Multisystem inflammatory syndrome in children during the COVID-19 waves: data from the Juvenile Inflammatory Rheumatism cohort.

Introduction: Multisystem inflammatory syndrome in children (MIS-C) is a new condition that first appeared in children and adolescents during the COVID-19 pandemic. We aimed to describe the diagnostic course, clinical and biological manifestations, and treatment of MIS-C during the first three COVID-19 waves. Methods: We extracted patient data from the Juvenile Inflammatory Rheumatism (JIR) cohort. We analyzed data for patients meeting the World Health Organization diagnostic criteria for MIS-C from the start of the COVID-19 pandemic from March 2020 to June 30, 2021. We then compared data for patients in wave one to those in waves two and three. Results: We identified 136 patients with MIS-C. The median age decreased but not significantly during the waves, from 9.9 years to 7.3 years (p = 0.105). Boys represented 52.2% (n = 71) of patients, and 46% (n = 41) of patients originated from sub-Saharan Africa (p < 0.001). Patients presented less diarrhea (p = 0.004), respiratory distress (p < 0.001), and myocarditis (p < 0.001) with progressive waves. Biological inflammation also decreased, namely, C-reactive protein level (p < 0.001), neutrophil count (p = 0.004), and albumin level (p < 0.001). Patients received more corticosteroids (p < 0.001) and required less ventilation support (p < 0.01) and less inotrope treatment (p < 0.001) in the later waves. The duration of hospitalization gradually decreased (p < 0.001), as did critical care unit admissions (p = 0.002). Conclusion: Over the three COVID-19 waves, with a change in the management of MIS-C, children in the JIR cohort in France showed a less severe disease course, in particular, a greater use of corticosteroids. This observation may reflect the impact of both improved management and different SARS-CoV-2 variant.

Polyclonal expansion of TCR Vbeta 21.3+ CD4+ and CD8+ T cells is a hallmark of Multisystem Inflammatory Syndrome in Children.

Multiple Inflammatory Syndrome in Children (MIS-C) is a delayed and severe complication of SARS-CoV-2 infection that strikes previously healthy children. As MIS-C combines clinical features of Kawasaki disease and Toxic Shock Syndrome (TSS), we aimed to compare the immunological profile of pediatric patients with these different conditions. We analyzed blood cytokine expression, and the T cell repertoire and phenotype in 36 MIS-C cases, which were compared to 16 KD, 58 TSS, and 42 COVID-19 cases. We observed an increase of serum inflammatory cytokines (IL-6, IL-10, IL-18, TNF-α, IFNγ, CD25s, MCP1, IL-1RA) in MIS-C, TSS and KD, contrasting with low expression of HLA-DR in monocytes. We detected a specific expansion of activated T cells expressing the Vß21.3 T cell receptor ß chain variable region in both CD4 and CD8 subsets in 75% of MIS-C patients and not in any patient with TSS, KD, or acute COVID-19; this correlated with the cytokine storm detected. The T cell repertoire returned to baseline within weeks after MIS-C resolution. Vß21.3+ T cells from MIS-C patients expressed high levels of HLA-DR, CD38 and CX3CR1 but had weak responses to SARS-CoV-2 peptides in vitro. Consistently, the T cell expansion was not associated with specific classical HLA alleles. Thus, our data suggested that MIS-C is characterized by a polyclonal Vß21.3 T cell expansion not directed against SARS-CoV-2 antigenic peptides, which is not seen in KD, TSS and acute COVID-19.

Association of Intravenous Immunoglobulins Plus Methylprednisolone vs Immunoglobulins Alone With Course of Fever in Multisystem Inflammatory Syndrome in Children.

