Assessing the metabolic activity of l-aromatic amino acid decarboxylase (AADC) [1] with 6-l-[18F]fluoro-3,4-dihydroxyphenylalanine (6-l-[18F]FDOPA) PET is widely used for the diagnosis and staging of Parkinson’s disease (PD). Here, DDC is linked to Parkinson disease.