The penetrance rate of Parkin-mediated PD is almost 100% (Schulte and Gasser, 2011), but recently we identified an asymptomatic homozygous Parkin mutation carrier (MC) who, despite the complete loss of Parkin, has not developed PD in her seventies (Koentjoro et al., 2012), suggesting the existence of a protective mechanism against Parkin deficiency. Here, PRKN is linked to Parkinson disease.