A case of radiation pneumonitis with eosinophilia in bronchoalveolar lavage fluid

: A 78-year-old man was admitted to our hospital for irradiation therapy of non-resectable primary lung squamous cell carcinoma of the right middle lobe (T3N2M0). The Linac irradiation through opposing 2 gates (2Gy per day and 60Gy in total) was performed to the affected area including the metastatic right hilar and mediastinal lymphadenopathy. One week after completing the irradiation therapy, fever developed with infiltrates in the area from the right middle lobe to the right lower lobe, which did not necessarily coincide with the irradiated area. Antibiotic therapies were not effective. Both the serum LDH level and eosinophil count in the peripheral blood increased. Bronchoalveolar lavage was performed at the right B8, and differential cell counts of the lavage fluid were: macrophages, 17%; lymphocytes, 60%; neutrophils, 5%; and eosinophils, 18%. No significant organisms were obtained by culture of the lavage fluid. The %VC and DLCO/VA became lower than before the irradiation therapy. Thus, the patient was given a diagnosis of radiation pneumonitis. Treatment with 40mg/day oral prednisolone was commenced with a stepwise dose-reduction (5mg every two weeks) until reaching the maintenance dose of 15mg/day. The serum LDH level and blood eosinophil count recovered promptly to the normal range. The pulmonary infiltrates and the lung functions substantially improved. There have been few reports of radiation pneumonitis in which eosinophil counts increased in peripheral blood and bronchoalveolar lavage fluid after irradiation therapy. In the present case report, the possible mechanisms for the irradiation-induced eosinophilia were also reviewed.