Hi,
I have read several people in a young onset PD forum who have experienced olfactory hallucinations. Turns out this is yet another aspect of PD...there are some case studies reported but not a lot out there; I'm sure this research will grow and most likely we'll see a range of olfactory dysfunction as a biomarker.
Hope this helps! - Laura
http://archneur.ama-assn.org/cgi/con...ract/65/9/1237