IgG autoantibodies from a lichen planos pemphigoides patient recognize theNC16A domain of the bullous pemphigoid antigen 180

Lichen planus pemphigoides (LPP) most likely encompasses a heterogeneous gr oup of subepidermal autoimmune blistering disorders occurring in associatio n with lichen planus. We describe the case of a 49-year-old patient with fe atures characteristic of LPP. Direct immunofluorescence microscopy studies demonstrated linear deposits of C3 along the cutaneous basement membrane, w hile circulating IgG autoantibodies directed against the epidermal side of skin separated by 1 M NaCl were detected. The patient's serum contained IgG autoantibodies immunoblotting a recombinant form of bullous pemphigoid ant igen 180 (BP180), but not the COOH-terminus of BP230. By using deletion mut ants, it was found that IgG reactivity was restricted to the NC16A domain o f BP180, the region harboring the major antigenic sites targeted by IgG aut oantibodies from patients with the bullous pemphigoid group of disorders. O ur findings provide support to the idea that a subset of patients with LPP have a distinct form of bullous pemphigoid associated with lichen planus.