Pulmonary Alveolar Proteinosis
PAP

• 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

  • Hypersensitivity Pneumonitis
  • Pneumocystis Carinii Pneumonia
  • Pulmonary Edema
  • Sarcoidosis
  • Lung cancer

  Treatment

  • 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

  Complications

  • 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.

  Prognosis

  • 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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