Prader–Willi syndrome
Rare genetic disorder involving an imprinted genomic region / From Wikipedia, the free encyclopedia
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Prader–Willi syndrome (PWS) is a rare genetic disorder caused by a loss of function of specific genes on chromosome 15.[2] In newborns, symptoms include weak muscles, poor feeding, and slow development.[2] Beginning in childhood, those affected become constantly hungry, which often leads to obesity and type 2 diabetes.[2] Mild to moderate intellectual impairment and behavioral problems are also typical of the disorder.[2] Often, affected individuals have a narrow forehead, small hands and feet, short height, and light skin and hair. Most are unable to have children.[2]
Prader–Willi syndrome | |
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Other names | Prader–Labhart–Willi-Fanconi syndrome[1] Prader-Willi-Down syndrome |
Pronunciation | |
Specialty | Genetics, endocrinology, pediatrics |
Symptoms | Babies: weak muscles, poor feeding, slow development[2] Children: constantly hungry, intellectual impairment, behavioural problems[2] |
Usual onset | occurs at or near the time of conception for unknown reasons |
Duration | Entire lifespan |
Types | There are three main molecular mechanisms that result in PWS: paternal deletion, maternal UPD 15, and imprinting defects |
Causes | Genetic disorder (typically new mutation)[2] |
Diagnostic method | Genetic testing |
Treatment | Feeding therapy, physical therapy, occupational therapy, strict food supervision, exercise program, counseling[3] |
Medication | Growth hormone therapy[3] |
Frequency | 1 in 15,000–20,000 people[2] |
About 74% of cases occur when part of the father's chromosome 15 is deleted.[2] In another 25% of cases, the affected person has two copies of the maternal chromosome 15 from the mother and lacks the paternal copy.[2] As parts of the chromosome from the mother are turned off through imprinting, they end up with no working copies of certain genes.[2] PWS is not generally inherited, but rather the genetic changes happen during the formation of the egg, sperm, or in early development.[2] No risk factors are known for the disorder.[4] Those who have one child with PWS have less than a 1% chance of the next child being affected.[4] A similar mechanism occurs in Angelman syndrome, except the defective chromosome 15 is from the mother, or two copies are from the father.[5][6]
Prader–Willi syndrome has no cure.[7] Treatment may improve outcomes, especially if carried out early.[7] In newborns, feeding difficulties may be supported with feeding tubes.[3] Strict food supervision is typically required, starting around the age of three, in combination with an exercise program.[3] Growth hormone therapy also improves outcomes.[3] Counseling and medications may help with some behavioral problems.[3] Group homes are often necessary in adulthood.[3]
PWS affects between 1 in 10,000 to 30,000 people worldwide.[2] The condition is named after Swiss physicians Andrea Prader and Heinrich Willi who, together with Alexis Labhart, described it in detail in 1956.[1] An earlier description was made in 1887 by British physician John Langdon Down.[8][9]