than 90% of patients, often with a lower zone predominance. A subpleural or peribronchiolar distribution is noted in up to 50% of patients. Ground glass appearance or hazy opacities associated with the consolidation are detected in most patients. Histologically, cryptogenic organizing pneumonia is characterized by the presence of polypoid plugs of loose organizing connective tissue (Masson bodies) within alveolar ducts, alveoli, and bronchioles. Unusual presentations of organizing pneumonia While patchy bilateral disease is typical, there are unusual variants of organizing pneumonia where it may appear as multiple nodules or masses. One rare presentation, focal organizing pneumonia, may be indistinguishable from lung cancer based on imaging alone, requiring biopsy or surgical resection to make the diagnosis. Complications Rare cases of COP have induced with lobar cicatricial atelectasis. Treatment Systemic steroids are considered the first line treatment for organizing pneumonia, with patient's often having clinical improvement within 72 hours of steroid initiation and most patient's achieving recovery. A prolonged treatment course is indicated, with patients usually requiring at least 4-6 months of treatment. Patient's who are treated with larger doses of steroids require prophylaxis against pneumocystis jirovecii. Relapses may occur and are more likely to occur in severe disease or when steroids are tapered too soon or too quickly. Alternative or adjunct treatment options include macrolide antibiotics (due to anti-inflammatory properties), azathioprine and cyclophosphamide. References External links Pneumonia