Pulmonary alveolar proteinosis (PAP) is a rare condition that may occur more frequently in persons with one or more risk factors. Some cases are idiopathic and occur in persons without any known risk factors.


Epidemiologic features:

(1) male

(2) familial

(3) Caucasian


Environmental exposures:

(1) cigarette smoking

(2) organic dusts (aluminum, silica, titanium, nitrogen dioxide)


Immunosuppression or autoimmunity:

(1) lung transplant

(2) immunoglobulin deficiency

(3) hematologic malignancies (AML)

(4) autoantibodies against granulocyte-macrophage colony stimulating factor (GM-CSF)


Uncertain (special care needs to be taken to exclude false positive diagnosis):

(1) pulmonary amyloidosis (amyloid protein may mimic PAP globules)

(2) opportunistic infections (may represent complicating conditions rather than preceding events):

(2a) Nocardia species

(2b) Pneumocystis carinii (PCP)

(2c) cytomegalovirus (CMV)

(2d) Histoplasma capsulatum

(2e) Mycobacterium species (tuberculosis and nontuberculous)


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