Both Corticosteroids and Intravenous Immunoglobulin Protect From Aneurysms in Children With Multisystem Inflammatory Syndrome (MIS-C): A Multicenter Ambispective Study.

Background: Multisystem inflammatory syndrome in children (MIS-C) is a post-COVID-19 condition resembling Kawasaki disease, including developing coronary aneurysms. Optimal treatment remains uncertain. This study aims to identify effective therapies for preventing aneurysms in MIS-C and associated risk factors.

Methods: This multicenter, ambispective study included hospitalized patients 0-18 years old with MIS-C between March 2020 and June 2023 from cohorts in Poland, Spain, Catalonia and Colombia. Logistic regression analyzed aneurysm risk factors. Treatment efficacy was assessed using Kaplan-Meier and Cox proportional hazards models, with post hoc Tukey's tests for pairwise comparisons.

Results: Among 853 patients, 33 (4%) developed aneurysms, with a median age of 5.86 years (interquartile range, 3.00-11.7). All immunomodulatory treatments reduced aneurysm risk compared with no immunomodulatory treatment: corticosteroids + intravenous immunoglobulin (IVIG) [odds ratio (OR): 0.29; 95% confident interval (CI): 0.13-0.68], corticosteroids alone (OR: 0.27; 95% CI: 0.04-1.02) and IVIG alone (OR: 0.49; 95% CI: 0.18-1.28). Kaplan-Meier analysis showed a significantly lower 7-day aneurysm-free probability without immunomodulatory treatment (92%; 95% CI: 87%-96%, P = 0.011). Hazard ratios indicated a reduction in aneurysm risk with corticosteroids+IVIG [hazard ratio (HR) = 0.29; 95% CI: 0.13-0.65], corticosteroids alone (HR = 0.25; 95% CI: 0.06-1.13) and IVIG alone (HR = 0.49; 95% CI: 0.19-1.25), but no significant differences were observed between these treatments. No additional aneurysm risk factors were identified.

Conclusions: Corticosteroids, IVIG and their combination appear to be protective against aneurysms in children with MIS-C compared with no immunomodulatory treatment. Although the 3 therapies showed no significant differences when compared with each other, only the combination significantly reduced the risk. Corticosteroids may still be a useful option when IVIG is limited.