Pathogenesis, immunology, and immune-targeted management of the multisystem inflammatory syndrome in children (MIS-C) or pediatric inflammatory multisystem syndrome (PIMS): EAACI Position Paper.

Multisystem inflammatory syndrome in children (MIS-C) is a rare, but severe complication of coronavirus disease 2019 (COVID-19). It develops approximately 4 weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and involves hyperinflammation with multisystem injury, commonly progressing to shock. The exact pathomechanism of MIS-C is not known, but immunological dysregulation leading to cytokine storm plays a central role. In response to the emergence of MIS-C, the European Academy of Allergy and Clinical Immunology (EAACI) established a task force (TF) within the Immunology Section in May 2021. With the use of an online Delphi process, TF formulated clinical statements regarding immunological background of MIS-C, diagnosis, treatment, follow-up, and the role of COVID-19 vaccinations. MIS-C case definition is broad, and diagnosis is made based on clinical presentation. The immunological mechanism leading to MIS-C is unclear and depends on activating multiple pathways leading to hyperinflammation. Current management of MIS-C relies on supportive care in combination with immunosuppressive and/or immunomodulatory agents. The most frequently used agents are systemic steroids and intravenous immunoglobulin. Despite good overall short-term outcome, MIS-C patients should be followed-up at regular intervals after discharge, focusing on cardiac disease, organ damage, and inflammatory activity. COVID-19 vaccination is a safe and effective measure to prevent MIS-C. In anticipation of further research, we propose a convenient and clinically practical algorithm for managing MIS-C developed by the Immunology Section of the EAACI.

Myocardial deformation assessed by CMR in children after multisystem inflammatory syndrome (MIS-C).

BACKGROUND: Short-term sequelae of Multisystem Inflammatory Syndrome in Children (MIS-C), recently published by our institution, showed rapid improvement of the cardiac abnormalities within a few weeks after the onset of the disease. However, subtle residual abnormalities, affecting mainly the myocardial interstitium, were shown in some of the patients. The current study aimed to assess myocardial deformation with CMR shortly after MIS-C. METHODS: Sixty children were included into the study; 30 following MIS-C (onset-to-scan mean 27 days, SD 11) and 30 controls. Strain values were compared between patients and controls and additionally to published paediatric normal CMR values. U-Mann Whitney test was used for comparison of the myocardial deformation between patients and controls. RESULTS: Median age of the patients was 9.0 years (range 0.99-14.4) and controls 9.8 years (range 4.7-14.9). All conventional CMR parameters in patients were in normal range. Strain values were significantly lower in patients than in controls. When compared to published centile graphs, radial and circumferential global strain was within 2.5th and 97.5th centile in all patients. Eleven patients had global longitudinal strain between 2.5th centile and 50th centile, 1 patient was below 2.5th centile and all the others above 50th centile. Only 3 controls had global longitudinal strain between 2.5th centile and 50th centile, all other had higher strain. CONCLUSIONS: This study demonstrates that myocardial deformation indices measured by CMR are within normal range in the vast majority of the patients within a few weeks after the onset of MIS-C. However, when compared to healthy controls, all strain parameters were lower in patients.

Cardiac Abnormalities Seen in Pediatric Patients During the SARS-CoV2 Pandemic: An International Experience.

Background During the SARS-CoV2 pandemic, there has been increase in hyperinflammatory presentation in previously healthy children with a variety of cardiac manifestations. Our objective is to describe the cardiac manifestations found in an international cohort of 55 pediatric cases with multi-system inflammatory syndrome (MIS-C) during the SARS-CoV2 pandemic. Methods and Results We reviewed data on previously healthy pediatric patients (≤18 years) with structurally normal hearts who presented at hospitals in the United States, United Kingdom, Spain and Pakistan with MIS-C and had consultation with a pediatric cardiologist. Data collected included demographics, clinical presentation, laboratory values, electrocardiographic abnormalities, echocardiographic findings and initial therapies. A total of 55 patients presented with MIS-C. Thirty-five patients (64%) had evidence of decreased left ventricular function, 17 (31%) had valvulitis, 12 (22%) with pericardial effusion and 11 (20%) with coronary abnormalities. Twenty-seven (49%) required ICU admission and 24 (44%) had evidence of shock. Eleven patients (20%) fulfilled complete Kawasaki disease criteria and had lower NT pro-BNP, D-dimer and ferritin levels compared with those who did not fulfill criteria. Electrophysiologic abnormalities occurred in 6 patients and included complete atrioventricular (AV) block, transient AV block and ventricular tachycardia. Conclusions We describe the first international cohort of pediatric patients with MIS-C during the SARS-CoV2 pandemic with a range of cardiac manifestations. This paper brings awareness and alertness to the global medical community to recognize these children during the pandemic and understand the need for early cardiology evaluation and follow-up.

Multisystem Inflammatory Syndrome in Children: An International Survey.

OBJECTIVES: To describe presentation, hospital course, and predictors of bad outcome in multisystem inflammatory syndrome in children (MIS-C). METHODS: Retrospective data review of a case series of children meeting the published definition for MIS-C who were discharged or died between March 1, 2020, and June 15, 2020, from 33 participating European, Asian, and American hospitals. Data were collected through a Web-based survey and included clinical, laboratory, electrocardiographic, and echocardiographic findings and treatment management. RESULTS: We included 183 patients with MIS-C: male sex, 109 (59.6%); mean age 7.0 ± 4.7 years; Black race, 56 (30.6%); obesity, 48 (26.2%). Overall, 114 of 183 (62.3%) had evidence of severe acute respiratory syndrome coronavirus 2 infection. All presented with fever, 117 of 183 (63.9%) with gastrointestinal symptoms, and 79 of 183 (43.2%) with shock, which was associated with Black race, higher inflammation, and imaging abnormalities. Twenty-seven patients (14.7%) fulfilled criteria for Kawasaki disease. These patients were younger and had no shock and fewer gastrointestinal, cardiorespiratory, and neurologic symptoms. The remaining 77 patients (49.3%) had mainly fever and inflammation. Inotropic support, mechanical ventilation, and extracorporeal membrane oxygenation were indicated in 72 (39.3%), 43 (23.5%), and 4 (2.2%) patients, respectively. A shorter duration of symptoms before admission was found to be associated with poor patient outcome and for extracorporeal membrane oxygenation and/or death, with 72.3% (95% confidence interval: 0.56-0.90; P = .006) increased risk per day reduction and 63.3% (95% confidence interval: 0.47-0.82; P < .0001) increased risk per day reduction respectively. CONCLUSIONS: In this case series, children with MIS-C presented with a wide clinical spectrum, including Kawasaki disease-like, life-threatening shock and milder forms with mainly fever and inflammation. A shorter duration of symptoms before admission was associated with a worse outcome.