Bullous pemphigoid following adjuvant radiotherapy for breast cancer: a case report

Bullous pemphigoid (BP) is an autoimmune cutaneous blistering disease that predominantly affects elderly patients. Radiotherapy represents a rare triggering factor and may clinically mimic radiation-induced dermatitis, potentially leading to delayed diagnosis.

An 85-year-old woman underwent breast-conserving surgery and adjuvant radiotherapy for multifocal invasive lobular carcinoma of the right breast. The immediate post-radiotherapy course was unremarkable. Approximately 7 weeks after completion of radiotherapy, the patient developed acute-onset pruritic blistering lesions confined to the irradiated breast, later spreading to the upper arm and back. Initial clinical assessment suggested late-onset radiation dermatitis. Due to the delayed and progressive presentation, further diagnostic evaluation was performed. Histopathology revealed subepidermal blister formation with inflammatory infiltrates. Direct immunofluorescence demonstrated linear IgG and C3 deposition along the basement membrane zone, while serology showed elevated BP230 antibodies, confirming the diagnosis of BP. Treatment with high-potency topical corticosteroids and systemic doxycycline resulted in marked clinical improvement.

This case highlights BP as a rare delayed complication of breast radiotherapy. Acute-onset blistering lesions outside the typical timeframe of radiodermatitis should prompt consideration of autoimmune cutaneous disease. Establishing a strong physician-patient relationship combined with an interdisciplinary approach is essential to ensure early diagnosis and favorable clinical outcomes.