Insights on Kawasaki disease and multisystem inflammatory syndrome; relationship with COVID-19 infection.

At the beginning of coronavirus disease 2019 (COVID-19) children seemed to be less affected and with milder symptoms than adults. Afterward, however, a warning was released regarding the possible association between COVID-19 and Kawasaki disease (KD) or Kawasaki-like disease. Thereafter, labels of Paediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS) in Europe and Multisystem Inflammatory Syndrome in Children (MIS-C) in the USA were coined to refer to this new disease entity. The reality is that PIMS-TS/MIS-C resembles certain KD complications such as toxic shock syndrome and macrophage activation syndrome than to classic KD. PIMS-TS/MIS-C and KD share the viral origin (however just supposed for KD) and consequent dysregulated innate immune system inflammatory reaction. PIMS-TS/MISC symptoms occur about 2-4 weeks after the onset of COVID-19 or having been exposed to somebody positive for COVID-19, rather than in the acute phase of the infection. Clinically PIMS-TS/MIS-C affects older children than KD and presents more often with gastrointestinal symptoms, shock, and multi-organ dysfunction. myocarditis is more common in PIMS-TS/MIS-C than coronary artery aneurysms formation seen in KD. There are also differences in laboratory tests and immunology responses in KD and PIMS-TS/MIS-C. Thus PIMS-TS/MIS-C seems to be a new and multifaceted entity, distinct from KD, notwithstanding some common features in both. The dysregulated innate immune system reaction is responsible for PIMS-TS/MIS-C onset and outcome. A multidisciplinary approach, involving paediatric intensivists, paediatric cardiologists, infectious disease specialists, immunologists, and rheumatologists, is needed for the treatment of these children.