The Immunology of Multisystem Inflammatory Syndrome in Children with COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is typically very mild and often asymptomatic in children. A complication is the rare multisystem inflammatory syndrome in children (MIS-C) associated with COVID-19, presenting 4-6 weeks after infection as high fever, organ dysfunction, and strongly elevated markers of inflammation. The pathogenesis is unclear but has overlapping features with Kawasaki disease suggestive of vasculitis and a likely autoimmune etiology. We apply systems-level analyses of blood immune cells, cytokines, and autoantibodies in healthy children, children with Kawasaki disease enrolled prior to COVID-19, children infected with SARS-CoV-2, and children presenting with MIS-C. We find that the inflammatory response in MIS-C differs from the cytokine storm of severe acute COVID-19, shares several features with Kawasaki disease, but also differs from this condition with respect to T cell subsets, interleukin (IL)-17A, and biomarkers associated with arterial damage. Finally, autoantibody profiling suggests multiple autoantibodies that could be involved in the pathogenesis of MIS-C.

Proteomic mapping identifies serum marker signatures associated with MIS-C specific hyperinflammation and cardiovascular manifestation.

Multisystem inflammatory syndrome in children (MIS-C) shares several clinical and immunological features with Kawasaki Disease (KD) and pediatric hyperinflammation, but the immuno-phenotypic overlap among these clinical mimics is still incompletely understood. Here we analyzed serum samples from treatment-naïve patients with MIS-C (n = 31) and KD (n = 11), pediatric hyperinflammation (n = 13) and healthy controls (HC, n = 10) by proximity extension assay (PEA) to profile 184 blood biomarkers. Collectively, immunophenotypic overlap between MIS-C and hyperinflammation exceeds overlap with KD. Overexpression of IL-17A in MIS-C and KD could best separate these conditions from hyperinflammatory conditions, while those were hallmarked by overabundance of adenosin deaminase and IL-18. Depletion in serum TNF-related subfamily member 9 (TNFRSF9) and apoptosis inducing ligand (TRAIL) linked with cardiovascular manifestations and myocarditis in MIS-C. Altogether, our analysis highlights important differences in molecular marker signatures also across different MIS-C and KD cohorts and suggests several previously unidentified molecular associations in context of cardiovascular inflammation.

Human Genetic and Immunological Determinants of SARS-CoV-2 Infection and Multisystem Inflammatory Syndrome in Children.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces pneumonia and acute respiratory failure in Coronavirus Disease 2019 (COVID-19) patients with inborn errors of immunity to type I interferon (IFN-I). The impact of SARS-CoV-2 infection varies widely, ranging from mild respiratory symptoms to life-threatening illness and organ failure, with a higher incidence in men than in women. Approximately 3 to 5% of critical COVID-19 patients under 60 and a smaller percentage of elderly patients exhibit genetic defects in IFN-I production, including X-chromosome-linked TLR7 and autosomal TLR3 deficiencies. Around 15 to 20% of cases over 70 years old, and a smaller percentage of younger patients, present with preexisting autoantibodies neutralizing type I interferons. Additionally, innate errors affecting the control of the response to type I interferon have been associated with pediatric multisystem inflammatory syndrome (MIS-C). Several studies have described rare errors of immunity, such as XIAP deficiency, CYBB, SOCS1, OAS1/2, and RNASEL, as underlying factors in MIS-C susceptibility. However, further investigations in expanded patient cohorts are needed to validate these findings and pave the way for new genetic approaches to MIS-C. This review aims to present recent evidence from the scientific literature on genetic and immunological abnormalities predisposing individuals to critical SARS-CoV-2 infection through IFN-I. We will also discuss multisystem inflammatory syndrome in children (MIS-C). Understanding the immunological mechanisms and pathogenesis of severe COVID-19 may inform personalized patient care and population protection strategies against future serious viral infections.

Cardiac manifestations in children with the multisystem inflammatory syndrome (MIS-C) associated with SARS-CoV-2 infection: Systematic review and meta-analysis.

