Multisystem inflammatory syndrome in children and COVID-19 are distinct presentations of SARS-CoV-2

Plasma Protein Biomarkers Distinguish Multisystem Inflammatory Syndrome in Children From Other Pediatric Infectious and Inflammatory Diseases

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious hyperinflammatory complication following infection with severe acute respiratory syndrome coronavirus 2. The mechanisms underpinning the pathophysiology of MIS-C are poorly understood. Moreover, clinically distinguishing MIS-C from other childhood infectious and inflammatory conditions, such as Kawasaki disease or severe bacterial and viral infections, is challenging due to overlapping clinical and laboratory features. We aimed to determine a set of plasma protein biomarkers that could discriminate MIS-C from those other diseases.

METHODS

Seven candidate protein biomarkers for MIS-C were selected based on literature and from whole blood RNA sequencing data from patients with MIS-C and other diseases. Plasma concentrations of ARG1, CCL20, CD163, CORIN, CXCL9, PCSK9 and ADAMTS2 were quantified in MIS-C (n = 22), Kawasaki disease (n = 23), definite bacterial (n = 28) and viral (n = 27) disease and healthy controls (n = 8). Logistic regression models were used to determine the discriminatory ability of individual proteins and protein combinations to identify MIS-C and association with severity of illness.

RESULTS

Plasma levels of CD163, CXCL9 and PCSK9 were significantly elevated in MIS-C with a combined area under the receiver operating characteristic curve of 85.7% (95% confidence interval: 76.6%-94.8%) for discriminating MIS-C from other childhood diseases. Lower ARG1 and CORIN plasma levels were significantly associated with severe MIS-C cases requiring inotropes, pediatric intensive care unit admission or with shock.

CONCLUSION

Our findings demonstrate the feasibility of a host protein biomarker signature for MIS-C and may provide new insight into its pathophysiology.

Knowledge framework of intravenous immunoglobulin resistance in the field of Kawasaki disease: A bibliometric analysis (1997-2023)

BACKGROUND

Kawasaki disease (KD) is an autoimmune disease with cardiovascular disease as its main complication, mainly affecting children under 5 years old. KD treatment has made tremendous progress in recent years, but intravenous immunoglobulin (IVIG) resistance remains a major dilemma. Bibliometric analysis had not been used previously to summarize and analyze publications related to IVIG resistance in KD. This study aimed to provide an overview of the knowledge framework and research hotspots in this field through bibliometrics, and provide references for future basic and clinical research.

METHODS

Through bibliometric analysis of relevant literature published on the Web of Science Core Collection (WoSCC) database between 1997 and 2023, we investigated the cooccurrence and collaboration relationships among countries, institutions, journals, and authors and summarized key research topics and hotspots.

RESULTS

Following screening, a total of 364 publications were downloaded, comprising 328 articles and 36 reviews. The number of articles on IVIG resistance increased year on year and the top three most productive countries were China, Japan, and the United States. Frontiers in Pediatrics had the most published articles, and the Journal of Pediatrics had the most citations. IVIG resistance had been studied by 1889 authors, of whom Kuo Ho Chang had published the most papers.

CONCLUSION

Research in the field was focused on risk factors, therapy (atorvastatin, tumor necrosis factor-alpha inhibitors), pathogenesis (gene expression), and similar diseases (multisystem inflammatory syndrome in children, MIS-C). "Treatment," "risk factor," and "prediction" were important keywords, providing a valuable reference for scholars studying this field. We suggest that, in the future, more active international collaborations are carried out to study the pathogenesis of IVIG insensitivity, using high-throughput sequencing technology. We also recommend that machine learning techniques are applied to explore the predictive variables of IVIG resistance.

SARS-CoV-2 Infection in the Pediatric Oncology Population: The Definitive Comprehensive Report of the Infectious Diseases Working Group of AIEOP

OBJECTIVE

The objective of this study was to assess the clinical impact and outcome of the SARS-CoV-2 infection on children with cancer or those who received a hematopoietic stem cell transplantation.

METHODS

AIEOP (Italian Association of Pediatric Hematology and Oncology) performed a nationwide multicenter observational cohort study, including consecutive patients between April 2020 and November 2022.

RESULTS

Twenty-five Italian centers participated and 455 patients were enrolled. We reported a significant increasing trend of symptomatic cases over the years, while the number of nonmild infections remained stable. Early infection after oncologic diagnosis (<60 days) and severe neutropenia were identified as independent risk factors for developing moderate, severe, or critical infections. The percentage of patients who were asymptomatic and mildly symptomatic and who stopped chemotherapy reduced over the years of the pandemic. Nine patients died, but no death was attributed to SARS-CoV-2 infection.

CONCLUSIONS

SARS-CoV-2 infection presented a self-limiting benign course in the Italian pediatric oncohematology population during the pandemic, and its main consequence has been the discontinuation of cancer-directed therapies. The rate of patients who were asymptomatic and stopped chemotherapy reduced over the years, suggesting that the continuation of chemotherapy is a feasible option.

The impact of conflict on infectious disease: a systematic literature review

BACKGROUND

Conflict situations, armed or not, have been associated with emergence and transmission of infectious diseases. This review aims to identify the pathways through which infectious diseases emerge within conflict situations and to outline appropriate infectious disease preparedness and response strategies.

METHODS

A systematic review was performed representing published evidence from January 2000 to October 2023. Ovid Medline and Embase were utilised to obtain literature on infectious diseases in any conflict settings. The systematic review adhered to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis). No geographical restrictions were imposed.

FINDINGS

Our review identified 51 studies covering AIDS, Hepatitis B, Tuberculosis, Cholera, Coronavirus 2, Ebola, Poliomyelitis, Malaria, Leishmaniasis, Measles, Diphtheria, Dengue and Acute Bacterial Meningitis within conflict settings in Europe, Middle East, Asia, and Africa since October 2023. Key factors contributing to disease emergence and transmission in conflict situations included population displacement, destruction of vital infrastructure, reduction in functioning healthcare systems and healthcare personnel, disruption of disease control programmes (including reduced surveillance, diagnostic delays, and interrupted vaccinations), reduced access by healthcare providers to populations within areas of active conflict, increased population vulnerability due to limited access to healthcare services, and disruptions in the supply chain of safe water, food, and medication. To mitigate these infectious disease risks reported preparedness and response strategies included both disease-specific intervention strategies as well as broader concepts such as the education of conflict-affected populations through infectious disease awareness programmes, investing in and enabling health care in locations with displaced populations, intensifying immunisation campaigns, and ensuring political commitment and intersectoral collaborations between governments and international organisations.

CONCLUSION

Conflict plays a direct and indirect role in the transmission and propagation of infectious diseases. The findings from this review can assist decision-makers in the development of evidence-based preparedness and response strategies for the timely and effective containment of infectious disease outbreaks in conflict zones and amongst conflict-driven displaced populations.

FUNDING

European Centre for Disease Prevention and Control under specific contract No. 22 ECD.13,154 within Framework contract ECDC/2019/001 Lot 1B.

Treatment of multisystem inflammatory syndrome in children

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C), a relatively uncommon but severe pediatric complication, is associated with coronavirus disease 2019 (COVID-19). A variety of treatment approaches, including intravenous immunoglobulins (IVIGs), glucocorticoids (GCs) and biologic agents, such as anakinra and infliximab, have been described for the management of COVID-19-related MIS-C. Anticoagulant therapy is also important. However, a well-developed treatment system has not been established, and many issues remain controversial. Several recently published articles related to the treatment of MIS-C have been released. Hence, in this review, we identified relevant articles published recently and summarized the treatment of MIS-C more comprehensively and systematically.

DATA SOURCES

We reviewed the literature on the treatment of MIS-C through 20 September 2023. The PubMed/Medline, Web of Science, EMBASE, and Cochrane Library databases were searched with the combination of the terms "multisystem inflammatory syndrome", "MIS-C", "PIMS-TS", "therapy", "treatment", "drug", "IVIG", "GCs", "intravenous immunoglobulin", "corticosteroids", "biological agent", and "aspirin".

