In the prodromal LRRK2 PD group, all of the participants have abnormal DAT-SPECT scans: 31 percent (4/13) grade 2, 38 percent (5/13) grade 3 with an asymmetric tracer uptake with normal or almost normal uptake in the putamen of one hemisphere and reduced uptake in the contralateral putamen and 31 percent (4/13) grade 4 with a posterior-anterior degeneration pattern. Here, SLC6A3 is linked to Parkinson disease.