ARDS and diffuse alveolar damage: a pathologist's perspective.

Diffuse alveolar damage (DAD) is the histologic correlate of most patients with adult respiratory distress syndrome (ARDS). It is a relatively straight forward diagnosis and the main differential diagnosis clinically is acute pneumonia and histologically is bronchiolitis obliterans and organizing pneumonia (BOOP). The histologic progression of DAD includes 3 phases (exudative, proliferative, and fibrotic) that correlate with the time rather than its specific cause. The factors that govern which patients will do well and which will develop a fulminant course is not known.