RESULTS

The severity of MIS-C varies, and different treatment schemes should be used according to the specific condition. Ongoing research and data collection are vital to better understand the pathophysiology and optimal management of MIS-C.

CONCLUSIONS

MIS-C is a disease involving multiple systems and has great heterogeneity. With the accumulation of additional experience, we have garnered fresh insights into its treatment strategies. However, there remains a critical need for greater standardization in treatment protocols, alongside the pressing necessity for more robust and meticulously conducted studies to deepen our understanding of these protocols. Supplementary file1 (MP4 208044 kb).

Electrocardiography in Children Hospitalized for COVID-19 and Not Suffering from Multisystem Inflammatory Syndrome in Children (MIS-C): An Observational Study

The risk of cardiac involvement with electrophysiological abnormalities during COVID-19 infection has been reported in adults but remains poorly studied in children. Our aim was to determine the frequency of cardiac involvement and the necessity of routine cardiac evaluation in children hospitalized for COVID-19. This observational study included 127 children, with a median (IQR) age of 2 (0.83-6.0) years, who were hospitalized for COVID-19 between 1 January 2021 and 31 August 2022, 62 (48.8%) of whom were males. Each patient underwent an ECG on admission and discharge as well as a laboratory assessment. A comparison between patients with COVID-19 and healthy controls showed significantly higher HR (p < 0.0001) and lower PR values (p = 0.02) in the first group. No arrhythmias or other electrocardiographic abnormalities were detected during hospitalization. The median levels of troponin, NT-proBNP, ferritin, and D-dimer were significantly higher in children aged <2 years, but they fell within the normal range for their age. Our results indicate that a detectable cardiac involvement is very rare in children hospitalized for COVID-19 and not suffering from Multisystem Inflammatory Syndrome in Children (MIS-C) and suggest that routine electrocardiographic assessment is not mandatory in these patients in the absence of cardiac symptoms/signs.

A genetically modulated Toll-like-receptor-tolerant phenotype in peripheral blood cells of children with multisystem inflammatory syndrome

Dysregulated innate immune responses contribute to multisystem inflammatory syndrome in children (MIS-C), characterized by gastrointestinal, mucocutaneous, and/or cardiovascular injury occurring weeks after SARS-CoV-2 exposure. To investigate innate immune functions in MIS-C, we stimulated ex vivo peripheral blood cells from MIS-C patients with agonists of Toll-like receptors (TLR), key innate immune response initiators. We found severely dampened cytokine responses and elevated gene expression of negative regulators of TLR signaling. Increased plasma levels of zonulin, a gut leakage marker, were also detected. These effects were also observed in children enrolled months after MIS-C recovery. Moreover, cells from MIS-C children carrying rare genetic variants of lysosomal trafficking regulator (LYST) were less refractory to TLR stimulation and exhibited lysosomal and mitochondrial abnormalities with altered energy metabolism. Our results strongly suggest that MIS-C hyperinflammation and/or excessive or prolonged stimulation with gut-originated TLR ligands drive immune cells to a lasting refractory state. TLR hyporesponsiveness is likely beneficial, as suggested by excess lymphopenia among rare LYST variant carriers. Our findings point to cellular mechanisms underlying TLR hyporesponsiveness; identify genetic determinants that may explain the MIS-C clinical spectrum; suggest potential associations between innate refractory states and long COVID; and highlight the need to monitor long-term consequences of MIS-C.

Elevation of IL-17 Cytokines Distinguishes Kawasaki Disease From Other Pediatric Inflammatory Disorders

OBJECTIVE

Kawasaki disease (KD) is a systemic vasculitis of young children that can lead to development of coronary artery aneurysms. We aimed to identify diagnostic markers to distinguish KD from other pediatric inflammatory diseases.

METHODS

We used the proximity extension assay to profile proinflammatory mediators in plasma samples from healthy pediatric controls (n = 30), febrile controls (n = 26), and patients with KD (n = 23), multisystem inflammatory syndrome in children (MIS-C; n = 25), macrophage activation syndrome (n = 13), systemic and nonsystemic juvenile idiopathic arthritis (n = 14 and n = 10, respectively), and juvenile dermatomyositis (n = 9). We validated the key findings using serum samples from additional patients with KD (n = 37) and febrile controls (n = 28).

RESULTS

High-fidelity proteomic profiling revealed distinct patterns of cytokine and chemokine expression across pediatric inflammatory diseases. Although KD and MIS-C exhibited many similarities, KD differed from MIS-C and other febrile diseases in that most patients exhibited elevation in one or more members of the interleukin-17 (IL-17) cytokine family, IL-17A, IL-17C, and IL-17F. IL-17A was particularly sensitive and specific, discriminating KD from febrile controls with an area under the receiver operator characteristic curve of 0.95 (95% confidence interval 0.89-1.00) in the derivation set and 0.91 (0.85-0.98) in the validation set. Elevation of all three IL-17-family cytokines was observed in over 50% of KD patients, including 19 of 20 with coronary artery aneurysms, but was rare in all other comparator groups.

CONCLUSION

Elevation of IL-17 family cytokines is a hallmark of KD and may help distinguish KD from its clinical mimics.

Emergency myelopoiesis distinguishes multisystem inflammatory syndrome in children from pediatric severe COVID-19

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a hyperinflammatory condition caused by recent SARS-CoV-2 infection, but the underlying immunological mechanisms driving this distinct syndrome are unknown.

METHODS

We utilized high dimensional flow cytometry, cell-free (cf) DNA, and cytokine and chemokine profiling to identify mechanisms of critical illness distinguishing MIS-C from severe acute COVID-19 (SAC).

RESULTS

Compared to SAC, MIS-C patients demonstrated profound innate immune cell death and features of emergency myelopoiesis (EM), an understudied phenomenon observed in severe inflammation. EM signatures were characterized by fewer mature myeloid cells in the periphery and decreased expression of HLA-DR and CD86 on antigen presenting cells. IL-27, a cytokine known to drive hematopoietic stem cells towards EM, was increased in MIS-C, and correlated with immature cell signatures in MIS-C. Upon recovery, EM signatures decreased, and IL-27 plasma levels returned to normal levels. Despite profound lymphopenia, we report a lack of cfDNA released by adaptive immune cells and increased CCR7 expression on T cells indicative of egress out of peripheral blood.

CONCLUSIONS

Immune cell signatures of EM combined with elevated innate immune cell-derived cfDNA levels distinguish MIS-C from SAC in children and provide mechanistic insight into dysregulated immunity contributing towards MIS-C, offering potential diagnostic and therapeutic targets.

Metabolomic and Immunologic Discriminators of MIS-C at Emergency Room Presentation

Multisystem Inflammatory Syndrome in Childhood (MIS-C) follows SARS-CoV-2 infection and frequently leads to intensive care unit admission. The inability to rapidly discriminate MIS-C from similar febrile illnesses delays treatment and leads to misdiagnosis. To identify diagnostic discriminators at the time of emergency department presentation, we enrolled 104 children who met MIS-C screening criteria, 14 of whom were eventually diagnosed with MIS-C. Before treatment, we collected breath samples for volatiles and peripheral blood for measurement of plasma proteins and immune cell features. Clinical and laboratory features were used as inputs for a machine learning model to determine diagnostic importance. MIS-C was associated with significant changes in breath volatile organic compound (VOC) composition as well as increased plasma levels of secretory phospholipase A2 (PLA2G2A) and lipopolysaccharide binding protein (LBP). In an integrated model of all analytes, the proportion of TCRVβ21.3+ non-naive CD4 T cells expressing Ki-67 had a high sensitivity and specificity for MIS-C, with diagnostic accuracy further enhanced by low sodium and high PLA2G2A. We anticipate that accurate diagnosis will become increasingly difficult as MIS-C becomes less common. Clinical validation and application of this diagnostic model may improve outcomes in children presenting with multisystem febrile illnesses.

