Immunological features of the multisystem inflammatory syndrome associated with SARS-CoV-2 in children.

A particular group of children developed severe multisystem inflammation associated with current or recent SARS-CoV-2 infection or contact with a COVID-19 patient in the previous few weeks. The condition was defined as multisystem inflammatory syndrome (MIS) in children (MIS-C). As the definition of CDC and WHO is fast widely accepted, the lack of an international consensus on the definition of the syndrome cases, however, leads to some difficulties for clinicians. Additionally, MIS-C shares some immunological, pathological features with the conditions, such as cytokine storm, long COVID and/or post-COVID syndrome. The picture is further complicated by the existence of the syndrome in adults (MIS-A). Therefore, we have compared these conditions from the immunological point of view in our review based on the published case reports, studies, systematic reviews and metaanalyses. This knowledge is essential not only for immunologists. The paediatricians must be familiar with the immunological bases of the syndrome and implement it in on-time recognition and diagnosis and minimize systemic damage of this life-threatening condition at the earliest stage possible. Further investigations still need to be done to find and develop the best effective therapy and prophylactics.