What is pulmonary alveolar proteinosis?Pulmonary alveolar proteinosis (PAP) is a rare lung disorder in which the tiny air sacs of the lungs (alveoli) fill up with a secreted material known as surfactant. Pulmonary alveolar proteinosis is a rare lung disorder characterized by the filling of the air sacs of the lungs (alveoli) with grainy material consisting mostly of protein and fat. Breathing becomes progressively
difficult. The disorder occurs in different forms, ranging from mild to severe.
Pulmonary alveolar proteinosis is a disease in which a phospholipid (a compound widely distributed in living cells) accumulates within spaces in the lungs where oxygen and carbon dioxide are exchanged. Surfactant is normally necessary for the air sacs to remain open, however, patients with PAP accumulate surfactant abnormally. This accumulation of surfactant interferes with the ability of oxygen to diffuse from the alveoli into the capillaries of the lung producing symptoms.
Pulmonary alveolar proteinosis is increasingly being recognized as an important cause of diffuse pulmonary disease. The disease generally affects people between the ages of 20 and 60 who have not previously had lung disease. The cause of pulmonary alveolar proteinosis is unknown. Occasionally, it is related to exposure to toxic substances, such as inorganic dusts, infection with Pneumocystis carinii, certain cancers, and immunosuppressant drugs.
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 is 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 is 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 is an autoimmune disease in which the immune system attacks GM-CSF. Acquired pulmonary alveolar proteinosis can be treated successfully by whole-lung lavage.