[Multisystem inflammatory syndrome in children in the context of coronavirus disease 2019 pandemic]

Multisystem inflammatory syndrome in children (MIS-C) is a complex syndrome characterized by multi-organ involvement that has emerged in the context of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak. The clinical presentation of MIS-C is similar to Kawasaki disease but predominantly presents with fever and gastrointestinal symptoms, and severe cases can involve toxic shock and cardiac dysfunction. Epidemiological findings indicate that the majority of MIS-C patients test positive for SARS-CoV-2 antibodies. The pathogenesis and pathophysiology of MIS-C remain unclear, though immune dysregulation following SARS-CoV-2 infection is considered a major contributing factor. Current treatment approaches for MIS-C primarily involve intravenous immunoglobulin therapy and symptomatic supportive care. This review article provides a comprehensive overview of the definition, epidemiology, pathogenesis, clinical presentation, diagnosis, treatment, and prognosis of MIS-C.

Multisystem Inflammatory Syndrome in Children during the COVID-19 Pandemic: A Review of Clinical Manifestations, Cardiac Complications and Medical Management

The SARS-CoV-2 pandemic has led to widespread research on associated clinical syndromes. While pediatric patients were initially deemed as a low-risk population for severe COVID-related disease, an increasing number of case reports have revealed a rare but potentially life-threatening syndrome, multisystem inflammatory syndrome in children (MIS-C). MIS-C is hypothesized to be due to hyperactivation of the immune system via a cytokine storm which leads to end-organ damage via endothelial dysfunction and changes in vascular permeability. Laboratory studies have displayed increased inflammatory markers such as C-reactive protein, erythrocyte sedimentation rate, D-dimer, tumor necrosis factor-alpha, and various interleukins. Studies have reported a wide range of clinical manifestations, including but not limited to fever, hypotension, shock, rash, coagulopathy, and gastrointestinal distress. Cardiac imaging and screening tests have revealed several complications, such as left ventricular failure, arrhythmias, and pericardial effusions. Medical management of MIS-C and cardiac sequelae have included supportive care, intravenous immunoglobulins, and corticosteroids, as well as immunomodulators, monoclonal antibodies, aspirin, and therapeutic anticoagulation, which have prevented serious outcomes in the majority of pediatric patients. Future multicenter and large-scale research is required for precise risk-stratification of MIS-C as well as long-term monitoring of sequelae. In this review, we aim to (1) outline the laboratory findings and clinical manifestations of MIS-C, and (2) describe cardiac complications and medical management of MIS-C.

Type I interferon signature and cycling lymphocytes in macrophage activation syndrome

BACKGROUNDMacrophage activation syndrome (MAS) is a life-threatening complication of Still's disease (SD) characterized by overt immune cell activation and cytokine storm. We aimed to further understand the immunologic landscape of SD and MAS.METHODWe profiled PBMCs from people in a healthy control group and patients with SD with or without MAS using bulk RNA-Seq and single-cell RNA-Seq (scRNA-Seq). We validated and expanded the findings by mass cytometry, flow cytometry, and in vitro studies.RESULTSBulk RNA-Seq of PBMCs from patients with SD-associated MAS revealed strong expression of genes associated with type I interferon (IFN-I) signaling and cell proliferation, in addition to the expected IFN-γ signal, compared with people in the healthy control group and patients with SD without MAS. scRNA-Seq analysis of more than 65,000 total PBMCs confirmed IFN-I and IFN-γ signatures and localized the cell proliferation signature to cycling CD38+HLA-DR+ cells within CD4+ T cell, CD8+ T cell, and NK cell populations. CD38+HLA-DR+ lymphocytes exhibited prominent IFN-γ production, glycolysis, and mTOR signaling. Cell-cell interaction modeling suggested a network linking CD38+HLA-DR+ lymphocytes with monocytes through IFN-γ signaling. Notably, the expansion of CD38+HLA-DR+ lymphocytes in MAS was greater than in other systemic inflammatory conditions in children. In vitro stimulation of PBMCs demonstrated that IFN-I and IL-15 - both elevated in MAS patients - synergistically augmented the generation of CD38+HLA-DR+ lymphocytes, while Janus kinase inhibition mitigated this response.CONCLUSIONMAS associated with SD is characterized by overproduction of IFN-I, which may act in synergy with IL-15 to generate CD38+HLA-DR+ cycling lymphocytes that produce IFN-γ.

B cell phenotype and serum levels of interferons, BAFF, and APRIL in multisystem inflammatory syndrome in children associated with COVID-19 (MIS-C)

BACKGROUND

Multisystem inflammatory syndrome in children associated with COVID-19 (MIS-C) is a late complication of pediatric COVID-19, which follows weeks after the original SARS-CoV-2 infection, regardless of its severity. It is characterized by hyperinflammation, neutrophilia, lymphopenia, and activation of T cells with elevated IFN-γ. Observing the production of autoantibodies and parallels with systemic autoimmune disorders, such as systemic lupus erythematodes (SLE), we explored B cell phenotype and serum levels of type I, II, and III interferons, as well as the cytokines BAFF and APRIL in a cohort of MIS-C patients and healthy children after COVID-19.

RESULTS

We documented a significant elevation of IFN-γ, but not IFN-α and IFN-λ in MIS-C patients. BAFF was elevated in MIS-C patient sera and accompanied by decreased BAFFR expression on all B cell subtypes. The proportion of plasmablasts was significantly lower in patients compared to healthy post-COVID children. We noted the pre-IVIG presence of ENA Ro60 autoantibodies in 4/35 tested MIS-C patients.

CONCLUSIONS

Our work shows the involvement of humoral immunity in MIS-C and hints at parallels with the pathophysiology of SLE, with autoreactive B cells driven towards autoantibody production by elevated BAFF.

Case report: Thrombotic microangiopathy in pediatric multisystem inflammatory syndrome associated with COVID-19: a case series

Introduction

This report provides insight into three distinct pediatric cases exhibiting a nexus between multisystem inflammatory syndrome in children (MIS-C) and thrombotic microangiopathy (TMA) triggered by COVID-19. The aim is to underscore the range of clinical presentations and the essentiality of early interventions.

Case presentations

This report presents three cases aged 10 months, 7 years, and 3 years with persistent fever, diarrhea, nausea, and vomiting. The first case, a 10-month-old girl, demonstrated acute kidney injury (AKI) and microangiopathic hemolytic anemia (MAHA) following a COVID-19 infection. Despite initial negative SARS-CoV-2 RT-PCR results, her condition escalated rapidly, presenting increased levels of LDH (peaking at 4,200 U/L) and requiring renal replacement therapy (RRT) to manage deteriorating renal function. Interventions with eculizumab and anakinra led to marked improvements, with a stable follow-up of 13 months post-hospitalization. The second case involved a 7-year-old girl who developed symptoms of MIS-C, hemolytic uremic syndrome (HUS), and posterior reversible encephalopathy syndrome (PRES) post-exposure to COVID-19, evidenced by heightened LDH levels (3,522 U/L at peak). After a precarious period of deteriorating kidney function and exacerbated hypertension, she responded positively to treatments, inclusive of IVIG, steroid therapies, and eculizumab, with a favorable 6-month follow-up showcasing stable laboratory results. The third case discusses a 3-year-old boy, without any medical history, manifesting HUS symptoms and COVID-19 infection. He exhibited increased LDH levels (peaking at 3,946 U/L) alongside elevated creatinine, marking renal impairment. He responded well to hemodialysis, IVIG, and steroid therapy, showcasing substantial recovery by the 19th day of hospitalization, which marked his discharge with a tapering steroid regimen.

Conclusion

This case series underscores that MIS-C-associated TMA is a significant complication in pediatric COVID-19. Our findings illuminate the potential for treatment success but simultaneously emphasize the need for a more comprehensive understanding of the underlying pathophysiology.

Acute kidney injury in critically ill children with COVID-19 and MIS-C

BACKGROUND

This study's objective was to investigate the incidence of acute kidney injury (AKI) in children with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and multisystem inflammatory syndrome (MIS-C) and to report our clinical experience.

