Demonstration of intercellular immunofluorescence and epidermal hysteresis in bullous fixed drug eruption due to phenolphthalein.

Abstract

Summary.— We have reported a case of severe bullous erythema multiforme type of fixed drug eruption in which (1) multiple drugs were erroneously first indicated as the cause; (2) a false positive bullous patch test was obtained and discovered to be an intracorneal artefact, reflecting a new phenomenon, epidermal hysteresis; (3) a relationship to auto-sensitization and pemphigus was discerned by the demonstration of direct intercellular immunofluorescence in the lower epidermis of the affected fixed sites only; (4) phenolphthalein was finally proven to be the specific cause by double-blind oral challenge.