Historical Perspective and Current Case Definition

Acute lower respiratory tract illness of 60 days duration 

Organizing Diffuse Alveolar Damage on surgical lung biopsy 

Absence of any known inciting event or predisposing condition including infection, SIRS, environmental or toxic exposures, connective tissue disease, prior ILD Absence of a previously abnormal chest X-ray 

Abbreviations. SIRS, systemic inflammatory response syndrome ILD, interstitial lung disease. 

With the publication of two international consensus statements on the IIP, the American Thoracic Society and the European Respiratory Society formally recognized AIP as a distinct IIP with cardinal features of rapid symptom onset, unknown causation, and the presence of a DAD pattern on surgical lung biopsy (8,9). As these same clinical and pathologic features are present in patients with known causes of lower respiratory tract disease, in particular the acute respiratory distress syndrome (ARDS) and overwhelming lower respiratory tract infection, AIP is by necessity, a diagnosis of exclusion (Table 1). 

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