METHODS

Acute COVID-19 and MIS-C-diagnosed patients observed in two pediatric intensive care units (PICUs) between 2019 and 2021 were examined for AKI and retrospectively compared to children with AKI.

RESULTS

The study comprised 163 children, of whom 98 (60.1%) were diagnosed with acute COVID-19 and 65 (39.9%) with MIS-C. AKI was observed in 40 (40.8%) of the acute COVID-19 patients and 18 (27.7%) of the MIS-C patients. Low calcium level and hypotension were linked with AKI at initial presentation (OR: 0.56, 95% CI: 0.369-0.560, p = 0.006 and OR: 3.64, 95% CI: 1.885-7.152, p = 0.001, respectively). A history of nephrotoxic medication usage played an essential role in the development of AKI in patients who acquired AKI after hospitalization (p = 0.001, odds ratio: 9.32, confidence interval: 3.106-27.973). In clinical practice, individuals with respiratory distress and cough had a high chance of having AKI (OR: 4.47, 95% confidence interval: 2.25-8,892 and OR: 3.48, 95% confidence interval: 1.76-6.88). AKI patients had a greater demand for respiratory assistance and a longer period of stay in the PICU.

CONCLUSIONS

AKI in the COVID-19 and MIS-C patient groups is related with increased mortality and extended hospitalization, according to the findings. These statistics imply that identifying and preventing risk factors is necessary. A higher resolution version of the Graphical abstract is available as Supplementary information.

Clinical Presentation and Management of Multisystem Inflammatory Syndrome in Children With COVID-19: A Systematic Review

Multisystem inflammatory syndrome in children (MIS-C) is a relatively new syndrome associated with coronavirus disease 2019 (COVID-19) that is characterized by a severe clinical course compared to pediatric COVID-19. This review aimed to compile the available evidence on the clinical presentation and management of MIS-C in children with COVID-19. During this systematic review, a comprehensive search was performed in the following databases: PubMed, Embase, Medline, Google Scholar, Cochrane, and Scopus, using predetermined search terms, such as Medical Subject Headings (MeSH) and keywords to find relevant studies on the MIS-C. Relevant data were extracted, and the quality of the studies was evaluated using suitable methods. The collected findings were synthesized and discussed in the study. The World Health Organization's (WHO) definition of MIS-C was the most favored due to its precision and inclusiveness. MIS-C primarily affected children aged 6-12 years, with male predominance. MIS-C involves a range of systems, including gastrointestinal, cardiovascular, hematologic, mucocutaneous, and respiratory. Radiographic findings revealed cardiovascular abnormalities, solid visceral organ involvement, and bowel abnormalities, reflecting a systemic inflammatory process. Laboratory investigations unveiled elevated inflammatory markers, neutrophil activation, release of extracellular traps in vessels, elevated procalcitonin, hyponatremia, hypoalbuminemia, low hemoglobin, and thrombocytopenia. The inflammatory markers and autoantibody profiles are essential in differentiating MIS-C from COVID-19. The preferred treatment primarily involves immunomodulatory therapies like intravenous immunoglobulin (IVIG), glucocorticoids, and interleukin-6 or 1RA inhibitors or a combination of those. In severe cases, extracorporeal membrane oxygenation (ECMO) and mechanical ventilation are necessary, leading to reduced mortality and quick recovery. This review found that the average hospital stay was seven days, and most discharged children fully recovered within seven days. MIS-C is a life-threatening post-COVID-19 condition and involves multiple systems due to systemic inflammation, with elevated inflammation markers. Recognition of multisystem involvement is crucial, and prompt identification and multidisciplinary treatment are vital for optimal outcomes.

Innate immune dysregulation in multisystem inflammatory syndrome in children (MIS-C)

MIS-C is a systemic inflammation disorder with poorly characterised immunopathological mechanisms. We compared changes in the systemic immune response in children with MIS-C (n = 12, 5-13 years) to healthy controls (n = 14, 5-15 years). Analysis was done in whole blood treated with LPS. Expression of CD11b and Toll-like receptor-4 (TLR4) in neutrophils and monocytes were analysed by flow cytometry. Serum cytokines (IL-1β, IL-2, IL-6, IL-8, IL-10, IL-Ira, TNF-α, TNF-β, IFN-Υ, VEGF, EPO and GM-CSF) and mRNA levels of inflammasome molecules (NLRP3, ASC and IL-1β) were evaluated. Subpopulations of lymphocytes (CD3+, CD19+, CD56+, CD4+, CD8+, TCR Vδ1+, TCR Vδ2+) were assessed at basal levels. Absolute counts of neutrophils and NLR were high in children with MIS-C while absolute counts of lymphocytes were low. Children with MIS-C had increased levels of IL-6, IL-10, TNF-β and VEGF serum cytokines at the basal level, and significantly increased TNF-β post-LPS, compared to controls. IL-1RA and EPO decreased at baseline and post-LPS in MIS-C patients compared to controls. The percentage of CD3+ cells, NK cells and Vδ1 was lower while B cells were higher in children with MIS-C than in controls. Dysregulated immune response in children with MIS-C was evident and may be amenable to immunomodulation.

Pediatric endocrinopathies related to COVID-19: an update

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the seventh coronavirus to be linked to human disease. The SARS-CoV-2 virus may have several pathophysiologic interactions with endocrine systems, resulting in disruptions in glucose metabolism, hypothalamus and pituitary function, adrenal function, and mineral metabolism. An increasing amount of evidence demonstrates both the influence of underlying endocrine abnormalities on the outcome of COVID-19 and the effect of the SARS-CoV-2 virus on endocrine systems. However, a systematic examination of the link to pediatric endocrine diseases has been missing.

DATA SOURCES

The purpose of this review is to discuss the impact of SARS-CoV-2 infection on endocrine systems and to summarize the available knowledge on COVID-19 consequences in children with underlying endocrine abnormalities. For this purpose, a literature search was conducted in EMBASE, and data that were discussed about the effects of COVID-19 on endocrine systems were used in the current study.

RESULTS

Treatment suggestions were provided for endocrinopathies associated with SARS-CoV-2 infection.

CONCLUSIONS

With the global outbreak of COVID-19, it is critical for pediatric endocrinologists to understand how SARS-CoV-2 interacts with the endocrine system and the therapeutic concerns for children with underlying problems who develop COVID-19. While children and adults share certain risk factors for SARS-CoV-2 infection sequelae, it is becoming obvious that pediatric responses are different and that adult study results cannot be generalized. While pediatric research gives some insight, it also shows the need for more study in this area.

SARS-CoV-2 infection and recovery in children: Distinct T cell responses in MIS-C compared to COVID-19

SARS-CoV-2 infection for most children results in mild or minimal symptoms, though in rare cases severe disease can develop, including a multisystem inflammatory syndrome (MIS-C) with myocarditis. Here, we present longitudinal profiling of immune responses during acute disease and following recovery in children who developed MIS-C, relative to children who experienced more typical symptoms of COVID-19. T cells in acute MIS-C exhibited transient signatures of activation, inflammation, and tissue residency which correlated with cardiac disease severity, while T cells in acute COVID-19 upregulated markers of follicular helper T cells for promoting antibody production. The resultant memory immune response in recovery showed increased frequencies of virus-specific memory T cells with pro-inflammatory functions in children with prior MIS-C compared to COVID-19 while both cohorts generated comparable antibody responses. Together our results reveal distinct effector and memory T cell responses in pediatric SARS-CoV-2 infection delineated by clinical syndrome, and a potential role for tissue-derived T cells in the immune pathology of systemic disease.

Clinical outcomes and safety of anakinra in the treatment of multisystem inflammatory syndrome in children: a single center observational study

BACKGROUND AND OBJECTIVE

Evidence for the treatment of multisystem inflammatory syndrome in children (MIS-C) is lacking. Anakinra, which targets IL-1-mediated inflammation, is reserved for refractory cases of MIS-C; however, its use in the treatment of MIS-C is not clearly established.

