What are some lethal infections or diseases that aren't inherited and could kill a teenager?

I'm writing a short story, and the daughter has to fall ill with a disease (or such) which, while curable, is very expensive in its treatments. It can't be a hereditary disease, and it can't result from sex or drug use- though something from painting would be fine. It has to be painful and long-drawn out. Any help would be greatly appreciated. Thanks :)