Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of a lipoproteinaceous substance in the distal air spaces which positively stains with periodic acid-Schiff (PAS).
The typical age at presentation is the third or forth decade. The main symptoms consist of shortness of breath and cough. The physical examination is often normal and inspiratory crackles are the most common abnormality. Pulmonary function tests show a restrictive ventilatory defect and a decreased diffusion capacity. Bilateral air space consolidation is a typical but non-specific feature appearing on chest radiography. High resolution computed tomography scanning (HRCT) reveals ground-glass opacification usually associated with thickened interlobular septa, distinctly visible within the affected lung, referred to as 'crazy paving' pattern.
The diagnosis of PAP can be made on the basis of HRCT features in conjunction with the typical bronchoalveolar lavage (BAL) findings of milky fluid consisting of basophilic granular extracellular deposits with enlarged foamy macrophages and cellular debris (May-Grünwald Giemsa). If non conclusive, PAP is diagnosed by examination of lung tissue obtained by transbronchial or videoassisted lung biopsy.
Most commonly treatment consists of whole lung lavage, but some patients may be successfully treated with daily subcutaneous GM-CSF (granulocyte-macrophage colony-stimulating factor).
Last update: June 2004
- Pr Annette BOEHLER
- Pr Erich RUSSI