SLC6A3 and Parkinson disease: The clinical relevance of DAT integrity evaluation by diagnostic imaging techniques, such as single photon emission computed tomography (SPECT) and positron emission tomography (PET), are based on the differentiation between degenerative parkinsonism and other conditions not associated with dopamine loss, such as essential tremor, drug-induced parkinsonism, vascular parkinsonism, and psychogenic parkinsonism [6,7].