Background and Aims: Neurofilament light chain (NfLs) is an intermediate filament neuronal‐specific cytoskeletal axonal protein, whose blood and CSF levels are increased in various neurodegenerative diseases, reflecting neuro‐axonal degeneration; in uncomplicated Parkinson's Disease (PD) however, such levels are within normal limits. This evidence concerns the gene NEFL and Parkinson disease.