I could believe that PD has an autoimmune and/or infectious component. When I wass 40 years old I got a terrible case of Lyme meningitis. I lived out in the country and had deer in my yard all the time. I subsequently developed scleraderma and took Minocycline for 3 years which helped a great deal and I don't have even a trace of scleroderma now. (I am 70 yrs old now). I developed PD about 5 years ago.