Hypersensitivity pneumonitis (HP) is an inflammatory interstitial lung disease caused by recurring exposure to a variety of occupational and environmental antigens. It features widely variable clinical, radiologic, and histopathologic findings. Because the clinical findings of HP mimic multiple other diseases, a high degree of clinical suspicion and a thorough occupational and environmental history are essential for accurate diagnosis. There is no single pathognomonic feature for HP; rather, diagnosis relies on a constellation of clinical, radiologic, and pathologic findings. The radiologic manifestations, particularly the high-resolution computed tomography (HRCT) pattern, provide important clues and frequently point clinicians towards the correct diagnosis. The HRCT findings in HP may include ground-glass opacification, centrilobular nodules, air trapping (mosaic pattern), fibrosis, emphysema, or more frequently a combination of these. The combination of a mosaic pattern with ground-glass opacification and centrilobular nodules is particularly suggestive of the diagnosis. The best long-term prognosis is achieved with early diagnosis and removal from exposure.
*Division of Environmental and Occupational Health Sciences, Department of Medicine, National Jewish Medical and Research Center, Denver, CO; †Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Health Sciences Center, Denver, CO; ‡Department of Preventive Medicine and Biometrics, University of Colorado Health Sciences Center, Denver, CO; §Department of Radiology, University of Colorado Health Sciences Center, Denver, CO.
Address correspondence and reprint requests to Dr. Cecile S. Rose, National Jewish Medical and Research Center, 1400 Jackson Street, Room G211, Denver, CO 80206. E-mail: firstname.lastname@example.org