Multisystem Inflammatory Syndrome in Children (MIS-C) Associated with Recent Omicron COVID-19 Subtypes is Rare but...

Area of Science:

• Pediatrics
• Infectious Diseases
• Cardiology

Background:

• Multisystem inflammatory syndrome in children (MIS-C) is a rare post-SARS-CoV-2 complication.
• Previous data indicated decreased MIS-C frequency and cardiovascular severity with Omicron variants starting late 2021.
• JN.1, a SARS-CoV-2 Omicron subtype, became predominant in early 2024.

Purpose of the Study:

• To compare MIS-C prevalence and cardiovascular manifestations in children diagnosed in early 2024 or later versus those diagnosed with older Omicron subtypes (2022-2023).

Main Methods:

• A single-center retrospective study comparing two cohorts of MIS-C patients.
• Cohort 1: Diagnosed from January 2024 to April 2025.
• Cohort 2: Diagnosed from January 2022 to December 2023.

Main Results:

• Fewer MIS-C hospitalizations occurred in the recent cohort (6 patients) compared to the prior cohort (26 patients) (p=0.01).
• The recent cohort showed significantly higher rates of left ventricular dysfunction (6/6 vs. 4/26, p=0.0002), troponin elevation (6/6 vs. 11/26, p=0.019), and vasodilation requiring vasopressors (5/6 vs. 2/26, p=0.016).
• Two recent patients required extracorporeal membrane oxygenation (ECMO), and one died from refractory vasodilation. All survivors recovered cardiovascular function within a week.

Conclusions:

• While MIS-C incidence may be lower with current Omicron variants, cardiovascular involvement can be more severe.
• Despite rapid recovery in most survivors, the potential for severe cardiac complications necessitates ongoing monitoring and vigilance for MIS-C.