Lichen planus pemphigoides with IgG autoantibodies to the 180 kd bullous pemphigoid antigen (type XVII collagen)

We describe a 75-year-old patient with pruritic papules on her trunk and ex tremities, typical of lichen planus, who later experienced subepidermal bli sters. These clinical features are consistent with lichen planus pemphigoid es. Immunofluorescence of perilesional skin showed linear deposits of C3 al ong the dermoepidermal junction. Circulating IgG autoantibodies were found to be directed against an epidermal; component of the dermoepidermal juncti on because the patient's serum labeled the epidermal side of 1 mol/L NaCl-s plit skin. The patient's IgG autoantibodies were directed exclusively again st the 180 kd bullous pemphigoid antigen (BPAg2, type XVII collagen) detect ed in human keratinocyte lysate by Western blot assay. No reactivity was fo und against the 230 kd bullous pemphigoid antigen, type VII collagen, or th e laminin-5 subunits. This study demonstrates that BPAg2 is recognized, not only by bullous pemphigoid sera, but also by lichen planus pemphigoides se ra. Our findings attest to the similarity of immunopathology in these two s ubepidermal blistering skin diseases.