Importance: Multisystem inflammatory syndrome in children (MIS-C) is the most severe pediatric disease associated with severe acute respiratory syndrome coronavirus 2 infection, potentially life-threatening, but the optimal therapeutic strategy remains unknown. Objective: To compare intravenous immunoglobulins (IVIG) plus methylprednisolone vs IVIG alone as initial therapy in MIS-C. Design, Setting, and Participants: Retrospective cohort study drawn from a national surveillance system with propensity score-matched analysis. All cases with suspected MIS-C were reported to the French National Public Health Agency. Confirmed MIS-C cases fulfilling the World Health Organization definition were included. The study started on April 1, 2020, and follow-up ended on January 6, 2021. Exposures: IVIG and methylprednisolone vs IVIG alone. Main Outcomes and Measures: The primary outcome was persistence of fever 2 days after the introduction of initial therapy or recrudescence of fever within 7 days, which defined treatment failure. Secondary outcomes included a second-line therapy, hemodynamic support, acute left ventricular dysfunction after first-line therapy, and length of stay in the pediatric intensive care unit. The primary analysis involved propensity score matching with a minimum caliper of 0.1. Results: Among 181 children with suspected MIS-C, 111 fulfilled the World Health Organization definition (58 females [52%]; median age, 8.6 years [interquartile range, 4.7 to 12.1]). Five children did not receive either treatment. Overall, 3 of 34 children (9%) in the IVIG and methylprednisolone group and 37 of 72 (51%) in the IVIG alone group did not respond to treatment. Treatment with IVIG and methylprednisolone vs IVIG alone was associated with lower risk of treatment failure (absolute risk difference, -0.28 [95% CI, -0.48 to -0.08]; odds ratio [OR], 0.25 [95% CI, 0.09 to 0.70]; P = .008). IVIG and methylprednisolone therapy vs IVIG alone was also significantly associated with lower risk of use of second-line therapy (absolute risk difference, -0.22 [95% CI, -0.40 to -0.04]; OR, 0.19 [95% CI, 0.06 to 0.61]; P = .004), hemodynamic support (absolute risk difference, -0.17 [95% CI, -0.34 to -0.004]; OR, 0.21 [95% CI, 0.06 to 0.76]), acute left ventricular dysfunction occurring after initial therapy (absolute risk difference, -0.18 [95% CI, -0.35 to -0.01]; OR, 0.20 [95% CI, 0.06 to 0.66]), and duration of stay in the pediatric intensive care unit (median, 4 vs 6 days; difference in days, -2.4 [95% CI, -4.0 to -0.7]). Conclusions and Relevance: Among children with MIS-C, treatment with IVIG and methylprednisolone vs IVIG alone was associated with a more favorable fever course. Study interpretation is limited by the observational design.

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.

Distinctive Features of Kawasaki Disease Following SARS-CoV-2 Infection: a Controlled Study in Paris, France.

BACKGROUND: An outbreak of multisystem inflammatory syndrome in children, including Kawasaki disease (KD), emerged during COVID-19 pandemic. We explored whether Kawasaki-like disease (KD), when associated with confirmed SARS-CoV-2 infection, has specific characteristics. METHODS: We included children and adolescents with KD criteria admitted in the department of general pediatrics of a university hospital in Paris, France, between January 1, 2018, and May 26, 2020. The incidence of KD was compared between the outbreak and a pre-outbreak control period (January 1, 2018, to April 25). Characteristics of patients with positive SARS-CoV-2 testing (KD-SARS-CoV-2) were compared to those of the pre-outbreak period (classic KD). RESULTS: A total of 30 and 59 children with KD were admitted during the outbreak and pre-outbreak periods, respectively (incidence ratio 13.2 [8.3-21.0]). During the outbreak, 23/30 (77%) children were diagnosed as KD-SARS-CoV-2. When compared with patients with classic KD, those with KD-SARS-CoV-2 were more frequently of sub-Saharan African ancestry (OR 4.4 [1.6-12.6]) and older (median 8.2 vs. 4.0 years, p < 0.001), had more often initial gastrointestinal (OR 84 [4.9-1456]) and neurological (OR 7.3 [1.9-27.7] manifestations, and shock syndrome (OR 13.7 [4.2-45.1]). They had significantly higher CRP and ferritin levels. Noticeably, they had more frequently myocarditis (OR 387 [38-3933]). CONCLUSIONS: Children and adolescents with KD-SARS-CoV-2 have specific features when compared with those with classic KD. These findings should raise awareness and facilitate the study of their pathogenesis.

Association between SARS-CoV-2 infection and Kawasaki-like multisystem inflammatory syndrome: a retrospective matched case-control study, Paris, France, April to May 2020.