According to the World Health Organisation, as of October 2022, there have been 55,560,329 reported cases of SARS-COV-2 in patients under 19 years old. It is estimated that about 0.06% of these patients may develop MIS-C, representing more than 2 million children worldwide. This systematic review and meta-analysis examined the pooled prevalence of cardiovascular manifestation and cardiac complications in children hospitalised with MIS-C. The PROSPERO register number is CRD42022327212. We included case-report studies, case-control studies, cohort studies, and cross-sectional studies, as well as clinical trials or studies describing cardiac manifestations of MIS-C and its sequelae in a paediatric population. Initially, 285 studies were selected, but there were 154 duplicates, and 81 were excluded because they did not fit the eligibility criteria. Thus, 50 studies were selected for review, and 30 were included in the meta-analysis. A total sample size of 1445 children was included. The combined prevalence of myocarditis or pericarditis was 34.3% (95% CI: 25.0%-44.2%). The combined prevalence for echocardiogram anomalies was 40.8% (95% CI: 30.5%-51.5%), that of Kawasaki disease presentation was 14.8% (95% CI: 7.5%-23.7%), and that of coronary dilation was 15.2% (95% CI: 11.0%-19.8%). The rate of electrocardiogram anomalies was 5.3% (95% CI: 0.8%-12.3%), and the mortality rate was 0.5% (CI 95%: 0%-1.2%). Furthermore, 186 children still had complications at discharge, with a combined prevalence of such long-lasting manifestations of 9.3% (95% CI: 5.6%-13.7%). Studies that assess whether these children will have an increased cardiovascular risk with a greater chance of acute myocardial infarction, arrhythmias, or thrombosis will be essential for healthcare planning.

Effectiveness of early Anakinra on cardiac function in children with multisystem inflammatory syndrome of COVID-19: a systematic review.

BACKGROUND: Multisystem Inflammatory Syndrome in Children (MIS-C) associated with SARS-CoV-2 can lead to severe cardiovascular complications. Anakinra, an interleukin-1 receptor antagonist, is proposed to benefit the hyperinflammatory state of MIS-C, potentially improving cardiac function. This systematic review evaluated the effectiveness of early Anakinra administration on cardiac outcomes in children with MIS-C. METHODS: A comprehensive search across PubMed, Embase, and Web of Science until March 2024 identified studies using Anakinra to treat MIS-C with reported cardiac outcomes. Observational cohorts and clinical trials were included, with data extraction focusing on cardiac function metrics and inflammatory markers. Study quality was assessed using the Newcastle-Ottawa Scale. RESULTS: Six studies met the inclusion criteria, ranging from retrospective cohorts to prospective clinical studies, predominantly from the USA. Anakinra dosages ranged from 2.3 to 10 mg/kg based on disease severity. Several studies showed significant improvements in left ventricular ejection fraction and reductions in inflammatory markers like C-reactive protein, suggesting Anakinra's role in enhancing cardiac function and mitigating inflammation. However, findings on vasoactive support needs were mixed, and some studies did not report significant changes in acute cardiac support requirements. CONCLUSION: Early Anakinra administration shows potential for improving cardiac function and reducing inflammation in children with MIS-C, particularly those with severe manifestations. However, the existing evidence is limited by the observational nature of most studies and lacks randomized controlled trials (RCTs). Further high-quality RCTs are necessary to conclusively determine Anakinra's effectiveness and optimize its use in MIS-C management for better long-term cardiac outcomes and standardized treatment protocols.

Clinical presentation and management of multisystem inflammatory syndrome in children associated with covid-19: a retrospective observational descriptive study in a pediatric hospital in Syria.

