Sometimes Prader-Willi Syndrome can be caused by a chromosomal rearrangement also known as translocation, mutation or even another defect that abnormally turns off genes on the parental chromosome 15.

There are a plethora of effects that accompany Prader-Willi Syndrome such as: weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. During childhood some effects are: instable appetite, which leads to chronic over eating (hyperphagia), and obesity. In addition to the obesity effect, some children develop type two diabetes, mellitus. Some more effects are: mild to moderate intellectual impairment and learning disabilities, behavioral problems, temper outbursts, stubbornness, compulsive behavior, sleep abnormalities, distinctive facial features (narrow forehead, almond-shaped eyes, triangular mouth, short, small hands and feet), delayed puberty/incomplete, and infertility.

Some treatments for Prader-Willi Syndrome are: feeding tubes, strict supervision of daily food intake, growth hormone therapy, eye treatment, spine treatment, sleep study, physical therapy, behavioral therapy, medication, special needs programs, sex hormone treatment, and sex hormone replacement.

One's doctor usually suspects Prader-Willi Syndrome based on clinical symptoms, but one can be born with significant hypotonia or it can be confirmed with a blood test.

If one keeps on with their treatment and keeps their obesity in check, they can live an average lifetime.

Most cases are not inherited. The genetics occur randomly and people typically have no history of the disorder in their family. But, in rare cases it can be inherited.