PINK1 and Parkinson disease: 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).