chronic foot fungus, not covered under doctrine

NP- my wife has chronic skin issue on the sole, heel and toes of her feet. I get that it is not covered under the doctrine. I also get that I can't ask for her for it to be added to the doctrine, is that right? but that you can? she does not have the power to ask that it be added herself. what gives here, I am reading this wrong?

Thanks,
John