C: Generalized Bullous Fixed Drug Reaction
Dermatology was consulted in the emergency department, saw the patient, and obtained a biopsy. She was started on clobetasol 0.5% BID and instructed to remain off of SMX/TMP. At her outpatient follow-up appointment with dermatology, she had developed new lesions, so was transitioned to a course of prednisone. She was then lost to follow-up.
GBFDR is a type of fixed drug reaction characterized by widespread red-brown macules as well as blisters, vesicles, and/or bullae, that rupture easily, leaving erosions or shallow ulcers. After the acute inflammatory response, there is post-inflammatory hyperpigmentation persists lasting weeks to months. Patients generally have minimal or no systemic symptoms. Dermatologic findings typically develop within 48 hours after ingestion of the offending agent, but they can develop as late as two weeks following the exposure, as seen in this case. This patient had been taking SMX/TMP, diphenhydramine, and ibuprofen, all of which have been implicated in GBFDR. A tissue sample was taken from our patient which most consistent with the diagnosis of GBFDR.
Erythema Multiforme (EM) is an acute, immune-mediated disorder affecting the skin and/or mucous membranes. The classic rash of EM is a “target” or “iris” lesion, described as concentric erythematous rings separated by rings of near normal color. The photos provided in this case do not match the expected dermatologic findings of EM.
GBFDR may be misdiagnosed as Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) in severe cases. While GBFDR may have mucosal involvement, it is generally much less common and severe than as seen in SJS/TEN. Additionally, SJS/TEN is more commonly associated with systemic symptoms. In this case, the lack of mucosal involvement and systemic symptoms makes TEN less likely. Furthermore, given that the total body surface area is <30%, TEN by definition cannot be the correct answer.
Patients with Pemphigus Vulgaris generally present with painful, persistent erosions of the oral mucosa with skin lesions typically occurring weeks to months later. It is extremely rare for this condition to present with minimal or no mucosal involvement; thus the absence of mucosal involvement makes this answer choice less likely.
Staphylococcal scalded skin syndrome (SSSS) is a condition caused by exfoliative toxins produced by certain strains of Staphylococcus aureus. Children with SSSS generally have a prodrome of irritability, generalized fatigue, and fever followed by tender erythema and the development of fragile bullae beginning typically on the central face, neck, axillae, and groin. The skin develops a classic wrinkled appearance referred to as “sad man facies,” due to the formation of the flaccid bullae. The rash depicted in the images above is not consistent with the rash of SSSS.
References
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