• Moslem Bahadori, Shahriar Dabiri, Abdolreza Javadi, Simin Shamsi Meymandi, Sajjadeh Movahedinia, Manzumeh Shamsi Meymandi, Parisa Khorasani, Mehrdad Farrokhnia, Meysam Yousefi, Farhad Sarrafzadeh, Hamid Abosaidi, Saeedeh Shojaeepour, Abbas Mortazaizadeh, Mitra Rezaei, Bahram Dabiri, Nader Mohabati, Hanie Ranjbar, Sara Rashidinejad, and Abdolamir Feizy.
• Distinguished Professor of Pathology; Tehran University of Medical Sciences, Academy of Medical Sciences, Tehran, Iran.
• Arch Iran Med. 2021 May 1; 24 (5): 419-426.

BackgroundThe pathogenesis of the COVID19 pandemic, that has killed one million nine hundred people and infected more the 90 million until end of 2020, has been studied by many researchers. Here, we try to explain its biological behavior based on our recent autopsy information and review of literature.MethodsIn this study, patients with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) result were considered eligible for enrollment. Histopathological examinations were done on 13 people who were hospitalized in Afzalipour hospital, Kerman, Iran. Clinical and laboratory data were reviewed. Tissue examination was done by light microscopy, immunohistochemistry and electron microscopy.ResultsThe most frequent co-morbidity in the patients was cardiovascular disease. The common initial symptoms of COVID-19 infection were dyspnea and cough. In all cases, the number of white blood cells was higher than the normal range. Common histopathological findings were variable degrees of vasculitis as degenerative to necrotic changes of endothelium and trafficking of inflammatory cells in the vessel wall with fibrinoid necrosis. Tissue damage included interstitial acute inflammatory cells reaction with degenerative to necrotic changes of the parenchymal cells. CD34 and Factor VIII immunohistochemistry staining showed endothelial cell degeneration to necrosis at the vessel wall and infiltration by inflammatory cells. Electron microscopic features confirmed the degenerative damages in the endothelial cells.ConclusionOur histopathological studies suggest that the main focus of the viral damage is the endothelial cells (endotheliopathica) in involved organs. Also, our findings suggest that degeneration of leukocytes occurs at the site of inflammation and release of cytokines (leukocytoclastica) resulting in a cytokine storm.© 2021 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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