OBJECTIVE: Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 is a rare and serious medical condition. This study aims to review the clinical presentation, laboratory parameters, outcomes, and management of MIS-C cases in a pediatric hospital in Syria. METHODS: This retrospective observational study aimed to investigate MIS-C between May 2020 and October 2021. Data collection involved extracting information from medical records, and patients were identified based on the case definition established by the World Health Organization (WHO). Various laboratory investigations, diagnostic evaluations, clinical presentations, and treatments were performed to assess patients. Descriptive statistical analysis was conducted using Microsoft Excel. RESULTS: A total of 232 COVID-19 cases were reported with COVID-19 Infection. Among these cases, 25 (10.77%) were identified as MIS-C. The median age of the patients was 5.5 years, with the majority being male patients (72%). Patients experienced fever (100%), bilateral conjunctivitis (88%), rash (84%), gastrointestinal symptoms (76%), and cardiac dysfunction (72%). Other notable findings included oral cavity changes (64%), edema (36%), cervical lymphadenopathy (36%), and neurological manifestations (28%). Respiratory symptoms were uncommon (16%). All patients recovered, with no recorded deaths. CONCLUSION: The predominant presence of positive SARS-CoV-2 IgG in the majority of patients in this study supports the post-infectious nature of MIS-C. Respiratory symptoms were less prevalent in both pediatric COVID-19 and MIS-C patients. Early supportive care is crucial in management, although additional research is needed to establish definitive guidelines. Larger studies are necessary to overcome the limitations of this study and to enhance our understanding of MIS-C in pediatric COVID-19 patients.

Acute kidney injury in children with moderate-severe COVID-19 and multisystem inflammatory syndrome in children: a referral center experience.

BACKGROUND: Data on the characteristics of acute kidney injury (AKI) in pediatric COVID-19 and MIS-C are limited. We aimed to define the frequency, associated factors and early outcome of AKI in moderate, severe or critical COVID-19 and MIS-C; and to present a tertiary referral center experience from Türkiye. METHODS: Hospitalized patients ≤ 18 years of age with confirmed COVID-19 or MIS-C at Ihsan Dogramaci Children's Hospital, Hacettepe University, between March 2020-December 2021 were enrolled. The characteristics of AKI in the COVID-19 group were investigated in moderate, severe and critically ill patients; patients with mild COVID-19 were excluded. RESULTS: The median (Q1-Q3) age in the COVID-19 (n = 66) and MIS-C (n = 111) groups was 10.7 years (3.9-15.2) and 8.7 years (4.5-12.7), respectively. The frequency of AKI was 22.7% (15/66) in COVID-19 and 15.3% (17/111) in MIS-C; all MIS-C patients with AKI and 73.3% (11/15) of COVID-19 patients with AKI had AKI at the time of admission. Multivariate analyses revealed need for vasoactive/inotropic agents [Odds ratio (OR) 19.233, p = 0.002] and presence of vomiting and/or diarrhea (OR 4.465, p = 0.036) as independent risk factors of AKI in COVID-19 patients; and need for vasoactive/inotropic agents (OR 22.542, p = 0.020), procalcitonin and ferritin levels as independent risk factors of AKI in the MIS-C group. Age was correlated with lymphocyte count (r = -0.513, p < 0.001) and troponin level (r = 0.518, p < 0.001) in MIS-C patients. Length of hospital stay was significantly longer in both groups with AKI, compared to those without AKI. Mortality was 9.1% in the COVID-19 group; and was associated with AKI (p = 0.021). There was no mortality in MIS-C patients. AKI recovery at discharge was 63.6% in COVID-19 survivors and 100% in MIS-C patients. CONCLUSIONS: Independent risk factors for AKI were need for vasoactive/inotropic agents and vomiting/diarrhea in moderate, severe or critical COVID-19 patients; and need for vasoactive/inotropic agents and severe inflammation in MIS-C patients. Our findings suggest that inflammation and cardiac dysfunction are associated with AKI in MIS-C patients; and the association with age in this group merits further studies in larger groups. Early outcome is favorable; long-term follow-up for kidney functions is needed.

Multisystem inflammatory syndrome in children (MIS-C): A nationwide collaborative study in the Greek population.

