Every time I read about something like this, I wonder how people can make it through medical school without dying of anxiety. So many terminal illnesses that could already be killing you with no early warning signs... how can they sleep!?
As a European working in the US medical system, my general impression is that US people fear death much more than in Europe, where people bother much more about suffering than dying in itself. I don't really understand why, but americans seem in my experience far more willing to undergo invasive procedures to live longer, even if it means bad quality life.
I can relate my only illness anxiety experience though: I had some lab tests done for autoimmune diseases, and came back negative for everything except a liver antibody test. The disease that the test is specific for has initial symptoms of fatigue and itching. You can imagine how most students have some amount of fatigue, and I must have had some contact dermatitis from something else giving me an itching sensation. There was a week long period where I thought my life was going to revolve around when I'd get a liver transplant.
(... at least until we perfect the longevity treatments ;) ).