A Movement Disorder Specialist should be able to tell the difference, at least once the disease has advanced a bit. In the early stages, I think it is difficult to be certain if a person is atypical. Response to medications may be one indicator, but the symptoms are, over time, different.

Who knows? I have been waiting for over 1.5 years for something other than a-typical Parkinson’s . It sucks, can’t get into studies or anything.