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ObjectivesMacrophage activation syndrome (MAS) is a severe, life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) and adult onset Still’s disease (AOSD). The objective of this study was to confirm the adequacy of an emapalumab dosing regimen in relation to interferon-γ (IFNγ) activity by assessing efficacy and safety. The efficacy outcome was MAS remission by week 8, based on clinical and laboratory criteria.MethodsWe studied emapalumab, a human anti–IFNγ antibody, administered with background glucocorticoids, in a prospective open-label, single-group trial involving patients who had MAS secondary to sJIA or AOSD and had previously failed high-dose glucocorticoids. The study foresaw 4-week treatment that could be shortened or prolonged based on investigator’s assessment of response. Patients could enter a long-term (12 months) follow-up study.ResultsFourteen patients received emapalumab. All patients completed the trial, entered the long-term follow-up and were alive at the end of the follow-up. The investigated dosing regimen, based on an initial loading dose followed by maintenance doses, was appropriate, as shown by rapid neutralisation of IFNγ activity, demonstrated by prompt decrease in serum C-X-C motif chemokine ligand 9 (CXCL9) levels. By week 8, remission of MAS was achieved in 13 of the 14 patients at a median time of 25 days. Viral infections and positive viral tests were observed during the trial and during the long-term follow-up.ConclusionsNeutralisation of IFNγ with emapalumab was efficacious in inducing remission of MAS secondary to sJIA or AOSD in patients who had failed high-dose glucocorticoids.KEY MESSAGESWhat is already known on this topic?Macrophage activation syndrome (MAS) is a severe and potentially life-threatening complication of systemic juvenile idiopathic arthritis and adult-onset Still’s disease. There are no therapeutic options that have been prospectively investigated in MAS. Data in animal models andex vivodata from humans with MAS led to the hypothesis that interferon-γ (IFNγ) has a pathogenic role in MAS.What does this study add?This open-label multicentre trial using emapalumab, an anti–IFNγ antibody, in patients who have failed to respond to high-dose glucocorticoids, demonstrates that IFNγ has a pathogenic role in MAS and that its neutralisation leads to MAS remission.How might this affect research, clinical practice or policy?The results of this study show that neutralisation of IFNγ with emapalumab is a therapeutic option for patients with severe MAS who have failed standard of care with high-dose glucocorticoids.

Systemic juvenile idiopathic arthritis (JIA) associated with lung disease (JIA-LD) is a potentially life threating complication in children with systemic JIA. Although high-resolution computed tomography (HRCT) is considered the gold standard imaging modality for evaluating interstitial lung disease (ILD), lung ultrasound (US) has shown utility for ILD screening in adults with connective tissue diseases at lower cost and without using ionizing radiation. The goals of this pilot study were to describe lung US features in children with known systemic JIA-LD and to assess the feasibility of lung US in this population.Children age 18 years with systemic JIA-LD and healthy controls were enrolled. Lung US acquisition was performed at 14 lung positions. Demographic, clinical, and HRCT data were collected and reviewed. Feasibility was assessed through patient surveys. Lung US findings were qualitatively and semiquantitatively assessed and compared to HRCT findings.Lung US was performed in 9 children with systemic JIA-LD and 6 healthy controls and took 12 minutes on average to perform. Lung US findings in systemic JIA-LD included focal to diffuse pleural irregularity, granularity, and thickening, with associated scattered or coalesced B-lines, and subpleural consolidations. Lung US findings appeared to correspond to HRCT findings.Lung US in systemic JIA-LD reveals highly conspicuous abnormalities in the pleura and subpleura that appear to correlate with peripheral lung findings on HRCT. Lung US is a feasible imaging tool in children even from an early age. This study suggests a potential role of lung US in systemic JIA-LD screening, diagnosis, and/or prognostication.

PURPOSE OF REVIEW: This review is meant to describe the genetic associations with pediatric severe COVID-19 pneumonia and the postinfectious complication of the multisystem inflammatory syndrome in children (MIS-C). Multiple genetic approaches have been carried out, primarily in adults with extrapolation to children, including genome-wide association studies (GWAS), whole exome and whole genome sequencing (WES/WGS), and target gene analyses. RECENT FINDINGS: Data from adults with severe COVID-19 have identified genomic regions (human leukocyte antigen locus and 3p21.31) as potential risk factors. Genes related to viral entry into cells (ABO blood group locus, ACE2, TMPRS22) have been linked to severe COVID-19 patients by GWAS and target gene approaches. Type I interferon (e.g. IFNAR2) and antiviral gene (e.g. TLR7) associations have been identified by several genetic approaches in severe COVID-19. WES has noted associations with several immune regulatory genes (e.g. SOCS1). Target gene approaches have identified mutations in perforin-mediated cytolytic pathway genes in children and adults with severe COVID-19 and children with MIS-C. SUMMARY: Several genetic associations have been identified in individuals with severe COVID-19 and MIS-C via various genetic approaches. Broadly speaking, COVID-19 genetic associations include genes involved with antiviral functions, viral cell entry, immune regulation, chemotaxis of white blood cells, and lymphocyte cytolytic function.

ObjectivesThe purpose of this study was to examine how the treatment and severity of multisystem inflammatory syndrome in children (MIS-C) has changed over more than two years of the COVID-19 pandemic in the United States.MethodsElectronic health record data were retrieved from the PEDSnet network as part of the NIH Researching COVID to Enhance Recovery (RECOVER) Initiative. The study included data for children ages 0 to 20 years hospitalized for MIS-C from March 1, 2020 through July 20, 2022. Descriptive statistics for MIS-C treatments and laboratory results were computed for three time periods of interest: March 1, 2020 – May 31, 2021 (pre-Delta); June 1 – December 31, 2021 (primarily Delta); January 1 – July 20, 2022 (primarily Omicron). Standardized differences measured the effect size of the difference between Omicron and pre-Omicron cohorts.ResultsThe study included 946 children with a diagnosis of MIS-C. The largest differences in the Omicron period compared to prior years were decreases in the percentage of children with abnormal troponin (effect size = 0.40), abnormal lymphocytes (effect size = 0.33), and intensive care unit (ICU) visits (effect size = 0.34). There were small decreases in the Omicron period for the majority of treatments and abnormal laboratory measurements examined, including infliximab, anticoagulants, furosemide, aspirin, IVIG without steroids, echocardiograms, mechanical ventilation, platelets, ferritin, and sodium.ConclusionsThis study provides the first evidence that the severity of MIS-C declined in the first half of the year 2022 relative to prior years of the COVID-19 pandemic in the United States.Article SummaryUsing electronic health record data for 946 children, we found evidence that the severity of MIS-C declined during the first half of the year 2022.What’s Known on This SubjectThe clinical management of multisystem inflammatory syndrome in children (MIS-C) has commonly included intravenous immune globulin, steroids, and non-steroidal anti-inflammatory agents. Many children with MIS-C have required intravenous fluids, inotropes and vasopressors, and in some cases, mechanical ventilation.What This Study AddsRecent decreases in the percentage of children with MIS-C that have abnormal troponin, abnormal lymphocytes, or intensive care unit visits provide evidence that the severity of MIS-C has declined in the first half of the year 2022.

