Personality disorders are categorised as mental illness and you will find them in the DSM etc, but I'm not sure they should be. It's the person's personality, it's who they are, it's only categorised as a 'disorder' because society has decided that they don't like it. Homosexuality was once pathologised just because society didn't like it but this is no longer the case.
I think it's very dangerous to pathologise personality because it ends up with people excusing certain types of behaviour and the prospect of diminished responsibility starts being spoken about. If you go down this route, then we will eventually end up with people being excused of rape because they have 'rapist personality disorder' or NPD or whatever. It's not a pathology, it's just who you are! Being an anus does not make you mentally ill!