Secondary pulmonary alveolar proteinosis predominant in the transplanted lung in patients with idiopathic interstitial pneumonia: an autopsy case

A man in his 40 s with idiopathic interstitial pneumonia underwent cadaveric left single-lung transplantation from a brain-dead donor in October 2014. In October 2015, chest high-resolution computed tomography revealed centrilobular ground-glass opacities (GGOs) predominantly in the transplanted left lung, and subsequently, the shadows progressed to a geographic GGO without crazy paving. Bronchoalveolar lavage fluid analysis revealed an opaque and milky appearance, and cytopathology demonstrated foamy alveolar macrophages and abundant granular, acellular, eosinophilic, and amorphous material in the background. There was no evidence of infection. Serum anti-granulocyte-macrophage colony-stimulating factor antibody testing was negative. We diagnosed the patient with secondary pulmonary alveolar proteinosis (PAP) following lung transplantation. Autopsy revealed PAP findings predominant in the transplanted left lung, which also had dilated lymphatic vessels. In addition to defects in alveolar macrophage function from immunosuppressive therapy, impaired lymphatic drainage due to transplantation would contribute to the onset of secondary PAP in the transplanted lung.