Thromboembolic involvement and its possible pathogenesis in COVID-19 mortality: lesson from post-mortem reports.

The emergence of Coronavirus Disease 19 (COVID-19) as a pandemic has claimed hundreds of thousands of lives worldwide since its initial breakout. With increasing reports from clinical observations and autopsy findings, it became clear that the disease causes acute respiratory distress syndrome (ARDS), as well as a broad spectrum of systemic and multiorgan pathologies, including angiopathy, endothelialitis, and thrombosis. Coagulopathy is associated with the activity of megakaryocytes, which play crucial roles in modulating the platelet homeostasis. Only a few autopsy reports include findings on thrombosis formation and the presence of megakaryocytes. Here we review and summarize the possible involvement and the pathophysiology of the thromboembolic events in COVID-19 patients based on post-mortem reports. We reviewed post-mortem reports from March 2020 to September 2020. Eleven autopsy reports that demonstrated thromboembolic involvement findings, either macroscopically or microscopically, were included in this review. All studies reported similar pulmonary gross findings. Not all studies described thrombi formation and megakaryocyte findings. Pulmonary embolism, coagulopathy, severe endothelial injury, and widespread thrombosis are frequent in COVID-19 patients, following many patients with high-level D-Dimer, increased fibrinogen, abnormal prothrombic coagulation, and thrombocytopenia. Reports showed that thrombus was also found in the lower extremities' deep veins and the prostatic venous plexus. In conclusion, a complex interaction of SARS-CoV-2 virus invasion with platelets, leukocytes, endothelial cells, inflammation, immune response, and the possible involvement of megakaryocytes may increase the cumulative risk of thrombosis by a yet unclear cellular and humoral interaction.

Increased number of pulmonary megakaryocytes in COVID-19 patients with diffuse alveolar damage: an autopsy study with clinical correlation and review of the literature.

Pulmonary megakaryocytes participate in the pathogenesis of lung damage, particularly in acute lung injury. Although megakaryocytes are not mentioned as a characteristic histologic finding associated to pulmonary injury, a few studies reveal that their number is increased in diffuse alveolar damage (DAD). In this autopsy study, we have observed a relevant number of pulmonary megakaryocytes in COVID-19 patients dying with acute lung injury (7.61 ± 5.59 megakaryocytes per 25 high-power fields vs. 1.14 ± 0.86 for the control group, p < 0.05). We analyzed samples of 18 patients, most of whom died after prolonged disease and use of mechanical ventilation. Most patients showed advanced DAD and abnormal coagulation parameters with high levels of fibrinogen, D-dimers, and variable thrombocytopenia. For comparison, pulmonary samples from a group of 14 non-COVID-19 patients dying with DAD were reviewed. They showed similar pulmonary histopathologic findings and an increase in the number of megakaryocytes (4 ± 4.17 vs. 1.14 ± 0.86 for the control group, p < 0.05). Megakaryocyte count in the COVID-19 group was greater but did not reach statistical significance (7.61 ± 5.59 vs. 4 ± 4.17, p = 0.063). Regardless of the cause, pulmonary megakaryocytes are increased in patients with DAD. Their high number seen in COVID-19 patients suggests a relation with the thrombotic events so often seen these patients. Since the lung is considered an active site of megakaryopoiesis, a prothrombotic status leading to platelet activation, aggregation and consumption may trigger a compensatory pulmonary response.

A proof of evidence supporting abnormal immunothrombosis in severe COVID-19: naked megakaryocyte nuclei increase in the bone marrow and lungs of critically ill patients.

Coronavirus disease 2019 (COVID-19) is a global public health emergency with many clinical facets, and new knowledge about its pathogenetic mechanisms is deemed necessary; among these, there are certainly coagulation disorders. In the history of medicine, autopsies and tissue sampling have played a fundamental role in order to understand the pathogenesis of emerging diseases, including infectious ones; compared to the past, histopathology can be now expanded by innovative techniques and modern technologies. For the first time in worldwide literature, we provide a detailed postmortem and biopsy report on the marked increase, up to 1 order of magnitude, of naked megakaryocyte nuclei in the bone marrow and lungs from serious COVID-19 patients. Most likely related to high interleukin-6 serum levels stimulating megakaryocytopoiesis, this phenomenon concurs to explain well the pulmonary abnormal immunothrombosis in these critically ill patients, all without molecular or electron microscopy signs of megakaryocyte infection.

