Just play it cool.
It's likely the interviewer has seen your essay.
If it comes up, talk openly about it, and be brief. Otherwise, leave it alone. If it makes you feel better, you could take in an article about it to hand over in case he wants more info.
Most likely, the interviewer will look at your past academic success and judge how well you'll do there. If you handled high school well in spite of the PDD, then he'll figure you'll keep up the good record in college.
Break a leg! 
_________________
Whatever you can do,
Or dream you can do,
Begin it.
Boldness has genius,
Power and magic in it.
--Goethe