Cryptogenic organizing pneumonia
Common symptoms of COP include a flu-like prodrome and nonproductive cough.
Frequently, dyspnea is the chief symptom of patients presenting to primary care settings. The differential diagnosis is broad and commonly includes both pulmonary and cardiac disease. Common pulmonary diagnoses for patients with dyspnea include exacerbation of an underlying illness, infectious processes, and inflammatory disease.1 When patients present with acute dyspnea associated with fever and cough, community-acquired pneumonia (CAP) is often diagnosed. A less common, yet clinically important, alternative diagnosis for patients with these symptoms is cryptogenic organizing pneumonia (COP).
COP is a relatively uncommon disease process with a presentation that can mimic that of CAP. However, the management of COP differs significantly from the management of CAP, and it is important to distinguish between the two disorders. Clinicians often fail to recognize COP, leading to a delay in diagnosis.2 The purpose of this article is to increase awareness of COP among primary care clinicians.
Definition of terms
Organizing pneumonia is both an inflammatory and a fibrotic lung disorder that can occur following a variety of pulmonary insults.3 The term organizing implies that the underlying lung parenchyma remains intact. The term pneumonia is defined as "filling of the alveoli by inflammatory exudate."4 Organizing pneumonia is not a specific diagnosis, but rather a spectrum of disorders that share histopathologic features.3,5 In the majority of patients with organizing pneumonia, the inciting insult cannot be identified,6,7 and this condition has been designated as cryptogenic organizing pneumonia (COP)8; cryptogenic means of obscure or unknown origin.9
COP has also been identified in the literature by a variety of other terms, including bronchiolitis obliterans organizing pneumonia (BOOP), chronic pneumonia, and organizing diffuse alveolar damage.10 In 2001, the American Thoracic Society and the European Respiratory Society formed a multidisciplinary group to standardize the terminology used to describe interstitial lung diseases. The consensus recommendation of this group was that COP is preferable to other terminology for two primary reasons11: first, it focuses on the essential histologic features of the disorder; and second, it avoids confusion with other airway diseases, including constrictive bronchiolitis obliterans.11 In this article, the recommended term, COP, is used; however, other terms are mentioned because many sources reference them.