Which feature is typically seen in usual interstitial pneumonia but not in nonspecific interstitial pneumonia?

• A. Interstitial edema
• B. Pleural plaques
• C. Honeycombing
• D. Pneumothorax

Answer: (C)

The key idea is that honeycombing is a hallmark of usual interstitial pneumonia (UIP) and is not a feature of nonspecific interstitial pneumonia (NSIP). In UIP, the fibrosis becomes end-stage and forms cystic, thick-walled airspaces—subpleural and basilar in distribution—known as honeycombing. This reflects ongoing architectural distortion and irreversible remodeling of the lung. NSIP, in contrast, shows more uniform interstitial involvement with preserved overall architecture and lacks the distinctive cystic, honeycomb changes; it may present with ground-glass opacities or reticulation but not the end-stage cystic remodeling seen in UIP.

So the feature best distinguishing UIP from NSIP is honeycombing. Interstitial edema is a nonspecific acute change, pleural plaques point to asbestos exposure, and pneumothorax isn’t a defining feature of these patterns.