Prader-Willi syndrome

Last reviewed 06/2021

Prader-Willi syndrome is a disorder which affects 1 in 15000 births and is characterised by:

  • neonatal hypotonia
  • behavioural disturbance, particularly hyperphagia
  • mild-to-moderate mental retardation

60% of cases have a small deletion of the paternal chromosome 15q11-13. The majority of the remainder have two apparently normal apparently normal (but maternally inherited) chromosome 15s (See genetics section for more details).