SLC6A3 and Parkinson disease: The most reliable way to differentiate PD from other causes of parkinsonism is dopamine transporter (DAT) imaging by 123I‐N‐ω‐fluoropropyl‐2β‐carbomethoxy‐3β‐(4‐iodophenyl) nortropane (123I‐FP‐CIT) single photon emission computed tomography (SPECT) as a proxy of nigrostriatal degeneration.