Is prader willi syndrome hereditary?

Yes and no: Prader-willi syndrome involves early low tone with later overeating and obesity since the person is never full. It is genetic, with ~70% of cases having deletion (missing part) of chromosome 15 and the others having altered parental patterning (genomic imprinting). Although always due to a genetic change, it is rarely inherited and has a low recurrence risk for parents of an affected child.

Not typically: Prader willi is most commonly a random genetic abnormality that occurs early in development of fetus. There is usually no history of the disease in the family.