Bullous Pemphigoid (BP) is an autoimmune blisters disease, typically characterized by BP180 and BP230 autoantibodies (AAb). Atypical manifestations of BP include additional mucous membrane involvement which evokes the epidermolysis bullosa acquisita (EBA), another skin autoimmune disease characterized by type 7 collagen
(Col-7) AAb. We wondered whether anti-Col7 AAb detection could help in excluding EBA or in better characterizing those BP patients. Anti-BP180, -BP230 and -Col7 AAb were measured by ELISA in the serum of unselected patients with BP fulfilling at baseline (n=71) clinical and histo/immunopathological criterias, and at time of relapse (n=24). The mean age of BP patients with mucosal involvement (BPwM) was lower than those without mucosal involvement (BPw/oM) (75±12 vs 82±7, P<0.05). At baseline, anti-col7 AAb were detected in 2 out of 24 BPwM patients, but not in those with BPw/oM (n=47). Both, total and skin BPDAI scores were lower in BPw/oM versus BPwM patients (38±22 vs 61±29, and 38±22 vs 57±28, respectively). At the time of relapse, 10 out of 24 BP patients displayed detectable concentrations of anti-Col7 AAb, independently of mucosal involvement. Beside, anti-Col7 AAb concentrations increased (p<0.01) in the serum of BP patients with sustained concentrations of antiBP180 at time of relapse, but not when anti-BP180 concentrations decreased with respect to baseline concentrations. The serum concentrations of anti-BP230 did not vary in all BP patients with relapse. Thus, our study shows that anti-Col7 AAb detection was not useful to discriminate BP from EBA at baseline, but stratifies BP patients at time of relapse by highlighting, along with anti-BP180 AAb detection, a potential epitope spreading mechanism in a subpopulation of BP patients with relapse.

Anti-type 7 collagen antibodies identifies a subpopulation of BP patients with relapse