A Marked Improvement in Mild but Progressive Autoimmune Pulmonary Alveolar Proteinosis Treated with Inhaled Granulocyte-Macrophage Colony-Stimulating Factor Therapy: A Case Report.

A 46-year-old man was diagnosed with autoimmune pulmonary alveolar proteinosis (aPAP). Despite repeated segmental bronchoscopic lavage, his symptoms, pulmonary function, and radiological findings gradually worsened, and he declined whole-lung lavage. Although classified as disease severity score 2 (partial pressure of arterial oxygen 75.2 mmHg), inhaled granulocyte-macrophage colony-stimulating factor (GM-CSF) therapy (sargramostim) was initiated. After 6 months, a marked improvement was observed, and the alveolar-arterial oxygen difference decreased from 21.8 to 1.1 mmHg. Given the limited evidence in milder cases, this report suggests that early intervention with inhaled sargramostim may be effective in relatively mild but progressive aPAP.