This revision: 26th April 2013 .
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Prader–Willi syndrome (abbreviated PWS) is a rare genetic disorder in which seven genes on chromosome 15 (q 11–13) are deleted or unexpressed (chromosome 15q partial deletion) on the paternal chromosome.
Characteristic of PWS is "low muscle tone, short stature, incomplete sexual development, cognitive disabilities, problem behaviors, and a chronic feeling of hunger that can lead to excessive eating and life-threatening obesity."
The incidence of PWS is between 1 in 25,000 and 1 in 10,000 live births.
PWS has the sister syndrome Angelman syndrome, in which maternal derived genetic material is affected in the same genetic region.
With the recent benefits of early diagnosis and ongoing interventions, the obesity rate among children with Prader-Willi Syndrome has decreased to be similar to the typical population. With behavioural therapy and other treatments, the effects of the syndrome can be reduced.
Individuals with PWS are at risk of learning and attention difficulties. Curfs and Fryns (1992) conducted research into the varying degrees of learning disability found in PWS. Their results were as follows:
- 5%: IQ above 85 (average to low average intelligence)
- 27%: IQ 70 – 85 (borderline intellectual functioning)
- 39%: IQ 50 – 70 (mild intellectual disability)
- 27%: IQ 35 – 50 (moderate intellectual disability)
- 1%: IQ 20 – 35 (severe intellectual disability)
- <1%: IQ <20 (profound intellectual disability)
Children with PWS show an unusual cognitive profile. They are often strong in visual organization and perception, including reading and vocabulary, but their spoken language (sometimes affected by hypernasality) is generally poorer than their comprehension. A marked skill in completing jigsaw puzzles has been noted, but this may be an effect of increased practice.
Auditory information processing and sequential processing are relatively poor, as are arithmetic and writing skills, visual and auditory short term memory and auditory attention span. These sometimes improve with age, but deficits in these areas remain throughout adulthood.
Prader–Willi syndrome is also frequently associated with an extreme and insatiable appetite, often resulting in morbid obesity. It is the most common genetic cause of morbid obesity in children. There is currently no consensus as to the cause for this particular symptom, although genetic abnormalities in chromosome 15 disrupt the normal functioning of the hypothalamus.
The main mental health difficulties experienced by people with PWS include compulsive behaviour (usually manifested in skin-picking) and anxiety. Psychiatric symptoms, for example, hallucinations, paranoia and depression, have been described in some cases and affect approximately 5–10% of young adults. Psychiatric and behavioural problems are the most common cause of hospitalization.
Prader–Willi syndrome has no cure; however, several treatments are in place to lessen the condition's symptoms;
During infancy, subjects should undergo therapies to improve muscle tone.
Speech and occupational therapy are also indicated.
During the school years, children benefit from a highly structured learning environment as well as extra help.
The largest problem associated with the syndrome is severe obesity.