Increased Serum B Cell Activating Factor and a Proliferation-inducing Ligand Are Associated with Interstitial Lung Disease in Patients with Juvenile Dermatomyositis

Neutrophil and mononuclear leukocyte pathways and upstream regulators revealed by serum proteomics of adult and juvenile dermatomyositis

OBJECTIVES

Serum protein abundance was assessed in adult and juvenile dermatomyositis (DM and JDM) patients to determine differentially regulated proteins, altered pathways, and candidate disease activity biomarkers.

METHODS

Serum protein expression from 17 active adult DM and JDM patients each was compared to matched, healthy control subjects by a multiplex immunoassay. Pathway analysis and protein clustering of the differentially regulated proteins were examined to assess underlying mechanisms. Candidate disease activity biomarkers were identified by correlating protein expression with disease activity measures.

RESULTS

Seventy-eight of 172 proteins were differentially expressed in the sera of DM and JDM patients compared to healthy controls. Forty-eight proteins were differentially expressed in DM, 32 proteins in JDM, and 14 proteins in both DM and JDM. Twelve additional differentially expressed proteins were identified after combining the DM and JDM cohorts. C-X-C motif chemokine ligand 10 (CXCL10) was the most strongly upregulated protein in both DM and JDM sera. Other highly upregulated proteins in DM included S100 calcium binding protein A12 (S100A12), CXCL9, and nicotinamide phosphoribosyltransferase (NAMPT), while highly upregulated proteins in JDM included matrix metallopeptidase 3 (MMP3), growth differentiation factor 15 (GDF15), and von Willebrand factor (vWF). Pathway analysis indicated that phosphoinositide 3-kinase (PI3K), p38 mitogen-activated protein kinase (MAPK), and toll-like receptor 7 (TLR7) signaling were activated in DM and JDM. Additional pathways specific to DM or JDM were identified. A protein cluster associated with neutrophils and mononuclear leukocytes and a cluster of interferon-associated proteins were observed in both DM and JDM. Twenty-two proteins in DM and 24 proteins in JDM sera correlated with global, muscle, and/or skin disease activity. Seven proteins correlated with disease activity measures in both DM and JDM sera. IL-1 receptor like 1 (IL1RL1) emerged as a candidate global disease activity biomarker in DM and JDM.

CONCLUSION

Coordinate analysis of protein expression in DM and JDM patient sera by a multiplex immunoassay validated previous gene expression studies and identified novel dysregulated proteins, altered signaling pathways, and candidate disease activity biomarkers. These findings may further inform the assessment of DM and JDM patients and aid in the identification of potential therapeutic targets.

Advances in Juvenile Dermatomyositis: Pathophysiology, Diagnosis, Treatment and Interstitial Lung Diseases-A Narrative Review

Juvenile idiopathic inflammatory myopathy (JIIM) is a rare systemic autoimmune disease characterized by skeletal muscle weakness with or without a skin rash. Juvenile dermatomyositis (JDM) is the most common subtype of JIIM, accounting for 80% of JIIM. Recent studies identified several myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs). Each MSA or MAA is associated with distinct clinical features and outcomes, although there are several differences in the prevalence of MSA/MAA and autoantibody-phenotype relationships between age and ethnic groups. Histopathological studies have revealed critical roles of type I interferons and vasculopathy in the development of JDM. Serological classification mostly corresponds to clinicopathological classification. Novel therapeutic agents, such as biologics and Janus kinase inhibitors (JAKi), have been developed; however, to date, there is a lack of high-level evidence. As advances in treatment have reduced the mortality rate of JIIM, recent studies have focused on medium- and long-term outcomes. However, rapidly progressive interstitial lung disease (RP-ILD) remains a major cause of death in anti-melanoma differentiation gene 5 autoantibody-positive JDM. Early diagnosis and intervention using a multi-drug regimen is critical for the treatment of RP-ILD. Rituximab and JAKi may reduce mortality in patients with JDM-associated RP-ILD refractory to conventional therapy.

