Organizing pneumonia (OP) is a type of diffuse interstitial lung disease characterized by a specific histopathologic pattern of response to lung injury. When the etiology of the injury is unknown and in the absence of inflammatory or connective tissue disease, this entity is termed cryptogenic organizing pneumonia (COP) or primary organizing pneumonia (POP). Disease states in which the etiology of underlying injury is known is termed secondary organizing pneumonia (SOP). Causes of SOP include drug toxicity, chronic heart or renal failure, rheumatic disease, collagen vascular disease, infection, immunodeficiency, autoimmune disease, and interstitial lung disease.

OP is characterized by the accumulation of inflammatory cells, fibroblasts, and myofibroblasts in the lumens of bronchioles and alveoli creating plugs of debris. This leads to alveolar epithelial injury, which is followed by leakage of plasma cells and the recruitment of fibroblasts and fibrin within the alveolar lumen. This accumulation of granulation tissue within the alveolar sacs extends into the alveolar ducts as well as the bronchioles causing symptom onset. The clinical presentation of OP is variable and involves nonspecific symptoms such as mild fever, cough, malaise, anorexia, weight loss, and progressive dyspnea. Some reports describe wheezing and clubbing, but these symptoms occur in only 5% of cases. While “crackles” is the most common abnormal finding of OP on auscultation, 25% of reported cases present with a completely normal pulmonary exam.

The decision to treat patients for OP depends on the clinician’s ability to rule out other potentially reversible causes of dyspnea as well as the number of criteria met for this diagnosis of exclusion, based on histopathologic, radiographic, and clinical findings. Diagnosis is made via biopsy; though surgical biopsy via thoracoscopy has remained the gold standard, trans-bronchial biopsy has recently gained prevalence. We aim to present a suspected case of COP as an uncommon cause of interstitial lung disease.