Multisystem inflammatory syndrome in children (MIS-C) is a rare but severe hyperinflammatory condition that may occur following SARS-CoV-2 infection. This retrospective, descriptive study of children hospitalized with multisystem inflammatory syndrome in children (MIS-C) in 12 tertiary care centers from 3/11/2020 to 12/31/2021. Demographics, clinical and laboratory characteristics, treatment and outcomes are described. Among 145 patients (95 males, median age 8.2 years) included, 123 met the WHO criteria for MIS-C, while 112 (77%) had serological evidence of SARS-CoV-2 infection. Fever was present in 99%, gastrointestinal symptoms in 77%, mucocutaneous involvement in 68% and respiratory symptoms in 28%. Fifty-five patients (38%) developed myocarditis, 29 (20%) pericarditis and 19 (13%) coronary aneurysms. Among the above cases 11/55 (20%), 1/29 (3.4%) and 5/19 (26.3%), respectively, cardiac complications had not fully resolved at discharge. Underlying comorbidities were reported in 18%. Median CRP value was 155 mg/l, ferritin 535 ng/ml, PCT 1.6 ng/ml and WBC 14.2 × 109/mm3. Most patients had elevated troponin (41.3%) and/or NT-pro-BNP (49.6%). Intravenous immunoglobulin plus corticosteroids were used in 117/145 (80.6%), monotherapy with IVIG alone in 13/145 (8.9%) and with corticosteroids alone in 2/145 (1.3%). Anti-IL1 treatment was added in 15 patients (10.3%). Thirty-three patients (23%) were admitted to the PICU, 14% developed shock and 1 required ECMO. Mortality rate was 0.68%. The incidence of MIS-C was estimated at 0.69/1000 SARS-CoV-2 infections. Patients who presented with shock had higher levels of NT-pro-BNP compared to those who did not (p < 0.001). Acute kidney injury and/or myocarditis were associated with higher risk of developing shock. CONCLUSION: MIS-C is a novel, infrequent but serious disease entity. Cardiac manifestations included myocarditis and pericarditis, which resolved in most patients before discharge. Timely initiation of immunomodulatory therapy was shown to be effective. NT-pro-BNP levels may provide a better prediction and monitoring of the disease course. Further research is required to elucidate the pathogenesis, risk factors and optimal management, and long-term outcomes of this clinical entity. WHAT IS KNOWN: • MIS-C is an infrequent but serious disease entity. • Patients with MIS-C present with multi-organ dysfunction, primarily involving the gastrointestinal and cardiovascular systems. WHAT IS NEW: • NT-pro-BNP levels may provide a better prediction and monitoring of the disease course. • Acute kidney injury and/or myocarditis were associated with higher risk of developing shock.

Long-term health outcome and quality of life in children with multisystem inflammatory syndrome: findings from multidisciplinary follow-up at an Italian tertiary-care paediatric hospital.

Multisystem inflammatory syndrome is a severe complication of SARS-CoV-2 infection in children (MIS-C). To date, data on long-term sequelae mainly concern cardiac outcomes. All ≤ 18 year olds consecutively admitted to the Buzzi Children's Hospital with a diagnosis of MIS-C between October 1, 2020, and May 31, 2022, were followed up for up to 12 months by a dedicated multidisciplinary team. They underwent laboratory tests, multi-organ clinical and instrumental assessments, and psychosocial evaluation. 56/62 patients, 40 M, mean age 8.7 years (95% CI 7.7, 9.7), completed the follow-up. Cardiological, gastroenterological, pneumological, and neurological evaluations, including IQ and EEG, were normal. Alterations of HOMA-IR index and/or TyG index, observed in almost all patients during hospitalisation, persisted in about a third of the population at 12 months. At 6 and 12 months respectively, impairment of adaptive functions was observed in 38/56 patients (67.9%) and 25/56 (44.6%), emotional and behavioural problems in 10/56 (17.9%) and 9/56 (16.1%), and decline in QoL in 14/56 (25.0%) and 9/56 (16.1%). Psychosocial well-being impairment was significantly more frequent in the subgroup with persistent glycometabolic dysfunction at 12 months (75% vs. 40.9% p < 0.001). CONLUSION: The mechanisms that might explain the long-term persistence of both metabolic alterations and neuro-behavioural outcomes and their possible relationship are far from being clarified. Our study points out to the potential long-term effects of pandemics and to the importance of a multidisciplinary follow-up to detect potential negative sequelae in different areas of health, both physical and psychosocial. WHAT IS KNOWN: • Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infection. • Few data exist on the medium- and long-term outcomes of MIS-C, mostly focused on cardiac involvement. Emerging evidence shows neurological and psychological sequelae at mid- and long-term follow-up. WHAT IS NEW: • This study reveals that MIS-C may lead to long-term glycometabolic dysfunctions joined to impairment in the realm of general well-being and decline in quality of life, in a subgroup of children. • This study highlights the importance of a long-term multidisciplinary follow-up of children hospitalised with MIS-C, in order to detect the potential long-term sequelae in different areas of health, both physical and psychosocial well-being.

