Epidemiology, Clinical Features, and Outcomes of Multisystem Inflammatory Syndrome in Children (MIS-C) and Adolescents—a Live Systematic Review and Meta-analysis

Purpose of Review A multisystem inflammatory condition occurring in children and adolescents with COVID-19 has become increasingly recognized and widely studied globally. This review aims to investigate and synthesize evolving evidence on its clinical characteristics, management, and outcomes in pediatric patients. Recent Findings We retrieved data from PubMed, EMBASE, Cochrane Library, WHO COVID-19 Database, Google Scholar, and preprint databases, covering a timeline from December 1, 2019, to July 31, 2021. A total of 123 eligible studies were included in the final descriptive and risk factor analyses. We comprehensively reviewed reported multisystem inflammatory syndrome in children (MIS-C) cases from published and preprint studies of various designs to provide an updated evidence on epidemiology, clinical, laboratory and imaging findings, management, and short-term outcomes. Latest evidence suggests that African black and non-Hispanic white are the two most common ethnic groups, constituting 24.89% (95% CI 23.30–26.48%) and 25.18% (95% CI 23.51–26.85%) of the MIS-C population, respectively. Typical symptoms of MIS-C include fever (90.85%, 95% CI 89.86–91.84%), not-specified gastrointestinal symptoms (51.98%, 95% CI 50.13–53.83%), rash (49.63%, 95% CI 47.80–51.47%), abdominal pain (48.97%, 95% CI 47.09–50.85%), conjunctivitis (46.93%, 95% CI 45.17–48.69%), vomiting (43.79%, 95% CI 41.90–45.68%), respiratory symptoms (41.75%, 95% CI 40.01–43.49%), and diarrhea (40.10%, 95% CI 38.23–41.97%). MIS-C patients are less likely to develop conjunctivitis (OR 0.27, 95% CI 0.11–0.67), cervical adenopathy (OR 0.21, 95% CI 0.07–0.68), and rash (OR 0.44, 95% CI 0.26–0.77), in comparison with Kawasaki disease patients. Our review revealed that the majority of MIS-C cases (95.21%) to be full recovered while only 2.41% died from this syndrome. We found significant disparity between low- and middle-income countries and high-income countries in terms of clinical outcomes. Summary MIS-C, which appears to be linked to COVID-19, may cause severe inflammation in organs and tissues. Although there is emerging new evidence about the characteristics of this syndrome, its risk factors, and clinical prognosis, much remains unknown about the causality, the optimal prevention and treatment interventions, and long-term outcomes of the MIS-C patients.