Cryptogenic Organizing Pneumonia
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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, 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
More common than originally thought and may be sudden and very severe in geriatric patients
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
- 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
Except for prevention of relapse, none known