BackgroundMulti-system inflammatory syndrome in children (MIS-C) represents one of the most severe post-acute sequelae of SARS-CoV-2 infection in children, and there is a critical need to characterize its disease patterns for improved recognition and management. Our objective was to characterize subphenotypes of MIS-C based on presentation, demographics and laboratory parameters.MethodsWe conducted a retrospective cohort study of children with MIS-C from March 1, 2020 - April 30, 2022 and cared for in 8 pediatric medical centers that participate in PEDSnet. We included demographics, symptoms, conditions, laboratory values, medications and outcomes (ICU admission, death), and grouped variables into eight categories according to organ system involvement. We used a heterogeneity-adaptive latent class analysis model to identify three clinically-relevant subphenotypes. We further characterized the sociodemographic and clinical characteristics of each subphenotype, and evaluated their temporal patterns.FindingsWe identified 1186 children hospitalized with MIS-C. The highest proportion of children (44·4%) were aged between 5-11 years, with a male predominance (61.0%), and non- Hispanic white ethnicity (40·2%). Most (67·8%) children did not have a chronic condition. Class 1 represented children with a severe clinical phenotype, with 72·5% admitted to the ICU, higher inflammatory markers, hypotension/shock/dehydration, cardiac involvement, acute kidney injury and respiratory involvement. Class 2 represented a moderate presentation, with 4-6 organ systems involved, and some overlapping features with acute COVID-19. Class 3 represented a mild presentation, with fewer organ systems involved, lower CRP, troponin values and less cardiac involvement. Class 1 initially represented 51·1% of children early in the pandemic, which decreased to 33·9% from the pre-delta period to the omicron period.InterpretationMIS-C has a spectrum of clinical severity, with degree of laboratory abnormalities rather than the number of organ systems involved providing more useful indicators of severity. The proportion of severe/critical MIS-C decreased over time.Research in contextEvidence before this studyWe searched PubMed and preprint articles from December 2019, to July 2022, for studies published in English that investigated the clinical subphenotypes of MIS-C using the terms “multi-system inflammatory syndrome in children” or “pediatric inflammatory multisystem syndrome” and “phenotypes”. Most previous research described the symptoms, clinical characteristics and risk factors associated with MIS-C and how these differ from acute COVID-19, Kawasaki Disease and Toxic Shock Syndrome. One single-center study of 63 patients conducted in 2020 divided patients into Kawasaki and non-Kawasaki disease subphenotypes. Another CDC study evaluated 3 subclasses of MIS-C in 570 children, with one class representing the highest number of organ systems, a second class with predominant respiratory system involvement, and a third class with features overlapping with Kawasaki Disease. However, this study evaluated cases from March to July 2020, during the early phase of the pandemic when misclassification of cases as Kawasaki disease or acute COVID-19 may have occurred. Therefore, it is not known from the existing literature whether the presentation of MIS-C has changed with newer variants such as delta and omicron.Added value of this studyPEDSnet provides one of the largest MIS-C cohorts described so far, providing sufficient power for detailed analyses on MIS-C subphenotypes. Our analyses span the entire length of the pandemic, including the more recent omicron wave, and provide an update on the presentations of MIS-C and its temporal dynamics. We found that children have a spectrum of illness that can be characterized as mild (lower inflammatory markers, fewer organ systems involved), moderate (4-6 organ involvement with clinical overlap with acute COVID-19) and severe (higher inflammatory markers, critically ill, more likely to have cardiac involvement, with hypotension/shock and need for vasopressors).Implications of all the available evidenceThese results provide an update to the subphenotypes of MIS-C including the more recent delta and omicron periods and aid in the understanding of the various presentations of MIS-C. These and other findings provide a useful framework for clinicians in the recognition of MIS-C, identify factors associated with children at risk for increased severity, including the importance of laboratory parameters, for risk stratification, and to facilitate early evaluation, diagnosis and treatment.

Using electronic health record data combined with primary chart review, we identified 7 children across 8 pediatric medical centers with a diagnosis of Multisystem Inflammatory Syndrome in Children (MIS-C) who were managed as outpatients. These findings should prompt a discussion about modifying the case definition to allow for such a possibility.

PURPOSE: Biomarkers for juvenile idiopathic arthritis-associated uveitis (JIA-U) are needed. We aimed to measure inflammatory biomarkers in tears as a non-invasive method to identify biomarkers of uveitis activity. METHODS: Tears were collected from children with JIA-U (n=20) and pediatric controls (n=20) using Schirmer strips. S100A8, A9, A12, IL-18, IL-8, IP-10, MCP-1, RANTES, and sICAM-1 were measured by ELISA and Luminex assays. Levels of biomarkers were compared between children with JIA-U and controls, and active and inactive JIA-U. RESULTS: IL-8, sICAM-1, and S100A12 levels were similar between JIA-U and controls, but differed by activity. Active JIA-U had significantly increased S100A12 compared to inactive JIA-U (mean 27,722.5 pg/ML (SE 1.3) vs. 5,937.2 (1.3), p=0.002), IL-8 (73.5 [1.2] vs. 36.2 [1.2], p=0.009), and sICAM-1 (15,822.7 [1.2) vs. 8,778.0 [1.6], p=0.024). CONCLUSION: We detected inflammatory biomarkers non-invasively in tears of children with JIA-U. IL-8, sICAM-1, and S100A12 are potential biomarkers for uveitis activity.

To provide guidance on the management of Multisystem Inflammatory Syndrome in Children (MIS-C), a condition characterized by fever, inflammation, and multiorgan dysfunction that manifests late in the course of SARS-CoV-2 infection. Recommendations are also provided for children with hyperinflammation during COVID-19, the acute, infectious phase of SARS-CoV-2 infection.The Task Force is composed of 9 pediatric rheumatologists and 2 adult rheumatologists, 2 pediatric cardiologists, 2 pediatric infectious disease specialists, and 1 pediatric critical care physician. Preliminary statements addressing clinical questions related to MIS-C and hyperinflammation in COVID-19 were developed based on evidence reports. Consensus was built through a modified Delphi process that involved anonymous voting and webinar discussion. A 9-point scale was used to determine the appropriateness of each statement (median scores of 1-3 for inappropriate, 4-6 for uncertain, and 7-9 for appropriate). Consensus was rated as low, moderate, or high based on dispersion of the votes. Approved guidance statements were those that were classified as appropriate with moderate or high levels of consensus, which were prespecified before voting.The guidance was approved in June 2020 and updated in November 2020 and October 2021, and consists of 41 final guidance statements accompanied by flow diagrams depicting the diagnostic pathway for MIS-C and recommendations for initial immunomodulatory treatment of MIS-C.Our understanding of SARS-CoV-2-related syndromes in the pediatric population continues to evolve. This guidance document reflects currently available evidence coupled with expert opinion, and will be revised as further evidence becomes available.

OBJECTIVE: To provide guidance on the management of multisystem inflammatory syndrome in children (MIS-C), a condition characterized by fever, inflammation, and multiorgan dysfunction that manifests late in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and to provide recommendations for children with hyperinflammation during coronavirus disease 2019 (COVID-19), the acute, infectious phase of SARS-CoV-2 infection. METHODS: A multidisciplinary task force was convened by the American College of Rheumatology (ACR) to provide guidance on the management of MIS-C associated with SARS-CoV-2 and hyperinflammation in COVID-19. The task force was composed of 9 pediatric rheumatologists, 2 adult rheumatologists, 2 pediatric cardiologists, 2 pediatric infectious disease specialists, and 1 pediatric critical care physician. Preliminary statements addressing clinical questions related to MIS-C and hyperinflammation in COVID-19 were developed based on evidence reports. Consensus was built through a modified Delphi process that involved 2 rounds of anonymous voting and 2 webinars. A 9-point scale was used to determine the appropriateness of each statement (median scores of 1-3 for inappropriate, 4-6 for uncertain, and 7-9 for appropriate), and consensus was rated as low, moderate, or high based on dispersion of the votes along the numeric scale. Approved guidance statements were those that were classified as appropriate with moderate or high levels of consensus, as prespecified prior to voting. RESULTS: The ACR task force approved a total of 128 guidance statements addressing the management of MIS-C and hyperinflammation in pediatric COVID-19. These statements were refined into 40 final clinical guidance statements, accompanied by a flow diagram depicting the diagnostic pathway for MIS-C. CONCLUSION: Our understanding of SARS-CoV-2-related syndromes in the pediatric population continues to evolve. The guidance provided in this "living document" reflects currently available evidence, coupled with expert opinion, and will be revised as further evidence becomes available.

