Hello and welcome along
P can affect anyone with a genetic predisposition. The gene came from someone in your family, the rest of them are plain lucky for not triggering it if they carry it! I too went through my early life wondering how on earth I could have P when no one in my family sufferered...then a month before my maternal grandmother died, at the age of 65, she got it too! My sister, also just before she died, triggered it too!
Both of them were very ill, so yes, I would say any trauma to the head or body can trigger it. I have no idea what triggered mine - I was about 10 and it just appeared. No illness.
Hope you find PHO informative and supportive.
SJ