Bullous Pemphigoid Mimicking Infection in a Diabetic Foot: A Diagnostic Challenge

Summary: Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disorder that classically presents with tense bullae. In patients with diabetes and chronic wounds, atypical BP may mimic postoperative infection or ischemia, resulting in delayed diagnosis and unnecessary antimicrobial or surgical escalation. We report a 51-year-old man with poorly controlled type 2 diabetes and advanced chronic kidney disease who underwent partial first-ray amputation for wet gangrene. During postoperative wound healing, he developed widespread, sterile tense bullae on the feet and extremities. Clinical reassessment prompted dermatology consultation, skin biopsy, and direct immunofluorescence to establish the diagnosis. Histopathology and direct immunofluorescence confirmed BP. The patient was treated with doxycycline and high-potency topical corticosteroid therapy, avoiding systemic immunosuppression in the setting of significant comorbidities. New blister formation ceased and cutaneous lesions resolved with continued progression of wound healing. In diabetic foot care, sudden sterile bullae, especially when extending beyond pressure areas or lacking inflammatory signs, should prompt consideration of BP and early biopsy with direct immunofluorescence. Early dermatology involvement supports conservative, tissue-sparing management and helps avoid misdiagnosis as infection or ischemia.