a complex genetic condition that affects many parts of the body. It is estimated that Prader-Willi Syndrome affects between 1 in 10,000 to 25,000 people. In infancy, this condition is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. Beginning in childhood, affected individuals develop an insatiable appetite and chronic overeating (hyperphagia). As a result, most experience rapid weight gain leading to obesity. People with Prader-Willi Syndrome typically have intellectual impairment or learning disabilities and behavioral problems. Many people with this disorder also have distinctive facial features and short stature. The genitals in both males and females are underdeveloped, and most affected individuals are unable to conceive children (infertile). Additionally, some people with Prader-Willi Syndrome have unusually fair skin and light-colored hair.
Cause: Prader-Willi Syndrome is caused by the loss of active genes in a specific region of chromosome 15. People normally inherit one copy of this chromosome from each parent. Some genes are active only on the copy that is inherited from a person's father (the paternal copy). This parent-specific gene activation is called genomic imprinting. Prader-Willi Syndrome occurs when the region of the paternal chromosome 15 containing these genes is missing. Most cases of Prader-Willi Syndrome are not inherited, particularly those caused by a deletion in the paternal chromosome 15 or by maternal uniparental disomy. These genetic changes occur as random events during the formation of reproductive cells or in early fetal development. Affected people typically have no history of the disorder in their family. Researchers have determined, however, that a deletion of the OCA2 gene on chromosome 15 is associated with unusually fair skin and light-colored hair in some affected individuals.
Symptoms may include:
- Almond-shaped eyes
- Delayed motor development
- Floppy newborn infant
- Insatiable appetite, food craving
- Irregular areas of skin that look like bands, stripes, or lines
- Narrow bifrontal skull
- Rapid weight gain
- Skeletal (limb) abnormalities
- Slow mental development
- Small for Gestational age
- Undescended testicles in the male infant
- Very small hands and feet in comparison to body
- abnormal glucose tolerance
- above normal level of insulin in the blood
- excessive carbon dioxide levels
- failure to respond to luteinizing hormone releasing factor
- lack of oxygen supply
Treatment: Obesity represents the greatest problem to health. Limiting caloric intake will control the obesity but the family, neighbors, school, and other institutions must cooperate closely as the child will attempt to obtain food wherever possible. Exercise can increase lean body mass in children with Prader-Willi Syndrome.
Growth hormone has also been shown to improve physical strength and agility in patients with Prader-Willi Syndrome. There have been some concerns regarding the effect of GH on lung function in children with this condition. Parents should discuss the possible side effects with the child's doctor.
A very small penis in the male infant may be corrected with testosterone.
Low levels of sex hormones may be corrected at puberty with hormone replacement.
Support Groups: For additional resources and support, see:
Possible Complications
- diabetes
- right-sided heart failure
- orthopedic problems
