Bullous Pemphigoid with Atypical Skin Lesions and Acute Interstitial Nephritis: A Case Report and Focused Literature Review

Abstract

BACKGROUND The hallmark of bullous pemphigoid (BP) is widespread tense blisters arising on normal or erythematous skin, often with marked pruritus, the diagnosis of which is confirmed by direct immunofluorescence (DIF). BP is an autoimmune process that can be induced, though rarely, by medications. Drug-induced BP often has atypical clinical presentation, which requires a good understanding of other dermatological conditions with similar presentations, in particular, bullous subtype of erythema multiforme. End organ involvement warrants differentiating it from one of the severe cutaneous adverse reaction (SCAR) syndromes. CASE REPORT A 76-year-old African American male presented with extensive targetoid purplish skin lesions that clinically resembled atypical erythema multiforme, and one tense blister that raised a concern for BP. The patient presented 6 weeks after treatment with cephalexin for a urinary tract infection. Initial workup showed serum eosinophilia, acute kidney injury and eosinophiluria requiring deliberations on SCAR syndromes. A skin biopsy at an intralesional location showed a negative DIF, however, a skin biopsy at a perilesional site showed a positive DIF, confirming the diagnosis of BP. CONCLUSIONS This case demonstrates an atypical presentation of BP induced by drugs. It emphasizes the need for a greater level of awareness of diagnosis and treatment of the various entities that fall under adverse drug reactions in the elderly. It also highlights the need for appropriate choice of skin biopsy techniques (intralesional versus perilesional) to avoid misdiagnosis, as well as lessons on how to approach dermatologic conditions with end organ involvement for hospitalists and other medical professionals who routinely deal with undifferentiated disease conditions.

Figure 1.

A single tense blister on the dorsal left hand, with minimal surrounding erythema.

Figure 2.

Atypical purplish targetoid lesions comprising discrete macules with central darkening and confluent patches. The shallow central ulcerations and scaling in some appear to be a secondary change after the rupture of blisters.

Figure 3.

Symmetrical involvement the arms and trunk by a mix of diffuse plaque and discrete targetoid macules.

Figure 4.

Symmetrical involvement the lower extremities, including plantar surfaces, by a mix of diffuse plaque and discrete targetoid macules.

Figure 5.

Histologic sections of skin biopsy showing changes involving all skin layers, including superficial necrotic keratinocytes, epidermal spongiosis, vacuolar changes at the interface, and basal cell layer, along with dilated dermal venules with Inflammatory infiltrate composed of lymphocytes, neutrophils and eosinophils.