This study evaluates inhaled molgramostim (recombinant human (rh) Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF)) in the treatment of autoimmune pulmonary alveolar proteinosis patients. A third of the patients will receive inhaled molgramostim daily for 24 weeks, a third will receive inhaled molgramostim intermittently (seven days on, seven days off) for 24 weeks and a third will receive inhaled matching placebo for 24 weeks.