On HRCT chest, a patient with interstitial lung disease shows diffuse ground-glass opacities with superimposed intralobular reticulation and subpleural honeycomb cysts bilaterally. The secondary pulmonary lobule demonstrates a 'crazy-paving' pattern in non-dependent zones. Which diagnosis is MOST consistent?
- A Usual interstitial pneumonia (UIP)
- B Pulmonary alveolar proteinosis (PAP) ✓
- C Acute interstitial pneumonia (AIP)
- D Desquamative interstitial pneumonia (DIP)
Correct answer: B. Pulmonary alveolar proteinosis (PAP)
Explanation
Crazy-paving pattern on HRCT — ground-glass opacity with superimposed interlobular septal thickening and intralobular lines resembling 'crazy paving stones' — is the hallmark of pulmonary alveolar proteinosis (PAP), caused by accumulation of PAS-positive lipoproteinaceous material in alveoli. UIP shows basal-predominant subpleural honeycombing with traction bronchiectasis. AIP (Hamman-Rich) shows diffuse bilateral ground-glass in acute setting. DIP shows diffuse lower-zone ground-glass but not the characteristic crazy-paving reticular superimposition.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.