Pathological features of explant lungs with fibrosis in autoimmune pulmonary alveolar proteinosis

Association of fibrosis with autoimmune pulmonary alveolar proteinosis (aPAP) is rare. However, prognoses of such cases are poor and the process of the formation of fibrosis is still unknown. In this study, we report a case of aPAP with progressive fibrosis occurring in a 46-year-old woman. She had undergone several repetitions of whole lung lavage (WLL) for 7 years and granulocyte-macrophage colony-stimulating factor (GM-CSF) inhalation for 3 months; however, the progression of fibrosis was not hindered. Eventually, she was treated with bilateral lung transplantation. The computed tomography (CT) image suggested pulmonary fibrotic changes in her lung similar to usual interstitial pneumonia. However, the pathological analyses of explant lungs revealed that the fibrosis was not similar to ordinary interstitial pneumonias and suggested that the dysfunction of alveolar macrophage in removing the excess surfactant of alveolar spaces played an important role in the fibrogenesis in aPAP.