Antibody to bullous pemphigoid antigen 1 binds to the antigen at perilesional but not uninvolved skin, in localized bullous pemphigoid.

We describe a 59-year-old woman who presented with vesicles, bullae and crusts on her lower legs. Direct immunofluorescence findings for perilesional skin showed linear depositions of IgG and C3 at the basement membrane zone, while no deposition was observed in intact thigh skin, 20 cm distant from the edge of the erosion. On indirect immunofluorescence study using normal human skin, circulating IgG autoantibody to the basement membrane zone (BMZ) was observed in the patient's serum at a titer of 1: 160, which reacted with an antigen located on the epidermal side of normal skin split by 1M NaCl and which stained the BMZ of the thigh skin of the patient that was negative in direct immunofluorescence study. Immunoblot analysis using epidermal extracts demonstrated the presence of IgG antibody directed to 230 kDa bullous pemphigoid antigen (BPAG1) in the patient's serum. These findings suggest that antibody to BPAG1 binds to an antigen uncovered by unknown causes at perilesional, but not at uninvolved skin in the present case of localized bullous pemphigoid.