From Pruritus to Bullae: Recognizing Furosemide-Induced Bullous Pemphigoid in an Elderly Male Patient.

Bullous pemphigoid (BP) is an autoimmune blistering disorder characterized by tense bullae and severe generalized pruritus. However, atypical presentations in elderly patients may involve localized pruritus prior to the development of bullae, which can obscure the diagnosis and delay appropriate treatment. We present a case of BP induced by furosemide in an 83-year-old male patient with congestive heart failure. The patient initially experienced persistent pruritus on the bilateral arms and back, which emerged approximately three months after initiating furosemide therapy. This pruritus was initially attributed to xerosis. Subsequently, erythematous papules developed in these areas, raising suspicion for atypical scabies, although they did not respond to permethrin treatment. A shave biopsy revealed subepidermal bullous disease with numerous eosinophils, and direct immunofluorescence confirmed the diagnosis of BP, showing linear IgG and granular C3 deposition at the basement membrane zone. The papules then evolved into tense bullae, and serologic testing supported the diagnosis with elevated IgG titers and positive BP180 antibodies. Furosemide was discontinued as the likely trigger. Initial treatment with prednisone led to improvement; however, bullae reappeared upon tapering the medication. Further management with doxycycline and topical triamcinolone resulted in enhanced improvement. Ultimately, biweekly dupilumab injections effectively controlled the symptoms. This case underscores the diagnostic challenges of BP, particularly in the elderly, where isolated pruritus may precede the appearance of visible bullous lesions. Clinicians should maintain a high index of suspicion for BP in elderly patients with unexplained pruritus, especially when standard treatments are ineffective. Additionally, this case highlights the importance of considering drug-induced BP, with furosemide recognized as a potential trigger.