Novel B-cell subsets as potential biomarkers in idiopathic inflammatory myopathies: insights into disease pathogenesis and disease activity

Idiopathic inflammatory myopathies are a heterogeneous group of rare autoimmune disorders characterized by progressive muscle weakness and the histopathologic findings of inflammatory infiltrates in muscle tissue. Although their pathogenesis remains indefinite, the association of autoantibodies with clinical manifestations and the evidence of high effectiveness of depleting therapies suggest that B cells could be implicated. Therefore, we explored the landscape of peripheral B cells in this disease by multiparametric flow cytometry, finding significant numerical decreases in memory and double-negative subsets, as well as an expansion of the naive compartment relative to healthy controls, that contribute to defining disease-associated B-cell subset signatures and correlating with different clinical features of patients. Additionally, we determined the potential value of these subsets as diagnostic biomarkers, thus positioning B cells as neglected key elements possibly participating in idiopathic inflammatory myopathy onset or development.

Proof-of-concept study evaluating humoral primary immunodeficiencies via CJ:KREC ratio and serum BAFF level

Humoral primary immunodeficiencies are the most prevalent form of primary immunodeficiency (PID). Currently, there is no convenient method to quantify newly formed B cells. The aim of this proof-of-concept study was to quantitate the ratio of coding joints (CJs) to Kappa-deleting recombination excision circles (KRECs) and serum B cell activating factor (BAFF) in patients with humoral primary immunodeficiency and assess if they correlate with disease severity. This IRB-approved study was conducted at one academic children's hospital. Patients with humoral PIDs and healthy controls were included. CJ and KREC levels were measured via qPCR. Serum BAFF levels were measured using Mesoscale. 16 patients with humoral PID and 5 healthy controls were included. The mean CJ:KREC ratio in the CVID, antibody deficiency syndromes, and controls groups, respectively were 13.04 ± 9.5, 5.25 ± 4.1, and 4.38 ± 2.5 (p = 0.059). The mean serum BAFF levels in CVID, antibody deficiency syndromes and controls were 216.3 ± 290 pg/mL, 107.9 ± 94 pg/mL and 50.9 ± 12 pg/mL, respectively (p = 0.271). When the CVID patients were subdivided into CVID with or without lymphoproliferative features, the BAFF level was substantially higher in the CVID with lymphoproliferation cohort (mean 372.4 ± 361 pg/mL, p = 0.031). Elevated CJ:KREC ratio was observed in CVID, although statistical significance was not achieved, likely due to the small sample size. Serum BAFF levels were significantly higher in CVID patients with lymphoproliferative features. We speculate that the CJ:KREC ratio and serum BAFF levels can be utilized in patients with humoral PID, once more extensive studies confirm this exploratory investigation.

Elevated serum B-cell activator factor levels predict rapid progressive interstitial lung disease in anti-melanoma differentiation associated protein 5 antibody positive dermatomyositis

BACKGROUND

Rapid progressive interstitial lung disease (RP-ILD) is the leading cause of anti-melanoma differentiation associated protein 5 antibody positive dermatomyositis (anti-MDA5+DM) related death. Elevated serum B-cell activating factor (BAFF) levels have been implicated in connective tissue diseases associated ILD. Here, we evaluate whether BAFF could be a prognostic biomarker for predicting RP-ILD in anti-MDA5+DM patients.

METHODS

Serums were collected from 39 patients with anti-MDA5+DM (20 with RP-ILD and 19 with non-RP-ILD), 20 antisynthase syndrome (ASS) patients and 20 healthy controls (HC). BAFF concentration was measured by an enzyme-linked immunosorbent assay.

RESULTS

Serum BAFF level was higher in anti-MDA5+DM patients than those in ASS patients and HC (3882.32 ± 1880.09 vs. 2540.89 ± 1403.04 and 2486.28 ± 767.97 pg/mL, p = 0.0056 and 0.0038, respectively). Within anti-MDA5+DM groups, RP-ILD patients exhibited higher BAFF concentration than non-RP-ILD group (4549.78 ± 1839.97 vs. 3297.28 ± 1794.69 pg/mL, p = 0.04). The BAFF concentration was positively correlated with levels of C-reactive protein (CRP), dehydrogenase (LDH) and cytokeratin (CK) in anti-MDA5+DM patients (r = 0.350, p = 0.035; r = 0.393, p = 0.016; r = 0.518, p = 0.001; respectively). The best cut-off value of BAFF concentration was 2971.5 pg/mL by ROC curve (AUC area = 0.690, p = 0.045) and BAFF > 2971.5 pg/mL was an independent risk factor for RP-ILD using multivariate analysis (OR = 9.389, 95% CI = 1.609-54.769; p = 0.013).

