Post COVID-19 paediatric inflammatory syndrome (PIMS-TS/MIS-C): what have we learned?

During the early phase of the COVID-19 pandemic, PIMS-TS emerged as a new hyper-inflammatory disorder affecting children. These children were often unstable requiring admission to critical care. Children with PIMS-TS displayed symptoms mimicking other inflammatory processes but it was quickly apparent this was a novel condition requiring its own treatment regime. Through international co-operative resource sharing, agreement grew over several treatment options including biological agents, IVIG and steroids leading to consensus guidance based on anecdotal and limited observed data. As our understanding of COVID-19 grew with each wave of the pandemic, so has our understanding of PIMS-TS. Several large trials, including the RECOVERY and BATS trials, are now able to provide an evidence base for the treatment of this condition, and challenge some of the management practices that were widely utilized. IV Immunoglobulin, for example, has been shown not to change outcomes and would therefore no longer be recommended for treatment, whereas methylprednisolone did show some improvements over usual supportive care. Epidemiology data shows PIMS-TS to have been a temporally limited condition, reducing in prevalence with each variant of COVID-19. Looking at overall outcome data, this was thankfully a condition with overall very low mortality and limited long term morbidity.