Symptoms, which include nonproductive cough, dyspnea, and fever, develop approximately eight weeks after completion of a course of radiotherapy consisting of 4,000 cGy, and they develop one week earlier for each additional 1,000 cGy administered. Onset is usually subacute. Physical examination may reveal rales and signs of consolidation. Hyperpigmentation of the skin overlying the irradiated lung is common but does not correlate with the severity of lung injury. Laboratory findings include nonspecific leukocytosis and hypoxemia.
Lavage also reveals excess lymphocytes, from both involved and uninvolved areas.
Drug-induced lung injury causes similar cytopathic changes in type II cells, but usually, neutrophilic inflammation is also present. The chest roentgenogram shows an infiltrate of variable density. A highly characteristic infiltrate has sharp edges and conforms exactly to the radiation port. Many patients gradually improve over a few weeks. When the disease is severe, glucocorticoid therapy is often used, with uncertain benefit.