We assessed the association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and Kawasaki disease (KD)-like multisystem inflammatory syndrome in a retrospective case-control study in France. RT-PCR and serological tests revealed SARS-CoV-2 infection in 17/23 cases vs 11/102 controls (matched odds ratio: 26.4; 95% confidence interval: 6.0-116.9), indicating strong association between SARS-CoV-2 infection and KD-like illness. Clinicians should keep a high level of suspicion for KD-like illness during the COVID-19 pandemic.

Paediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2 mimicking Kawasaki disease (Kawa-COVID-19): a multicentre cohort.

BACKGROUND: Current data suggest that COVID-19 is less frequent in children, with a milder course. However, over the past weeks, an increase in the number of children presenting to hospitals in the greater Paris region with a phenotype resembling Kawasaki disease (KD) has led to an alert by the French national health authorities. METHODS: Multicentre compilation of patients with KD in Paris region since April 2020, associated with the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ('Kawa-COVID-19'). A historical cohort of 'classical' KD served as a comparator. RESULTS: Sixteen patients were included (sex ratio=1, median age 10 years IQR (4·7 to 12.5)). SARS-CoV-2 was detected in 12 cases (69%), while a further three cases had documented recent contact with a quantitative PCR-positive individual (19%). Cardiac involvement included myocarditis in 44% (n=7). Factors prognostic for the development of severe disease (ie, requiring intensive care, n=7) were age over 5 years and ferritinaemia >1400 µg/L. Only five patients (31%) were successfully treated with a single intravenous immunoglobulin (IVIg) infusion, while 10 patients (62%) required a second line of treatment. The Kawa-COVID-19 cohort differed from a comparator group of 'classical' KD by older age at onset 10 vs 2 years (p<0.0001), lower platelet count (188 vs 383 G/L (p<0.0001)), a higher rate of myocarditis 7/16 vs 3/220 (p=0.0001) and resistance to first IVIg treatment 10/16 vs 45/220 (p=0.004). CONCLUSION: Kawa-COVID-19 likely represents a new systemic inflammatory syndrome temporally associated with SARS-CoV-2 infection in children. Further prospective international studies are necessary to confirm these findings and better understand the pathophysiology of Kawa-COVID-19. Trial registration number NCT02377245.

Kawasaki-like multisystem inflammatory syndrome in children during the covid-19 pandemic in Paris, France: prospective observational study.

OBJECTIVES: To describe the characteristics of children and adolescents affected by an outbreak of Kawasaki-like multisystem inflammatory syndrome and to evaluate a potential temporal association with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. DESIGN: Prospective observational study. SETTING: General paediatric department of a university hospital in Paris, France. PARTICIPANTS: 21 children and adolescents (aged ≤18 years) with features of Kawasaki disease who were admitted to hospital between 27 April and 11 May 2020 and followed up until discharge by 15 May 2020. MAIN OUTCOME MEASURES: The primary outcomes were clinical and biological data, imaging and echocardiographic findings, treatment, and outcomes. Nasopharyngeal swabs were prospectively tested for SARS-CoV-2 using reverse transcription-polymerase chain reaction (RT-PCR) and blood samples were tested for IgG antibodies to the virus. RESULTS: 21 children and adolescents (median age 7.9 (range 3.7-16.6) years) were admitted with features of Kawasaki disease over a 15 day period, with 12 (57%) of African ancestry. 12 (57%) presented with Kawasaki disease shock syndrome and 16 (76%) with myocarditis. 17 (81%) required intensive care support. All 21 patients had noticeable gastrointestinal symptoms during the early stage of illness and high levels of inflammatory markers. 19 (90%) had evidence of recent SARS-CoV-2 infection (positive RT-PCR result in 8/21, positive IgG antibody detection in 19/21). All 21 patients received intravenous immunoglobulin and 10 (48%) also received corticosteroids. The clinical outcome was favourable in all patients. Moderate coronary artery dilations were detected in 5 (24%) of the patients during hospital stay. By 15 May 2020, after 8 (5-17) days of hospital stay, all patients were discharged home. CONCLUSIONS: The ongoing outbreak of Kawasaki-like multisystem inflammatory syndrome among children and adolescents in the Paris area might be related to SARS-CoV-2. In this study an unusually high proportion of the affected children and adolescents had gastrointestinal symptoms, Kawasaki disease shock syndrome, and were of African ancestry.