COL17A1 and diabetes mellitus: Although there were significant differences in the prevalence of anti-full-length BP180 IgG between DM cases with and without DPP4i treatment in this study, the anti-full-length BP180 autoantibody-positive cases are likely to have been significantly older than the anti-full-length BP180 IgG-negative cases in the DM cases with DPP4i.