Editorial: Multisystem inflammatory syndrome in children

Editorial on the Research Topic Multisystem inflammatory syndrome in childrenMultisystem inflammatory syndrome is a severe complication associated with COVID-19, initially recognized as a distinct clinical entity in 2020 (1).In a bulletin from the UK's National Health Service (NHS) in late April 2020, highlighting a new multi-system inflammatory condition involving a small number of children, the term "PIMS" (Pediatric Inflammatory Multisystem Syndrome associated with SARS-CoV-2) was initially used.Primarily observed in pediatric patients, it was subsequently classified by the Centers for Disease Control and Prevention as Multisystem Inflammatory Syndrome in Children (MIS-C) (2).MIS-C manifests as a rare delayed hyperinflammatory response following SARS-CoV-2 infection.Although the exact pathophysiology remains unclear, the SARS-CoV-2 coronavirus seems to trigger a dysregulated pathological immune response in the host, leading to systemic vasculitis and widespread acute organ damage (3).Like the viral infection caused by COVID-19, also other infectious agents, such as the Epstein-Barr virus (EBV), have also provided the opportunity to analyze the complex mechanisms leading to hyperinflammatory states.EBV can influence the expression and modulation of TLR7 and TLR9 signaling pathways, and consequently the transcription factor NF-κB activation (Tan et al.) (4).Liu et al. observed how the type of interplay between EBV and TLRs defines the disease outcome.Patients with chronic active EBV (CAEBV) showed a sustained and heightened activation of TLR7 and TLR9 along with their downstream signaling mediators (Liu et al.).This could suggest how a deficit in the self-regulation of negative feedback mechanisms associated with TLRs predisposes to a prolonged, and excessive inflammatory response, potentially contributing to an unfavorable outcome.MIS-C presents with a heterogeneous clinical profile and variable severity, involving multiple organs and characterized by a state of hyperinflammation, often requiring intensive care.It shares clinical similarities with Kawasaki Disease (KD)-like shock syndrome, explaining how treatment protocols have been mostly derived from those used in KD (5).About cardiac manifestations of these diseases, myocarditis and left ventricular systolic dysfunction are very common in MIS-C patients and rare in KD.Regarding the occurrence