Bullous lichen planus: diagnosis by indirect immunofluorescence and treatment with dapsone.

Bullous lichen planus may be confused with other subepidermal bullous dermatoses, especially if bullae arise on normal-appearing skin. We present two patients who were originally thought, on the basis of clinical and histopathologic criteria, to have bullous pemphigoid. However, results of standard indirect and direct immunofluorescence assays did not support the diagnosis of bullous pemphigoid. Further investigation using the indirect autologous immunofluorescence assay revealed deposits of immunoglobulins in the stratum granulosum. Moreover, the indirect allogeneic immunofluorescence assay (using papular lichen planus lesional substrates from different patients) was positive for the same pattern, confirming the diagnosis of bullous lichen planus. Bullous lichen planus with bullous pemphigoid-like histologic features can be differentiated from bullous pemphigoid on the basis of the indirect autologous and allogeneic immunofluorescence assays for circulating antigranulosum antibodies. Both patients were treated with systemic corticosteroids. One patient went into remission with this therapy alone; the other patient had a favorable response when dapsone was given with systemic corticosteroids. The suggestion that there is a subset of bullous lichen planus with bullous pemphigoid-like histologic features that responds to dapsone needs to be explored.