In three PD cases, we identified a duplication encompassing CYP2E1. Cytochrome P450 2E1 (CYP2E1), which is located in dopamine containing neurons in the substantia nigra, has been hypothesized to be of importance for the pathophysiology of PD, either by its production of reactive oxygen species (ROS) or by its capability to detoxify putative neurotoxins. Here, CYP2E1 is linked to Parkinson disease.