Case Presentation:

A 71–year–old woman with a history of inverse psoriasis (occurs on skin folds versus extensor surfances), breast cancer status post right lumpectomy and radiation, last treated 3 months ago, presents to the hospital with right breast erythema, blistering, and pain. Erythema was first noted one month prior to presentation. She was seen by her primary care physician, oncologist and dermatologist over the past month and her symptoms progressed despite treatment with topical nystatin, triamcinolone, Silvasorb, oral dicloxacillin, and keflex. She denied fevers, chills, or increase of her baseline psoriatic lesions. Physical exam was notable for diffuse erythema of her right breast with overlying intact and ruptured bullae, and macerated skin in the breast fold (Figure 1). Skin was warm to touch. Skin exam was otherwise notable for scattered psoriatic plaques in fold of pannus and anterior right thigh. Punch biopsies were performed on her affected breast. Initial working diagnosis was combination of psoriasis flare, radiation dermatitis and overlying cellulitis, leading to an atypical dermatitis presentation. She was initiated on IV unasyn with continued topical application of Silvasorb. Biopsy results returned 48 hours after hospitalization. H&E stain demonstrated eosinophils at the dermal–epidermal junction and direct immunofluorescence demonstrated linear deposition of C3 at subepidermal blister base, consistent with bullous pemphigus. Treatment was changed to topical clobetasol, Silvasorb and oral nicotinamide. She was discharged home with outpatient dermatology follow up.


Bullous pemphigus is an autoimmune disorder that generally presents with widespread blistering skin lesions in older women. Although this patient fit the typical demographics of affected patients, the localization of her skin lesions was atypical, leading to greater consideration of alternate diagnoses on her initial outpatient and inpatient presentations. The primary alternate consideration was an atypical presentation of a combination of more common skin conditions, namely radiation dermatitis, cellulitis, and the patient’s known diagnosis of psoriasis. Although none of these disorders alone typically present with the patient’s skin findings, this was felt to be more likely an atypical presentation of a combination of more common skin disorders, than an atypical presentation of a singular rare skin disorder. The utilization of skin biopsy ultimately led to the correct diagnosis and patient treatment.


This case highlights the importance of considering both the “horse” and “zebra” when presented with atypical patient presentations. Although common conditions should be considered initially, it is important to avoid diagnostic anchoring when faced with lack of clinical improvement.