A 78-year-old man presented with multiple, centrifugal
erythema, which tended to coalesce, producing polycyclic configurations. The patient developed an annular, narrow
blister that was always visible along the margin of the
erythema. Histology of a biopsy specimen revealed hydropic degeneration of basal cells, exocytosis of lymphoid cells, and subepidermal
blister with
necrosis of individual keratinocytes in the
blister roof. Direct immunofluorescence studies showed a weak
IgG deposition at the basement membrane zone, in a linear fashion, which was confined to the outer side of the
blister. Immunoblotting of the patient's serum with human epidermal extract demonstrated circulating
antibodies, which reacted to 230 kDa BP
antigen 1. These findings suggest that this case is characteristic of both
erythema multiforme and
bullous pemphigoid and it seems likely that this condition could be a manifestation of
epitope spreading, although the exact process in the development of immunological disturbances could not be elucidated.