Cardiac megakaryocytes in SARS-CoV-2-positive autopsies

Abstract

Thromboembolic phenomena are an important complication of infection by severe acute respiratory coronavirus 2 (SARS-CoV-2). Increasing focus on the management of the thrombotic complications of Coronavirus Disease 2019 (COVID-19) has led to further investigation into the role of platelets, and their precursor cell, the megakaryocyte, during the disease course. Previously published postmortem evaluations of patients who succumbed to COVID-19 have reported the presence of megakaryocytes in the cardiac microvasculature. Our series evaluated a cohort of autopsies performed on SARS-CoV-2-positive patients in 2020 (n = 36) and prepandemic autopsies performed in early 2020 (n = 12) and selected to represent comorbidities common in cases of severe COVID-19, in addition to infectious and noninfectious pulmonary disease and thromboembolic phenomena. Cases were assessed for the presence of cardiac megakaryocytes and correlated with the presence of pulmonary emboli and laboratory platelet parameters and inflammatory markers. Cardiac megakaryocytes were detected in 64% (23/36) of COVID-19 autopsies, and 40% (5/12) prepandemic autopsies, with averages of 1.77 and 0.84 megakaryocytes per cm² , respectively. Within the COVID-19 cohort, autopsies with detected megakaryocytes had significantly higher platelet counts compared with cases throughout; other platelet parameters were not statistically significant between groups. Although studies have supported a role of platelets and megakaryocytes in the response to viral infections, including SARS-CoV-2, our findings suggest cardiac megakaryocytes may be representative of a nonspecific inflammatory response and are frequent in, but not exclusive to, COVID-19 autopsies.

Keywords: COVID-19; SARS-CoV-2; megakaryocytes; platelets.

Figure 1

Cardiac megakaryocytes were identified in both COVID‐19‐positive and prepandemic autopsies. Megakaryocytes are challenging to identify on H&E alone, in part due to their unusual morphology that differs significantly from bone marrow megakaryocytes. The morphologic features, such as lobulated nuclei, condensed chromatin and scant cytoplasm, and presence between cardiomyocytes can help megakaryocyte identification. Morphology was similar in COVID‐19‐positive (A,C) and prepandemic cases (B, D). Immunohistochemistry for CD42b allows for enumeration of megakaryocytes in COVID‐19‐positive (E) and prepandemic decedents (F).

Figure 2

Comparison of platelet counts between all COVID‐19 and prepandemic autopsies.