sorry, don't know any dermatologists in Seattle, but just wanted to warn you:
I had 2 skin biopsies, but the dermatologist did NOT warn me that having been gluten-free for a month and having been on prednisone would screw up the test results. Also, the biopsies were quite deep, and left two pea-sized scars on my arm that are still red and obvious and it's been 18 months since the biopsies were taken.
So I am left with ugly, permanent scars, and we didn't rule out celiac, or confirm it, either.
Since going gluten-free, my rash has only hinted at coming back a couple of times when I inadvertently had gluten, so I assume that it was, in fact, DH. Even if it wasn't, I definitely have a problem with gluten, but I decided NOT to push for an official diagnosis after reading here on this board of people who were denied health and/or life insurance after being diagnosed with celiac.
Are you sure you NEED the biopsy? Is there something other than celiac you are looking to either confirm or rule out?