PATIENTS AND METHODS

To examine a role for anakinra in MIS-C, we performed a single center observational cohort study of all MIS-C patients diagnosed at our children's hospital from May 15 to November 15, 2020. Demographics, clinical features, diagnostic testing, and cardiac function parameters were compared between MIS-C patients treated with intravenous immunoglobulin (IVIG) monotherapy and IVIG with anakinra (IVIG + anakinra).

RESULTS

Among 46 patients with confirmed MIS-C, 32 (70%) were in the IVIG + anakinra group, of which 9 (28%) were also given corticosteroids (CS). No patients were treated with anakinra alone. MIS-C patients in the IVIG + anakinra group were enriched in a CV shock phenotype (p = 0.02), and those with CV shock were treated with higher doses of anakinra for a longer duration. Furthermore, MIS-C patients in the IVIG + anakinra group exhibited improvements in fever and cardiac function with or without CS. No significant adverse events were observed, and no differences in IL-1β levels were found among MIS-C patients in the IVIG + anakinra group.

CONCLUSIONS

Anakinra treatment, which was co-administered with IVIG primarily in patients with severe MIS-C, was associated with improvements in fever and cardiac function, and demonstrated a favorable side-effect profile. These findings suggest a role for adjunctive anakinra in the treatment of severe MIS-C.

Endocrine manifestations of COVID-19 in children: A scoping review

In this review, we explore associations between SARS CoV-2 infection and the endocrine system and metabolism in children and adolescents. PubMed, Scopus and Google scholar databases were searched to identify published data on endocrine manifestations of COVID-19 in children up to 31 March 2023, including diabetes, obesity, puberty, thyroid disorders, adrenal disorders and pituitary disorders. Data on changes in disease pattern/ incidence, disease control, and other effects due to the COVID-19 pandemic, as well as effects of pre-existing endocrine conditions on severity of COVID-19 infection are presented, and practice points and research needs provided under each section.

Evaluation of tumour necrosis factor alpha-stimulated gene-6 and fibroblast growth factor-2 levels in patients diagnosed with multi-system inflammatory syndrome in children

Investigations are still ongoing about the pathophysiology of multi-system inflammatory syndrome in children, which can progress with serious morbidity and mortality after COVID-19 infection. In this study, we aimed to investigate whether fibroblast growth factor-2 and tumour necrosis factor alpha-stimulated gene-6 levels play a role in the diagnosis of the disease and on cardiac involvement. Twenty-three patients (11 girls, 12 boys) and 26 healthy controls (10 girls, 16 boys) were included in the study. The mean age of the patient and control group was 8.45 ± 2.43 and 10.73 ± 4.27 years, respectively. There was no difference between the fibroblast growth factor-2 and tumour necrosis factor alpha-stimulated gene-6 levels of the patient and control groups. When the patients with myocardial involvement in the patient group were compared with the patients without myocardial involvement in terms of fibroblast growth factor-2 and tumour necrosis factor alpha-stimulated gene-6 levels, no difference was found between these groups. The correlation of fibroblast growth factor-2 and tumour necrosis factor alpha-stimulated gene-6 levels with other laboratory parameters was investigated in the patient group. Fibroblast growth factor-2 was moderately inversely correlated with white blood cell count (r = -0.541, p = 0.008), absolute neutrophil count (r = -0.502, p = 0.015) and C-reactive protein (r = -0.528, p = 0.010). Fibroblast growth factor-2 was strongly inversely correlated with erythrocyte sedimentation rate (r = -0.694, p =<0.001). Our data show that fibroblast growth factor-2 and tumour necrosis factor alpha stimulated gene-6 do not provide sufficient information about diagnosis and cardiac involvement in multi-system inflammatory syndrome in children.

Pediatric multisystem inflammatory syndrome associated with COVID-19: Insights in pathogenesis and clinical management

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been a major challenge to be faced in recent years. While adults suffered the highest morbidity and mortality rates of coronavirus disease 2019, children were thought to be exclusively asymptomatic or to present with mild conditions. However, around April 2020, there was an outbreak of a new clinical syndrome related to SARS-CoV-2 in children - multisystemic inflammatory syndrome in children (MIS-C) - which comprises a severe and uncon-trolled hyperinflammatory response with multiorgan involvement. The Centers for Disease Control and Prevention considers a suspected case of MIS-C an individual aged < 21 years presenting with fever, high inflammatory markers levels, and evidence of clinically severe illness, with multisystem (> 2) organ involvement, no alternative plausible diagnoses, and positive for recent SARS-CoV-2 infection. Despite its severity, there are no definitive disease management guidelines for this condition. Conversely, the complex pathogenesis of MIS-C is still not completely understood, although it seems to rely upon immune dysregulation. Hence, in this study, we aim to bring together current evidence regarding the pathogenic mechanisms of MIS-C, clinical picture and management, in order to provide insights for clinical practice and implications for future research directions.

Cytokine Storm Syndromes in Pediatric Patients

Cytokine storm syndromes (CSS) represent a diverse group of disorders characterized by severe overactivation of the immune system. In the majority of patients, CSS arise from a combination of host factors, including genetic risk and predisposing conditions, and acute triggers such as infections. CSS present differently in adults than in children, who are more likely to present with monogenic forms of these disorders. Individual CSS are rare, but in aggregate represent an important cause of severe illness in both children and adults. We present 3 rare, illustrative cases of CSS in pediatric patients that describe the spectrum of CSS.

Emerging Insights Into the Pathophysiology of Multisystem Inflammatory Syndrome Associated With COVID-19 in Children

Multisystem inflammatory syndrome in children (MIS-C) has emerged as a rare delayed hyperinflammatory response to SARS-CoV-2 infection and causes severe morbidity in the pediatric age group. Although MIS-C shares many clinical similarities to Kawasaki disease (KD), important differences in epidemiologic, clinical, immunologic, and potentially genetic factors exist and suggest potential differences in pathophysiology and points to be explored and explained. Epidemiologic features include male predominance, peak age of 6 to12 years, and specific racial or ethnicity predilections. MIS-C is characterized by fever, prominent gastrointestinal symptoms, mucocutaneous manifestations, respiratory symptoms, and neurologic complaints, and patients often present with shock. Cardiac complications are frequent and include ventricular dysfunction, valvular regurgitation, pericardial effusion, coronary artery dilation and aneurysms, conduction abnormalities, and arrhythmias. Emerging evidence regarding potential immunologic mechanisms suggest that an exaggerated T-cell response to a superantigen on the SARS-CoV-2 spike glycoprotein-as well as the formation of autoantibodies against cardiovascular, gastrointestinal, and endothelial antigens-are major contributors to the inflammatory milieu of MIS-C. Further studies are needed to determine both shared and distinct immunologic pathway(s) that underlie the pathogenesis of MIS-C vs both acute SARS-CoV-2 infection and KD. There is evidence to suggest that the rare risk of more benign mRNA vaccine-associated myopericarditis is outweighed by a reduced risk of more severe MIS-C. In the current review, we synthesize the published literature to describe associated factors and potential mechanisms regarding an increased risk of MIS-C and cardiac complications, provide insights into the underlying immunologic pathophysiology, and define similarities and differences with KD.

Multi-Inflammatory Syndrome in Children (MIS-C) in 2023: Is It Time to Forget about It?

Multisystem inflammatory syndrome in children (MIS-C) is defined as a clinically serious condition requiring hospitalization involving fever, multi-system organ dysfunction, and an increase in inflammatory biomarkers. The syndrome was originally described as a post-infectious complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which usually causes COVID-19. During the COVID-19 pandemic, not only did the virus undergo mutations but vaccines against SARS-CoV-2 were also developed. Both these conditions led to a decrease in the incidence of MIS-C. This narrative review summarizes the recent updates for MIS-C, particularly regarding the change in incidence, the link between the SARS-CoV-2 vaccine and MIS-C, and new updates of MIS-C treatments.

