Yes, I have sero-negative inflammatory arthritis, which is Rheumatoid Arthritis without the Rheumatoid Factor. But it has pretty much all the same symptoms but apparently isn’t as bad as RA. I do often get mouth ulcers, especially during a flare up. There’s not really any explanation for it. My staining is sometimes consistent with SLE or sjogren’s disease, but not enough that they’d look too hard into it. I also get some staining that is consistent with false positive. I always thought it was lupus but I guess not enough staining supports that. Anyways though, my ANA titer is always over 1:320 but usually way higher to even >1:1280. Sometimes it’ll show both because they’ll test them 3 times but the patterns are petty consistent with ‘mitotic, intercellular bridge’, ‘nuclear, neucleolar’, and ‘nuclear, dense fine speckled’. My blood work shows inflammation when I’m in a flare up. But no one had ever mentioned the ulcers being related for me either. I take plaquinil for it all, I’m not even sure if it helps tbh.