Indeed for some heterozygous carriers of mutations in the PARK2 or PINK1 gene an increased risk to develop sporadic PD has been described (Hilker et al. 2001; Oliveira et al. 2003; Foroud et al. 2003) and also digenic cases of PD revealing an interplay of mutations in different genes related to the same pathology have been reported (Funayama et al. 2008). Here, PRKN is linked to Parkinson disease.