Focal and generalized onset seizures in children post-COVID (Omicron) recovery: 3 clinical case reports

Description of three cases of 4-7-year-old male children presenting with a seizure without a prior history of epilepsy, 2-4 weeks after recovering from COVID-19. All three children were admitted to the pediatric department at Laniado Hospital in Netanya, Israel, and presented with seizures without fever. We found common characteristics among the children that can imply a predisposition for neurological complications of Covid-19.

Defining the pediatric response to SARS-CoV-2 variants

The global population has been severely affected by the coronavirus disease 2019 (COVID-19) pandemic, however, with older age identified as a risk factor, children have been underprioritized. This article discusses the factors contributing to the less severe response observed in children following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including, differing viral entry receptor expression and immune responses. It also discusses how emerging and future variants could present a higher risk to children, including those with underlying comorbidities, in developing severe disease. Furthermore, this perspective discusses the differential inflammatory markers between critical and non-critical cases, as well as discussing the types of variants that may be more pathogenic to children. Importantly, this article highlights where more research is urgently required, in order to protect the most vulnerable of our children.

Multisystemic Inflammatory Syndrome in Children and Kawasaki Disease: Parallels in Pathogenesis and Treatment

PURPOSE OF REVIEW

Since it first appeared, multisystem inflammatory syndrome in children (MIS-C) associated with coronavirus disease 2019 (COVID-19) has been compared to Kawasaki disease (KD). Although there were early parallels between MIS-C and KD, key differences emerged over time. Here, we aim to compare the pathogenesis, clinical presentation, treatment, and outcomes of MIS-C and KD.

RECENT FINDINGS

In this article, we review and compare MIS-C and KD, highlighting differentiating features. We discuss the epidemiological and immunological factors along with clinical and laboratory features which discern MIS-C from KD. We also compare treatment and our understanding of long-term outcomes. Though parallels exist between MIS-C and KD, distinguishing the two is important for clinical management of patients, counseling about natural history, and determining long-term monitoring. While both MIS-C and KD are characterized by profound inflammation and inflammatory vasculopathy, further study is needed to determine whether they are distinct immunopathogenic disorders.

Complement and COVID-19: Three years on, what we know, what we don't know, and what we ought to know

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus was identified in China in 2019 as the causative agent of COVID-19, and quickly spread throughout the world, causing over 7 million deaths, of which 2 million occurred prior to the introduction of the first vaccine. In the following discussion, while recognising that complement is just one of many players in COVID-19, we focus on the relationship between complement and COVID-19 disease, with limited digression into directly-related areas such as the relationship between complement, kinin release, and coagulation. Prior to the 2019 COVID-19 outbreak, an important role for complement in coronavirus diseases had been established. Subsequently, multiple investigations of patients with COVID-19 confirmed that complement dysregulation is likely to be a major driver of disease pathology, in some, if not all, patients. These data fuelled evaluation of many complement-directed therapeutic agents in small patient cohorts, with claims of significant beneficial effect. As yet, these early results have not been reflected in larger clinical trials, posing questions such as who to treat, appropriate time to treat, duration of treatment, and optimal target for treatment. While significant control of the pandemic has been achieved through a global scientific and medical effort to comprehend the etiology of the disease, through extensive SARS-CoV-2 testing and quarantine measures, through vaccine development, and through improved therapy, possibly aided by attenuation of the dominant strains, it is not yet over. In this review, we summarise complement-relevant literature, emphasise its main conclusions, and formulate a hypothesis for complement involvement in COVID-19. Based on this we make suggestions as to how any future outbreak might be better managed in order to minimise impact on patients.

Thromboprophylaxis for Coagulopathy Related to COVID-19 in Pediatrics: A Narrative Review

In addition to harming the respiratory system, COVID-19 can affect multiple organs. Children may develop a specific complication of COVID-19 called multisystem inflammatory syndrome in children (MIS-C) which could influence the vascular system of children and cause multiple coagulopathies in the body. Information on the use of thromboprophylaxis in this condition was collected via the review of various articles. In general, different factors in immune system responses can trigger the initiation of thrombotic events. Studies have shown that starting anticoagulant prophylaxis, which contributes to decreased thrombotic events, is dependent on the patient's condition and D-dimer levels. However, further studies on pediatric populations are needed to establish the role of anticoagulants in children with this condition.

Saliva microRNA Profile in Children with and without Severe SARS-CoV-2 Infection

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) may impair immune modulating host microRNAs, causing severe disease. Our objectives were to determine the salivary miRNA profile in children with SARS-CoV-2 infection at presentation and compare the expression in those with and without severe outcomes. Children <18 years with SARS-CoV-2 infection evaluated at two hospitals between March 2021 and February 2022 were prospectively enrolled. Severe outcomes included respiratory failure, shock or death. Saliva microRNAs were quantified with RNA sequencing. Data on 197 infected children (severe = 45) were analyzed. Of the known human miRNAs, 1606 (60%) were measured and compared across saliva samples. There were 43 miRNAs with ≥2-fold difference between severe and non-severe cases (adjusted p-value < 0.05). The majority (31/43) were downregulated in severe cases. The largest between-group differences involved miR-4495, miR-296-5p, miR-548ao-3p and miR-1273c. These microRNAs displayed enrichment for 32 gene ontology pathways including viral processing and transforming growth factor beta and Fc-gamma receptor signaling. In conclusion, salivary miRNA levels are perturbed in children with severe COVID-19, with the majority of miRNAs being down regulated. Further studies are required to validate and determine the utility of salivary miRNAs as biomarkers of severe COVID-19.

Covid-19 infection in children and adolescents and its association with type 1 diabetes mellitus (T1d) presentation and management

Children seem to be affected by the new SARS-CoV-2 virus less severely than adults, with better prognosis and low mortality. Serious complications of COVID-19 infection in children include multisystem inflammatory response syndrome in COVID-19 infection (MIS-C), myo-or pericarditis and, less frequently, long COVID syndrome. On the other hand, adults with type 1 (T1D) or type 2 diabetes (T2D) are among the most vulnerable groups affected by COVID-19, with increased morbidity and mortality. Moreover, an association of SARS-CoV-2 with diabetes has been observed, possibly affecting the frequency and severity of the first clinical presentation of T1D or T2D, as well as the development of acute diabetes after COVID-19 infection. The present review summarizes the current data on the incidence of T1D among children and adolescents during the COVID-19 pandemic, as well as its severity. Moreover, it reports on the types of newly diagnosed diabetes after COVID infection and the possible pathogenetic mechanisms. Additionally, this study presents current data on the effect of SARS-CoV-2 on diabetes control in patients with known T1D and on the severity of clinical presentation of COVID infection in these patients. Finally, this review discusses the necessity of immunization against COVID 19 in children and adolescents with T1D.

Pediatric Inflammatory Multisystem Syndrome Temporally Associated With SARS-CoV-2 (PIMS-TS) and Serous Effusions in a Child With Severe Hypoalbuminemia: A Case Report

In April 2020, Pediatric Inflammatory Multisystem Syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 or SARS‑CoV‑2 (PIMS-TS) was described for the first time in children. Since then, many countries have registered hundreds of cases with clinical similarities to Kawasaki disease. We report the case of a five-year-old boy diagnosed with PIMS-TS who presented myocarditis with serous effusions (pleurisy, ascites, pericarditis) due to severe hypoalbuminemia. This case sheds light on the importance of hypoalbuminemia in evaluating the severity of PIMS-TS and preventing its complications. The patient was successfully treated with intravenous immunoglobulins and oral prednisone.