Macrophage activation syndrome (MAS), or secondary hemophagocytic lymphohistiocytosis (HLH), is a cytokine storm syndrome associated with multi-organ system dysfunction and high mortality rates. Laboratory and clinical features resemble primary HLH, which arises in infancy (1 in 50,000 live births) from homozygous mutations in various genes critical to the perforin-mediated cytolytic pathway employed by NK cells and cytotoxic CD8 T lymphocytes. MAS/secondary HLH is about ten times more common and typically presents beyond infancy extending into adulthood. The genetics of MAS are far less defined than for familial HLH. However, the distinction between familial HLH and MAS/secondary HLH is blurred by the finding of heterozygous perforin-pathway mutations in MAS patients, which may function as hypomorphic or partial dominant-negative alleles and contribute to disease pathogenesis. In addition, mutations in a variety of other pathogenic pathways have been noted in patients with MAS/secondary HLH. Many of these genetically disrupted pathways result in a similar cytokine storm syndrome, and can be broadly categorized as impaired viral control (e.g., SH2P1A), dysregulated inflammasome activity (e.g., NLRC4), other immune defects (e.g., IKBKG), and dysregulated metabolism (e.g., LIPA). Collectively these genetic lesions likely combine with states of chronic inflammation, as seen in various rheumatic diseases (e.g., still disease), with or without identified infections, to result in MAS pathology as explained by the threshold model of disease. This emerging paradigm may ultimately support genetic risk stratification for high-risk chronic and even acute inflammatory disorders. Moving forward, continued whole-exome and -genome sequencing will likely identify novel MAS gene associations, as well as noncoding mutations altering levels of gene expression.

We describe 10 children with Alagille syndrome and inflammatory arthritis. In our centers, the prevalence of chronic arthritis in patients with Alagille syndrome is approximately 50 times higher compared with the general population. Arthritis was refractory to most treatment. Patients with Alagille syndrome should routinely be screened for musculoskeletal symptoms.

Apolipoprotein L1 (APOL1) risk variants G1 and G2 are known to result in risk for kidney disease in patients of African ancestry. APOL1-associated nephropathy typically occurs in association with certain environmental factors or systemic diseases. As such, there has been increasing evidence of the role of interferon (IFN) pathways in the pathogenesis of APOL1-associated collapsing glomerulopathy in patients with human immunodeficiency virus (HIV) infection and systemic lupus erythematosus, 2 conditions that are associated with high IFN levels. Collapsing glomerulopathy has also been described in patients receiving exogenous IFN therapy administered for various medical conditions. We describe a patient with a genetic condition that results in an increased IFN state, stimulator of IFN genes (STING)-associated vasculopathy with onset in infancy (SAVI), who developed collapsing glomerulopathy during a flare of his disease. The patient was found to have APOL1 G1 and G2 risk variants. This case supports the role of IFN in inducing APOL1-associated collapsing glomerulopathy.

Background Serum phagocyte-derived alarmins S100A8/9 and S100A12 are considered useful for the assessment of inflammatory diseases. Our study evaluated the use of S100 proteins in a pediatric clinical setting for estimating disease activity and supporting diagnosis. Methods Patients (n = 136) who had S100 proteins tested as part of clinical care were included in this study and relevant information obtained from the medical record: C-reactive protein (CRP), disease activity status (inactive: = 0 joint; active: > 0 active joint), systemic symptoms in systemic JIA (sJIA), and symptoms of flare of other autoinflammatory and fever syndromes. Patients were categorized as: sJIA, non-systemic JIA (nsJIA), other defined autoinflammatory syndromes (AID) and systemic undifferentiated recurring fever syndromes (SURFS). Results Patients with sJIA (n = 21) had significantly higher levels of S100A8/9 and S100A12 compared to patients with nsJIA (n = 49), other AIDs (n = 8) or SURFS (n = 14) (all p p = 0.0002 and p = 0.0002 respectively). Conclusion Compared to other autoinflammatory and fever syndromes, sJIA patients have markedly higher levels of S100A8/9 and S100A12 proteins which may assist with diagnosis. S100 levels slightly outperformed CRP in distinguishing sJIA from other diagnoses and in sJIA disease activity. S100 proteins may aid in monitoring disease activity in sJIA patients.

Macrophage activation syndrome (MAS) is a subtype of haemophagocytic lymphohistiocytosis (HLH), and a well-described complication of systemic juvenile idiopathic arthritis (SJIA), triggered by disease onset or flare, infection, or some medications. Here, we report a 20-year-old man with previously well-controlled SJIA, who developed first time MAS after acute Epstein-Barr virus (EBV) infection, with MAS recurrence due to a drug reaction, ‘3-week sulfasalazine syndrome’, secondary to prophylactic trimethoprim/sulfamethoxazole. Both episodes of MAS were minimally responsive to pulse corticosteroids. Initial EBV-driven MAS was treated with multiple doses of emapalumab prior to resolution, while MAS secondary to sulfasalazine-induced 3-week syndrome required the initiation of ruxolitinib. This case exhibits two rare but life-threatening causes of MAS/secondary HLH in a single patient and the difficulties in their diagnosis and management.

ObjectiveMacrophage activation syndrome (MAS) is a life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) characterised by a vicious cycle of immune amplification that can culminate in overwhelming inflammation and multiorgan failure. The clinical features of MAS overlap with those of active sJIA, complicating early diagnosis and treatment. We evaluated adenosine deaminase 2 (ADA2), a protein of unknown function released principally by monocytes and macrophages, as a novel biomarker of MAS.MethodsWe established age-based normal ranges of peripheral blood ADA2 activity in 324 healthy children and adults. We compared these ranges with 173 children with inflammatory and immune-mediated diseases, including systemic and non-systemic JIA, Kawasaki disease, paediatric systemic lupus erythematosus and juvenile dermatomyositis.ResultsADA2 elevation beyond the upper limit of normal in children was largely restricted to sJIA with concomitant MAS, a finding confirmed in a validation cohort of sJIA patients with inactive disease, active sJIA without MAS or sJIA with MAS. ADA2 activity strongly correlated with MAS biomarkers including ferritin, interleukin (IL)-18 and the interferon (IFN)-γ-inducible chemokine CXCL9 but displayed minimal association with the inflammatory markers C reactive protein and erythrocyte sedimentation rate. Correspondingly, ADA2 paralleled disease activity based on serial measurements in patients with recurrent MAS episodes. IL-18 and IFN-γ elicited ADA2 production by peripheral blood mononuclear cells, and ADA2 was abundant in MAS haemophagocytes.ConclusionsThese findings collectively identify the utility of plasma ADA2 activity as a biomarker of MAS and lend further support to a pivotal role of macrophage activation in this condition.

