Hypersensitivity pneumonitis (HP) may be a challenging diagnosis given the wide variability of its clinical, radiographic, and pathologic manifestations. A multidisciplinary approach to diagnosis is critical in maintaining a high specificity for HP. An in-depth knowledge of all 3 arms of the multidisciplinary approach helps clinicians, radiologists, and pathologists interpret their own findings in the context of the entire presentation. In some cases, the combination of clinical findings (ie, an identifiable exposure) and typical findings on high-resolution computed tomography is considered diagnostic of HP, and pathologic confirmation is not necessary. As many as 50% of patients do not have a clear exposure, however. These patients may be difficult to distinguish from idiopathic disorders. In these cases, high-resolution computed tomography and pathology are the primary data points that may suggest the correct diagnosis. The goal of this paper is to discuss recent advances in HP and to present the spectrum of clinical, radiographic, and pathologic findings.
Departments of *Radiology and Biomedical Imaging
§Internal Medicine, University of California San Francisco, San Francisco, CA
‡Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence to: Brett M. Elicker, MD, Department of Radiology and Biomedical Imaging, University of California San Francisco, 505 Parnassus Avenue, Box 0628, San Francisco, CA 94143 (e-mail: firstname.lastname@example.org).