Personally, I would be very upfront about it. At this point in time, my psoriasis only affects my scalp and occasionally my forehead, so for me, it's not a huge issue that people first notice when they look at me. Every time I talk about it to someone for the first time I make sure that I get the point across that it's not contagious so that they aren't completely bothered by it.

From the post, I assume that your psoriasis affects various parts of your body. I understand the blow of confidence you feel (I had psoriasis affect my entire body at one point and I am forever grateful that it doesn't anymore). Honestly, I would go through the basics of psoriasis (what it does, how it affects you) and the possible risks it brings in a relationship (chance of passing in on through offspring) so that your possible partner has a full understanding of the situation. If they feel uncomfortable by it and want to move on, simply let them. At least no one will feel as if time was wasted.