Tocilizumab for Severe COVID-19 Infection and Multisystem Inflammatory Syndrome in Adults and Children

Coronavirus disease 2019 (COVID-19) rapidly emerged as a global pandemic, placing imminent stress and burden on healthcare resources and workers worldwide. Many patients who present with a severe COVID-19 infection are at high risk of developing severe acute respiratory distress syndrome (ARDS), leading to a vast number of patients requiring mechanical ventilation and a high mortality rate. Similar to Middle East respiratory syndrome, COVID-19 demonstrates an initial viral replication phase that manifests as a variety of symptoms typically flu-like in nature, followed by a profound inflammatory response leading to rapid production of cytokines and uncontrolled inflammation. There have also been many cases of COVID-19 in pediatric patients presenting with elevated inflammatory markers and multisystem involvement labeled as a multisystem inflammatory syndrome (MIS-C) by the world health organization (WHO). The recent treatment of systemic inflammatory response to COVID-19 targets the secondary phase involving cytokine release syndrome. The detrimental effects of IL-6 can be profound and elevated levels are associated with a higher mortality rate and mechanical ventilation. Tocilizumab is an IL-6 inhibitor most widely investigated to target cytokine storm syndrome. Since June 2021, the FDA enacted an emergency use authorization for tocilizumab in the treatment of COVID-19. Several clinical trials have investigated tocilizumab combined with corticosteroids for treating severe ARDS associated with COVID-19. An increasing amount of evidence suggests that targeting the cytokine storm syndrome related to COVID-19 can lead to improved outcomes, especially in those patients requiring mechanical ventilation and with a critical illness. Additional studies are warranted to further look at the positive effects of tocilizumab in the COVID-19 population while additionally defining possible adverse effects.

Immunology of Multisystem Inflammatory Syndrome after COVID-19 in Children: A Review of the Current Evidence

Immune responses following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in children are still under investigation. Even though coronavirus disease 2019 (COVID-19) is usually mild in the pediatric population, some children exhibit severe clinical manifestations, require hospitalization, or develop the most severe condition: a multisystem inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2 infection. The activated innate, humoral and T-cell-mediated immunological pathways that lead certain pediatric populations to present with MIS-C or remain asymptomatic after SARS-CoV-2 infection are yet to be established. This review focuses on the immunological aspects of MIS-C with respect to innate, humoral, and cellular immunity. In addition, presents the role of the SARS-CoV-2 Spike protein as a superantigen in the pathophysiological mechanisms, discusses the great heterogeneity among the immunological studies in the pediatric population, and highlights possible reasons why some children with a certain genetic background present with MIS-C.

Circulating Spike Protein Detected in Post-COVID-19 mRNA Vaccine Myocarditis

BACKGROUND

Cases of adolescents and young adults developing myocarditis after vaccination with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-targeted mRNA vaccines have been reported globally, but the underlying immunoprofiles of these individuals have not been described in detail.

METHODS

From January 2021 through February 2022, we prospectively collected blood from 16 patients who were hospitalized at Massachusetts General for Children or Boston Children's Hospital for myocarditis, presenting with chest pain with elevated cardiac troponin T after SARS-CoV-2 vaccination. We performed extensive antibody profiling, including tests for SARS-CoV-2-specific humoral responses and assessment for autoantibodies or antibodies against the human-relevant virome, SARS-CoV-2-specific T-cell analysis, and cytokine and SARS-CoV-2 antigen profiling. Results were compared with those from 45 healthy, asymptomatic, age-matched vaccinated control subjects.

RESULTS

Extensive antibody profiling and T-cell responses in the individuals who developed postvaccine myocarditis were essentially indistinguishable from those of vaccinated control subjects, despite a modest increase in cytokine production. A notable finding was that markedly elevated levels of full-length spike protein (33.9±22.4 pg/mL), unbound by antibodies, were detected in the plasma of individuals with postvaccine myocarditis, whereas no free spike was detected in asymptomatic vaccinated control subjects (unpaired t test; P<0.0001).

CONCLUSIONS

Immunoprofiling of vaccinated adolescents and young adults revealed that the mRNA vaccine-induced immune responses did not differ between individuals who developed myocarditis and individuals who did not. However, free spike antigen was detected in the blood of adolescents and young adults who developed post-mRNA vaccine myocarditis, advancing insight into its potential underlying cause.

Multisystem Inflammatory Syndrome in Children

Multisystem inflammatory disease in children (MIS-C) is a condition typically seen 3 to 6 weeks after acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Believed to be a postinfection hyperinflammatory response, the clinical manifestation of this viral sequelae can vary significantly in severity and symptomatic presentation. Clinical prodrome includes persistent fever and dysfunction of at least two organ systems. Often developing after asymptomatic or mildly symptomatic coronavirus disease 2019 (COVID-19) infection, MIS-C is a diagnosis of exclusion that requires evaluation for other infectious or noninfectious etiology for symptoms. Vital sign instability, including fever, tachycardia, and hypotension; laboratory studies demonstrating elevated inflammatory markers and elevated cardiac markers; and positive SARS-CoV-2 polymerase chain reaction, SARS-CoV-2 antibodies, or exposure to someone with confirmed COVID-19 infection 4 to 6 weeks before clinical presentation are used to diagnose this condition. Skin and mucosal involvement, gastrointestinal symptoms, and neurologic manifestations are also commonly seen. An echocardiogram is indicated to evaluate for cardiac dysfunction, including but not limited to coronary artery enlargement, left ventricular dysfunction, arrythmias, or atrioventricular block. [Pediatr Ann. 2023;52(3):e114-e121.].

Clinical Characteristics and Laboratory Findings in Children with Multisystem Inflammatory Syndrome (MIS-C)-A Retrospective Study of a Tertiary Care Center from Constanta, Romania

A new hyper-inflammatory syndrome in children was identified after SARS-CoV-2 infection as a post-infectious complication that is temporally associated with coronavirus disease (COVID-19). Fever, rash, conjunctival hyperemia, and gastrointestinal problems are all clinical manifestations of multisystem inflammatory syndrome in children. This condition, in some cases, causes multisystem involvement, affecting multiple organ systems and necessitating admission to a pediatric intensive care unit. Due to limited clinical studies, it is necessary to analyze the characteristics of the pathology in order to improve the management and long-term follow-up of high-risk patients. The objective of the study was to analyze the clinical and paraclinical characteristics of children diagnosed with MIS-C. The clinical study is a retrospective, observational, descriptive research work that includes patients diagnosed with MIS-C, temporally associated with coronavirus disease, and it contains clinical characteristics, laboratory data, and demographic information. The majority of patients had normal or slightly increased leukocyte counts, which were associated with neutrophilia, lymphocytopenia, and significantly elevated inflammatory markers, including high levels of C-reactive protein, fibrinogen, the erythrocyte sedimentation rate, serum ferritin, and IL 6 and elevated levels of the cardiac enzymes NT-proBNP and D-dimers, owing to the cardiovascular system involvement in the pro-inflammatory process. At the same time, renal system involvement led to raised creatinine and high proteinuria in association with hypoalbuminemia. This characteristic of the pro-inflammatory status as well as multisystem impairment are highly suggestive of the post-infection immunological reaction of the multisystem syndrome temporally associated with SARS-CoV-2 infection.

Inborn errors of OAS-RNase L in SARS-CoV-2-related multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a rare and severe condition that follows benign COVID-19. We report autosomal recessive deficiencies of OAS1, OAS2, or RNASEL in five unrelated children with MIS-C. The cytosolic double-stranded RNA (dsRNA)-sensing OAS1 and OAS2 generate 2'-5'-linked oligoadenylates (2-5A) that activate the single-stranded RNA-degrading ribonuclease L (RNase L). Monocytic cell lines and primary myeloid cells with OAS1, OAS2, or RNase L deficiencies produce excessive amounts of inflammatory cytokines upon dsRNA or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) stimulation. Exogenous 2-5A suppresses cytokine production in OAS1-deficient but not RNase L-deficient cells. Cytokine production in RNase L-deficient cells is impaired by MDA5 or RIG-I deficiency and abolished by mitochondrial antiviral-signaling protein (MAVS) deficiency. Recessive OAS-RNase L deficiencies in these patients unleash the production of SARS-CoV-2-triggered, MAVS-mediated inflammatory cytokines by mononuclear phagocytes, thereby underlying MIS-C.

