Current Insights Into the Pathophysiology of Multisystem Inflammatory Syndrome in Children

Purpose of Review: We highlight the new clinical entity multisystem inflammatory syndrome in children (MIS-C), the progress in understanding its immunopathogenesis, and compare and contrast the clinical and immunologic features of MIS-C with Kawasaki disease (KD). Recent Findings: Studies show immune dysregulation in MIS-C including T lymphocyte depletion and activation, T cell receptor Vbeta skewing, elevated plasmablast frequencies, increased markers of vascular pathology, and decreased numbers and functional profiles of antigen-presenting cells. Summary: MIS-C is a late manifestation of infection with SARS-CoV-2 associated with marked immune activation and many potential mechanisms of immunopathogenesis. MIS-C and KD have clinical similarities but are distinct. Myocardial dysfunction with or without mild coronary artery dilation can occur in MIS-C but generally corrects within weeks. In contrast, the coronary arteries are the primary target in KD, and coronary artery sequelae can be lifelong. Supportive care and anti-inflammatory therapy appear to hasten improvement in children with MIS-C, and there is hope that vaccines will prevent its development.