Abstract: Prader-Willi syndrome is a complicated disorder (CVS, Respiratory illness), which has several symptoms related to hypothalamic insufficiency and affects many different systems such as respiratory, endocrine, neurologic and metabolic systems. Infantile hypotonia, developmental delays, mental impairment, behavioral problems, small stature, abnormality, distinctive facial features, obesity, hypogonadism, are significant results. The main causes of morbidity and mortality are behavioral issues and obesity. The absence of the typically active paternal genes in the proximal 15q imprinted region results in Prader-Willi syndrome, which is brought on by anomalies in this area. Such absence is brought about by maternal uniparental disomy, paternal interstitial deletion, mutations, or other abnormalities in the imprinting process.