Clinical characteristics, cardiac involvement, and medium-term outcomes of multisystem inflammatory syndrome in children: a Hungarian retrospective cohort study

Background Multisystem inflammatory syndrome in children (MIS-C) is a rare but severe post-infectious complication of SARS-CoV-2 infection, frequently associated with systemic inflammation and cardiac involvement. Limited data are available regarding medium-term recovery and patient-reported outcomes following MIS-C. Methods We conducted a retrospective analysis of paediatric patients diagnosed with MIS-C between September 2020 and March 2022. Demographic data, laboratory findings, cardiac imaging results, treatment modalities, and outcomes were analysed. Medium-term follow-up outcomes were assessed using a structured questionnaire administered between December 2025 and January 2026. The questionnaire evaluated symptom burden, functional recovery, school attendance, and healthcare utilisation. Results Fifty-four patients were included (mean age 9.0 years; 37 male, 68.5%). Seventeen patients (31.5%) required intensive care unit admission. SARS-CoV-2 serology was positive in 48/54 patients (88.9%; 48/49 of those tested). Laboratory findings demonstrated marked systemic inflammation with elevated C-reactive protein, procalcitonin, interleukin-6, and ferritin levels, and frequent elevation of cardiac biomarkers. Echocardiography revealed transient abnormalities including reduced left ventricular systolic function in 7/48 patients (14.6%), mean fractional shortening 38.7%, valvular regurgitation, small pericardial effusions, and coronary artery abnormalities in 8/48 patients (16.7%), four of whom met criteria for a small aneurysm. Follow-up cardiac magnetic resonance imaging was performed in 27/54 patients (50.0%) and was evaluable in 26; none showed MIS-C-related abnormalities. Most patients received intravenous immunoglobulin (88.9%) and systemic corticosteroids (83.3%); three (5.6%) required biologic therapy. All patients survived. Follow-up questionnaire data were available for 35 patients (64.8%) at a median of 4.7 years; all had returned to full-time school attendance, the majority reported physical activity tolerance comparable to their pre-illness level, and the median overall recovery score was 4 out of 4. Conclusions MIS-C was associated with significant systemic inflammation and frequent but reversible cardiac involvement. No MIS-C-related mortality occurred, and among the patients who underwent follow-up cardiac magnetic resonance imaging no persistent myocardial abnormality was identified. The uncontrolled design does not allow the contribution of treatment to these outcomes to be assessed. Medium-term questionnaire follow-up suggested good recovery overall, with high rates of return to normal daily activities and limited persistent symptom burden.