A serious condition involving a change of outlook on the victim, making them view popular, trendy or highly public things as bad, uninteresting or unbearable. They're often found making baseless assumptions or excuses to accusations of individualitis.
This is commonly found in hipsters and some victims who "hate" pop music.
Hipster: "God I hate Lady Gaga so much, her music pisses me off."
Hipster: "She's so weird and popular, I just hate it"
Friend: "I think you have individualitis."