Confusion and corticosteroids: 80-Year old woman with pruritic urticarial plaques and tense blisters

An 80–year old woman with adult-onset diabetes mellitus presented to dermatology clinic several years ago with a 12-month history of a pruritic urticarial skin eruption of the flank and extremities. Her visit to dermatology was prompted by the new development of superimposed tense blisters (Fig. 2.1). She denied symptoms to suggest oropharyngeal, conjunctival, or genital mucosal involvement. Skin biopsy of perilesional skin demonstrated a subepidermal separation with eosinophilic spongiosis. Direct immunofluorescence showed linear deposition of C3 only. Indirect immunofluorescence with human salt–split skin showed linear deposition of IgG on the epidermal side of the blister. Enzyme-linked immunosorbent assay for BP180 and BP230 were elevated at 34 and 73 units, respectively (normal: <9 units).