Prader-Willi syndrome is a syndrome characterized clinically by the following symptoms: hypotonia, hypogonadism, and extreme obesity. It was first described by Prader, Labhardt and Willi in 1956 on the basis of nine children with the tetrad of small stature, mental retardation, obesity and small hands and feet. Prader and Willi reviewed the condition in 1961, expanded the phenotype and drew attention to the presence of hypotonia in infancy and the development of diabetes mellitus in later childhood.

Prader-Willi syndrome is a rare genetic condition that causes a wide range of physical symptoms, learning difficulties and behavioural problems. It's usually noticed shortly after birth.

Symptoms of Prader-Willi syndrome

Typical symptoms of Prader-Willi syndrome include:

  • an excessive appetite and overeating, which can easily lead to dangerous weight gain
  • restricted growth (children are much shorter than average)
  • floppiness caused by weak muscles (hypotonia)
  • learning difficulties
  • lack of sexual development
  • behavioural problems, such as temper tantrums or stubbornness

Prader–Willi syndrome (PWS) is a neurodevelopmental disorder which is the most common cause of life-threatening obesity in children and arises from functional loss of genes expressed from the paternal chromosome 15. Approximately 95% of PWS cases result from either a 15q11–q13 deletion or uniparental maternal 15 disomy, whereas the remaining have imprinting defects (microdeletions or epimutations) or chromosomal translocations. No single gene causes PWS, but several genes in the critical region of chromosome 15 may be involved in processing of other genes. Reports of downstream candidate genes with altered processing associated with chromosome 15 defects may help clarify genotype/phenotype relationships in PWS.

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