A nasty, skin inflammatory infection caused by multiple stimuloses commonly found in ink pens. The rashes, and irritation that follow can be devastating. One knows when they are infected by this when red and grey bumps surface to the epidermis (outer layer of skin), and inflammation and proposterous itching begin to occur. There is no known cure for unmrellatidus.
Dude, have you seen Joe's skin? Its the nastiest thing in the world! I think he might have umbrellatidus from those stupid markers he has been playing with.