Clinical Pearls & Morning Reports
Published March 16, 2022
Cryptogenic organizing pneumonia (COP) has no identifiable cause and is classified as a form of idiopathic interstitial pneumonia. Read the NEJM Review Article here.
Q: What is the mean age at diagnosis of COP?
A: According to 37 published reports from centers around the world, which involved a total of 1490 patients with a confirmed diagnosis of COP, the mean age at diagnosis is 50 to 60 years (range, 17 to 95); COP is rarely reported in children. The incidence of cases is slightly higher among men than among women (52% among men). Approximately 54% of patients with COP have never smoked, and 46% are former or current smokers; of former or current smokers, less than 15% reported that they smoked at the time of diagnosis.
Q: What are some of the clinical features of COP?
A: The differential diagnosis of COP includes a broad spectrum of diseases that have similar clinical and radiologic features. The most important mimic of COP is community-acquired pneumonia. Often, it is the absence of a response to antibiotic treatment that suggests COP. Symptoms of COP are often subacute and can emerge over a period of several weeks to several months. Patients are often able to remember with some precision when their illness began. Common symptoms include dry cough (in 71% of reported cases) and dyspnea (in 62% of reported cases) that is mild to moderate and worsened by exertion. Influenza-like symptoms (i.e., nasal congestion, headache, chills and sweats, sore throat, cough, fatigue, myalgia, and fever) have been reported in 10 to 15% of cases. Fever is present in 44% of cases of COP. The incidence of hemoptysis is very low (<5%). The most common finding on physical examination is inspiratory crackles (in 60% of reported cases). Clubbing is rare (reported in <3% of cases).
A: The predominant pattern on high-resolution CT studies is peripheral and multifocal consolidation (with or without air bronchograms). The findings may be unilateral or bilateral. The lesions are found in all lung zones, with a slightly predominant subpleural and lower-lung-zone distribution. Other radiologic findings include ground-glass opacities; nodules that are approximately 8 mm in diameter, arranged in a well-defined acinar pattern, or smaller nodules in a more subtle, poorly defined pattern; a peribronchovascular pattern, with areas of consolidation surrounding the bronchovascular bundles; a linear and bandlike pattern, with subpleural opacities that are parallel or perpendicular to the pleura; and focal lesions. Radiologic abnormalities can also be manifested as migratory opacities with areas of spontaneous regression and new areas of consolidation. Mediastinal lymphadenopathy is rare. Small pleural effusions have been reported in rare cases.
A: Treatment of COP is empirical because no prospective, randomized treatment trials have been performed. Systemic glucocorticoid therapy is the preferred treatment for symptomatic patients with respiratory impairment due to COP. Glucocorticoid therapy usually induces clinical improvement, beginning within 24 to 72 hours. Patients usually have decreased symptoms, followed by resolution of the radiologic findings within 3 months after diagnosis. Relapse has been reported in less than 25% of cases, usually within the first year after the initial presentation. The prognosis and response to treatment for patients with COP are generally excellent. For patients who are hospitalized, the length of stay is usually less than 3 weeks, and improvement is generally rapid (often within 72 hours and rarely >10 days) after diagnosis and initiation of glucocorticoid treatment. Progressive respiratory failure requiring mechanical ventilation and resulting in death is rare in patients with organizing pneumonia.