MIS-C Treatment: Is glucocorticoid monotherapy enough for mild cases?

BACKGROUND: The effectiveness of using only glucocorticoids (GCs) in mild multisystem inflammatory syndrome (MIS-C) cases was compared with combined treatment [GCs + Intravenous immune globulin (IVIG)]. METHODS: This retrospective cohort study was conducted between June 1, 2020, and June 1, 2022, in a tertiary care center in Istanbul, Turkey. Clinical and investigational data of the MIS-C patients were analyzed. The patients were divided into two groups: those who received only GCs and those who received the GCs + IVIG combination. The primary outcome focused on assessing the deterioration of the patient's clinical condition, the occurrence of shock, admission to the pediatric intensive care unit (PICU), and the need for additional immunosuppressive medication. Secondary outcomes included evaluating the course of cardiovascular and infection-related complications observed at the one-year follow-up. RESULTS: Ninety-seven MIS-C patients with a median age of 41 (3- 214) months were enrolled. Fifty-six (57.7%) patients were male. All the patients had fever at admission with a temperature of 39 °C (37.5 °C-40.1 °C). Thirty-two patients (33%) had cardiac findings on echocardiography [left ventricular dysfunction (n= 13, 13.5%), coronary artery involvement (n= 11, 11.3%), and dilation of cardiac cavities and/or increased cardiac muscle thickness (n= 8, 8.2%)]. Thirteen patients (13.5%) required intensive care. All patients received GCs [only GCs (group I; n= 65, 67%)], and 32 patients (33%) with severe manifestations and/or cardiac involvement received GCs + IVIG (group II). No mortality was observed. None of the patients had any complaints at the one-year follow-up, and all echocardiography findings were normal. CONCLUSION: This study provides preliminary evidence that GC monotherapy is a safe treatment alternative for mild MIS-C cases without cardiac involvement.

Prognostic factors for multisystem inflammatory syndrome in children: A systematic review and meta-analysis.

AIM: Multisystem inflammatory syndrome in children (MIS-C) is a novel condition that can occur post-SARS-CoV-2 infection in children and adolescents. There is a paucity of evidence on the prognostic factors associated with MIS-C. The aim of this systematic review and meta-analysis was to summarise the prognostic factors for MIS-C development. METHODS: Five databases were systematically searched from January 2020 to May 2023 for studies reporting on prognostic factors for MIS-C using multivariable regression models. Random-effects meta-analyses were conducted to pool odds ratios for each prognostic factor. Risk of bias was rated using QUIPS and the GRADE framework was used to assess the certainty of evidence for each unique factor. RESULTS: Twelve observational studies (N = 18 024) were included, and 13 unique prognostic factors were amenable to meta-analysis. With moderate certainty, age <12 years, male sex and Black race probably increase the risk of MIS-C. Malignancy and underlying respiratory disease probably decrease the risk of MIS-C. Low-certainty evidence suggests that Asian race may increase the risk of MIS-C, and comorbidity may decrease the risk of MIS-C. CONCLUSION: Current literature presents several prognostic factors related to MIS-C following SARS-CoV-2 infection. Further research is necessary to elucidate the pathophysiologic mechanisms related to MIS-C.

Epidemiological and clinical evolution of multisystem inflammatory syndrome in children throughout the SARS-CoV-2 pandemic in a tertiary Italian children's hospital.