Gross and histopathological pulmonary findings in a COVID-19 associated death during self-isolation.

Forensic investigations generally contain extensive morphological examinations to accurately diagnose the cause of death. Thus, the appearance of a new disease often creates emerging challenges in morphological examinations due to the lack of available data from autopsy- or biopsy-based research. Since late December 2019, an outbreak of a novel seventh coronavirus disease has been reported in China caused by "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2). On March 11, 2020, the new clinical condition COVID-19 (Corona-Virus-Disease-19) was declared a pandemic by the World Health Organization (WHO). Patients with COVID-19 mainly have a mild disease course, but severe disease onset might result in death due to proceeded lung injury with massive alveolar damage and progressive respiratory failure. However, the detailed mechanisms that cause organ injury still remain unclear. We investigated the morphological findings of a COVID-19 patient who died during self-isolation. Pathologic examination revealed massive bilateral alveolar damage, indicating early-phase "acute respiratory distress syndrome" (ARDS). This case emphasizes the possibility of a rapid severe disease onset in previously mild clinical condition and highlights the necessity of a complete autopsy to gain a better understanding of the pathophysiological changes in SARS-CoV-2 infections.

Dying with SARS-CoV-2 infection-an autopsy study of the first consecutive 80 cases in Hamburg, Germany.

Autopsies of deceased with a confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can provide important insights into the novel disease and its course. Furthermore, autopsies are essential for the correct statistical recording of the coronavirus disease 2019 (COVID-19) deaths. In the northern German Federal State of Hamburg, all deaths of Hamburg citizens with ante- or postmortem PCR-confirmed SARS-CoV-2 infection have been autopsied since the outbreak of the pandemic in Germany. Our evaluation provides a systematic overview of the first 80 consecutive full autopsies. A proposal for the categorisation of deaths with SARS-CoV-2 infection is presented (category 1: definite COVID-19 death; category 2: probable COVID-19 death; category 3: possible COVID-19 death with an equal alternative cause of death; category 4: SARS-CoV-2 detection with cause of death not associated to COVID-19). In six cases, SARS-CoV-2 infection was diagnosed postmortem by a positive PCR test in a nasopharyngeal or lung tissue swab. In the other 74 cases, SARS-CoV-2 infection had already been known antemortem. The deceased were aged between 52 and 96 years (average 79.2 years, median 82.4 years). In the study cohort, 34 deceased were female (38%) and 46 male (62%). Overall, 38% of the deceased were overweight or obese. All deceased, except for two women, in whom no significant pre-existing conditions were found autoptically, had relevant comorbidities (in descending order of frequency): (1) diseases of the cardiovascular system, (2) lung diseases, (3) central nervous system diseases, (4) kidney diseases, and (5) diabetes mellitus. A total of 76 cases (95%) were classified as COVID-19 deaths, corresponding to categories 1-3. Four deaths (5%) were defined as non-COVID-19 deaths with virus-independent causes of death. In eight cases, pneumonia was combined with a fulminant pulmonary artery embolism. Peripheral pulmonary artery embolisms were found in nine other cases. Overall, deep vein thrombosis has been found in 40% of the cases. This study provides the largest overview of autopsies of SARS-CoV-2-infected patients presented so far.

SARS-CoV-2-related deaths in routine forensic autopsy practice: histopathological patterns.

"Severe acute respiratory syndrome" (SARS) due to coronavirus (SARS-CoV-2) infection is a well-known cause of death. Sometimes, demise can occur unexpectedly in apparently previous healthy individual after a brief period of trivial flu-like symptoms. In these doubtful cases, the forensic pathologist could be requested to define the cause of death occurred outside the hospital. In this report, the authors describe two autopsied cases of SARS-CoV-2-related deaths which occurred suddenly at home and were not preceded by hospitalization, highlighting associated histopathologic patterns and correlating them to pathophysiology of viral infection.

Inside the lungs of COVID-19 disease.

In the setting of the coronavirus disease 2019 (COVID-19) pandemic, only few data regarding lung pathology induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is available, especially without medical intervention interfering with the natural evolution of the disease. We present here the first case of forensic autopsy of a COVID-19 fatality occurring in a young woman, in the community. Diagnosis was made at necropsy and lung histology showed diffuse alveolar damage, edema, and interstitial pneumonia with a geographically heterogeneous pattern, mostly affecting the central part of the lungs. This death related to COVID-19 pathology highlights the heterogeneity and severity of central lung lesions after natural evolution of the disease.