For example, the clinical presentation and onset of PD does not differ between patients carrying a heterozygous LRRK2 mutation and patients carrying a digenic combination of LRRK2 and PARK2 mutations [Bras et al., 2008; Ferreira et al., 2007; Gao et al., 2009; Illarioshkin et al., 2007; Lesage et al., 2006; Marras et al., 2010]. This evidence concerns the gene LRRK2 and Parkinson disease.