ImportanceMinimal data are available regarding the postdischarge treatment of multisystem inflammatory syndrome in children (MIS-C).ObjectivesTo evaluate clinical characteristics associated with duration of postdischarge glucocorticoid use and assess postdischarge clinical course, laboratory test result trajectories, and adverse events in a multicenter cohort with MIS-C.Design, Setting, and ParticipantsThis retrospective cohort study included patients with MIS-C hospitalized with severe illness and followed up for 3 months in an ambulatory setting. Patients younger than 21 years who were admitted between May 15, 2020, and May 31, 2021, at 13 US hospitals were included. Inclusion criteria were inpatient treatment comprising intravenous immunoglobulin, diagnosis of cardiovascular dysfunction (vasopressor requirement or left ventricular ejection fraction ≤55%), and availability of complete outpatient data for 3 months.ExposuresGlucocorticoid treatment.Main Outcomes and MeasuresMain outcomes were patient characteristics associated with postdischarge glucocorticoid treatment, laboratory test result trajectories, and adverse events. Multivariable regression was used to evaluate factors associated with postdischarge weight gain (≥2 kg in 3 months) and hyperglycemia during illness.ResultsAmong 186 patients, the median age was 10.4 years (IQR, 6.7-14.2 years); most were male (107 [57.5%]), Black non-Hispanic (60 [32.3%]), and Hispanic or Latino (59 [31.7%]). Most children were critically ill (intensive care unit admission, 163 [87.6%]; vasopressor receipt, 134 [72.0%]) and received inpatient glucocorticoid treatment (178 [95.7%]). Most were discharged with continued glucocorticoid treatment (173 [93.0%]); median discharge dose was 42 mg/d (IQR, 30-60 mg/d) or 1.1 mg/kg/d (IQR, 0.7-1.7 mg/kg/d). Inpatient severity of illness was not associated with duration of postdischarge glucocorticoid treatment. Outpatient treatment duration varied (median, 23 days; IQR, 15-32 days). Time to normalization of C-reactive protein and ferritin levels was similar for glucocorticoid duration of less than 3 weeks vs 3 or more weeks. Readmission occurred in 7 patients (3.8%); none was for cardiovascular dysfunction. Hyperglycemia developed in 14 patients (8.1%). Seventy-five patients (43%) gained 2 kg or more after discharge (median 4.1 kg; IQR, 3.0-6.0 kg). Inpatient high-dose intravenous and oral glucocorticoid therapy was associated with postdischarge weight gain (adjusted odds ratio, 6.91; 95% CI, 1.92-24.91).Conclusions and RelevanceIn this multicenter cohort of patients with MIS-C and cardiovascular dysfunction, postdischarge glucocorticoid treatment was often prolonged, but clinical outcomes were similar in patients prescribed shorter courses. Outpatient weight gain was common. Readmission was infrequent, with none for cardiovascular dysfunction. These findings suggest that strategies are needed to optimize postdischarge glucocorticoid courses for patients with MIS-C.

Systemic JIA (SJIA) is distinguished from other forms of JIA by the prevalence of the severe, life-threatening complications macrophage activation syndrome (SJIA-MAS) and lung disease (SJIA-LD). Alternative therapeutics are urgently needed, as disease pathogenesis diverges from what is observed in SJIA, and currently available biologics are insufficient. SJIA-MAS, defined by a cytokine storm and dysregulated proliferation of T-lymphocytes, and SJIA-LD which presents with lymphocytic interstitial inflammation and pulmonary alveolar proteinosis, are both thought to be driven by IFNs, in particular the type II IFN-γ. Involvement of IFNs and a possible crosstalk of type I IFNs with existing biologics indicate a distinct role for the JAK-STAT signalling pathway in the pathogenesis of SJIA-MAS and SJIA-LD. Here, we review this role of JAK-STATs and IFNs in SJIA complications and discuss how new insights of ongoing research are shaping future therapeutic advances in the form of JAK inhibitors and antibodies targeting IFNs.

Objectives Systemic juvenile idiopathic arthritis (sJIA) is a childhood arthritis with features of autoinflammation and high risk of macrophage activation syndrome (MAS). IL-18 has been shown to have key roles in sJIA and MAS. We aimed to examine IL-18 levels in sJIA in relation to disease activity and history of MAS and other disease biomarkers namely S100 proteins and CXCL9. Methods Total IL-18, CXCL9 and S100 proteins levels were determined in 40 sJIA patients, and IL-18 levels were compared between patients with regards to disease activity, history of MAS, and other biomarkers. Results Total IL-18 levels were significantly higher in patients with active sJIA (median 16 499 pg/ml; interquartile range (IQR) 4816–61 839), and remained persistently elevated even in the majority of patients with inactive disease (1164 pg/ml; IQR 587–3444). Patients with history of MAS had significantly higher IL-18 levels (13 380 pg/ml; IQR 4212–62 628) as compared with those without MAS history (956.5 pg/ml; IQR 276.3–4262.5). Total IL-18 performed well with area under the curve of 0.8145 and 0.84 in predicting disease activity and history of MAS, respectively. We observed moderate correlation between IL-18 and CXCL9 (R = 0.56), S100A8/A9 (R = 0.47) and S100A12 (R = 0.46). The correlation was stronger for ferritin (R = 0.74) and overall for those with active disease. Conclusion Total IL-18 levels were elevated in the majority of sJIA patients regardless of clinical features, but were higher in patients with active disease and history of MAS. Change in IL-18 may reflect increased disease activity or development of MAS.

Although interest in "cytokine storms" has surged over the past decade, it was massively amplified in 2020 when it was suggested that a subset of patients with COVID-19 developed a form of cytokine storm. The concept of cytokine storm syndromes (CSS) encompasses diverse conditions or circumstances that coalesce around potentially lethal hyperinflammation with hemodynamic compromise and multiple organ dysfunction syndrome. Macrophage activation syndrome (MAS) is a prototypic form of CSS that develops in the context of rheumatic diseases, particularly systemic juvenile idiopathic arthritis. The treatment of MAS relies heavily upon corticosteroids and cytokine inhibitors, which have proven to be lifesaving therapies in MAS, as well as in other forms of CSS. Within months of the recognition of SARS-CoV2 as a human pathogen, descriptions of COVID-19 patients with hyperinflammation emerged. Physicians immediately grappled with identifying optimal therapeutic strategies for these patients, and despite clinical distinctions such as marked coagulopathy with endothelial injury associated with COVID-19, borrowed from the experiences with MAS and other CSS. Initial reports of patients treated with anti-cytokine agents in COVID-19 were promising, but recent large, better-controlled studies of these agents have had mixed results suggesting a more complex pathophysiology. Here, we discuss how the comparison of clinical features, immunologic parameters and therapeutic response data between MAS and hyperinflammation in COVID-19 can provide new insight into the pathophysiology of CSS.

Macrophage activation syndrome (MAS) is a life-threatening cytokine storm complicating systemic juvenile idiopathic arthritis (SJIA) driven by IFN-γ. SJIA and MAS are also associated with an unexplained emerging inflammatory lung disease (SJIA-LD), with our recent work supporting pulmonary activation of IFN-γ pathways pathologically linking SJIA-LD and MAS. Our objective was to mechanistically define the potentially novel observation of pulmonary inflammation in the TLR9 mouse model of MAS. In acute MAS, lungs exhibit mild but diffuse CD4-predominant, perivascular interstitial inflammation with elevated IFN-γ, IFN-induced chemokines, and alveolar macrophage (AMϕ) expression of IFN-γ-induced genes. Single-cell RNA sequencing confirmed IFN-driven transcriptional changes across lung cell types with myeloid expansion and detection of MAS-specific macrophage populations. Systemic MAS resolution was associated with increased AMϕ and interstitial lymphocytic infiltration. AMϕ transcriptomic analysis confirmed IFN-γ-induced proinflammatory polarization during acute MAS, which switches toward an antiinflammatory phenotype after systemic MAS resolution. Interestingly, recurrent MAS led to increased alveolar inflammation and lung injury, and it reset AMϕ polarization toward a proinflammatory state. Furthermore, in mice bearing macrophages insensitive to IFN-γ, both systemic features of MAS and pulmonary inflammation were attenuated. These findings demonstrate that experimental MAS induces IFN-γ-driven pulmonary inflammation replicating key features of SJIA-LD and provides a model system for testing potentially novel treatments directed toward SJIA-LD.

