6 Patterns > Fibrosis Pattern > Additional Features > w/ Acute Lung Injury

Fibrosis w/ Acute Lung Injury

Biopsies showing both acute lung injury and fibrosis are some of the most challenging cases.  However, a simple approach is to characterize the acute component (fibrin, OP, DAD) and the chronic component (UIP, NSIP, airway-centered) individually.  There are 4 main settings this pattern is seen in, acute exacerbation of UIP, flare of CTD, subacute on chronic HP, and acute on chronic aspiration.

Acute Exacerbation of Usual Interstitial Pneumonia

  • Background fibrosis should have peripheral and subpleural distribution typical of UIP.

  • Should have numerous fibroblast foci or other features of acute lung injury

  • "Normal" areas will be involved by acute lung injury (note the fibrin between the green dots and the reactive pneumocytes)

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Acute on Chronic Aspiration

  • Foreign material

  • Food

  • Polarizable material

Flare of Connective Tissue Disease

  • Often with a more "blue" appearance due to inflammatory cells.

  • Areas of cellular interstitial inflammation similar to cellular NSIP.

  • Lymphoid follicles with germinal centers

  • Pleuritis

  • Follicular bronchiolitis

Subacute on Chronic Hypersensitivity Pneumonitis

  • Should show giant cells and poorly formed interstitial granulomas.

Sample Signout

If no additional specific histologic features are identified, consider the following approach to signing the case out:

Acute on chronic interstitial lung disease (see comment).

Comment:  The biopsy shows histologic evidence of both acute and chronic ILD.  The predominant pattern of the acute component is _______ (select OP, DAD, fibrin, etc).  The predominant pattern of the chronic compoennt is ______ (select UIP, NSIP, airway-centered, etc).  No additional specific histologic features to indicate an etiology are identified.  There is a broad differential diagnosis including acute exacerbation of UIP, flare of CTD, subacute on chronic HP, and acute on chronic aspiration.  The diagnosis of ILD requires a multidisciplinary approach.  Correlation with imaging studies and clinical history is suggested.