New-Onset Complement-Mediated Thrombotic Microangiopathy during the COVID-19 Pandemic

The coronavirus disease-19 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus is alleged to enable a proinflammatory state that leads to the activation of the coagulation and the complement cascade. In this study, we aimed to establish the impact of the COVID-19 pandemic on patients with new onset of cTMA/aHUS in the Vienna TMA cohort and whether COVID-19 or SARS-CoV-2 vaccinations would pose a greater risk of initial manifestation of cTMA/aHUS.

We used the Vienna TMA cohort database to examine the prevalence of COVID-19-related and of SARS-CoV-2 vaccination-related aHUS/cTMA during the first 3 years of the COVID-19 pandemic in a large single-centre cohort.

Between March 2020 and May 2023, a total of 7 patients experienced their first aHUS/cTMA episode. No patient experienced a TMA relapse or more than one episode during the follow-up period. Three TMA episodes were attributable to either COVID-19 (n = 1; 33%) or SARS-CoV-2 vaccination (n = 2; 66%), respectively. All 3 patients had systemic signs of TMA, and TMA was confirmed by kidney biopsy in all cases. Among the 7 patients, we recorded five infections that triggered one TMA episode (20%) and 19 vaccinations triggered two TMA episodes (10%; p = 0.52, odds ratio 0.47; 95% CI: 0.04-8.39).

We speculate that both SARS-CoV-2 vaccinations and COVID-19 episodes can represent a triggering factor for aHUS/cTMA episodes in (genetically) vulnerable individuals. However, COVID-19 might have a stronger association and might be a stronger trigger than the SARS-CoV-2 vaccines. The incidence of new aHUS cases did not differ from the pre-pandemic era in a large tertiary care centre cohort.