Chemotherapy-induced radiation recall myositis

Myofasciitis syndrome encompasses a group of disorders characterized by chronic inflammation and/or fibrosis of the subcutaneous septa and muscular fascia. We report on a patient in whom myositis was diagnosed in the areas previously irradiated for papillary thyroid carcinoma and anal canal carcinoma respectively 21 and 3 years after radiotherapy. We are not able to explain why myopathy developed at the same time in two different sites at a different interval from the two radiotherapic schemes. We can suppose that the patient developed a subclinical regional myopathy after the first radiotherapic scheme. Radiation induced heritable mutations within surviving cells that were unable to tolerate the second damage by systemic chemotherapy. It is unclear how radiosensitization correlates with an ability to reactivate latent effects in normal tissue. Physicians using chemotherapic radiosensitizers should be aware of their potential to induce a delayed form of radiosensitization. We report this case to encourage physicians to be alert to the knowledge of the clinical, histologic and morphologic characteristics of radiation myositis in order to distinguish it from an infectious or immune fasciitis or myositis.