CONCLUSIONS

Serum BAFF could be a useful prognostic biomarker for early detecting RP-ILD risk in anti-MDA5+DM patients.

B Cell Lymphocytosis in Juvenile Dermatomyositis

In this study, we determined if B lymphocytosis may serve as a JDM biomarker for disease activity. Children with untreated JDM were divided into two groups based on age-adjusted B cell percentage (determined through flow cytometry): 90 JDM in the normal B cell group and 45 in the high B cell group. We compared through T-testing the age, sex, ethnicity, duration of untreated disease (DUD), disease activity scores for skin (sDAS), muscle (mDAS), total (tDAS), CMAS, and neopterin between these two groups. The patients in the high B cell group had a higher tDAS (p = 0.009), mDAS (p = 0.021), and neopterin (p = 0.0365). Secondary analyses included B cell values over time and BAFF levels in matched patients with JM (juvenile myositis) and concurrent interstitial lung disease (ILD); JM alone and healthy controls Patient B cell percentage and number was significantly higher after 3-6 months of therapy and then significantly lower on completion of therapy (p =< 0.0001). The JM groups had higher BAFF levels than controls 1304 vs. 692 ng/mL (p = 0.0124). This study supports B cell lymphocytosis as a JDM disease-activity biomarker and bolsters the basis for B cell-directed therapies in JDM.

Coding joint: kappa-deleting recombination excision circle ratio and B cell activating factor level: predicting juvenile dermatomyositis rituximab response, a proof-of-concept study

BACKGROUND

This pilot study's primary aim was to determine if oligoclonal B cell expansion in children with Juvenile Dermatomyositis (JDM) predicts response to Rituximab therapy. We evaluated: (1) tissue B cell depletion efficacy by measuring the ratio of Coding joint (CJ) to Kappa-deleting recombination excision circle (KREC) DNA, and (2) serum BAFF level upon B cell recovery.

METHODS

CJ and KREC values were measured via qPCR assessment of serial PBMC stored (- 80 °C) in the CureJM Center's BioRepository. Serum BAFF was quantitated by Mesoscale® technology. Oligoclonal B cell expansion was defined as a CJ:KREC ≥ 8 prior to Rituximab therapy. Detection of a CJ:KREC ratio ≤ 2.5 in the first sample after Rituximab was designated as adequate B cell depletion. A significant clinical response to therapy was defined as improvement in Disease Activity Score (DAS) by at least 2 points on consecutive visits within the first 12 months of therapy.

RESULTS

Six out of nine children with JDM showed oligoclonal B cell expansion prior to Rituximab (CJ:KREC ≥ 8). Of those 6 patients, 4 had evidence of effective B cell depletion after Rituximab (CJ:KREC ≤ 2.5), and all 4 of those subjects displayed a significant clinical response to Rituximab. Serum BAFF level increased in 8/9 children after Rituximab.

CONCLUSIONS

In this proof-of-concept study, JDM patients with oligoclonal B cell expansion prior to Rituximab have more favorable clinical outcomes after Rituximab. We speculate: (1) B cell depletion post-Rituximab predicts JDM clinical response; (2) increased BAFF post-Rituximab may contribute to disease flare.

Rituximab in the Treatment of Interstitial Lung Diseases Related to Anti-Melanoma Differentiation-Associated Gene 5 Dermatomyositis: A Systematic Review

Objective

The effectiveness of rituximab in anti-melanoma differentiation-associated gene 5 (MDA5) dermatomyositis (DM) with interstitial lung disease (ILD) has been explored only in isolated case reports and small series. This paper aims to review the current evidence regarding rituximab (RTX) use in the treatment of ILD related to anti-MDA5 DM (anti-MDA5 DM-ILD).

