Description

• 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

Epidemiology

• 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

Prevalence
Unknown

Etiology and Pathophysiology

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

Genetics
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