LRRK2 and Parkinson disease: Dominantly inherited monogenic mutations in the LRRK2 gene, in particular at c.6055 G > A that results in an amino acid substitution in the LRRK2 protein creating the LRRK2 p.G2019S heterozygote status, confer the highest genotypic and population attributable risk for PD, but the frequency of these mutations is low in the general population.