Pulmonary alveolar proteinosis (PAP) is a rare lung disease that results when the surfactant which coats the alveoli, also called the air sacs, in the lungs builds up and prevents oxygen from passing through into the blood.  This can make breathing difficult.

Key Facts

  • PAP is a rare disease which occurs in approximately seven people per million.
  • Autoimmune PAP or aPAP accounts for 90% of PAP diagnosis.
  • Symptoms of PAP are similar to other lung diseases, such as shortness of breath and cough, which can delay getting the correct diagnosis.
  • aPAP can be diagnosed using a blood test.

What Causes PAP

There are three primary pathways that result in PAP. They all result in the inability to clear the surfactant within the alveoli which causes a buildup of protein in the air sacs that makes oxygen exchange more difficult.

  • Autoimmune (aPAP) – This is the most common form of PAP.   It was previously called idiopathic PAP.   This type of PAP occurs because of the production of antibodies (anti-GM-CSF antibodies) that stop the macrophages (specialized cells) from doing their job of removing the extra surfactants from the lungs’ air sacs.
  • Congenital – This is the least common type of PAP and is the result of a genetic mutation which occurs at birth.
  • Secondary – This type of PAP is caused by another disease, such as myelodysplastic syndrome or chronic myelogenous leukemia, certain infections, and has also been linked to the inhalation of harmful toxins such as silica and talc.

How PAP Affects Your Body

PAP results in an inability of oxygen to be passed through your bloodstream to get to all the cells in your body.  PAP may result in:

  • Respiratory failure that may become life-threatening
  • Increased risk for infections

Who Is at Risk for PAP?

  • People who use tobacco products 
  • Occupational exposure
    • Stone cutters/quarry workers and others with silica exposure
    • Indium-exposed workers (such as those who work to manufacture liquid crystal displays (LCDs), touch screens, and solar cells).   
  • People with a hereditary disposition

Page last updated: March 4, 2024

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