Improvement of bullous pemphigoid following salvage radiation in PSA-recurrent prostate cancer: a potential paraneoplastic association.

This case describes a man in his 70s with a 12-year history of bullous pemphigoid (BP) and recurrent prostate cancer, both diagnosed in the same year. Initially managed with active surveillance, his prostate cancer progressed, requiring hormonal therapy, surgery, and, eventually due to recurrence, salvage radiation therapy (RT). Concurrently, his BP, characterised by blistering skin lesions, was managed with corticosteroids, azathioprine and methotrexate, though full control of disease activity was difficult. Following salvage RT and androgen deprivation therapy, his prostate-specific antigen (PSA) levels and BP improved significantly, leading to prostate cancer remission and near resolution of his BP.The patient continues methotrexate, with stable PSA and only minor localised BP activity. The temporal relationship between his prostate cancer and BP, including their simultaneous onset, recurrence and remission, suggests a possible paraneoplastic link. Understanding this relationship is crucial for accurate prognosis and effective treatment for men with prostate cancer and associated paraneoplastic syndromes.