Fig. 1

Clinical course. Chest computed tomography showed the appearance of mild bilateral pleural effusion 4 months after the initiation of durvalumab (b). Durvalumab was withdrawn after 13 courses of administration over 7 months. There were increases in the amount of bilateral pleural effusion (c), serum levels of globulin, IgG, and IgG4 8 months after the initiation of durvalumab. PSL, at a dose of 30 mg per day, was started and gradually decreased. PSL therapy for 4 months decreased the level of IgG4 from 2750 mg/dL to 370 mg/dL and induced complete disappearance of bilateral pleural effusion (d). LAMA: long-acting muscarinic antagonist; LABA: long-acting beta-agonist; ICS: inhaled corticosteroid; LTRA; leukotriene receptor antagonist; PSL: prednisolone