If you read onto my further comments I have stated that there could be an exception of being diagnosed with a personality disorder under 18 if it reaches an on-going criteria of someone having it over 18.

They don't do many underage diagnosis because adolescence is the time your personality is changing constantly and hasn't reached its adulthood which means it is unlikely but not impossible.

Oh, and I don't think they are two different things.. I mean, you have to have it to be diagnosed with it, unless it is a misdiagnosis.