Prader-Willi syndrome is a rare genetic disorder characterized by hypothalamic-pituitary abnormalities with severe hypotonia during the neonatal period and first two years of life and the onset of hyperphagia with a risk of morbid obesity during infancy and adulthood, learning difficulties and behavioral problems or severe psychiatric problems. The disease is MONDO_0008300 (Prader-Willi syndrome). Also known as: Prader Willi syndrome, Prader-Labhart-Willi syndrome, Prader-Willi-Labhart syndrome, Willi-Prader syndrome.