SARS-CoV-2 variants induce distinct disease and impact in the bone marrow and thymus of mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved to variants associated with milder disease. We employed the k18-hACE2 mouse model to study how differences in the course of infection by SARS-CoV-2 variants alpha, delta, and omicron relate to tissue pathology and the immune response triggered. We documented a variant-specific pattern of infection severity, inducing discrete lung and blood immune responses and differentially impacting primary lymphoid organs. Infections with variants alpha and delta promoted bone marrow (BM) emergency myelopoiesis, with blood and lung neutrophilia. The defects in the BM hematopoietic compartment extended to the thymus, with the infection by the alpha variant provoking a marked thymic atrophy. Importantly, the changes in the immune responses correlated with the severity of infection. Our study provides a comprehensive platform to investigate the modulation of disease by SARS-CoV-2 variants and underscores the impact of this infection on the function of primary lymphoid organs.

Rash and Gastrointestinal Dysfunction May Indicate Cardiac Involvement in Children with Multisystem Inflammatory System Associated with Coronavirus Disease 2019

This study aims to investigate the management of children diagnosed with “multisystem inflammatory syndrome” (MIS-C) potentially associated with coronavirus disease 2019 (COVID-19) at a tertiary health center. This is a retrospective review of 34 children who were diagnosed with MIS-C at the pediatrics department of the study center from August 2021 to December 2021. Data related to age, sex, body mass index, vital findings, laboratory data, clinical symptoms, ultrasonography, and echocardiography findings were acquired from hospital records. Cardiac markers were compared with respect to clinical symptoms and imaging. Fever (91.2%), rash (50%), and abdominal pain (44.1%) were the most observed symptoms. Echocardiography visualized mild mitral regurgitation in 12 patients (35.3%), pericardial effusion in 9 patients (26.5%), and mild coronary dilatation in 9 patients (26.5%). All patients received corticosteroids, whereas acetylsalicylic acid was prescribed in 29 patients (85.3%) and intravenous immunoglobulins were administered in 21 patients (61.8%). Serum probrain natriuretic peptide concentrations were significantly higher in MIS-C patients with rash than those without rash (9,592.2 ± 7,764.5 vs. 1,501.2 ± 1,385.4 pg/mL, p = 0.021). Serum troponin T concentrations were significantly higher in MIS-C patients with ileitis than those without ileitis (0.026 ± 0.024 vs. 0.008 ± 0.003 µg/L, p = 0.013). Serum troponin T concentrations were also significantly higher in MIS-C patients with pericardial effusion than those without pericardial effusion (0.022 ± 0.020 vs. 0.008 ± 0.007 µg/L, p = 0.036). The presence of rash and sonographic visualization of ileitis might act as signs for cardiac involvement in children exposed to COVID-19. To assess the cardiac involvement in MIS-C patients, cardiac enzymes should be measured and echocardiography examination should be performed.

The Notch1/CD22 signaling axis disrupts Treg function in SARS-CoV-2-associated multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcomes were previously correlated with Notch4 expression on Tregs, here, we show that Tregs in MIS-C were destabilized through a Notch1-dependent mechanism. Genetic analysis revealed that patients with MIS-C had enrichment of rare deleterious variants affecting inflammation and autoimmunity pathways, including dominant-negative mutations in the Notch1 regulators NUMB and NUMBL leading to Notch1 upregulation. Notch1 signaling in Tregs induced CD22, leading to their destabilization in a mTORC1-dependent manner and to the promotion of systemic inflammation. These results identify a Notch1/CD22 signaling axis that disrupts Treg function in MIS-C and point to distinct immune checkpoints controlled by individual Treg Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Coronavirus Infection in Neonates: Neurodevelopmental Outcomes at 18 Months of Age

Background

Although most neonates with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection experience only mild disease, its impact on neurodevelopmental outcomes is unknown. This study aimed to assess the 18-month neurodevelopmental outcomes of infants who had SARS-CoV-2 infection as neonates.

Methods

The authors conducted a prospective cohort study of neonates diagnosed with SARS-CoV-2 infection from June 2020 to December 2020 through nasopharyngeal coronavirus disease 2019 (COVID-19). A total of 58 neonates were identified from the Kuwait National COVID-19 Registry and enrolled. Historical controls were selected from the neonatal follow-up registry and matched in a 2 : 1 ratio based on sex and gestational age. When the subjects were 18 months of age, their neurodevelopmental outcomes were assessed by two trained assessors using the Bayley Scales of Infant and Toddler Development-3rd Edition (BSID-III).

Results

Forty children diagnosed with SARS-CoV-2 infection were included in the final analysis. The median age at infection was 18 days (range: 10-26 days). Eighteen (45%) patients were asymptomatic, 15 (37.5%) had a sepsis-like presentation, 5 (12.5%) exhibited respiratory distress, and 2 (5%) had a multisystem inflammatory syndrome in children (MIS-C)-like presentation. At the 18 months follow-up, only one child showed a severe developmental delay and one child had a language delay. BSID-III outcomes did not differ significantly between the SARS-CoV-2-infected and control groups.

Conclusions

There was no difference in neurodevelopmental outcomes at 18 months in children infected with SARS-CoV-2 compared with controls, although longer neurodevelopmental follow-up studies are required.

Assessing Biomarkers in Viral Infection

Current biomarkers to assess the risk of complications of both acute and chronic viral infection are suboptimal. Prevalent viral infections like human immunodeficiency virus (HIV), hepatitis B and C virus, herpes viruses, and, more recently, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may be associated with significant sequelae including the risk of cardiovascular disease, other end-organ diseases, and malignancies. This review considers some biomarkers which have been investigated in diagnosis and prognosis of key viral infections including inflammatory cytokines, markers of endothelial dysfunction and activation and coagulation, and the role that more conventional diagnostic markers, such as C-reactive protein and procalcitonin, can play in predicting these secondary complications, as markers of severity and to distinguish viral and bacterial infection. Although many of these are still only available in the research setting, these markers show promise for incorporation in diagnostic algorithms which may assist to predict adverse outcomes and to guide therapy.

Evaluation of immunoprotection against coronavirus disease 2019: Novel variants, vaccine inoculation, and complications

The strikingly rapidly mutating nature of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome has been a constant challenge during the coronavirus disease 2019 (COVID-19) pandemic. In this study, various techniques, including reverse transcription-quantitative polymerase chain reaction, antigen-detection rapid diagnostic tests, and high-throughput sequencing were analyzed under different scenarios and spectra for the etiological diagnosis of COVID-19 at the population scale. This study aimed to summarize the latest research progress and provide up-to-date understanding of the methodology used for the evaluation of the immunoprotection conditions against future variants of SARS-CoV-2. Our novel work reviewed the current methods for the evaluation of the immunoprotection status of a specific population (endogenous antibodies) before and after vaccine inoculation (administered with biopharmaceutical antibody products). The present knowledge of the immunoprotection status regarding the COVID-19 complications was also discussed. Knowledge on the immunoprotection status of specific populations can help guide the design of pharmaceutical antibody products, inform practice guidelines, and develop national regulations with respect to the timing of and need for extra rounds of vaccine boosters.

A cursed goodbye kiss from severe acute respiratory syndrome-coronavirus-2 to its pediatric hosts: multisystem inflammatory syndrome in children

PURPOSE OF REVIEW

We aimed to summarize a novel disease called multisystem inflammatory syndrome in children (MIS-C), which develops several weeks after a severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) illness.

RECENT FINDINGS

Given the rarity of the disease, the question of why a minority of children develop MIS-C is not known. Certain intrinsic susceptibility factors in the host have been described. In addition to hyperinflammation induced by the innate and acquired immune cells, evidence of molecular mimicry was presented for the disease pathogenesis. As there is an increasing number of infected individuals and mass vaccination schedules, concerns regarding the usefulness of the existing diagnostic criteria sets raised.

SUMMARY

Although children are likely to have a milder COVID-19 course compared with adults, MIS-C as a postinfectious and life-threatening complication was reported in the pediatric age. After 2 years of the disease definition, optimal treatment regimes, effective preventive measures, and long-term outcomes are still debated.

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.