Organizing Pneumocystis Pneumonia

Sometimes a pattern of bronchiolitis obliterans organizing pneumonia develops. The images below are from an AIDS patient who was treated for pneumocystis pneumonia for 19 days before death. Pneumothorax developed the day before death.

Figure 1. Organization

A respiratory bronchiole (note smooth muscle), an alveolar duct and an alveolus are filled with granulation tissue producing a pattern of bronchiolitis obliterans organizing pneumonia (BOOP). Most alveoli contain a few macrophages and are lined by hypertrophic type II cells.



Find the granulation tissue in the respiratory bronchiole (smooth muscle lies at the bottom of the bronchiole).

Find granulation tissue in an alveolar duct.

Find granulation tissue in an alveolus.

In this case, the BOOP pattern is probably a result of organizing alveolar damage.


Figure 2. Granulations Plus Foam

In another area, the granulation tissue surrounds some foamy exudate giving a clue to the underlying diagnosis. A GMS stain confirmed the diagnosis.

Find 2 clumps of foamy exudate characteristic of pneumocystis pneumonia.

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Granulation tissue in respiratory bronchiole




























Granulation tissue in alveolar duct






























Granulation tissue in alveolus






























Foamy exudate of pneumocystis within granulation tissue