In some cases, the cause of PAP is unknown. In others, it occurs with lung infection or an immune problem. It also can occur with cancers of the blood system, and after exposure to high levels of environmental substances, such as silica or aluminum dust.

People between 30 and 50 years old are most often affected. PAP is seen in men more often than in women. A form of the disorder is present at birth (congenital).

Symptoms of PAP may include any of the following:

• Shortness of breath
• Cough
• Fatigue
• Fever, if there is lung infection
• Bluish skin (cyanosis) in severe cases
• Weight loss

Sometimes, there are no symptoms.

Your health care provider will listen to the lungs with a stethoscope and may hear crackles (rales) in the lungs. Often, the physical examination is normal.

The following tests may be done:

• Bronchoscopy with saline wash of the lungs (lavage)
• Chest x-ray
• CT scan of the chest
• Lung function tests
• Open lung biopsy (surgical biopsy)

Treatment involves washing out the protein substance from the lung (whole-lung lavage) from time to time. Some people may need a lung transplant. Avoiding dusts that might have caused the condition is also recommended.

Another treatment that may be tried is a blood-stimulating drug called granulocyte-macrophage colony stimulating factor (GM-CSF), which is lacking in some people with alveolar proteinosis.

More information and support for people with pulmonary alveolar proteinosis and their families can be found at:

• National Organization for Rare Disorders -- rarediseases.org/rare-diseases/pulmonary-alveolar-proteinosis
• PAP Foundation -- www.papfoundation.org/

Some people with PAP go into remission. Others have a decline in lung function (respiratory failure) that gets worse, and they may need a lung transplant.

Call your provider if you develop serious breathing symptoms. Shortness of breath that gets worse over time may signal that your condition is developing into a medical emergency.

PAP; Alveolar proteinosis; Pulmonary alveolar phospholipoproteinosis; Alveolar lipoproteinosis phospholipidosis

Levine SM. Alveolar filling disorders. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 85.

Trapnell BC, Mccarthy C. Pulmonary alveolar proteinosis syndrome. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 98.

Updated by: Denis Hadjiliadis, MD, MHS, Paul F. Harron, Jr. Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.