Two cases of dermatoses koebnerizing within fields of previous radiotherapy.

We describe two patients with newly diagnosed dermatoses localizing to the radiotherapy field following treatment for breast cancer. Patient 1 was a 53-year-old woman who developed bullous morphoea on her left breast two years after radiotherapy. Patient 2 was a 43-year-old woman who developed urticaria pigmentosa on her right breast eight months after radiotherapy and similar lesions gradually developed beyond the radiotherapy field. Both patients experienced a significant delay in diagnosis due to diagnostic confusion and concern over breast cancer recurrence. Irradiated skin demonstrates gradual and sustained alterations in fibrosis due to the production of long-lived cytokines and chemokines. These changes can induce a koebnerizing response in conditions such as morphoea and urticaria pigmentosa. We explore the mechanisms behind radiotherapy-induced skin changes, and highlight the potential for radiotherapy to exacerbate or unmask underlying dermatoses and systemic disease in the months and years following treatment.