I do. A few actually. I think my number one suspicion is I have a Mustang GT, which are known to sound very aggressive and have a beautiful sound when you modify the exhaust. (Probably more of an American thing.) Anyway I modified the exhaust and no, it wasn't legal and it caused me to breathe a lot of gas fumes that you wouldn't smell in a car with ordinary legal exhaust. Got that car when I was 26 and I was diagnosed fairly soon after. I guess it would be important to note that I had a job that was very far away from me and it was a long commute. Basically...a lot of gas fumes...a huge risk for developing a MPN. Don't know if it could happen that quick. I still have the car...but now with legal, safe exhaust.
I think my second guess would be the amount of radiation I've been exposed to. After being a vet tech for 19 years I took many x-rays...thousands. And taking X-rays in animals is different than in humans because in humans you can tell them to sit still and leave the room but when you take x-rays on an animal you stand right there right next to the radiation beam in order to restrain them.
Third theory would be my ex-boyfriend was a crop duster and I was exposed to many pesticides.
Those are my 3 guesses. What are your guesses?