Histopathological findings of pericarditis in a patient with multisystem inflammatory syndrome in children associated with COVID-19: A case report.

Multisystem inflammatory syndrome in children (MIS-C), which is associated with the novel coronavirus disease 2019 (COVID-19), has been described as an inflammatory complication of exposure to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It carries a risk of serious and lethal complications, including cardiogenic shock. Here, we report the pathological findings of the pericardium in a 10-year-old child with MIS-C, who developed pericarditis-induced cardiac tamponade. In the patient's pericardium, the numbers of infiltrating CD68 + macrophages; CD3 + , CD4 + , and CD8 + T cells; and myeloperoxidase + granulocytes were increased, although the number of CD20 + B cells was not. These findings provide a clue to understanding the pathophysiology of MIS-C.