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Pulmonary Alveolar Proteinosis

Pulmonary Alveolar Proteinosis is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Pulmonary alveolar proteinosis (PAP) is a rare disease characterized by accumulation of lipoproteinaceous (surfactant-like) material in the alveolar spaces, leading to impaired gas exchange. Defects in surfactant clearance are thought to be responsible for the disease. There are three recognized categories of PAP (1).
  • Primary or idiopathic PAP (90% of cases)
    • Primary PAP, which is discussed here, has been found to be associated with anti–granulocyte-macrophage colony-stimulating-factor (GM-CSF) autoantibodies disrupting signaling pathways in macrophage activation (2).
  • Secondary PAP (<10% cases)
    • Secondary PAP is associated with environmental exposures, immunodeficiency disorders and hematologic disorders (mostly myelodysplastic syndrome), and malignancies (1).
  • Congenital PAP (2% of cases)
    • Congenital PAP results from several rare gene mutations.
  • Whole-lung lavage (WLL), the standard treatment for PAP, has improved prognosis (94% 5-year survival) (3).
  • System(s) affected: pulmonary

Epidemiology

  • Seen worldwide, with median age of onset at 39 years (4)
  • Male > female (2 to 3:1) incidence, however, may be confounded by increased smoking rates in males, a known association (3).

Incidence
Estimated 0.36 per million annually (5)

Prevalence
Estimated 3.7 per million (5)

Etiology and Pathophysiology

  • Primary PAP has recently been found to be associated with neutralizing anti–GM-CSF autoantibodies causing impaired functioning of alveolar macrophages, resulting in disruption in surfactant homeostasis (6). Surfactant accumulates in alveoli due to reduced clearance.
  • Primary PAP: autoimmune

Genetics
  • No genetic predilection in primary or secondary PAP
  • Congenital PAP mostly transmitted in autosomal-recessive pattern (1)

Risk Factors

  • Association between tobacco smoke exposure and primary PAP (3)
  • Exposure to environmental dusts, specifically silica, aluminum, cement, indium, titanium dioxide, nitrogen dioxide, and insulation fibers, has been associated with secondary PAP (2).
Pediatric Considerations
  • Congenital PAP leads to neonatal respiratory distress syndrome not responsive to surfactant or corticosteroids. It is caused by a mutation in surfactant-protein B or C genes, or GM-CSF receptor β- or α-chain abnormalities (2). Lung transplant is primary therapy for congenital PAP, but prognosis is poor (1)[C].
  • Hereditary PAP may present in children and is treated with WLL.

General Prevention

No specific measures for prevention; avoid tobacco smoke exposure.

Commonly Associated Conditions

No conditions commonly associated with primary PAP

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Citation

Stephens, Mark B., et al., editors. "Pulmonary Alveolar Proteinosis." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816243/all/Pulmonary_Alveolar_Proteinosis.
Pulmonary Alveolar Proteinosis. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816243/all/Pulmonary_Alveolar_Proteinosis. Accessed April 20, 2019.
Pulmonary Alveolar Proteinosis. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816243/all/Pulmonary_Alveolar_Proteinosis
Pulmonary Alveolar Proteinosis [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 April 20]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816243/all/Pulmonary_Alveolar_Proteinosis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Pulmonary Alveolar Proteinosis ID - 816243 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/816243/all/Pulmonary_Alveolar_Proteinosis PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -