BACKGROUND The study of autoinflammatory diseases has uncovered mechanisms underlying cytokine dysregulation and inflammation. METHODS We analyzed the DNA of an index patient with early-onset systemic inflammation, cutaneous vasculopathy, and pulmonary inflammation. We sequenced a candidate gene, TMEM173, encoding the stimulator of interferon genes (STING), in this patient and in five unrelated children with similar clinical phenotypes. Four children were evaluated clinically and immunologically. With the STING ligand cyclic guanosine monophosphate–adenosine monophosphate (cGAMP), we stimulated peripheral-blood mononuclear cells and fibroblasts from patients and controls, as well as commercially obtained endothelial cells, and then assayed transcription of IFNB1, the gene encoding interferon-β, in the stimulated cells. We analyzed IFNB1 reporter levels in HEK293T cells cotransfected with mutant or nonmutant STING constructs. Mutant STING leads to increased phosphorylation of signal transducer and activator of transcription 1 (STAT1), so we tested the effect of Janus kinase (JAK) inhibitors on STAT1 phosphorylation in lymphocytes from the affected children and controls. RESULTS We identified three mutations in exon 5 of TMEM173 in the six patients. Elevated transcription of IFNB1 and other gene targets of STING in peripheral-blood mono-nuclear cells from the patients indicated constitutive activation of the pathway that cannot be further up-regulated with stimulation. On stimulation with cGAMP, fibro-blasts from the patients showed increased transcription of IFNB1 but not of the genes encoding interleukin-1 (IL1), interleukin-6 (IL6), or tumor necrosis factor (TNF). HEK293T cells transfected with mutant constructs show elevated IFNB1 reporter levels. STING is expressed in endothelial cells, and exposure of these cells to cGAMP resulted in endothelial activation and apoptosis. Constitutive up-regulation of phosphorylated STAT1 in patients’ lymphocytes was reduced by JAK inhibitors. CONCLUSIONS STING-associated vasculopathy with onset in infancy (SAVI) is an autoinflammatory disease caused by gain-of-function mutations in TMEM173.

MIS-C is a newly defined post-viral myocarditis and inflammatory vasculopathy of children following COVID-19 infection. This review summarizes the literature on diagnosis, parameters of disease severity, and current treatment regimens. The clinical perspective was analyzed in light of potential immunopathogenesis and compared to other post-infectious and inflammatory illnesses of children affecting the heart. In this paradigm, the evidence supports the importance of endothelial injury and activation of the IL-1 pathway as a common determinant among MIS-C, Kawasaki disease, and Acute Rheumatic fever.

Objective To formulate consensus treatment plans (CTPs) for induction therapy of newly-diagnosed proliferative lupus nephritis (LN) in juvenile systemic lupus erythematosus (jSLE). Methods A structured consensus formation process was employed by the members of the Childhood Arthritis and Rheumatology Research Alliance (CARRA) after considering the existing medical evidence and current treatment approaches. Results After an initial Delphi survey (response rate 70%), a 2-day consensus conference, and two follow-up Delphi surveys (response rates 63–79%), consensus was achieved for a limited set of CTPs addressing the induction therapy of proliferative LN. These CTPs were developed for prototypic patients defined by eligibility characteristics, and included immunosuppressive therapy with either mycophenolic acid orally twice per day, or intravenous cyclophosphamide once per month at standardized doses for six months. Additionally, the CTPs describe three options for standardized use of glucocorticoids; including a primarily oral, a mixed oral/intravenous, and a primarily intravenous regimen. There was consensus on measures of effectiveness and safety of the CTPs. The CTPs were well accepted by the pediatric rheumatology providers treating children with LN, and up to 300 children per year in North America are expected to be candidates for the treatment with the CTPs. Conclusion CTPs for induction therapy of proliferative LN in jSLE based on the available scientific evidence and pediatric rheumatology group experience have been developed. Consistent use of the CTPs may improve the prognosis of proliferative LN, and support the conduct of comparative effectiveness studies aimed at optimizing therapeutic strategies for proliferative LN in jSLE.

Objective. Previous studies showed that etanercept treatment in patients with polyarticular-course juvenile rheumatoid arthritis (JRA) provided rapid clinical improvement that was sustained for up to 2 years. The goal of our study was to provide data on safety and efficacy after 4 years of etanercept treatment in patients with JRA. Conclusion. Etanercept offers an acceptable safety profile in children with polyarticular-course JRA and provides significant improvement in disease manifestations that are sustained for >4 years.

