SUMMARY
Radiation-induced lung injury (RILI) encompasses any lung toxicity induced by radiation therapy (RT) and manifests acutely as radiation pneumonitis and chronically as radiation fibrosis. Because most patients with thoracic and breast malignancies are expected to undergo RT in their lifetime, and that too with curative intent, the population at risk is significant. Radiotherapy has proven satisfactory outcomes; however, adverse pulmonary effects, like pneumonitis, can be life-threatening. Fortunately, the incidence of serious pulmonary complications from RT has decreased secondary to advances in radiation delivery techniques. Understanding the temporal relationship between RT and injury as well as the patient, disease, and radiation factors that help distinguish RILI from other etiologies is necessary to prevent misdiagnosis. Here we report a case of life-threatening pneumonitis following RT in a case of a carcinoma breast.