Cryptogenic Organizing Pneumonia



  • 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, and so forth, COP has no known precipitant.
  • May have a gradual or sudden onset
  • Unknown pathogenesis
  • Chest x-ray (CXR) typically 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 with 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 in geriatric patients

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
  • Males and females affected equally


Etiology and Pathophysiology

Idiopathic: a specific complex reaction of lung tissue leading to alveolar wall 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

There's more to see -- the rest of this topic is available only to subscribers.