Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Pulmonary Alveolar Proteinosis
- Radiologic Findings
- Chest PA shows bilateral patchy haziness in both lungs with slightly lower and peripheral predominance.
Chest CT shows patchy ground-glass opacities and internal reticular opacities of subpleural portion of both lungs.
- Brief Review
- Pulmonary alveolar proteinosis (PAP) is a rare lung disorder of unknown etiology characterized by alveolar filling with floccular material that stains positive using the periodic acid-Schiff (PAS) method and is derived from surfactant phospholipids and protein components.
Two forms are recognized, (1) primary (idiopathic) and (2) secondary (due to lung infections; hematologic malignancies; and inhalation of mineral dusts such as silica, titanium oxide, aluminum, and insecticides). Incidence of PAP is increased in patients with hematologic malignancies and AIDS, suggesting a relationship with immune dysfunction.
Patients with pulmonary alveolar proteinosis (PAP) typically present with a gradual onset of symptoms. As many as 30% of patients are asymptomatic, even with diffuse chest radiograph (CXR) abnormalities. Most common symptoms include Persistent dry cough (or scant sputum production) or Persistent dry cough (or scant sputum production).
Serologic studies are generally not useful. Flexible bronchoscopy with bronchoalveolar lavage (BAL) remains the criterion standard. Elevated levels of the proteins SP-A and SP-D in serum and BAL fluid may be useful. Elevated titer of neutralizing autoantibody against GM-CSF (immunoglobulin G [IgG] isotype) in serum and BAL fluid may be useful. Recent studies have proposed that deficiency of GM-CSF causes pulmonary alveolar proteinosis (PAP); all patients studied had the antibody to GM-CSF. Serum lactate dehydrogenase (LDH) level is usually elevated, but this finding is nonspecific.
The diagnosis can be made by BAL only if PAS staining is requested. Therefore, PAP is probably underdiagnosed.
CXR shows bilateral perihilar infiltrates with consolidation in a "bat-wing" configuration, which may mimic pulmonary edema, although with a typical absence of cardiomegaly or pleural effusion. Unilateral involvement occurs occasionally, and lymphadenopathy is rarely present. Typically, changes progress over weeks to months into a diffuse reticulogranular pattern. High-resolution computed tomography (HRCT) scan of the chest demonstrates areas of patchy ground-glass opacification with smooth interlobular septal thickening and intralobular interstitial thickening, which produces a polygonal pattern referred to as "crazy paving".
Management of pulmonary alveolar proteinosis (PAP) depends on the progression of the illness, coexisting infections, and degree of physiological impairment. The standard of care for PAP is mechanical removal of the lipoproteinaceous material by whole-lung lavage.
In secondary PAP, appropriate treatment of the underlying cause also is warranted.
GM-CSF has been shown to improve PAP in several patients and is being investigated.
Lung transplantation is the treatment of choice in patients with congenital PAP and in adult patients with end-stage interstitial fibrosis and cor pulmonale.
- References
- Am J Respir Crit Care Med 2002; 166: 215?35
- Keywords
- Lung, Interstitium, Metabolic and storage lung disesae,