Purpose of review The novel severe respiratory syndrome coronavirus-2 (SARS-CoV-2) virus has caused a world-wide pandemic with devastating effects. Fortunately, most children display only mild-to-moderate symptoms, but there are a subset that will have severe symptoms warranting treatment. This review evaluates the current evidence for antiviral and anti-inflammatory treatment of acute SARS-COV-2 infections, including coronavirus disease 2019 in pediatrics. Recent findings Treatment recommendations continue to evolve with emerging results from clinical trials. Initial therapies were tailored to repurposed medications, and have now transitioned toward more specific antiviral therapy. In addition to specific antiviral therapy, there is also support to modulate the immune system and reduce inflammatory damage seen in coronavirus disease 2019. Much of the data result from adult studies with subsequent extrapolation to pediatrics. Summary Recommended therapy will continue to adapt as results return from clinical trials. A continued commitment from the National Institutes of Health and research community to assist in determining optimal therapies for pediatric patients is essential. Until then, most recommendations will likely be informed from the results seen in adult populations.

Background: Multisystem inflammatory syndrome in children (MIS-C) is a potentially life-threatening hyperinflammatory syndrome that occurs after primary SARS-CoV-2 infection. The pathogenesis of MIS-C remains undefined, and whether specific inflammatory biomarker patterns can distinguish MIS-C from other hyperinflammatory syndromes including Kawasaki disease (KD) and macrophage activation syndrome (MAS) is unknown. Methods: We studied a prospective cohort of nineteen MIS-C and nine KD patients and an established cohort of eleven new onset SJIA and nine MAS associated SJIA patients. Clinical and laboratory features as well as S100A8/A9, S100A12, IL-18, CXCL9 and IL-6 levels were compared between disease groups. Findings: KD and MIS-C patients have similar S100 proteins and IL-18 profiles but are distinguished by significantly higher levels of the IFN-γ-induced chemokine CXCL9 in MIS-C. Stratifying MIS-C patients by CXCL9 levels revealed differential severity of clinical and laboratory presentation. MIS-C with high CXCL9 levels was associated with acute kidney injury, altered mental status, a higher frequency of shock (40 vs 90%), myocardial dysfunction (20 vs 50%), and more severe systemic inflammatory markers, cytopenia, and coagulopathy. The low CXCL9 MIS-C group in contrast resembled KD patients including the frequency of coronary involvement. We also found that elevated S100A8/A9, S100A12 and IL-18 were useful in distinguishing SJIA from KD with high sensitivity and specificity. Interpretation: Our findings show MIS-C is distinguished from KD primarily by elevated CXCL9. The stratification of CXCL9 levels of MIS-C patients provides support for MAS pathophysiology in patients with severe MIS-C, suggesting new approaches for diagnosis and management. Funding: This work was supported by an Academic Research Clinical (ARC) award to AG and GS from the Cincinnati Children’s Research Foundation. GS was supported by NIAMS/NIH K08-AR072075, AG by P30-AR070549, and JRS and GC by T32-AR069512. EV was supported by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG/448863690). Declaration of Interests: AG has served as a consultant and received research support from Novartis, Sobi, NovImmune and AB2Bio. GS consulting fees from Novartis and SOBI. All other authors report no disclosures. Ethics Approval Statement: The study was approved by the Institutional Review Board (CCHMC IRB2018-2408).

We thank Dr. Kotnik and colleagues for their commentary on the American College of Rheumatology's clinical guidance for pediatric patients with multisystem inflammatory syndrome in children (MIS-C). The use of anticoagulation in this population remains an intensely debated topic with little clinical evidence to guide treatment decisions. For this reason, the task force was only able to achieve consensus on recommending anticoagulation in patients with larger coronary artery aneurysms (CAAs) (z-score >10) and significant cardiac dysfunction (ejection fraction < 35%) based on the well-established risk for thrombosis in patients with these clinical features.(1, 2).