Methods

We conducted a review by searching PubMed, Web of Science, Embase, and Cochrane for articles with information on patients with anti-MDA5 DM and RTX treatment, published until August 2021, in English language. The selected studies listed variation in chest high-resolution computed tomography (HRCT) and/or pulmonary function test (PFT) as a primary outcome, in patients with anti-MDA5 DM-related ILD after using RTX.

Results

Of the 145 potentially eligible articles, 17 were selected. The information gathered from a total of 35 patients with anti-MDA5 DM-ILD was reviewed, including 13 men and 22 women. Patient age at onset was 47.60 ± 13.72 years old. A total of 11.43% (4/35) of the patients were found to have chronic ILD (C-ILD) and 88.57% (31/30) exhibited rapidly progressive ILD (RP-ILD). Most patients (29/30) had typical DM rashes. Prior to RTX administration, the majority of patients (27/35) were treated with medium- or high-dose glucocorticoids and at least one additional immunotherapeutic agent. With regard to RTX efficacy for ILD in anti-MDA5 DM, 71.43% (25/35) of the patients responded to treatment. Skin rash also improved in more than half of the patients after RTX treatment. The most common side effects were infections, reported by 37.14% (13/35) of the patients after using RTX.

Conclusion

As a CD20 targeting drug, RTX is a promising therapeutic tool for anti-MDA5 DM-ILD, although the risk of infections should be considered before treatment. Further prospective controlled studies are required to evaluate the optimal RTX treatment regimen.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021289714, identifier CRD42021289714.

Clinical and laboratory parameters predicting cancer in dermatomyositis patients with anti-TIF1γ antibodies

BACKGROUND

Dermatomyositis (DM) is a chronic acquired autoimmune disorder strongly associated with cancer development. Until now, identifying predictive markers indicating a high risk of cancer has challenged clinicians. Although anti-TIF1γ antibody is a major serological indicator for cancer-associated DM, many anti-TIF1γ antibody-positive DM patients lack malignancy.

OBJECTIVES

To determine clinical and laboratory parameters that support cancer prediction in anti-TIF1γ antibody-positive DM patients.

METHODS

Clinical and laboratory data were collected from cancer-associated and unassociated DM patients with anti-TIF1γ antibodies. Serum cytokine concentrations were measured with a cytokine array assay. The values of inflammatory cytokines in cancer prognosis were determined with a receiver operating characteristic curve analysis.

RESULTS

The cancer group had a significantly higher frequency of males, older mean age and higher anti-TIF1γ antibody levels. Some inflammatory cytokines, particularly tumour necrosis factor (TNF) and TNF receptor superfamilies, had increased levels in sera that were correlated with myositis markers, cutaneous severity and DM disease activity. Moreover, these cytokines had an area under the curve (AUC) ≥0.8 and high sensitivity and specificity at their specific cut-off, even higher than anti-TIF1γ levels in cancer prediction in our DM patients.

CONCLUSIONS

Our results suggest a close pathophysiological relationship among myositis, cancer and skin involvements in DM patients with anti-TIF1γ antibodies and the potential clinical significance of anti-TIF1γ antibody levels in evaluating disease severity and prognosis in DM patients. Some inflammatory cytokines, particularly TNF and TNF receptor superfamilies including BAFF, sTNF-R1 and sTNF-R2, may support cancer prediction in DM patients with anti-TIF1γ antibodies.

Cytokines and inflammatory mediators as promising markers of polymyositis/dermatomyositis

PURPOSE OF REVIEW

Idiopathic inflammatory myopathies (IIMs), known also as myositis, represent challenging group of heterogeneous muscle disorders characterized by symmetric proximal muscle weakness and evidence of muscle inflammation. The purpose of this review is to provide important updates on cytokines and inflammatory mediators related to myositis.

RECENT FINDINGS

In the past 5 years, multiple studies brought a fresh insight into the pathogenesis of myositis by introducing new factors or further characterizing the role of the well established mediators in myositis. Among the mediators reviewed in this article, special attention was paid to interferons, C-X-C motif chemokine ligand 10, interleukin-18 and the IL23/Th17 axis. Some of the recent work has also focused on the nontraditional cytokines, such as adipokines, myokines, S100 proteins, High Mobility Group Box 1 or B-cell activating factor and on several anti-inflammatory mediators. Moreover, microRNAs and their potential to reflect the disease activity or to regulate the inflammatory processes in myositis have recently been subject of intensive investigation. Some of the above-mentioned mediators have been proposed as promising clinical biomarkers or therapeutic targets for myositis.

