The comedo skin reaction to radiotherapy.

A 50-year-old man had a maxillectomy and post-operative radiotherapy for squamous carcinoma of the maxilla. The acute skin reaction merged at 2 months into a chronic comedo-type acneiform skin reaction in the irradiated area. Previous literature on this reaction to radiation is reviewed. The reaction is rare and occurs mostly in the head and neck area, more commonly in patients who have received acneigenic drugs, and with a latent period of between 2 weeks and 6 months from completion of radiotherapy. The pathogenesis of acne is discussed and a mechanism of post-irradiation acne is suggested.