Case report
A 77-year-old Japanese man was referred to us with a 1-year history of pruritic erythema, bulla and erosion on the head/neck, trunk and extremities (Fig. 1a). The patient had already been diagnosed with BP in the previous clinic based on a high titer of serum anti-BP180 NC16a domain antibodies. On the back, the erythema was found to be distributed away from the pigmented areas corresponding to the inactive lesion (Fig. 1b). An intact zone of about 2 cm in width clearly separated active erythematous lesions from inactive pigmented lesions. Cross-linked enzyme aggregate assay indicated >1,000 U/ml of serum anti-BP180 NC16a domain antibodies (normal range, <9.0 U/ml). Histopathological examination of the erythema and bullae revealed subepidermal blistering accompanied by eosinophilic infiltration (Fig. 2a). Direct immunofluorescence assay revealed immunoglobulin G deposition in the basement membrane zone (Fig. 2b). Bullous pemphigoid was diagnosed. Erythema and bullae improved after administration of high-dose systemic corticosteroid.
We furthermore approached the phenomenon of the distribution of the active lesion away from the inactive lesion by immunohistochemistry. We counted CD4+, CD25+ and FoxP3+ cells in the width of 4 mm of the tissue obtained from active lesion, inactive lesion, and intact skin (Table 1, Fig. 2c-2e). Compared to the intact skin, CD4+ cells were counted 2.22-fold and 1.83-fold in active lesion and inactive lesion, respectively. Similarly, CD25+ cells were counted 1.48-fold and 2.33-fold. FoxP3+ cells were counted 1.75-fold and 2.64-fold.