Clinical and Histopathologic Features of Myocarditis in Multisystem Inflammatory Syndrome (Adult)–Associated COVID-19

Abstract

BACKGROUND: Multisystem inflammatory syndrome (MIS) associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is a lifethreatening condition first described in children (MIS-C). It is characterized by a hyperinflammatory state that involves the cardiovascular, gastrointestinal, dermatologic, and neurologic systems without severe respiratory system involvement. Myocarditis is one of the cardiovascular presentations of MIS that might be complicated with cardiogenic shock. There are few case reports describing SARS-CoV-2-related MIS in adults (MIS-A).

Fulminant Myocarditis and Acute Appendicitis after COVID-19 Vaccination

“…Our myocardial biopsy showed cell infiltration (more macrophages than T and B cells) without ACE2, spike protein, or C4d expression in myocytes, which differed from our previously reported case of fulminant myocarditis after COVID-19 vaccination without MIS (27). These findings suggest that the pathophysiology of myocarditis following COVID-19 vaccination may be (28)(29)(30)(31)(32). Cardiac injury in MIS following viral infection may occur either because of direct cardiac invasion of the virus or inflammatory response by cytokine release (cytokine storm) (29).…”

SARS‐CoV‐2‐related Multisystem Inflammatory Syndrome in Adult complicated by myocarditis and cardiogenic shock

“… 25 , 26 In MIS‐A, EMB histopathology has shown an inflammatory infiltrate of macrophages, T lymphocytes and eosinophils. 27 , 28 , 29 , 30 It may be particularly useful if histological evaluation is expected to impact therapy. In this case, we estimated EMB would not add diagnostic clues given the typical clinical course of MIS‐A in the absence of a more likely alternative diagnosis, nor would it alter our therapeutic management.…”

“…Although not mandatory for the diagnosis of MIS‐A, endomyocardial biopsy (EMB) may be performed in suspected myocarditis and may provide differentiation between inflammatory, infectious and infiltrative causes 25,26 . In MIS‐A, EMB histopathology has shown an inflammatory infiltrate of macrophages, T lymphocytes and eosinophils 27–30 . It may be particularly useful if histological evaluation is expected to impact therapy.…”

Multisystem inflammatory syndrome in adults: Characteristics, treatment, and outcomes

“…Although the pathophysiology of MIS-A is poorly understood, it is supposed to be caused by an antibody-mediated process or dysregulated innate immune activation. 54,55 The reported histopathological presentations of SARS-CoV-2-associated myocarditis could be variable with different cell infiltrates, including cytotoxic T-cells, tissue-repair macrophages, lymphocytes, eosinophils, and neutrophils, in addition to severe myocardial necrosis. [56][57][58][59] for SARS-CoV-2.…”