Sure you can have one or the other or both. And sure the practician can misdiagnose, and in a way he has to because there's no such thing as a completely accurate diagnosis. The names of the diseases don't represent anything concrete, just a more or less strict group of symptoms, some more common, some less, that someone some day decided to call that way. Any diagnosis is nonexclusive.
I don't direct this to any one in particular, just to some people who in general go overboard with them. In what does a diagnosis matter? By applying a diagnosis a practician doesn't give you anything, he only approximates a name something that you already had walking in.
You don't have to evaluate yourself in terms of diseases more than anyoen else, a hundred years ago none of that stuff even had names. You're yourself, you have quirks, not every one of them is a disease, you know how you are, the only thing that matters is that you learn to work with it.
Sorry for the rant, just my 2¢ on the subject. I'll stop now before I turn into a scientologist.