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  • • Symptoms are nonspecific and include dyspnea, cough, fatigue, and malaise.
  • • Chest radiograph demonstrates diffuse alveolar infiltrates.
  • • Computed tomography of the chest demonstrates an alveolar filling process with a characteristic “crazy paving” pattern.
  • • Diagnosis confirmed by detection of periodic acid–Schiff-positive material in bronchoalveolar lavage or lung biopsy.

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Pulmonary alveolar proteinosis (PAP) was identified in 1958, based on experience with 27 patients in whom the major histological finding was filling of alveolar spaces by a lipid-rich, insoluble, periodic acid–Schiff-positive lipoproteinaceous material. The first case dated to 1953; the pathology was sufficiently distinctive that it was unlikely to have escaped previous notice. Subsequent studies of the abnormal alveolar contents revealed that the major biochemical components of this substance were phospholipids with small amounts of protein. Prakash suggested that the term “pulmonary alveolar phospholipoproteinosis” more appropriately characterized the disorder. However, this term is rarely used today.

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The amorphous, insoluble, proteinaceous material is deposited in alveoli and can exude into bronchioles. This material is unique in that it does not appear to stimulate an inflammatory response, although fibrosis is noted in some biopsies, particularly in late stages of disease.

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PAP is an uncommon, idiopathic disease. It is difficult to determine its exact frequency because of the absence of a national registry. The disease has been reported throughout the United States and in virtually all industrialized countries. In 1969, only 139 cases of PAP had been reported worldwide; by 1980, approximately 260 cases were recognized. Even now fewer that 500 cases have been reported. The ratio of male to female patients in most series is about 4 to 1, with most being 30 to 50 years of age. Many of the patients in published reports had been exposed to various dusts and chemicals such as silica and aluminum dust, but existence of the disease in unexposed siblings also suggests a genetic predisposition. Superimposed infections by unusual pathogens may occur. Infection by Nocardia asteroides is most commonly reported, followed by fungal and atypical mycobacterial infections. Amiodarone lung toxicity in humans has some features of a lung phospholipidosis. Experimental animals exposed to a variety of chemicals demonstrate pathological features identical to those in human PAP, and reports describe morphological findings identical to those in PAP following exposure to silica, fiberglass, volcanic ash, and aluminum dust. PAP is also associated with malignant diseases, especially acute or chronic myeloid leukemias. These forms are termed secondary PAP. Initial reports were in patients with chronic myeloid leukemias, but the disease also occurs in acute leukemia, multiple myeloma, Waldenstrom’s disease, and lymphoma. Primary and secondary PAP are indistinguishable from a morphological perspective as they share the same microscopic and ultrastructural pattern. However, their clinical response to lavage therapy is different. Secondary PAP is a rare cause of respiratory failure in patients with cancer and probably results from concomitant events, including exposure to pulmonary irritants as well as functional defects of alveolar macrophages. Recent data suggest that ...

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