Korean Guidelines for Diagnosis and Management of Interstitial Lung Disease: Cryptogenic Organizing Pneumonia.

Cryptogenic organizing pneumonia (COP), one of the idiopathic interstitial pneumonias (IIP), exhibits an acute or subacute course. It can be diagnosed after excluding secondary causes or diseases. COP accounts for approximately 5% to 10% of IIPs, with the average age of diagnosis ranging from 50 to 60 years. Patients primarily present with dry cough and dyspnea. They often experience fever, fatigue, and weight loss. Common radiologic findings on high-resolution computed tomography include localized consolidations, which are typically subpleural or located in the lower zones, though they can occur in all regions of the lungs. While treatment can be initiated without histopathological diagnosis, tissue biopsy may be necessary when the diagnosis is unclear. Response to steroid therapy is generally good, with rapid clinical improvement and a favorable prognosis, although relapses are common.