Several biomarkers, mostly imaging, have been proposed as supportive or exclusive for the diagnosis of PD, DLB, and MSA, including dopamine transporter single-photon emission computed tomography (DAT-SPECT) uptake as exclusive criterion for PD, the cingulate island sign in the fluorodeoxyglucose—positron emission tomography (FDG-PET) as supportive for DLB, and the “hot-cross bun” sign in the magnetic resonance imaging (MRI) for MSA [4,5,8]. The gene discussed is SLC6A3; the disease is Parkinson disease.