Case Report: Pathological features of explanted native lungs in a patient with end stage lung disease after resolution of severe COVID19 who underwent successful lung transplantation.

During the pandemic of COVID-19, lots of features of this disease have been discovered. However, the lung pathology and the correlated clinical features of the patients who recovered from the severe state of COVID-19 are still largely unknown. Especially for those who underwent diffuse alveolar damage (DAD), most of the morphological data were obtained from the autopsy specimens or biopsy samples. In the present report, the pathologic changes in the lungs of a patient who had successfully received lung transplantation at the recovery stage of severe COVID-19 were described. Diffuse alveolar damage, hyperplasia of interstitial fibroblast and alveolar type II epithelial cells, and the filling of macrophages in alveoli were observed. Hyperemia and thickening of blood vessels and interstitial lymphocytic inflammation were also prominent. SARS-COV-2 nuclear capsid was detected spotty in the alveolar epithelial after several times' negative nucleic acid results from his pharyngeal swab specimens. Evidence of combined virus infection, such as Cytomegalovirus, could also be found. A few eosinophils were found in the parenchymal of the lung, which combined with the elevated eosinophils in the blood, might indicate a recovery of this patient. This rare case provides a chance for us to observe the pathological changes in the diffuse fibrosis stage of severe COVID-19, which might help us to further understand how pulmonary fibrosis forms after severe pathogen infection.