To better understand if carriers of GBA and LRRK2 mutations with PD represent a specific disease subtype, we evaluated differences in disease natural history and manifestation in three genetically-defined groups: LRRK2 G2019S carriers, carriers of 17 mutations in GBA (Table 1), and iPD (defined in this instance as the PD population not carrying any of the before mentioned GBA or LRRK2 variants). This evidence concerns the gene LRRK2 and Parkinson disease.