Table 3 Summary of included papers

Craver et al. (2020)

1/0/17/no

Eosinophilic myocarditis

Positive

Diffuse inflammatory infiltrates composed of lymphocytes, macrophages with prominent eosinophils.

Congestion, acute focal hemorrhage, and edema, but no interstitial inflammation, diffuse alveolar damage, increased intra-alveolar hemosiderin-laden macrophages, viral inclusions, or viral cytopathic changes, eosinophilic infiltrates, vasculitis, or intraparenchymal lymphoid hyperplasia.

Beaudry et al. (2021)

1/1/18/yes

Positive

Diffuse lymphoplasmacytic inflammatory infiltrates, most marked in the septum. Diffuse lymphoplasmacytic inflammatory infiltrates, most marked in the septum. The inflammation clustered around and partially involved small arterioles, venules, and lymphatics but did not involve capillaries. There were only very focal areas of visible myocyte damage in the right ventricle. Myocardial injury was, in fact, more extensive and occurred too acutely to show diffuse histologic evidence.

Vascular congestion without inflammation, thrombi, or other abnormality.

Focal apoptosis of tubular cells but without frank inflammation, damage, or microthrombi.

Normal.

Dolhnikoff et al. (2020)

1/1/11/yes

Heart failure

Interstitial and perivascular myocardial inflammation containing lymphocytes, macrophages, a few neutrophils and eosinophils, and foci of cardiomyocyte necrosis; Myocardial necrosis indicated by C4d staining; Myocardial interstitial inflammation containing CD68+ and CD45+ cells.

Pulmonary tissue with focal exudative changes and mild pneumocyte hyperplasia; Fibrinous thrombi in small pulmonary arterioles.

Hepatic centrilobular necrosis

ATN

Reactive microglia

Lymphoid depletion and signs of hemophagocytosis.

de Almeida Monteiro et al. (2021)

1/n.r./0.6/no

DAD.

Bhatnagar et al. (2021)

4/n.r./n.r/no

Positive (3), Not performed (1)

Interstitial pneumonitis (1), pulmonary edema (1), DAD, bronchopneumonia (1), tracheobronchitis (1), mild hemorrhage (1).

Diorio et al. (2020)

1/1/18//no

Heart failure (1)

Duarte-Neto et al. (2021)

5/4/8.5 (0.6–15)/yes (3)

Disseminated thrombosis (1), COVID-19 pneumonia (1), SARS-COV-2 myocarditis (1), SARS-COV-2 colitis (1), SARS-COV-2 meningoencephalitis (1)

Positive (1), Negative (1), n.r (3)

Interstitial edema (4), pericarditis (1), myocarditis (2), endocarditis (1), myocardial necrosis (3)

Rare cells with cytopathic change (4); Large number of megakaryocytes (2); Typical SARS-COV-2 pneumonia with exudative DAD (3); Thrombi in arterial vessels (3) and septal capillaries (4), Congestion, oedema, foci of haemorrhage (4); Angiomatoid pattern (2); Various foci of coagulative necrosis (1).

Congestion (5), centrilobular necrosis (3), arterial thrombi with ischaemic necrosis (1), sinusoids thrombi (1) syncytial metaplasia of hepatocytes (1), cholestasis (1), hemophagocytosis by Kupffer cells (1), micro/macro vesicular steatosis, multinucleation, mild portal infiltrate (1), hepatocyte binucleation (1)

ATN (5), congestion (5), fibrin thrombi in glomerular capillaries (2), nephrocalcinosis (1), mesangial cell hyperplasia (1), hyaline cast (1), exudate in the Bowman space (1), granular casts (1).

Reactive microglia (5), neuronal ischaemia (5), congestion (5), oedema (2), capillary fibrin thrombi (1), Alzheimer type II glial cells (1).

Hypercellular, hemophagocytosis, emperipolesis by megakaryocytes (1), Normocellular, normomaturative (1); Mild nuclear atypia of megakaryocytes (1).

Pulmonary lymph nodes with lymphoid hypoplasia and hemophagocytosis (1)

Normal (1) Superficial perivascular mononuclear infiltrate (3) Superficial periadnexal mononuclear infiltrate (1)

Splenitis (5), hemorrhages (5), lymphoid hypoplasia with reactive cells (5) hemophagocytosis (2), sinusoidal fibrin thrombi (1)

Myolysis (5), necrotic fibers (4)

Oedema and mild inflammation (1), colitis with dense inflammatory cell infiltration (1), arteriolar microthrombi (1), appendicitis with peritonitis (1)

parotiditis (2), adrenal carcinoma with intense necrosis (1)

Adam et al. (2021)

2/1/11.5 (8–15)/n.r.

Positive (1), Negative (1)

Exudative and proliferative DAD, with epithelial atypia which extended throughout the respiratory epithelium (2).

Vacuolization of the cytoplasm and nucleus (1)