A 58-year-old male with progressive dyspnoea has HRCT showing areas of 'crazy-paving' pattern (ground-glass opacity superimposed on septal thickening). Which of the following diagnoses most characteristically produces this pattern?

• A Usual interstitial pneumonia (UIP)
• B Lymphoid interstitial pneumonia
• C Cryptogenic organising pneumonia
• D Pulmonary alveolar proteinosis ✓

Explanation

Crazy-paving pattern on HRCT — ground-glass opacity with superimposed interlobular and intralobular septal thickening creating a 'paved road' appearance — is the hallmark of pulmonary alveolar proteinosis (PAP). The PAS-positive lipoproteinaceous material fills alveoli while septal oedema creates the reticulation. UIP shows basal subpleural honeycombing with traction bronchiectasis; cryptogenic organising pneumonia shows peripheral consolidation; LIP shows diffuse ground-glass with scattered thin-walled cysts.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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