Autoimmune pulmonary alveolar proteinosis (PAP, previously known as idiopathic PAP) is a rare interstitial lung disease elicited by the formation of autoantibodies which neutralize the activity of granulocyte-macrophage colony-stimulating factor (GM-CSF) which decreases macrophage clearance of surfactant.~Currently, the standard treatment strategy for PAP is whole lung lavage (WLL)，which is invasive and has limitations. Inhaled GM-CSF therapy became a new option for PAP patients not only because of its effectiveness and safety, but it is convenient way for patients who are reluctant to do operation as well. We are planning to prospectively evaluate if inhaled granulocyte-macrophage colony stimulating factor would delay the increase in alveolar-arterial oxygen difference (A-aDO2, which is the most sensitive factor in evaluating APAP5), compared to placebo, for patients with mild-to-moderate autoimmune pulmonary alveolar over a two-year period.~A total of 42 subjects with APAP who meet the inclusion criteria will be enrolled at Peking Union Medical College Hospital and Nanjing Drum Tower Hospital. After observe APAP patients for 3 months to rule out patients who resolved spontaneously, the participants will undergo randomization (by random number table)and stratified into two different groups by their DSS. Then they will be treated by GM-CSF (using nebulizer, 150ug bid) every other week or no treatment for 6 months, and will be followed on an outpatient basis at 2 weeks, and 1, 3, 6, 9, 12, 15, 18, 21 and 24 months after initiation of therapy.
The purpose of the study is to evaluate if inhaled granulocyte-macrophage colony stimulating factor delay the increase in alveolar-arterial oxygen difference, compared to no treatment, for adult patients with mild-to-moderate autoimmune pulmonary alveolar proteinosis in China over a two-year period.