The problem is that I don't even know where to start looking; when I constructed Nicholas, I only knew that he was a dying man. I would appreciate if you could at least point me in the right direction.
so, I'm looking for this: a disease that can be cured, but couldn't be in this particular case. Nicholas has been ill for 3 years now, and a year ago the doctors send him home to die in peace. the important thing, plot-wise, is that his doctors couldn't really predict when is he going to die, just that this disease will soon kill him. Nicholas is still able to walk, although he is physicaly very weak; his brain, however, wasn't affected. his state also isn't critical enough to require everyday professional medical attention. (The disease doesn't need to match this exact descriptions; small changes would be acceptable.)
I'll appreciate any help you can give me, and that includes pointing me in the right direction. I've spent quite some time browsing medical books and the internet, but I'm feeling very lost indeed, since I don't really know what I'm looking for.