In many studies the prevalence of these heterozygous rare variants is (significantly) higher in patients than in control individuals (PARK2: [Brooks et al., 2009; Clark et al., 2006; Lesage et al., 2008; Nuytemans et al., 2009; Sun et al., 2006]/PINK1: [Abou-Sleiman et al., 2006; Bonifati et al., 2005; Brooks et al., 2009; Marongiu et al., 2008; Rogaeva et al., 2004; Valente et al., 2004b]), implying that the presence of a heterozygous recessive mutation might increase the carrier's susceptibility to develop PD. This evidence concerns the gene PRKN and Parkinson disease.