Multisystem inflammatory syndrome in children (MIS-C) is a potentially life-threatening disease temporally linked to SARS-CoV-2 whose incidence and clinical presentation may have been altered by the different SARS-CoV-2 variants and by vaccination. METHODS: We retrospectively collected the data of all MIS-C cases admitted to the Gaslini Children's Hospital, the hub for SARS-CoV-2 related diseases in Liguria region, Italy, from 01 October 2020, to 30 November 2022, evaluating the ratio between MIS-C cases and (1) COVID-19 paediatric cases in our region, (2) emergency department admissions and (3) emergency department febrile patients. We also compared MIS-C incidence in pre- post-vaccination periods. RESULTS: We observed a significant global decline in the incidence of MIS-Cover the four variant periods and after the starting of vaccination whereas clinical features, therapeutic management and severity did not significantly vary. CONCLUSIONS: In our setting, we demonstrated a significant decrease of MIS-C incidence according to the predominant variant and including not vaccinated children. Regardless of variant type, the patients showed similar phenotypes and severity throughout the pandemic. SARS-CoV-2 variants as well as immune protection after previous infections and/or vaccination may have interacted by playing different roles and reducing the incidence of MIS-C.

Kawasaki Disease-Associated Cytokine Storm Syndrome.

Kawasaki disease (KD) is a hyperinflammatory syndrome manifesting as an acute systemic vasculitis characterized by fever, nonsuppurative conjunctival injection, rash, oral mucositis, extremity changes, and cervical lymphadenopathy. KD predominantly affects young children and shares clinical features and immunobiology with other hyperinflammation syndromes including systemic juvenile idiopathic arthritis (sJIA) and multisystem inflammatory syndrome in children (MIS-C). Cytokine storm syndrome (CSS) is an acute complication in ~2% of KD patients; however, the incidence is likely underestimated as many clinical and laboratory features of both diseases overlap. CSS should be entertained when a child with KD is unresponsive to IVIG therapy with recalcitrant fever. Early recognition and prompt institution of immunomodulatory treatment can substantially reduce the mortality and morbidity of CSS in KD. Given the known pathogenetic role of IL-1ß in both syndromes, the early use of IL-1 blockers in refractory KD with CSS deserves consideration.

COVID-19-Related Multi-systemic Inflammatory Syndrome in Children (MIS-C).

Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infections in children. This syndrome manifests about a month after the initial viral infection and is characterized by fever, multiorgan dysfunction, and systemic inflammation. This chapter will review the emergence, epidemiology, clinical characteristics, diagnosis, pathophysiology, immunomodulatory treatment, prognosis, outcomes, and prevention of MIS-C. While the pathophysiology of MIS-C remains to be defined, it is a post-infection, hyperinflammatory syndrome of childhood with elevated inflammatory cytokines.

Criteria for Cytokine Storm Syndromes.

In the past two decades, there has been a great deal of work aimed to devise diagnostic guidelines, classification criteria, and diagnostic scores for cytokine storm syndromes (CSSs). The most notable effort has been the large-scale multinational study that led to the development of the 2016 classification criteria for macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (JIA). Future studies should scrutinize the validity of the proposed criteria, particularly in systemic JIA patients treated with biologics, in children with subtle or incomplete forms of MAS, and in patients with MAS complicating other rheumatologic disorders. More generic CSS criteria are also available but often lack sensitivity and specificity in a wide variety of patient populations and CSSs of different etiologies. The coronavirus disease 2019 (COVID-19)-related lung disease led to an evolution of the concept of a "cytokine storm." Emerging and unsolved challenges in the diagnosis of the different forms of CSSs highlight the need for diagnostic tools and well-established classification criteria to enable timely recognition and correct classification of patients.

Altered amino acid profile in patients with SARS-CoV-2 infection.

