... It's an auto-immune disease that redirects the immune system, which should be protecting the body against infectious agents, to waste its time damaging the body's own cells and is by definition a disability. It can also damage your nails and cause <u>pain</u>, something a lot of auto-immune diseases do, and correlates to other conditions.
A disability is a physical impairment that substantially limits a major life activity. This includes the functions of the immune system and "normal cell growth. Also a physiological disorder or condition, cosmetic disfigurement, or anatomical loss affecting one or more body systems (language in 29 CFR 1630.2(h)(1))
But I will be blunt. When someone tells you that a condition is a disability and your reaction is, "LOL NO IT ISN'T. I DON'T THINK IT'S BAD ENOUGH TO BE ONE," you need to fuck right off. People with disabilities should not have to spend half of their time trying to get people to believe they are "REALLY" disabled.