A 61-year-old woman, hospitalized for a persistent cough and dyspnea, had no history of bronchial asthma, but was undergoing chemotherapy for methotrexate-related lymphoproliferative disorder due to rheumatoid arthritis. Her peripheral blood eosinophil count was significantly increased, and chest CT revealed left lower lobe atelectasis and high-attenuation mucus. Bronchoscopy revealed mucous plugs and pathological examination revealed numerous eosinophils and filamentous fungi. Allergic bronchopulmonary mycosis (ABPM) caused by