Low plasma arginine bioavailability has been implicated in endothelial dysfunction and immune dysregulation. The role of arginine in COVID-19 is unknown, but could contribute to cellular damage if low. Our objective was to determine arginine bioavailability in adults and children with COVID-19 vs. healthy controls. We hypothesized that arginine bioavailability would be low in patients with COVID-19 and multisystem inflammatory syndrome in children (MIS-C). We conducted a prospective observational study of three patient cohorts; arginine bioavailability was determined in asymptomatic healthy controls, adults hospitalized with COVID-19, and hospitalized children/adolescents <21 y old with COVID-19, MIS-C, or asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection identified on admission screen. Mean patient plasma amino acids were compared to controls using the Student's t test. Arginine-to-ornithine ratio, a biomarker of arginase activity, and global arginine bioavailability ratio (GABR, arginine/[ornithine+citrulline]) were assessed in all three groups. A total of 80 patients were included (28 controls, 32 adults with COVID-19, and 20 pediatric patients with COVID-19/MIS-C). Mean plasma arginine and arginine bioavailability ratios were lower among adult and pediatric patients with COVID-19/MIS-C compared to controls. There was no difference between arginine bioavailability in children with COVID-19 vs. MIS-C. Adults and children with COVID-19 and MIS-C in our cohort had low arginine bioavailability compared to healthy adult controls. This may contribute to immune dysregulation and endothelial dysfunction in COVID-19. Low arginine-to-ornithine ratio in patients with COVID-19 or MIS-C suggests an elevation of arginase activity. Further study is merited to explore the role of arginine dysregulation in COVID-19.

One-Year Follow-Up Results of MIS-C Patients with Coronary Artery Involvement: A Multi-center Study.

Multisystem inflammatory syndrome (MIS-C) in children is a rare complication of SARS-CoV-2 infection. Knowing the course of the affected or unaffected coronary arteries in the patients under follow-up is important in terms of defining the long-term prognosis of the disease and determining the follow-up plan. This is a multicenter and retrospective study. The data were obtained from nine different centers. Between May 2020 and August 2022, 68 of 790 patients had coronary artery involvement. One-year echocardiographic data of 67 of 789 MIS-C patients with coronary artery involvement were analyzed. Existing pathologies of the coronary arteries were grouped as increased echogenicity, dilatation and aneurysm according to Z scores, and their changes over a 1-year period were determined. The data of all three groups are defined as frequency. SPSS Statistics version 22 was used to evaluate the data. In our study, aneurysm was observed in 16.4%, dilatation in 68.7% and increased echogenicity in 13.4% of the patients. All of the patients with involvement in the form of increased echogenicity recovered without sequelae by the end of the first month. No progression to aneurysm was observed in any of the patients with dilatation. No new-onset involvement was observed in patients with previously healthy coronary arteries during the convalescent period. In addition, from the sixth month follow-up period, there was no worsening in the amount of dilatation in any of the patients. At least 94% of the patients who completed the 12th month control period returned to normal.

Cardiac Function in Pediatric Patients with MIS-C Using Speckle Tracking and Conventional Echocardiography: A Longitudinal, Single-Center Study.

Cardiovascular involvement in Multisystem Inflammatory Syndrome in Children (MIS-C), a potential consequence of coronavirus disease-2019 (COVID-19), is common. Conventional transthoracic echocardiography (TTE) provides primary data on the function of the left and right ventricles, while Speckle Tracking Echocardiography (STE) is more sensitive. This study aims to assess longitudinal cardiac function using STE in these patients. This longitudinal study was conducted from late 2021 to early 2022 at Imam Hossein Children's Hospital, Isfahan. Cardiac function was assessed by STE at the time of diagnosis and again two months later. Demographics, clinical characteristics, ECG interpretations, imaging studies, and serum cardiac marker levels were collected. Thirty-five pediatric patients with a mean age of 5.1 years (range: 4 months to 17 years) were included and prospectively followed. Twenty-nine of them, comprising 14 males (48.3%) and 15 females (51.7%), underwent STE and were compared with 29 healthy age- and sex-matched children. Factors related to adverse events included reduced myocardial function, enlarged left atrium or ventricle, and mitral regurgitation (MR). Patients with comorbidities affecting strain measurements were excluded from the strain analyses. A significant difference was observed between the groups in regional strains in the basal and apical septal and middle lateral regions. Global strain rate (GLS) and strain rates were not significantly different but were still lower than the control group. Twenty percent of patients had abnormal GLS but normal left ventricular ejection fraction (LVEF). All patients exhibited reduced segmental myocardial strain in at least one segment. Four out of 26 recovered patients without comorbidities had abnormal GLS at follow-up, despite normal LVEF. STE proves more useful than conventional echocardiography in patients with MIS-C, revealing subclinical cardiac injury in the acute and post-acute phases.

