Lycanthropia (an archaic noun) refers to "a variety of melancholy in which the person believes himself to be changed into a wolf." (From Jeffrey Kacirk's Forgotten English) Therefore a lycanthrope is a werewolf - not someone who likes lichens. That would be "lichenthrope." According to Oxford Dictionaries lycanthrope is a 17th century term. So... not medieval but a decidedly early modern paranoia. It makes me wonder how the werewolf myth began in the first place.
As it is so close to Halloween, I should have put this word into spooky calligraphy, but alas, I ran out of time this morning.