The term bullous drug eruption connotes several heterogeneous diseases
in which blisters occur as a complication of the administration of dr
ugs. Blisters may occur in bullous erythema multiforme, fixed drug eru
ption, or severe dermatitis medicamentosa with blisters. The common de
nominator is thought to be a hypersensitivity reaction to a systemic m
edication. Nevertheless, little has been written about the blisters in
these disorders, and neither common nor distinct pathogenic mechanism
s have been proposed. We describe a patient who had a rapidly progress
ive bullous eruption that occurred within hours of receiving intraveno
us trimethoprim-sulfamethoxazole. Routine histologic study of lesional
skin demonstrated subepidermal blisters. Transmission electron micros
copy and immunomapping of various basement components revealed that th
e cleavage plane of the blister was well below the lamina densa. After
healing of the blistering process, no scarring or milia formation was
observed.