Abstract
Hypersensitivity pneumonitis (HP) is a complex inflammatory and/or fibrotic immune-mediated disease that involves lung parenchyma and small airways caused by an inhaled antigen in susceptible individuals. It is currently the third most frequent interstitial lung disease (ILD) after idiopathic pulmonary fibrosis (IPF) and connective tissue disease with ILD. Diagnosis of HP is often challenging as identifying a causative agent is one of the main arguments in diagnosis along with specific serum IgG testing, suggestive HRCT and/or BAL, and in some cases histopathological findings. However, in up to 60 % of cases, exposure is not identified despite a thorough exposure history. HP is more frequent associated with occupational exposures, up to 20%, but non-occupational environmental exposure remains an important cause. We present a case of bird fancier’s lung that illustrates the challenges and the importance of identifying the culprit antigen as the elimination of exposure in combination with corticosteroids can lead to improvement in lung function, symptoms and leads to a better prognosis and may stop of evolving in sever fibrotic forms of HP.