Evolution of Cardiovascular Findings in Multisystem Inflammatory Syndrome in Children (MIS-C) Across COVID-19 Variants: Common Trends and Unusual Presentations.

Multisystem inflammatory syndrome in children (MIS-C) is a rare condition following COVID-19 infection. Cardiac involvement is common and includes left ventricular systolic dysfunction, cardiac marker elevation, electrocardiogram (ECG) changes, and coronary artery dilation. This single-center retrospective cohort study compares cardiovascular disease between three major SARS-CoV-2 variants and describes the evolution of findings in medium-term follow-up. Of 69 total children (mean age 9.2 years, 58% male), 60 (87%) had cardiovascular involvement with the most common features being troponin elevation in 33 (47%) and left ventricular dysfunction in 22 (32%). Based on presumed infection timing, 61 patients were sorted into variant cohorts of Alpha, Delta, and Omicron. Hospitalization was longer for the Delta group (7.7 days) vs Alpha (5.1 days, p = 0.0065) and Omicron (4.9 days, p = 0.012). Troponin elevation was more common in Delta compared to Alpha (13/20 vs 7/25, p = 0.18), and cumulative evidence of cardiac injury (echocardiographic abnormality and/or troponin elevation) was more common in Delta (17/20) compared with Alpha (12/25, p = 0.013) or Omicron (8/16, p = 0.034). Forty-nine (77%) of the original cohort (n = 69) had no cardiac symptoms or findings beyond 3 months post-hospitalization. Cardiac MRI was performed in 28 patients (between 3 and 6 months post-hospitalization) and was normal in 25 patients (89%). The differences in the variant cohorts may be due to alteration of the immune landscape with higher severity of COVID-19 infection. Despite overall reassuring cardiac outcomes, it is important to note the variability of presentation and remain vigilant with future variants.

Left Atrial Strain in Multisystem Inflammatory Syndrome in Children and Associations with Systemic Inflammation and Cardiac Injury.

Multisystem inflammatory syndrome in children (MIS-C) commonly involves cardiac injury with both systolic and diastolic dysfunction. Left atrial strain (LAS) detects subclinical diastolic dysfunction in adults but is infrequently used in children. We evaluated LAS in MIS-C and the associations with systemic inflammation and cardiac injury. In this retrospective cohort study, LAS parameters [reservoir (LAS-r), conduit (LAS-cd), and contractile (LAS-ct)] obtained from admission echocardiograms of MIS-C patients were compared to healthy controls and between MIS-C patients with and without cardiac injury (BNP > 500 pg/ml or troponin-I > 0.04 ng/ml). Correlation and logistic regression analyses were performed to assess LAS associations with admission inflammatory and cardiac biomarkers. Reliability testing was performed. We identified 118 patients with MIS-C and 20 healthy controls. Median LAS parameters were reduced in MIS-C patients compared to controls (LAS-r: 31.8 vs. 43.1%, p < 0.001; LAS-cd: - 28.8 vs. - 34.5%, p = 0.006; LAS-ct: - 5.2 vs. - 9.3%, p < 0.001) and reduced in MIS-C patients with cardiac injury (n = 59) compared to no injury (n = 59) (LAS-r: 29.6 vs. 35.8%, p = 0.001; LAS-cd: - 26.5 vs. - 30.4%, p = 0.036; LAS-ct: - 4.6 vs. - 9.3%, p = 0.008). A discrete LAS-ct peak was absent in 65 (55%) MIS-C patients but present in all controls (p < 0.001). Procalcitonin correlated strongly with averaged E/e' (r = 0.55, p = 0.001). Moderate correlations were found for ESR and LAS-ct (r = - 0.41, p = 0.007) as well as BNP and LAS-r (r = - 0.39, p < 0.001) and LAS-ct (r = 0.31, p = 0.023). Troponin-I had only weak correlations. Intra-rater reliability was good for all LAS parameters, and inter-rater reliability was good to excellent for LAS-r, and fair for LAS-cd and LAS-ct. LAS analysis, particularly the absence of a LAS-ct peak, was reproducible and may be superior to conventional echocardiographic parameters for detecting diastolic dysfunction in MIS-C. No strain parameters on admission were independently associated with cardiac injury.