Diffuse Interstitial Pneumonitis

Diffuse Interstitial Pneumonitis

Tan-Lucien H. Mohammed, MD, FCCP

Jud W. Gurney, MD, FACR

Axial HRCT shows diffuse ground-glass opacities image and cysts image or emphysematous spaces. The patient was a heavy smoker.

Coronal HRCT MinIP reconstruction shows distribution of ground-glass opacities image and scattered cysts image. Diffuse interstitial pneumonitis was found at biopsy.


Abbreviations and Synonyms

  • Desquamative interstitial pneumonia (DIP), alveolar macrophage pneumonia


  • Chronic idiopathic interstitial pneumonia characterized by macrophage filling of alveolar spaces, probably related to cigarette smoking

    • Term “desquamative” is misnomer: Cells filling alveoli initially thought to represent desquamated alveolar lining cells

  • Continuum of smoking related lung injury: Respiratory bronchiolitis → respiratory bronchiolitis associated interstitial lung disease (RB-ILD) → DIP


General Features

  • Best diagnostic clue: Diffuse ground-glass opacities with scattered cysts in heavy smoker

  • Patient position/location

    • Lower lung predominance (70%)

    • Peripheral subpleural distribution (60%)

  • Morphology: Ground-glass attenuation predominant abnormality

CT Findings

  • Morphology

    • Ground-glass pattern (100%)

      • Predominant abnormality, bilateral and symmetric

      • Mean extent of pulmonary involvement (30%)

      • Typically ground-glass pattern panlobular, sharply demarcated from normal lung by interlobular septa, producing geometric pattern

      • Extent of ground-glass opacities directly correlated with pack-years of smoking

    • Distribution ground-glass pattern

      • Lower lung zones predominance (70%)

      • Peripheral predominance (60%)

      • Random distribution (25%)

      • Diffuse (20%)

      • Mid and upper lungs may be affected preferentially (15%)

  • Small well-defined cysts (80%)

    • Round, thin-walled, < 2 cm in diameter, typically occur within ground-glass opacities

    • Similar to cysts in lymphocytic interstitial pneumonia (LIP), may resolve with treatment

    • Superimposed emphysema common (60%) in older patients and also may produce small cystic spaces

  • Reticular pattern (60%)

    • Irregular linear opacities predominately in periphery lower lung zones

    • Usually intralobular (80%) and mild

    • Honeycombing (10%), uncommon and if present usually mild

  • Nodules

    • Uncommon, consider superimposed Langerhans cell histiocytosis or respiratory bronchiolitis

    • DIP, Langerhans cell histiocytosis, and respiratory bronchiolitis can be seen simultaneously

  • Adenopathy

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Diffuse Interstitial Pneumonitis

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