Pneumonia misinterpretation in COVID-19: Review and update

Editor,

A plethora of papers on Coronavirus-19 disease (COVID-19) patients, mainly derived from Chinese literature, attributed the clinical pulmonary symptoms and the features on chest computed tomography (CT) to pneumonia (Bai et al., 2020; Caruso et al., 2020; Chung et al., 2020; Fang et al., 2020; Han et al., 2020; Lei et al., 2020; Li et al., 2020; Pan et al., 2020; Song et al., 2020; D. Wang et al., 2020; Y. Wang et al., 2020; Xie et al., 2020; Zhou et al., 2020). However, because of the high fatality rates among hospitalized COVID-19 patients which have exceeded 10% (Rodriquez-Morales et al., 2020) the scientific community have been met with a great deal of skepticism about the features of pneumonia on chest CT and its correlation with death. Recently, based upon pathophysiology of the virus and autopsy studies, these aspects have been re-evaluated, with a significant impact on the clinical management of COVID-19 patients.

In COVID-19, the extremely high inflammatory parameters, including C reactive protein (CRP) and pro-inflammatory cytokines (IL-6, TNFα, IL-8, et al), can simulate vasculitis (Zhang et al., 2020). In addition, direct microvessel endothelium damage by the virus increases the endothelial cells within bloodstream resulting in a hypercoagulable state, diffuse blood clots (disseminated intravascular coagulation), and subsequent damage to other organs (heart, liver, kidneys) and organ systems (blood and immune systems) finally leading to "multiple organ injury" (Zhang et al., 2020, Wang et al., 2020c).

Autopsy results on COVID-19 patients have demonstrated that respiratory failure represents the cause of the death in COVID-19, likely related to diffuse alveolar damage (DAD) with massive capillary congestion and pulmonary embolism (PE) (Menter et al., 2020, Ackermann et al., 2020, Wichmann et al., 2020) and not secondary to pneumonia. The DAD resembles the typical histopathological patterns in the evolutive phases (acute, proliferative and advanced phase) and chest CT features such as ground-glass opacity, crazy-paving and consolidation, similar to that described in pneumonia (Wichmann et al., 2020). An autopsy study by Menter et al. (2020) revealed a discrepancy between the CT signs identified as ‘pneumonia, COVID-related’ and DAD. In patients who have died from COVID-19, autopsy studies have revealed pneumonia in 0 to 48% of cases (Menter et al., 2020, Ackermann et al., 2020, Wichmann et al., 2020). Finally, the histopathological findings in the lung of post-mortem COVID-19 are comparable to Middle East respiratory syndrome coronavirus (MERS-CoV) (Xu et al., 2020, Alsaad et al., 2018), suggesting that the pathogenesis and mechanisms of lung tissue damage are similar.

In conclusion, this review of the pneumonia in COVID-19 patients revealed a discrepancy between the CT signs identified as ‘pneumonia, COVID-related’ and histology. Lung histopathologic features are mainly related to DAD and/or associated with PE, with subsequent respiratory failure and death in COVID-19 patients.

This knowledge is essential in improving the clinical outcome and reducing mortality in COVID-19 patients.

Author contributions

Study design: MS; writing manuscript: MS; editing manuscript: MS; literature research: MS.

Funding

The authors declare that there are no sponsors for this study.

Ethical approval

Not required.