Definition of Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis: Lung disease characterized by progressive difficulty breathing (dyspnea) and cough due to the accumulation of lipoprotein material within the alveoli that impairs ventilation. Lung biopsy is the gold standard for the diagnosis but may not be required. The course of the disease ranges from spontaneous resolution to respiratory failure.

There are three distinct and different forms of pulmonary alveolar proteinosis:

• Congenital pulmonary alveolar proteinosis -- caused by mutations in the genes encoding surfactant protein B or C or the C chain of the receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF). Treatment is supportive. Lung transplantation has been reported to be successful.

• Secondary pulmonary alveolar proteinosis -- due to impairment of macrophages in the lungs, secondary to some cancers, immunosuppression, inhalation of dust such as silica or toxic fumes, and certain infections. Therapy is directed at the underlying condition.

• Acquired pulmonary alveolar proteinosis -- an autoimmune disease in which the immune system attacks GM-CSF. (GM-CSF plays a critical role in the regulation of mature alveolar macrophages in the lung.) Acquired pulmonary alveolar proteinosis can be treated successfully by whole-lung lavage.