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Pulmonary Alveolar Proteinosis

  • General Considerations
    • Rare disorder of unknown etiology
    • Alveoli are filled with PAS-positive proteinaceous material derived from surfactant phospholipids and proteins
    • Males are affected 4X more than females; the disease is most common from 20-50 years of age
    • It may be primary or secondary (to pulmonary infections, inhalation of silica or insecticides and hematologic malignancies)
    • Diagnosis is usually made by lung biopsy

    Clinical Findings

    • Almost 1/3 may be asymptomatic even with abnormal chest radiographs
    • Symptoms, which are usually gradual in onset, include:
      • Dry cough (or scant sputum production)
      • Progressive dyspnea
      • Fatigue and malaise
      • Weight loss
      • Intermittent low-grade fever and/or night sweats
      • Pleuritic chest pain
      • Rarely cyanosis or hemoptysis      

    Imaging Findings

    • Bilateral perihilar consolidation in a configuration which may mimic pulmonary edema, but without cardiomegaly or pleural effusions
    • Occasional unilateral; lymphadenopathy is rare
    • Typically, changes progress over weeks to months into a diffuse reticulogranular pattern
    • On CT
    • Areas of patchy ground-glass opacification with smooth interlobular septal thickening and intralobular interstitial thickening ® a polygonal pattern referred to as "crazy paving"
      • DDX for “crazy paving:” exogenous lipoid pneumonia, sarcoidosis, mucinous bronchoalveolar cell carcinoma, and acute respiratory distress syndrome

    Differential Diagnosis


    • Usual care for PAP is mechanical removal of the lipoproteinaceous material by whole-lung lavage.
    • Historically, systemic steroids have been used, as well as mucolytics (aerosol), and proteinase (aerosol) but without much success. 
    • Hyperbaric chamber or extracorporeal membrane oxygenation (ECMO) has been used to perform whole-lung lavages in cases of severe hypoxemia


    • Major complications are pulmonary infections with N asteroides, Pneumocystis carinii, and/or mycobacterium avium intracellulare
    • Pulmonary fibrosis and/or cor pulmonale also can complicate PAP.
    • Some association between anti-GM-CSF autoantibodies and some cases of cryptococcal meningitis in otherwise immunocompetent patients.


    • The mortality rate is reported to be under 10%
    • The mortality rate of secondary PAP depends on the underlying disease

Pulmonary Alveolar Proteinosis. There are areas of patchy ground-glass opacification with smooth interlobular septal thickening and intralobular interstitial thickening (white circles) a polygonal pattern referred to as "crazy paving"
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