Background:The calcium-binding proteins S100A8/A9 (calprotectin) and S100A12 (extracellular newly identified receptor for advanced glycation end-products binding protein [EN-RAGE]) are involved in multiple signalling pathways to mediate inflammation, can be secreted by activated monocytes/macrophages and exhibit cytokine-like extracellular functions. Circulating levels of these proteins have been associated with disease and clinical responses in systemic juvenile idiopathic arthritis (sJIA), including treatment response.1 Studies suggest that serum S100A8/A9 and S100A12, which are released at inflammation sites, are more specific biomarkers of local inflammation (e.g. in the synovium) than systemic biomarkers such as CRP and ESR.2,3Objectives:To investigate if baseline S100A8/A9 and S100A12 predict clinical response to abatacept treatment in polyarticular JIA (pJIA), and to assess whether changes from baseline in S100A8/A9 or S100A12 can be better prognostic markers for response to abatacept treatment than CRP in pJIA.Methods:Data are from a phase III trial of SC abatacept for the treatment of pJIA (NCT01844518).4 This 24-month, single-arm, open-label, international, multicentre, two-part study included male and female patients with pJIA aged 2–17 years. This analysis examined the correlation between biomarkers (S100A8/A9, S100A12 and high-sensitivity CRP [hsCRP]) and disease activity (measured using Juvenile Arthritis Disease Activity Score [JADAS]) at baseline, baseline biomarker values as predictors of future treatment response (ACR and JADAS endpoints), and the correlation between change from baseline in biomarker values and treatment response at Day 113.Results:Of 219 total patients, 158 (72%) had S100A8/A9 values and 155 (71%) had S100A12 values at baseline. Median S100A8/A9 and S100A12 values were 3295 ng/mL (normal range, 716–3004 ng/mL) and 176 ng/mL (normal range, 32–385 ng/mL), respectively. S100A8/A9, S100A12 and hsCRP (median 0.20 mg/dL; normal ≤0.6 mg/dL) had a low-to-moderate but significant association with disease activity at baseline; coefficients for associations between JADAS71-CRP low disease activity (LDA) and the biomarkers S100A8/A9, S100A12 and hsCRP were 0.23 (p=0.0038), 0.16 (p=0.0448) and 0.26 (p=0.0001), respectively. Baseline S100A8/A9 level above the median was associated with lower odds of ACR100 at Day 113 (p=0.0052). Figure 1 shows the associations of baseline biomarker values with Day 113 ACR and JADAS scores in the overall population. Baseline S100A8/A9 or S100A12 did not significantly influence ACR50 or ACR70 responses at Day 113, but high baseline values were associated with reduced odds of ACR90 (p=0.01), ACR100 (p=0.005), ACR-inactive disease (ID) (p=0.0001), and JADAS71-CRP (LDA) (p=0.02). By Day 477, elevated baseline S100A12 was still significantly associated with lower odds of ACR100 overall (0.467; p=0.0248) but baseline S100A8/A9 was not; at Day 645, neither was significantly associated with ACR100 response. At Day 113, changes from baseline in S100A8/A9 and S100A12 were correlated with ACR100 (coefficients of 0.22 [p=0.0082] and 0.26 [p=0.0015], respectively) and with ACR-ID (0.22 [p=0.0067] and 0.26 [p=0.0014], respectively); change in hsCRP was not significantly correlated with disease response.Conclusion:S100A8/A9 and S100A12 may serve as prognostic biomarkers to predict response to abatacept treatment at Day 113. Changes from baseline S100A8/A9 and S100A12 levels were more highly correlated with efficacy outcomes including ACR100 and ACR-ID at Day 113 compared with hsCRP.References:[1]Aljaberi N, et al. Pediatr Rheumatol Online J 2020;18:7.[2]Hammer H, et al. Arthritis Res Ther 2011;13:R178.[3]Nordal HH, et al. BMC Musculoskelet Disord 2014;15:335.[4]Brunner H, et al. Arthritis Rheumatol 2018;70:1144–1154.Acknowledgements:Professional medical writing and editorial assistance was provided by Rob Coover, MPH, at Caudex and was funded by Bristol Myers Squibb.Disclosure of Interests:Nicolino Ruperto Speakers bureau: NR has received honoraria for consultancies or speaker bureaus (< 10.000 USD each) from the following pharmaceutical companies in the past 3 years: Ablynx, Astrazeneca-Medimmune, Bayer, Biogen, Boehringer, Bristol Myers Squibb, Celgene, Eli Lilly, EMD Serono, GlaxoSmithKline, Hoffmann-La Roche, Janssen, Merck, Novartis, Pfizer, R-Pharma, Sinergie, Sobi and UCB, Consultant of: NR has received honoraria for consultancies or speaker bureaus (< 10.000 USD each) from the following pharmaceutical companies in the past 3 years: Ablynx, Astrazeneca-Medimmune, Bayer, Biogen, Boehringer, Bristol Myers Squibb, Celgene, Eli Lilly, EMD Serono, GlaxoSmithKline, Hoffmann-La Roche, Janssen, Merck, Novartis, Pfizer, R-Pharma, Sinergie, Sobi and UCB, Grant/research support from: The IRCCS Istituto Giannina Gaslini (IGG), where NR works as full-time public employee has received contributions (>10.000 USD each) from the following industries in the last 3 years: Bristol Myers Squibb, Eli Lilly, F Hoffmann-La Roche, GlaxoSmithKline, Janssen, Novartis, Pfizer, Sobi. This funding has been reinvested for the research activities of the hospital in a fully independent manner, without any commitment with third parties., Grant Schulert Speakers bureau: Novartis, Consultant of: SOBI, Alyssa Sproles: None declared, Sherry Thornton: None declared, Gabriel Vega Cornejo Speakers bureau: AbbVie, Grant/research support from: Bristol Myers Squibb, Eli Lilly, Janssen, Parexel, Sanofi, Jordi Anton Speakers bureau: AbbVie, Gebro, GlaxoSmithKline, Novartis, Pfizer, Roche, Sobi, Consultant of: AbbVie, Gebro, GlaxoSmithKline, Novartis, Pfizer, Roche, Sobi, Grant/research support from: AbbVie, Amgen, Gebro, GlaxoSmithKline, Lilly, Novartis, Novimmune, Pfizer, Roche, Sanofi, Sobi, Ruben Cuttica Speakers bureau: AbbVie, Bristol Myers Squibb, GlaxoSmithKline, Lilly, Novartis, Pfizer, Roche, UCB, Paid instructor for: AbbVie, Novartis, Pfizer, Roche, Consultant of: AbbVie, Bristol Myers Squibb, GlaxoSmithKline, Lilly, Novartis, Pfizer, Roche, UCB, Michael Henrickson: None declared, Ivan Foeldvari Consultant of: Bristol Myers Squibb, Gilead, Hexal, MEDAC, Novartis, Pfizer, Sanofi, Daniel Kingsbury Consultant of: Pfizer, Margarita Askelson Consultant of: Currently working for Syneos Health providing services to Bristol Myers Squibb, Jinqi Liu Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Sumanta Mukherjee Shareholder of: Bristol Myers Squibb, GlaxoSmithKline, Employee of: Bristol Myers Squibb, GlaxoSmithKline, Robert Wong Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Daniel J Lovell Speakers bureau: Genentech, Wyeth Pharm, Consultant of: Abbott, Amgen, AstraZeneca, Boehringer Ingelheim, Celgene, GlaxoSmithKline, Hoffman-La Roche, Novartis, Pfizer, Regeneron, Takeda, UBC, Wyeth Pharma, Xoma, Alberto Martini Speakers bureau: AbbVie, Novartis, Consultant of: AbbVie, Eli Lilly, EMD Serono, Idorsia, Janssen, Novartis, Pfizer, Alexei Grom Consultant of: AB2Bio, Novartis, Sobi (NovImmune), Grant/research support from: AB2Bio, Novartis, Sobi (NovImmune), Hermine Brunner Speakers bureau: GlaxoSmithKline, Novartis, Pfizer, Roche, Paid instructor for: Novartis, Pfizer (funds go to CCHMC/employer), Consultant of: Boehringer Ingelheim, Bristol Myers Squibb, GlaxoSmithKline, Janssen, Merck, Novartis, Pfizer, Roche, UCB (funds go to CCHMC/employer), Grant/research support from: Bristol Myers Squibb, Pfizer (funds go to CCHMC/employer).

OBJECTIVE Canakinumab is a human anti-interleukin-1β (anti-IL-1β) blocking agent that effectively neutralizes IL-1β-mediated signaling for treatment of systemic juvenile idiopathic arthritis (JIA). While many patients have dramatic clinical response to IL-1 blockade, approximately one-third fail to respond, but there are currently no validated clinical or immunologic predictors of response. We undertook this study to characterize distinct gene signatures for treatment response and nonresponse to canakinumab in systemic JIA patients. METHODS We performed a secondary analysis of whole-blood gene expression microarrays using blood samples obtained from healthy controls and systemic JIA patients at baseline and on day 3 after canakinumab treatment (GEO accession no. GSE80060). Patients were considered strong clinical responders if they met the ACR90 response (exhibited ≥90% improvement in the American College of Rheumatology [ACR] JIA response criteria; nonresponders were those who met ACR30 [exhibiting ≤30% improvement in the ACR JIA response criteria]). A random-effects model with patient identity as the random variable was used for differential expression analysis. RESULTS We identified a distinct gene expression signature in patients with a strong clinical response to canakinumab treatment as compared to nonresponders, mediated by up-regulation of neutrophil- and IL-1-associated genes and characterized by increasing divergence from control transcriptomes with increasing clinical response. We also identified a signature including up-regulated CD163 expression that was associated with canakinumab nonresponse. Intriguingly, canakinumab treatment induced either up- or down-regulation of type I interferon (IFN) genes, independent of clinical response. CONCLUSION Here, we identify a gene signature in systemic JIA patients prior to receiving treatment that distinguishes strong responders to canakinumab from nonresponders. Further prospective studies are needed to assess the utility of these insights for treatment decisions in systemic JIA and to track the association of up-regulated type I IFN signatures with systemic JIA complications.

