Which conditions are included in the differential diagnoses of pulmonary alveolar proteinosis (PAP)?

Updated: Dec 18, 2019
  • Author: Rodolfo Laucirica, MD; Chief Editor: Philip T Cagle, MD  more...
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Answer

The differential diagnosis of pulmonary alveolar proteinosis (PAP) includes other diseases associated with intra-alveolar exdudates. These include pulmonary edema, pneumocystis pneumonia, and alveolar mucinosis. Pulmonary edema has a homogeneous appearance and lacks the granularity typical of PAP (see the images below). The exudate of pneumocystis pneumonia has a frothy or foamy appearance due to the negative image of the cyst form of Pneumocystisjiroveci (formally known as carinii).

Pathology of pulmonary alveolar proteinosis. Contr Pathology of pulmonary alveolar proteinosis. Contrast between the granular exudate of pulmonary alveolar proteinosis (PAP) (media file 13885) and the frothy exudate of pneumocystis pneumonia in the transbronchial biopsy (A) (hematoxylin and eosin, x400) and broncheoalveolar lavage (BAL).
Pathology of pulmonary alveolar proteinosis. Contr Pathology of pulmonary alveolar proteinosis. Contrast between the granular exudate of pulmonary alveolar proteinosis (PAP) (media file 13885) and the frothy exudate of pneumocystis pneumonia in the transbronchial biopsy (B) (Papanicolaou, x600). Note the negative images of the cysts impart the foamy characteristic of the exudate.

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