Objective. To evaluate the long-term efficacy and safety of etanercept in children with juvenile rheumatoid arthritis (JRA) participating in an ongoing multicenter, open-label, extended-treatment trial. All patients had been participants in an initial randomized efficacy and safety trial of etanercept.Methods. Etanercept was administered at a dosage of 0.4 mg/kg (maximum 25 mg) subcutaneously twice each week. Safety and efficacy evaluations were performed every 3-4 months. The JRA 30% definition of improvement (DOI) was defined as improvement of >30% in at least 3 of 6 response variables used to assess disease activity, with no more than 1 variable worsening by more than 30%.Results. At the time of analysis, 48 of the 58 patients (83%) were still enrolled in the study; 43 of them (74%) had completed 2 years of treatment. Of these 43 patients, 81% met the JRA 30% DOI, 79% met the JRA 50% DOI, and 67% met the JRA 70% DOI. Ten children started low-dose methotrexate after year 1. Of the 32 children taking prednisone, the dosage was decreased to <5 mg/day in 26 (81%). Two children had serious infections (varicella with aseptic meningitis in one and complicated sepsis in the other). In general, adverse events were of the types seen in a general pediatric patient population.Conclusion. Children with severe, longstanding, methotrexate-resistant polyarticular JRA demonstrated sustained clinical improvement with >2 years of continuous etanercept treatment. Etanercept was generally well-tolerated. There were no increases in the rates of adverse events over time. However, children taking etanercept should be monitored closely for infections.Juvenile rheumatoid arthritis (JRA) is the most common rheumatic disease in children (1,2). The proinSupported by Immunex Corporation, Seattle, WA, who provided the study drug and grants to investigational sites.

When a child develops new-onset bone-joint complaints, the presence of subtle complete blood count changes combined with nighttime pain should lead to consideration of leukemia as the underlying cause.

The juvenile idiopathic inflammatory myopathies (JIIM) are rare, heterogeneous autoimmune diseases that share chronic muscle inflammation and weakness. JIIM broadly includes three major clinicopathologic groups: juvenile dermatomyositis, juvenile polymyositis, and overlap myositis. A growing spectrum of clinicopathologic groups and serologic phenotypes defined by the presence of myositis-specific or myositis-associated autoantibodies are now recognized, each with differing demographics, clinical manifestations, laboratory findings, and prognoses. With the first multi-center collaborative studies and controlled trials using standardized preliminarily validated outcome measures, the therapy of juvenile myositis has advanced. Although daily oral corticosteroids remain the backbone of treatment, disease-modifying anti-rheumatic drugs (DMARDs) are almost always used as adjunctive therapy. Methotrexate is the conventional DMARD for the initial therapy, either alone or combined with intravenous pulse methylprednisolone, and/or intravenous immunoglobulin for patients with moderate to severe disease. Cyclosporine may be added to these or serve as an alternative to methotrexate. Other drugs and biologic therapies, including mycophenolate mofetil, tacrolimus, cyclophosphamide, rituximab, and infliximab, might benefit selected patients with recalcitrant disease, unacceptable steroid toxicity, or patients with risk factors for poor prognosis. The treatment of cutaneous disease, calcinosis, and the role for rehabilitation are also discussed.

Objective Autoantibodies recognizing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) are associated with statin exposure, the HLA allele DRB1*11:01, and necrotizing muscle biopsies in adult myositis patients. The aim of this study was to characterize the features of pediatric anti-HMGCR-positive myositis patients. Methods The sera of 440 juvenile myositis patients were screened for anti-HMGCR autoantibodies. Demographic and clinical features, responses to therapy, and HLA alleles were assessed. The features of anti-HMGCR-positive patients were compared to those of previously described adult patients with this autoantibody and to children with other myositis-specific autoantibodies (MSAs). Results Five (1.1%) of 440 patients were anti-HMGCR-positive; none had taken statin medications. Three patients had rashes characteristic of juvenile dermatomyositis and two patients had immune-mediated necrotizing myopathies. The median highest creatine kinase (CK) level of anti-HMGCR-positive subjects was 17,000 IU/L. All patients had severe proximal muscle weakness, distal weakness, muscle atrophy, joint contractures, and arthralgias, which were all more prevalent in HMGCR-positive subjects compared to MSA-negative patients or those with other MSAs. Anti-HMGCR-positive patients had only partial responses to multiple immunosuppressive medications and often a chronic course. The DRB1*07:01allele was present in all 5 patients compared to 26.25% of healthy controls (Pcorrected=0.01); none of the 5 pediatric patients had DRB1*11:01. Conclusions Compared to children with other MSAs, muscle disease appeared to be more severe in those with anti-HMGCR autoantibodies. Like adults, children with anti-HMGCR autoantibodies have severe weakness and high CK levels. In contrast to adults, anti-HMGCR-positive children have a strong association with HLA DRB1*07:01.