Hemophagocytic lymphohistiocytosis (HLH) represents a potentially life-threatening episode of overwhelming inflammation characterized by activation of T lymphocytes, hemophagocytic macrophages, and marked hyperferritinemia1,2. Historically, HLH has been classified as having a primary, genetic cause (familial HLH) or occurring secondary to an identified trigger including various infections, malignancies, or rheumatic diseases. When occurring in the setting of inflammatory or autoimmune disease, rheumatologists call secondary HLH the macrophage activation syndrome (MAS), and it is reflected as MAS-HLH in the updated Histiocyte Society nomenclature3. Episodes of MAS-HLH have been reported in nearly all rheumatic diseases, but are most commonly recognized in patients with systemic juvenile idiopathic arthritis (sJIA) or adult-onset Still disease (AOSD), systemic lupus erythematosus (SLE), Kawasaki disease, and certain monogenic autoinflammatory disorders4,5. In contrast, the inflammatory myopathies including dermatomyositis (DM) and polymyositis (PM) have typically been considered low-risk for development of MAS-HLH. In the current issue of The Journal , Liang and colleagues6 present a large series of patients with adult idiopathic inflammatory myopathies that challenges this conventional wisdom, and suggest that MAS-HLH may represent an underappreciated cause of mortality in these disorders. In this report, the authors identified 424 adult patients admitted to their institution over an 8-year period with DM, PM, or clinically amyopathic dermatomyositis (CADM)6. Interestingly, they found that 18 (4.2%) satisfied the 2004 diagnostic criteria for HLH7. … Address correspondence to Dr. G.S. Schulert, Division of Rheumatology, Cincinnati Children’s Hospital Medical Center, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45208 USA. Email: Grant.schulert{at}cchmc.org.

BACKGROUND. Undifferentiated systemic autoinflammatory diseases (USAIDs) present diagnostic and therapeutic challenges. Chronic interferon (IFN) signaling and cytokine dysregulation may identify diseases with available targeted treatments. METHODS. Sixty-six consecutively referred USAID patients underwent underwent screening for the presence of an interferon signature using a standardized type-I IFN-response-gene score (IRG-S), cytokine profiling, and genetic evaluation by next-generation sequencing. RESULTS. Thirty-six USAID patients (55%) had elevated IRG-S. Neutrophilic panniculitis (40% vs. 0%), basal ganglia calcifications (46% vs. 0%), interstitial lung disease (47% vs. 5%), and myositis (60% vs. 10%) were more prevalent in patients with elevated IRG-S. Moderate IRG-S elevation and highly elevated serum IL-18 distinguished 8 patients with pulmonary alveolar proteinosis (PAP) and recurrent macrophage activation syndrome (MAS). Among patients with panniculitis and progressive cytopenias, 2 patients were compound heterozygous for potentially novel LRBA mutations, 4 patients harbored potentially novel splice variants in IKBKG (which encodes NF-κB essential modulator [NEMO]), and 6 patients had de novo frameshift mutations in SAMD9L. Of additional 12 patients with elevated IRG-S and CANDLE-, SAVI- or Aicardi-Goutières syndrome-like (AGS-like) phenotypes, 5 patients carried mutations in either SAMHD1, TREX1, PSMB8, or PSMG2. Two patients had anti-MDA5 autoantibody-positive juvenile dermatomyositis, and 7 could not be classified. Patients with LRBA, IKBKG, and SAMD9L mutations showed a pattern of IRG elevation that suggests prominent NF-κB activation different from the canonical interferonopathies CANDLE, SAVI, and AGS. CONCLUSIONS. In patients with elevated IRG-S, we identified characteristic clinical features and 3 additional autoinflammatory diseases: IL-18-mediated PAP and recurrent MAS (IL-18PAP-MAS), NEMO deleted exon 5-autoinflammatory syndrome (NEMO-NDAS), and SAMD9L-associated autoinflammatory disease (SAMD9L-SAAD). The IRG-S expands the diagnostic armamentarium in evaluating USAIDs and points to different pathways regulating IRG expression. Fil: de Jesus, Adriana A.. National Institute Of Allergy And Infectious Diseases; Estados Unidos Fil: Hou, Yangfeng. Shandong University; China Fil: Brooks, Stephen. National Institute Of Arthritis And Musculoskeletal And Skin Diseases; Estados Unidos Fil: Malle, Louise. cahn School of Medicine at Mount Sinai; Estados Unidos Fil: Biancotto, Angelique. No especifíca; Fil: Huang, Yan. National Institute Of Allergy And Infectious Diseases; Estados Unidos Fil: Calvo, Katherine R.. National Institutes of Health; Estados Unidos Fil: Marrero, Bernadette. No especifíca; Fil: Moir, Susan. No especifíca; Fil: Oler, Andrew J.. National Institute Of Allergy And Infectious Diseases ; Estados Unidos Fil: Deng, Zuoming. National Institute Of Arthritis And Musculoskeletal And Skin Diseases; Estados Unidos Fil: Montealegre Sanchez, Gina A.. National Institute Of Allergy And Infectious Diseases ; Estados Unidos Fil: Ahmed, Amina. No especifíca; Fil: Allenspach, Eric. Washington State University; Estados Unidos Fil: Arabshahi, Bita. Virginia Commonwealth University; Estados Unidos Fil: Behrens, Edward. University of Pennsylvania; Estados Unidos Fil: Benseler, Susanne. University of Calgary; Canadá Fil: Bezrodnik, Liliana. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Bout Tabaku, Sharon. No especifíca; Fil: Brescia, AnneMarie C.. No especifíca; Fil: Brown, Diane. No especifíca; Fil: Burnham, Jon M.. University of Pennsylvania; Estados Unidos Fil: Caldirola, Maria Soledad. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; Argentina. Gobierno de la Ciudad de Buenos Aires. Instituto Multidisciplinario de Investigaciones en Patologías Pediátricas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto Multidisciplinario de Investigaciones en Patologías Pediátricas; Argentina Fil: Carrasco, Ruy. No especifíca; Fil: Chan, Alice Y.. University of California; Estados Unidos Fil: Cimaz, Rolando. Università degli Studi di Milano; Italia Fil: Dancey, Paul. Janeway Children's Hospital And Rehabilitation Centre; Canadá Fil: Dare, Jason. University of Arkansas for Medical Sciences; Estados Unidos Fil: DeGuzman, Marietta. Baylor College Of Medicine; Estados Unidos Fil: Dimitriades, Victoria. No especifíca; Fil: Ferguson, Ian. University of Yale. School of Medicine; Estados Unidos Fil: Ferguson, Polly. University of Iowa; Estados Unidos Fil: Finn, Laura. University of Washington; Estados Unidos Fil: Gattorno, Marco. No especifíca; Fil: Grom, Alexei A.. No especifíca; Fil: Hanson, Eric P.. No especifíca; Fil: Hashkes, Philip J.. No especifíca; Fil: Hedrich, Christian M.. University of Liverpool; Reino Unido Fil: Herzog, Ronit. University of New York; Estados Unidos Fil: Horneff, Gerd. Universitat zu Köln; Alemania Fil: Jerath, Rita. Augusta University; Estados Unidos Fil: Kessler, Elizabeth. University of Missouri; Estados Unidos Fil: Kim, Hanna. No especifíca; Fil: Kingsbury, Daniel J.. No especifíca; Fil: Laxer, Ronald M.. University Of Toronto. Hospital For Sick Children; Canadá Fil: Lee, Pui Y.. Children's Hospital Boston; Estados Unidos Fil: Lee Kirsch, Min Ae. Technische Universität Dresden; Alemania Fil: Lewandowski, Laura. No especifíca; Fil: Li, Suzanne. Hackensack University Medical Center; Estados Unidos Fil: Lilleby, Vibke. Oslo University Hospital; Noruega Fil: Mammadova, Vafa. Azerbaijan Medical University; Azerbaiyán Fil: Moorthy, Lakshmi N.. Robert Wood Johnson Medical School; Estados Unidos Fil: Nasrullayeva, Gulnara. Azerbaijan Medical University; Azerbaiyán Fil: O'Neil, Kathleen M.. Riley Hospital for Children; Estados Unidos Fil: Onel, Karen. Hospital for Special Surgery; Estados Unidos Fil: Ozen, Seza. Hacettepe University; Turquía Fil: Pan, Nancy. Hospital for Special Surgery; Estados Unidos Fil: Pillet, Pascal. Children Hospital Pellegrin-Enfants; Francia Fil: Piotto, Daniela G.P.. Universidade Federal de Sao Paulo; Brasil Fil: Punaro, Marilynn G.. University of Texas; Estados Unidos Fil: Reiff, Andreas. University of Nebraska; Estados Unidos Fil: Reinhardt, Adam. University of Nebraska; Estados Unidos Fil: Rider, Lisa G.. No especifíca; Fil: Rivas Chacon, Rafael. Nicklaus Children’s Hospital; Estados Unidos Fil: Ronis, Tova. Children’s National Health System; Estados Unidos Fil: Rösen Wolff, Angela. Technische Universität Dresden; Alemania Fil: Roth, Johannes. Children’s Hospital of Eastern Ontario; Canadá Fil: Mckerran Ruth, Natasha. Medical University of South Carolina; Estados Unidos Fil: Rygg, Marite. Norwegian University of Science and Technology; Noruega Fil: Schmeling, Heinrike. University of Calgary; Canadá Fil: Schulert, Grant. Children’s Hospital Medical Center; Estados Unidos Fil: Scott, Christiaan. University of Cape Town; Sudáfrica Fil: Seminario, Gisella. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; Argentina Fil: Shulman, Andrew. University of California at Irvine; Estados Unidos Fil: Sivaraman, Vidya. Nationwide Children’s Hospital; Estados Unidos Fil: Son, Mary Beth. Boston Children’s Hospital; Estados Unidos Fil: Stepanovskiy, Yuriy. Shupyk National Medical Academy for Postgraduate Education; Ucrania Fil: Stringer, Elizabeth. Dalhousie University Halifax; Canadá Fil: Taber, Sara. Hospital for Special Surgery; Estados Unidos Fil: Terreri, Maria Teresa. Universidade Federal de Sao Paulo; Brasil Fil: Tifft, Cynthia. No especifíca; Fil: Torgerson, Troy. University of Washington; Estados Unidos Fil: Tosi, Laura. Children’s National Health System; Estados Unidos Fil: van Royen Kerkhof, Annet. Wilhelmina Children’s Hospital Utrech; Países Bajos Fil: Wampler Muskardin, Theresa. New York University School of Medicine; Estados Unidos Fil: Canna, Scott W.. University of Pittsburgh; Estados Unidos Fil: Goldbach Mansky, Raphaela. National Institute Of Allergy And Infectious Diseases ; Estados Unidos

