6 Patterns > Acute Lung Injury Pattern > Subpatterns > w/ Hayline Membranes > Idiopathic DAD/ARDS

Idiopathic DAD/ARDS

In about 50% of cases of DAD with hyaline membranes, you will not be able to identify any histologic clues to point to a definitive etiology. In those cases, the biopsy may represent the idiopathic clinical syndrome, acute respiratory distress syndrome (ARDS).

SEE BELOW FOR SAMPLE SIGNOUT

ARDS1.jpg

If you are considering a diagnosis of infectious DAD, the biopsy should show the following features:

  • Hyaline membranes

  • Edema

  • Variable organization

Pink biopsy of ALI from Low Power

Hyaline Membranes

Edema

Organization

Biopsies with the following features may not be idiopathic DAD:

  • Robust lymphoplasmacytic interstitial inflammation (consider CTD)

  • Pleuritis (consider CTD)

  • Necrosis, neutrophils, granulomas, and viral cytopathic effect (consider infection)

  • Lymphoid follicles (consider CTD)

  • Interstitial giant cells or poorly formed granulomas (consider chronic HP)

  • Foamy macrophages and type II pneumocytes (consider drug reaction)

  • Foreign material (consider aspiration or intravenous)

  • Alveolar hemosiderin laden macrophages and capillaritis (consider alveolar hemorrhage syndrome)

  • Background fibrosis (consider acute on chronic ILD)

Clinical Presentation

  • Acute presentation with SOB and cough

Radiology

  • Bilateral ground glass opacities

Sample Signout

If you are suspicious for an infectious etiology for the ALI biopsy, consider the following approach to signing the case out:

Acute and organizing diffuse alveolar damage (see comment)

Comment:  The biopsy shows an acute and organizing acute lung injury process.  The presence of hyaline membranes is consistent with DAD.  No specific histologic features to point to a definitive diagnosis is identified.  Infections stains on multiple blocks are negative.  Although there is a broad differential diagnosis, this could represent the idiopathic clinical syndrome, acute respiratory distress syndrome (ARDS).  Correlation with final culture studies and infectious serologic studies is suggested.