Serum Antibody Against Granulocyte/Macrophage Colony-Stimulating Factor and KL-6 in Idiopathic Pulmonary Alveolar Proteinosis

Here we describe a case of idiopathic pulmonary alveolar proteinosis (I-PAP), in which anti-granulocyte/ macrophage colony-stimulating factor (GM-CSF) antibody and high level of KL-6 were found in the serum. Anti-GM-CSF antibody is responsible for I-PAP, and KL-6 is a serum marker for the activity of diffuse interstitial lung disease. A 38-year-old woman, who had no symptoms, was found to have an abnormal shadow on chest radiograph 5 years previously at a health check up. Chest radiograph showed a patchy shadow in the left lower lung field. Thoracoscopic biopsy was performed because the shadow had gradually expanded during the 5 years. Histological examination revealed proteinous material filling the alveoli and positive staining by the PAS method, suggesting PAP. Anti-GM-CSF antibody and a high level of KL-6 were detected in the serum at the time of diagnosis. Three years later, the shadow disappeared spontaneously. During this period, the level of KL-6 dramatically decreased, although that of GM-CSF antibody remained unchanged. The present case suggests that the serum level of the anti-GM-CSF antibody represents a useful marker for the diagnosis but not for follow-up of the clinical course. On the contrary, KL-6 is an excellent marker for the assessment of the clinical course of I-PAP.