COVID-19: Multisystem Inflammatory Syndrome in Children existed before the pandemic

In April 2020, a particular form of shock associated with myocarditis and systemic inflammation was identified in children, manifesting following SARS-CoV2 infection. This phenomenon was named Pediatric Inflammatory Multi-Systemic Syndrome (PIMS or MIS-C) and was considered a new clinical entity. It is the most severe form of SARS-CoV-2-associated disease in children.

This syndrome appeared around 4 weeks after a COVID-19 infection, most often asymptomatic, in around one case per 10,000 infections in children at the time of the first waves. Having affected almost 1,100 children in France, the incidence has now fallen, and PIMS are now very rare.

In 2021, the team led by Prof. Alexandre Belot¹ , a pediatrician at the Hospices civils de Lyon's Hôpital Femme Mère Enfant (HFME) and researcher at the Centre International de Recherche en Infectiologie (CIRI - Inserm/CNRS/ENS de Lyon/Université Claude Bernard Lyon 1) had discovered a marker for the disease corresponding to a specific activation of a family of white blood cells.

In a new study published in the New England Journal of Medicine, the same team, with the help of international collaborators, was able to trace cases of this disease occurring before 2019, not linked to SARS-CoV2. This unidentified disease at the time was often confused with infectious toxic shock, or Kawasaki disease, in its form with shock.

"We initially studied over a hundred children hospitalized in Lyon's intensive care unit between 2006 and 2018 for shock with hypotension and inflammation. We were surprised to find the PIMS marker in 3 children. By going back over the symptoms of these children, we discovered that they corresponded exactly to the presentation of MIS-C described in 2020 with COVID-19," reports Pr Belot. With more than 13 years of hindsight for some cases, these children did not present any recurrence or otable symptoms during the COVID pandemic.

A total of six cases of PIMS/MIS-C have been reported since 2010, two of which suggest prior infection with other coronaviruses (including seasonal), raising the hypothesis of a more general role for coronaviruses in post-infectious inflammatory manifestations.

This syndrome may therefore occur in the absence of SARS-CoV-2, broadening our understanding of pediatric inflammatory diseases. This work will enable us to consider earlier management of children, and will also encourage us to pay particular attention to this syndrome in the event of new epidemics of respiratory infections, notably with Coronavirus.

1. CIRI's Lymphocyte Activation and Signal Transduction Team (LYACTS)

Source
Pre-COVID-19 and SARS-CoV-2-negative cases of Multisystem Inflammatory Syndrome in Children
Benezech S°, Khoryati L°, Cognard J, Netea S, Khan T, Moreews M, Saker K, De Guillebon JM, Khaldi-
Plassart S, Pescarmona R, Viel S, Malcus C, Perret M, Ar Gouilh M, Vabret A, Venet F, Remy S, Chopin E,
Lina G, Vandenesch F, Rousseaux N, Bastard P, Zhang SY, Casanova JL, Trouillet-Assant S, Walzer T,
Kuijpers T, Javouhey E, Dauwalder O, Marr N, Belot A. N Engl J Med (2023).
Doi : 10.1056/NEJMc2307574

Scientific contact
Alexandre Belot, Pediatrics professor at the Université Claude Bernard Lyon 1 and hospital practitioner at the Hospices Civils de Lyon (PUPH), CIRI & HFME member
alexandre.belot@chu-lyon.fr | tel : +33 (0)4 27 85 61 26