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

Updated: Dec 18, 2019
  • Author: Roger B Olade, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

The patient's age at the manifestation of signs/symptoms of pulmonary alveolar proteinosis is crucial in the establishing differential diagnosis and determining the correct diagnosis. [2] Essential to the diagnostic approach is identifying potential genetic or autoimmune etiologies, exposure to environmental agents, and associations to other diseases. [2]

Thus, the differential diagnosis includes other diseases associated with intra-alveolar exdudates, such as pulmonary edemapneumocystis pneumonia, and alveolar mucinosis. Pulmonary edema has a homogenous 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 Pneumocystis jiroveci (formerly known as carinii).

Pulmonary alveolar proteinosis. Contrast between t Pulmonary alveolar proteinosis. Contrast between the granular exudate of pulmonary alveolar proteinosis (PAP) and frothy exudate of pneumocystis pneumonia in the transbronchial biopsy (A) (hematoxylin and eosin, x400) and broncheoalveolar lavage (BAL).
Pulmonary alveolar proteinosis. Contrast between t Pulmonary alveolar proteinosis. Contrast between the granular exudate of pulmonary alveolar proteinosis (PAP) and 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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