ObjectivesSystemic juvenile idiopathic arthritis (SJIA) confers high risk for macrophage activation syndrome (MAS), a life-threatening cytokine storm driven by interferon (IFN)-γ. SJIA monocytes display IFN-γ hyper-responsiveness, but the molecular basis of this remains unclear. The objective of this study is to identify circulating monocyte and bone marrow macrophage (BMM) polarisation phenotypes in SJIA including molecular features contributing to IFN response.MethodsBulk RNA-seq was performed on peripheral blood monocytes (n=26 SJIA patients) and single cell (sc) RNA-seq was performed on BMM (n=1). Cultured macrophages were used to define consequences of tripartite motif containing 8 (TRIM8) knockdown on IFN-γ signalling.ResultsBulk RNA-seq of SJIA monocytes revealed marked transcriptional changes in patients with elevated ferritin levels. We identified substantial overlap with multiple polarisation states but little evidence of IFN-induced signature. Interestingly, among the most highly upregulated genes was TRIM8, a positive regulator of IFN-γ signalling. In contrast to PBMC from SJIA patients without MAS, scRNA-seq of BMM from a patient with SJIA and MAS identified distinct subpopulations of BMM with altered transcriptomes, including upregulated IFN-γ response pathways. These BMM also showed significantly increased expression of TRIM8. In vitro knockdown of TRIM8 in macrophages significantly reduced IFN-γ responsiveness.ConclusionsMacrophages with an ‘IFN-γ response’ phenotype and TRIM8 overexpression were expanded in the bone marrow from an MAS patient. TRIM8 is also upregulated in SJIA monocytes, and augments macrophage IFN-γ response in vitro, providing both a candidate molecular mechanism and potential therapeutic target for monocyte hyper-responsiveness to IFNγ in cytokine storms including MAS.

Poor outcomes in COVID-19 correlate with clinical and laboratory features of cytokine storm syndrome. Broad screening for cytokine storm and early, targeted antiinflammatory therapy may prevent immunopathology and could help conserve limited health care resources. While studies are ongoing, extrapolating from clinical experience in cytokine storm syndromes may benefit the multidisciplinary teams caring for patients with severe COVID-19.

Chromatin undergoes extensive reprogramming during immune cell differentiation. Here we report the repression of controlled histone H3 amino terminus proteolytic cleavage (H3ΔN) during monocyte-to-macrophage development. This abundant histone mark in human peripheral blood monocytes is catalyzed by neutrophil serine proteases (NSPs) cathepsin G, neutrophil elastase and proteinase 3. NSPs are repressed as monocytes mature into macrophages. Integrative epigenomic analysis reveals widespread H3ΔN distribution across the genome in a monocytic cell line and primary monocytes, which becomes largely undetectable in fully differentiated macrophages. H3ΔN is enriched at permissive chromatin and actively transcribed genes. Simultaneous NSP depletion in monocytic cells results in H3ΔN loss and further increase in chromatin accessibility, which likely primes the chromatin for gene expression reprogramming. Importantly, H3ΔN is reduced in monocytes from patients with systemic juvenile idiopathic arthritis, an autoinflammatory disease with prominent macrophage involvement. Overall, we uncover an epigenetic mechanism that primes the chromatin to facilitate macrophage development. Chromatin undergoes extensive reprogramming during immune cell differentiation. Here Kuo and colleagues uncover an epigenetic mechanism that primes the chromatin to facilitate macrophage development.

Systemic juvenile idiopathic arthritis (SJIA) is a severe childhood arthropathy with features of autoinflammation. Monocytes and macrophages in SJIA have a complex phenotype with both pro- and anti-inflammatory properties that combine features of several well characterized in vitro conditions used to activate macrophages. An important anti-inflammatory phenotype is expression of CD163, a scavenger receptor that sequesters toxic pro-inflammatory complexes that is highly expressed in both active SJIA and macrophage activation syndrome (MAS). CD163 is most strongly up-regulated by IL-10 (M(IL-10)), and not by other conditions that reflect features seen in SJIA monocytes such as M(LPS+IC). MicroRNA plays key roles in integrating cellular signals such as those in macrophage polarization, and as such we hypothesize microRNAs regulate macrophage functional responses in SJIA including CD163 expression. We find that 2 microRNAs previously found to be elevated in active SJIA, miR-125a-5p and miR-181c, significantly reduced macrophage CD163 expression through 2 distinct mechanisms. Neither microRNA was elevated in M(IL-10) with robust CD163 expression, but were instead induced in M(LPS+IC) where they restricted CD163 mRNA expression. Mir-181 species directly targeted CD163 mRNA for degradation. In contrast, miR-125a-5p functions indirectly, as transcriptome analysis of miR-125a-5p overexpression identified “cytokine-cytokine receptor interactions” as the most significantly repressed gene pathway, including decreased IL10RA, required for IL-10-mediated CD163 expression. Finally, overexpression of miR-181c inhibited CD163 anti-inflammatory responses to hemoglobin or high mobility group box 1 (HMGB1) complexes. Together, these data show that microRNA utilizes multiple mechanisms to integrate well-characterized polarization phenotypes and regulate macrophage functional properties seen in SJIA.