A 48-year-old nonsmoking woman, three weeks after a viral upper respiratory infection, develops progressive dry cough and breathlessness. Pulmonary function tests show restriction. HRCT reveals patchy bilateral peripheral consolidations that migrate between scans. Surgical biopsy shows polypoid plugs of loose organizing connective tissue filling alveolar ducts and spaces with preserved underlying architecture. She improves dramatically with corticosteroids. The most likely diagnosis is:

• A Idiopathic pulmonary fibrosis
• B Desquamative interstitial pneumonia
• C Acute eosinophilic pneumonia
• D Cryptogenic organizing pneumonia ✓

Explanation

Cryptogenic organizing pneumonia shows Masson bodies, polypoid tufts of loose myofibroblastic tissue within alveolar ducts and spaces, with an intact alveolar framework, migrating peripheral consolidation on HRCT, and brisk steroid responsiveness, often after a preceding flu-like illness. In idiopathic pulmonary fibrosis the architecture is remodeled with honeycombing and fibroblastic foci, and steroids do not reverse it. Desquamative interstitial pneumonia shows macrophage-filled alveoli in smokers, and eosinophilic pneumonia requires prominent tissue eosinophils, both absent here.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.