Hypersensitivity pneumonitis

Eunhee S. Yi

Research output: Contribution to journalReview articlepeer-review

42 Scopus citations


Hypersensitivity pneumonitis (HP) is a group of immunologically mediated lung diseases caused by the inhalation of environmental agents in susceptible individuals. Most HP patients are non-smokers and have been exposed to organic dusts from vegetable or animal products. Some HP cases are associated with exposures to relatively simple chemical compounds. HP may present as an acute, subacute, or chronic disease and may follow various clinical courses. The type of exposure is thought to be more important in the clinical outcome than the nature of the antigen. A diagnosis of HP is often considered on the basis of clinical history of exposure with resulting respiratory symptoms, but the definitive diagnosis requires a constellation of clinical, radiologic, laboratory, and pathologic findings. The characteristic histologic triad in HP includes bronchiolitis, interstitial lymphocytic infiltration, and granulomas; however, biopsy in HP cases may lack the diagnostic triad and manifest as nonspecific interstitial pneumonia (NSIP). Avoiding exposure to the offending antigen(s) is usually sufficient to resolve symptoms and physiological abnormalities. Pulmonary fibrosis and physiological abnormalities occurring in chronic HP may be irreversible. Steroid therapy is helpful for symptomatic relief, but probably does not affect the long-term prognosis. Type III and type IV hypersensitivity reactions are involved in the pathogenesis; alveolar macrophages and T cells (Th-1 type) play a central role in the immune responses after antigen exposure via their increased interaction and secretion of regulatory mediators.

Original languageEnglish (US)
Pages (from-to)581-629
Number of pages49
JournalCritical reviews in clinical laboratory sciences
Issue number6
StatePublished - 2002


  • Extrinsic allergic alveolitis
  • Farmer's lung
  • Hot tub lung
  • Hypersensitivity pneumonitis
  • Metal worker's lung
  • Nonspecific interstitial pneumonia (NSIP)
  • Pigeon breeder's lung

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • Clinical Biochemistry
  • Biochemistry, medical


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