Pulmonary Alveolar Proteinosis (PAP)

At a Glance

Pulmonary alveolar proteinosis (PAP) is a rare lung disorder characterized by diffuse alveolar accumulation of surfactant proteins and phospholipids. Pulmonary alveolar proteinosis occurs four times more frequently in males than females, most commonly in those 20-50 years of age, and is marked by dyspnea and a typically nonproductive cough. Pulmonary alveolar proteinosis may be idiopathic (primary), associated with lung infections, malignant neoplasms, AIDS, or secondary to inhalation of foreign materials, including insecticides, silica, aluminum, titanium oxide and indium-tin oxide. A neonatal form has been observed in infants with a genetic deficiency of surfactant-associated protein B (SP-B).

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Most PAP patients are either deficient of GM-CSF or possess neutralizing antibodies to GM-CSF. These findings may occur in serum and/or bronchoalveolar lavage (BAL) fluid. Currently, GM-CSF and anti-GM-CSF tests are not widely available and are not well-standardized. Demonstration of floccular, eosinophilic, periodic acid-Schiff (PAS)-positive alveolar material in BAL fluid or lung biopsy tissue remains the diagnostic sine qua non. A series of transbronchial biopsies of affected lung segments is usually sufficient to allow for a diagnosis.

Association of PAP with insecticides or inorganic dust exposures is made on the basis of a careful history. Decreased alveolar macrophage levels of the transcription factor, peroxisome proliferator-activated receptor-gamma (PPAR-gamma), have been documented in some patients, but clinical assays for PPAR-gamma are not routinely available.

The most important follow-up tests in PAP patients are studies to rule out unusual infections (e.g., Pneumocystis carinii, Nocardia asteroides, and Mycobacterium avium-intracellulare.)

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Adequate diagnostic lung tissue is required to make a diagnosis of PAP. The pathologist should be alerted to facilitate PAS stain preparation.

What Lab Results Are Absolutely Confirmatory?

Pulmonary alveolar proteinosis is a diagnosis made on the basis of biopsy findings.