Table 1.

Comparison between haemophagocytic syndrome (HS) and COVID-19 (adapted from Valga et al.).

Characteristics	HS	COVID-19
Anaemia	Common	Common
Thrombocytopaenia	+	+
Haptoglobin	Normal or reduced	Unknown
LDH	Elevated	High?
Ferritin	Yes	Yes
Hypertransaminasaemia	Yes	Yes
Schistocytes	No	Unknown
D-dimer	High	High
Fibrinogen	Low	High
Coagulation test	Abnormal	Abnormal
Antiphospholipid antibodies	Rare	Rare
Main cytokines involved	Interferon-gamma TNF-alpha, IL-1beta, IL-6, IL-8, IL-10, IL-18	IL-6, IL-1beta, IL-2, IL-17, IL-8, TNF-alpha, IL-7, GCSF, interferon-gamma
Histology	Histiocytes with haemophagocytosis	Endothelial damage
		Microthrombi
		Haemophagocytosis (described)
Complement alteration	Sometimes	Yes
Systemic involvement	Yes	Yes
Therapy	Etoposide	Anticoagulant (heparin)?
	Steroids	Antivirals?
	Immunoglobulin	Steroids?
	Cyclosporin A	Tocilizumab?
	Anti-TNF antibodies	Eculizumab?
	BMT

BMT: bone marrow transplant. GCSF: granulocyte colony-stimulating factor.