A 50-year-old man with progressive dyspnea and no fever has chest imaging showing bilateral interstitial linear opacities with ground-glass shadows. Pulmonary function tests indicate a restrictive pattern. Which set of pathological changes is most likely in the lungs?

• A. Uniform dilation of airspaces distal to the respiratory bronchiole
• B. Honeycomb lung with widespread alveolar septal fibrosis
• C. Chronic inflammation of bronchial walls with prominent eosinophilic infiltrate
• D. Chronic inflammation of bronchial walls with hyperplasia & hypertrophy of mucus glands

Answer: (B)

Fibrosis of the lung interstitium producing a restrictive defect is the key idea. Progressive interstitial fibrosis thickens and stiffens the lung’s elastic framework, which lowers lung compliance and reduces volumes, matching a restrictive pattern on pulmonary function tests and the interstitial/ground-glass radiographic appearance.

Pathologically, this ends in widespread fibrosis of the alveolar septa with architectural distortion of the lung parenchyma, often progressing to honeycombing—cystic, thick-walled airspaces at the periphery. This reflects the end-stage remodeling of chronic interstitial lung disease and explains the combination of impaired gas exchange and reduced lung volumes.

The other scenarios describe airway-centered diseases with different physiology and histology: emphysema shows uniform dilation of distal airspaces and an obstructive pattern; chronic bronchitis and eosinophilic bronchitis involve chronic airway inflammation with mucus gland changes or eosinophils, typically with obstructive features rather than interstitial fibrosis.