Diagnostic algorithm for pulmonary alveolar proteinosis (PAP) in adults*

HRCT: high resolution computed tomography; CBC: complete blood count; MARS: methionyl-tRNA synthetase; BAL: bronchoalveolar lavage; TBLB: transbronchial lung biopsy; GM-CSF: granulocyte monocyte-colony stimulating factor; PAS: periodic acid-Schiff.
* Surfactant-related genetic variants typically present in infancy or childhood.
¶ "Crazy-paving" pattern on HRCT is due to thickening of interlobular and intralobular septa. While crazy-paving is often present in autoimmune PAP, it is seen less often in secondary causes of PAP. Crazy-paving is not specific to PAP.
Δ Depending on test availability, can test for antibodies to GM-CSF before or after BAL. Testing is usually performed before surgical lung biopsy, as a confident diagnosis of autoimmune PAP can be made with compatible HRCT and BAL in combination with antibodies to GM-CSF.
◊ Typical cytologic/histopathologic findings of PAP:

• Copious amorphous PAS positive material
• Alveolar macrophages engorged with PAS positive material
• Few inflammatory cells
• Stains and cultures for Pneumocystis jirovecii and other organisms negative