Two-year follow-up on multisystem inflammatory syndrome in children (MIS-c): findings from a tertiary paediatric hospital in Latvia

This study aimed to assess long-term recovery from multisystem inflammatory syndrome in children (MIS-c) 24 months after admission. This prospective longitudinal cohort study included 21 children diagnosed with MIS-c according to Centers for Disease Control and Prevention (CDC) criteria and admitted to Children's Clinical University Hospital in Riga. Outpatient follow-up consisted of repeated visits at 3, 6, 12, and 24 months after the acute phase of MIS-c. In addition to the initial interview and physical examination, the patients were asked to perform functional tests (six-minute walking test (6-MWT) and orthostatic intolerance test (OIT)) and complete validated tools (Chalder Fatigue Questionnaire (CFQ-11) and Karolinska Sleep Questionnaire (KSQ)). The median age of the study group was 6 years (IQR, 5.0-10.0 years; range, 1-16 years). The KSQ showed that sleep quality, non-restorative sleep, and daytime sleepiness were more associated with the 1-3-month period than with long-term sequelae. At 1-3 months, all children exhibited physical and psychological fatigue (bi-modal score ≥ 4). By 6 months, no patient showed fatigue (bi-modal score < 3). The OIT showed no signs of orthostatic intolerance, orthostatic hypotension, or POTS among patients. Heart rate and blood pressure changes were mild. The 6-MWT showed significant improvement in walking distance.

CONCLUSIONS: Most improvements in sleep quality, reduction in fatigue, orthostatic compensation, and aerobic capacity occur within the first 6 months after acute MIS-c, with no long-term sequelae.

WHAT IS KNOWN: • Multisystem inflammatory syndrome in children (MIS-c) is a potentially life-threatening complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. • Data on long-term outcomes of patients with MIS-c are scarce, providing very limited insights into children's well-being after 12 months.

WHAT IS NEW: • Our two-year study indicated that for most patients, physical and psychological health improvements occurred within the first 6 months after acute MIS-c, without long-term consequences. • RDW/PLT may serve as a practical early marker of oxidative stress response in neonates, reinforcing the safety of phototherapy while raising questions for preterm care.