In one study, three of 16 LRRK2-G2019S-NMC (18.8%) were positive for RT-QuIC reaction; none of them developed manifest signs of PD during a 3-year follow-up; however, this subgroup tended to present altered DAT SPECT and fit the criteria for prodromal PD more frequently than NMC without positive RT-QuIC response [59]. This evidence concerns the gene SLC6A3 and Parkinson disease.