title: Hypersensitivity pneumonitis: spectrum of high-resolution CT and pathologic findings.
abstract: OBJECTIVE
  The purpose of this article is to illustrate the spectrum of pathologic and high-resolution CT features of hypersensitivity pneumonitis (HP).
  
  
  CONCLUSIONS
  High-resolution CT plays an important role in the diagnosis of HP. A confident diagnosis of subacute HP is based on the presence of ground-glass opacities, poorly defined centrilobular nodules, and mosaic attenuation on inspiratory images and of air trapping on expiratory CT images. Chronic HP is characterized on high-resolution CT by the presence of reticulation due to fibrosis superimposed on findings of subacute HP. Histologically, subacute HP is characterized by the presence of cellular bronchiolitis, noncaseating granulomas, and bronchiolocentric lymphocytic interstitial pneumonitis. Areas of organizing pneumonia also may be seen. The high-resolution CT and pathologic features of chronic HP frequently overlap with those of nonspecific interstitial pneumonia and usual interstitial pneumonia. Awareness of the various manifestations of HP is important for early diagnosis and management.
authors.affiliation: Department of Radiology, Vancouver General Hospital, University of British Columbia, 899 W 12th Ave., Vancouver, BC, Canada V5Z 1M9. isabela.silva@vch.ca
authors.forename: C Isabela S
authors.initials: CI
authors.lastname: Silva
authors.forename: Andrew
authors.initials: A
authors.lastname: Churg
authors.forename: Nestor L
authors.initials: NL
authors.lastname: Müller
mesh_terms: D000542:Alveolitis, Extrinsic Allergic / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology*; D017410:Practice Guidelines as Topic; D010818:Practice Patterns, Physicians'; D011856:Radiographic Image Enhancement; D014057:Tomography, X-Ray Computed