SNRPN and Prader-Willi syndrome: Diagnostically, PWS is confirmed by abnormal DNA methylation within the PWS critical region which encompasses a variety of genes including SNRPN. In fact, this differential DNA methylation is the only technique that may be used to diagnose the three distinct genetic causes of PWS as well as distinguish PWS from Angelman Syndrome (Glenn et al., 1996; Glenn et al., 1997).