What do you fear most?

[Domino Quartz]

Isn't there some sort of disease or genetic disorder that actually makes you allergic to yourself? Like your antibodies target healthy cells as well?
I may be talking nonesense, my knowledge in the field of medicine is rudimentary to say the least.

I think those are called autoimmune disorders, or something. Arthritis is an example, in which your immune system attacks the cells in your joints.