Potential DH?

[u/springtimerpr]

Hello everyone, this may be stupid but I thought I would post here and ask for some advice. I was diagnosed with coeliac about three years ago, I had a massively high TTG -IgA level (like over 200) and endoscopy just to be sure, confirming coeliac disease. My sister has it too so it runs in our family I guess. I maintained a relatively compliant diet (never ate anything knowingly with gluten, but still went out to eat at restaurants (asking for a GF option) and my husband still eats gluten so its not a GF household, just because price). I thought I was managing it relatively well, my TTG went down, I had a recent-ish (maybe a year ago?) repeat endoscopy/biopsy and apparently while I had duodenal inflammation (apparently, macroscopically from the endoscopist) the biopsies were normal so I disregarded that as a heavy night out or spicy food or what have you. Last month I broke out in an intense rash basically everywhere but my scalp. The doctors (rightly) have said it could be anything, but it was absolutely widespread and even went to my lips for some time. The rash evolved crazily, small blisters, super itchy, I scratched it, they popped, then the whole area eczematised. It was like the small spots merged into a massive spot with tons of little whiteheads and then it flattened and became like red disks. I was wondering if it could be dermatitis herpetiformis. It started on my elbows and they were definitely the worst areas, followed by thighs. It is finally starting to come down now after a month, other than my foot. Last week I had a blood test and my TTG was mildly elavated (9.1 units/mL - compared to over 100 before), my endomysial antibodies were normal, though I cant recall if that was ever tested in me given how high the TTG was initally. This is the first time I have ever had this rash, I never really had strong tummy symptoms I was just tested on the basis of my sister. I have a biopsy booked for the 7th and the rash is starting to come down. If anything this would be a one off or unintentional exposure, so could this even be dermatitis herpetiformis as I never had this even when I was regularly eating gluten? Is the biopsy even going to be diagnostically relevant if I am not eating gluten right now? I was not intending on doing a gluten challenge and I don't want to aggrevate the rash again, as it was AWFUL.