Radiotherapy-induced Pemphigus Foliaceous: a rare adverse effect of breast cancer therapy

An Unusual and Exaggerated Local Cutaneous Reaction Following Re-Irradiation and Fulvestrant Administration: A Clinical Conundrum

A 56-year-old female with a history of Luminal A breast cancer, previously treated with surgery, radiotherapy, and systemic therapy, underwent palliative re-irradiation in November 2024 for painful bone metastases. Three weeks later, following the initiation of Fulvestrant, she developed a grade 3 erythematous reaction localized to the re-irradiated area. The reaction persisted with minimal improvement over two months, despite symptomatic management. No infectious or allergic etiologies were identified, and dosimetric analysis confirmed that the delivered radiation dose to the skin was insufficient to directly induce such a reaction. Notably, the erythema was most pronounced along a pre-existing surgical scar, suggesting a localized inflammatory response. Given the temporal relationship with Fulvestrant administration, we hypothesize a drug-induced recall-like phenomenon, though no previous reports have specifically linked Fulvestrant to such an event. This case underscores the need for awareness of unexpected cutaneous reactions following re-irradiation and highlights the potential role of systemic therapies in modulating local tissue responses.

Case for diagnosis. Radiotherapy-induced pemphigus vegetans

A 73-year-old male patient developed a poorly differentiated squamous cell carcinoma in the anal canal nine months ago. He was treated with two cycles of 5-fluorouracil and cisplatin and concomitant radiotherapy (6 MeV linear photon accelerator, total dose of 54 Gy), with complete remission. Since forty-five days he presentes a painful perianal and intergluteal erosion with circinate pustular borders. Light microscopy showed pseudoepitheliomatous hyperplasia of the epidermis with microabscesses of inflammatory cells (neutrophils and eosinophils) and acantholytic keratinocytes . Indirect immunofluorescence was positive for IgG, with an intercellular pattern, 1:80 titer. The diagnosis of radiotherapy-induced pemphigus vegetans was established and there was significant regression with oral prednisone (40 mg) and topical betamethasone.

Radiation-Associated Pemphigus Vulgaris in a Patient With Preceding Malignancy: Treatment With Rituximab as a Valuable Option

Pemphigus is a chronic autoimmune blistering disorder, characterized by (muco-)cutaneous erosions due to autoantibodies against desmoglein 3 and/or 1. Pemphigus induction might be associated with drugs, malignancy or radiation therapy (RT); the latter being only rarely described. A rigorous literature review revealed around 30 cases of RT-associated pemphigus, which had been primarily treated with topical and/or systemic steroids, in some cases also dapsone or few other immunosuppressive agents were given. The most common underlying cancer type was breast cancer. We here present a 63-year-old male patient, who was pre-treated with adjuvant RT for larynx carcinoma 3 months before admission. He developed extensive cutaneous, ocular, and oral erosions. Despite the clinical picture comparable to a paraneoplastic pemphigus, the diagnosis of pemphigus vulgaris of mucocutaneous type was established based on the direct immunofluorescence, showing positive cell surface IgG and discrete C3 deposits, with matching cell surface IgG pattern on monkey esophagus. Serum autoantibodies to desmoglein 1 and 3 were highly positive. No further autoantibodies were found, thus paraneoplastic pemphigus was excluded. The patient was treated with high dose prednisolone, partially given intravenously up to 2 mg/kg per day, as well as topical disinfectants and class IV steroid cream. To stabilize the disease rituximab 2 × 1,000 mg was given, leading to clinical and serological remission for up to 2 years now. We show that rituximab represents a good treatment option for the frequently treatment-refractory RT-associated pemphigus, a clinically and immunologically specific RT-induced skin disorder, resulting in long-term clinical, and serological remission.