Autoimmune Pulmonary Alveolar Proteinosis during the Treatment of Idiopathic Inflammatory Myopathy.

Approximately 50% of idiopathic inflammatory myopathies (IIMs) are associated with interstitial lung disease (ILD). Typically, IIM-ILD manifests as nonspecific interstitial pneumonia. We herein report a rare case of a 78-year-old man with autoimmune pulmonary alveolar proteinosis (PAP) that developed during IIM treatment. The diagnosis of autoimmune PAP was based on detecting anti-granulocyte-macrophage colony-stimulating factor antibodies. We postulated that PAP may have been induced by IIM treatment with prednisolone. Our case suggests that the possibility of autoimmune PAP should be considered in patients with lung lesions during the clinical course of IIM.