Neurosin is a protease that in vitro degrades alpha-synuclein, the main constituent of Lewy bodies found in brains of patients with synucleinopathy including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Several studies have reported reduced cerebrospinal fluid (CSF) levels of alpha-synuclein in synucleinopathy patients and recent data also proposes a significant role of