Profiling of hypersensitivity pneumonitis diagnosed at a UK specialist service for ILD and occupational lung diseases

Abstract

Introduction: Diagnosing hypersensitivity pneumonitis (HP) requires a full exposure history to identify offending antigens and interstitial lung disease (ILD) board meeting consensus is recommended. Our aim was to describe the distribution of presentations and causes of HP at our UK regional specialist unit for ILD and occupational lung diseases. Methods: We searched the ILD board (2005-2016) and occupational lung disease (2002-2016) clinical databases for cases of HP diagnosed at our specialist unit. We gathered data on demographics (age, gender, and smoking status), symptoms and signs, occupational and environmental exposures, causative agent, lung function, diagnostic classification and bronchiolo-alveolar cell count. Data was grouped by classification and results compared. Results: There were 174 cases of HP classified as 6% acute, 32% subacute and 60% chronic. Mean age=62, 51% of patients were male, 11% were current smokers. Fever, chills and recurrent symptoms were commoner in acute/sub-acute presentations than chronic HP. Mean cell counts were lymphocytes=26%, neutrophils=17%, eosinophils=1%, with no significant difference in lymphocyte count between subacute and chronic HP. Commonest causes were cryptogenic (48%), occupational (28%; incl. metalworking fluid (MWF)=21%) and non-occupational (24% incl. avian=15%, drugs=6%). Conclusions: This large UKseries includes 14 years’ worth of data from both ILD and occupational lung diseases regional specialised services. Causation is not established in a large minority despite specialist assessment. A detailed occupational history, particularly in relation to MWF, birds, chemicals and moulds/fungi remains essential.