COL17A1 and Erythema: In BP patients without mucosal involvement at baseline, serum anti-BP180 ELISA values were significantly correlated with all BPDAI scores except mucosal BPDAI, i.e., total, skin, blister/erosion, and erythema/urticaria BPDAI scores (P < 0.0001, Figures 3A–D, Table 4A).