What are the features of the proliferative phase of diffuse alveolar damage (DAD) in sepsis/septic shock?

Updated: Oct 07, 2020
  • Author: Andre Kalil, MD, MPH; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

The proliferative phase is prominent in the second and third week after the onset of ARDS, but it may begin as early as day 3. Organization of the intra-alveolar and interstitial exudate, infiltration with chronic inflammatory cells, parenchymal necrosis, and interstitial myofibroblast reaction occur. Proliferation of type II cells and fibroblasts, which convert the exudate to cellular granulation tissue, is noted, as is excessive collagen deposition, transforming into fibrous tissue (see the images below).

Photomicrograph showing delayed stage (proliferati Photomicrograph showing delayed stage (proliferative or organizing stage) of diffuse alveolar damage (DAD). Proliferation of type II pneumocytes has occurred; hyaline membranes as well as collagen and fibroblasts are present.
Photomicrograph showing delayed stage (proliferati Photomicrograph showing delayed stage (proliferative or organizing stage) of diffuse alveolar damage (DAD). Fibrin stain depicts collagenous tissue, which may develop into fibrotic stage of DAD.

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