Lung lesions caused by COVID-19 in comparison with bacterial pneumonia and influenza pneumonia: pathomorphological features

Abstract

This review aimed to summarize the literature data regarding the pathomorphology of lung lesions in COVID-19 and compare it with lung lesions in bacterial pneumonia and pneumonia caused by influenza virus. The analysis of scientific literature containing studies of domestic and foreign authors of different years related to morphology and anatomical pathology of lung injury was carried out. Special attention was paid to the data devoted to COVID-19 obtained between 2019 and 2021. Based on the study, the main aspects of lung lesions were identified and grouped into blocks depending on the etiology of the process. The review collects and summarizes information on etiology, pathogenesis and stages of disease development, outcomes and morphological picture during the autopsy of patients with bacterial pneumonia, influenza pneumonia and COVID-19 pneumonia. The common features and differences in the course, outcomes and typical morphological findings, most characteristics for each of the diseases were presented in the table. There is a great similarity of morphological findings in influenza pneumonia and COVID-19 pneumonia despite the background of the difference in their epidemiology. Most Russian and foreign authors agree that a key factor in the pathogenesis of the development of COVID-19 is the presence of a specific receptor-mediated pathway of penetration into the cells of the respiratory epithelium. According to most authors, the main morphological difference that determines the severity and unfavorable outcome of COVID-19 is angiopathy and microthrombosis of the pulmonary capillary bed, which aggravate the typical picture of viral pneumonia.