Vitiligo at the site of radiotherapy for nasopharyngeal carcinoma.

Cases of vitiligo following radiotherapy have been reported in patients with a history of vitiligo, possibly resulting from the Koebner phenomenon. As vitiligo in general is caused by melanocyte depletion, there is an increased radiosensitivity of this cell type in this disorder. However, vitiligo at sites of irradiation may be linked to a proposed auto-cytotoxic mechanism that may occur through inhibition of thioredoxin reductase by high extracellular calcium levels observed in keratinocytes of vitiligo patients. High levels of thioredoxin and thioredoxin reductases have been shown to protect from ionizing radiation-induced cell death. Thus, inhibition of thioredoxin reductase in vitiligo might account for the increased radiosensitivity of melanocytes in this disorder. We describe a patient who developed depigmentation at the site of radiation following radiotherapy for nasopharyngeal carcinoma. She had no history of vitiligo. Occurrence of depigmentation on the irradiated skin seemed to be related to radiation injury in our patient. Our case suggests that radiation injury to the skin can trigger vitiligo in patients who have no history of vitiligo. Thus, prior to therapy, the possibility of development of vitiligo should be taken into account for patients who are candidates for radiotherapy, even if they have no history of vitiligo.