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Cryptogenic Organizing Pneumonia

Cryptogenic Organizing Pneumonia is a topic covered in the 5-Minute Clinical Consult.

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  • Cryptogenic organizing pneumonia or COP is the idiopathic inflammatory process of diffuse interstitial granulation extending to the distal airways and alveoli.
  • As opposed to secondary organizing pneumonia that has multiple causative etiologies such as medication, infection, connective tissue disease, malignancy, COP has no known precipitant.
  • May have a gradual or sudden onset
  • Unknown pathogenesis
  • Chest x-ray (CXR) shows a pattern of bilateral, diffuse, or patchy infiltrates and consolidative or ground glass opacifications. There may be air bronchograms as well.
  • Completely reversible restrictive problem. Most cases will respond to corticosteroids, which may have to be given for a year or more.
  • Synonym(s): previously known as bronchiolitis obliterans organizing pneumonia or BOOP; intraluminal fibrosis of distal airways; idiopathic BOOP; obliterative bronchiolitis

Geriatric Considerations
More common than originally thought and may be sudden and very severe

Pediatric Considerations
Rare but has been reported after viral pneumonia


  • Incidence/prevalence in the United States: estimated at 0.01% but may be underdiagnosed
  • Predominant age: most commonly seen in age 50s to 60s


Etiology and Pathophysiology

Idiopathic: a specific complex reaction of lung tissue to alveolar cell injury

No known genetic component

Risk Factors

  • Immunocompromised patients, including transplant recipients and AIDS patients
  • Other autoimmune conditions
  • Gastroesophageal reflux disease causing microaspiration
  • Reported frequency of tobacco use in diagnosed cases 25–50%, making smoking unlikely to be a precipitating factor

General Prevention

Except for prevention of relapse, none known

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Stephens, Mark B., et al., editors. "Cryptogenic Organizing Pneumonia." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688229/all/Cryptogenic_Organizing_Pneumonia.
Cryptogenic Organizing Pneumonia. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688229/all/Cryptogenic_Organizing_Pneumonia. Accessed March 22, 2019.
Cryptogenic Organizing Pneumonia. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688229/all/Cryptogenic_Organizing_Pneumonia
Cryptogenic Organizing Pneumonia [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 March 22]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688229/all/Cryptogenic_Organizing_Pneumonia.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Cryptogenic Organizing Pneumonia ID - 1688229 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688229/all/Cryptogenic_Organizing_Pneumonia PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -