While vaccines are starting to become available for the prevention of SARS-Cov-2 infection, it is anticipated that the Coronavirus 2019 (COVID-19) pandemic will continue for at least the next year.^1,2BBC News. https://www.bbc.com/news/world-us-canada-55265477. Published December 12, 2020. Accessed December 16, 2020.
Scudellari M. Nature. 2020;584(7819):22-25. It was previously reported that infected patients have an increased risk of thrombosis.^3,4Long B et al. Am J Emerg Med. 2020;38(7):1504-1507.
Bansal M. Diabetes Metab Syndr. 2020;14(3):247-250. Recent literature suggests that SARS-CoV-2 infection may also lead to thrombotic microangiopathy (TMA) in children.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063.

A proposed mechanism of SARS-CoV-2-mediated TMA is via complement dysregulation resulting in unregulated C5b9 membrane attack complex formation.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. The clinically available biomarker soluble C5B9 (sC5b9) may be an indicator of severity of haematopoietic stem cell transplant-associated TMA (HSCT-TMA), with patients having notable elevations in sC5b9 having increased mortality.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. It is now hypothesized that sC5b9 is a marker of TMA in paediatric patients with SARS-CoV-2 infections.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063.

A total of 50 paediatric patients were admitted to the Children’s Hospital of Philadelphia with a positive SARS-CoV-2 RT-PCR test or who met the clinical criteria for multisystem inflammatory syndrome in children (MIS-C) were prospectively enrolled during the COVID-19 pandemic.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. Patients were classified into three groups, minimal COVID-19 (n=21), severe COVID-19 (n=11), or MIS-C (n=18).⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. Subject samples were compared to a normal control obtained from the institutional’s coagulation laboratory.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063.

The median sC5b9 level in the health control patients was 57ng/mL, and differed significantly from patients enrolled in this study, with minimal COVID-19 patients having a median level of 392ng/mL, severe COVID-19 patients a level of 646ng/mL, and MIS-C patients a level of 630ng/mL.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. There were no statistically significant differences between the three groups.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063.

The elevations in sC5b9 levels were observed in patients even with minimal disease or incidental finding of SARS-CoV-2 infection, suggesting that any exposure to the virus may result in elevations of this biomarker.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. Schistocytes were also prevalent in blood smears of patients with minimal COVID-19, severe COVID-19, and MIS-C.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063. IL-8 was also significantly elevated in severe COVID-19 and MIS-C patients, indicating more severe endothelial dysfunction in these two groups of patients.⁵Diorio C et al. Blood Adv. 2020;4(23):6051-6063.