Abstract
Chronic hypersensitivity pneumonitis is an interstitial pneumonia caused by an immunological reaction to the chronic inhalation of an antigen. Little is known, however, about the pathological change of the pulmonary lesions. A 33-year-old man was diagnosed with chronic bird-related hypersensitivity pneumonitis based on the findings of a surgical lung biopsy and an inhalation provocation test. He underwent lung transplantation at 8 years after the diagnosis because of disease progression. We conclude that the analysis of the explant suggests that the presence of extensive fibrosis in the centrilobular and perilobular area with bridging fibrosis is a form of pathological progression of chronic hypersensitivity pneumonitis.