SUMMARY

Several recent studies contributed to a better understanding of the pathogenesis of myositis and highlighted the clinical significance of certain inflammatory mediators. Application of these new findings may help to develop innovative approaches for patients' phenotyping, disease activity monitoring and potentially novel therapies.

Biologics in refractory idiopathic inflammatory myositis (IIM): What experience in juvenile vs adult myositis tells us about the use of biologics in pediatric IIM

Juvenile dermatomyositis (JDM) is an extremely heterogeneous orphan disease with limited amount of dedicated research on the subject matter. Recent research suggests that JDM may not just be the classic antibody driven complements mediated microangiopathy as was thought to be in the past. The etiopathogenesis of JDM also involves inappropriate stimulation of innate immune system followed by dysregulation of the adaptive immune response through dendritic cells. Many variable immune factors such as genetics, major histocompatibility complex expressions, immunohistochemical variabilities, and diversity in specific and associated autoantibodies may make individual IIM and JDM cases unique. The diversity in IIM and JDM also explains individual variability in response to specific therapies. Classifying and matching the right patients to the right treatment is crucial to the successful treatment of these patients with better outcomes. Sub-type specific biologic therapy may be the best current treatment that can match the patient to the best treatment options. A PubMed search was performed to find all the available cases of refractory myositis patients treated with biologics up to July 2020. Using this search this article reviews all the current biologic treatment options and experiences for both adults and children in the context of recent basic science to assist pediatric rheumatologists in choosing the optimal biologic therapy for a child with recalcitrant JDM.

Distribution of anti-melanoma differentiation associated gene 5 (MDA5) IgG subclasses in MDA5+ dermatomyositis

OBJECTIVES

The anti-melanoma differentiation-associated gene 5 (MDA5) antibody is the main predictor of interstitial lung disease (ILD) in dermatomyositis (DM) and clinically amyopathic dermatomyositis (CADM). Nevertheless, a subset of MDA5+ patients have a favorable prognosis. We aimed to determine the possibility of using anti-MDA5 antibody isotypes and IgG subclasses for evaluating ILD risk.

METHODS

The isotypes (IgG, IgA and IgM) of anti-MDA5 were detected in serum samples of 36 anti-MDA5+ patients with DM/CADM using enzyme-linked immunosorbent assay (ELISA). IgG subclasses of anti-MDA5 antibodies were further investigated. Laboratory findings and cumulative survival were analyzed based on the isotypes of anti-MDA5 and subclasses of anti-MDA5 IgG.

RESULTS

Among the MDA5+ patients with DM/CADM, the positive rates of anti-MDA5 IgG, IgA, IgM were 100%, 97%, and 6%, respectively. The positive rates of anti-MDA5 IgG1, IgG2, IgG3, and IgG4 were 72%, 25%, 0%, and 28%, respectively. The incidence of acute interstitial pneumonia, mortality rate, and serum ferritin were significantly higher in anti-MDA5 IgG1+ patients than those in anti-MDA5 IgG1- patients with DM/CADM (P = 0.0027, 0.015, 0.0011, respectively). The sensitivity and specificity of anti-MDA5 IgG1 for predicting mortality were 100% and 41.7%, respectively. A combination of anti-MDA5 IgG1 and IgG4 for predicting mortality, yielded better specificity (87.5%).

CONCLUSION

IgA and IgG are the primary anti-MDA5 antibody isotypes. Anti-MDA5 IgG1 is the primary component of MDA5 IgG subclasses and anti-MDA5 IgG1 and IgG4 might serve as useful biomarkers for predicting mortality in DM-ILD.

Elevated serum B-cell activating factor levels in patients with dermatomyositis: Association with interstitial lung disease

Patients with dermatomyositis (DM) frequently have myositis-specific autoantibodies (MSA), which are closely associated with different clinical features. Patients with anti-aminoacyl-tRNA synthetase antibody (ARS-Ab) and anti-melanoma differentiation-associated gene 5 (MDA5)-Ab often have interstitial lung disease (ILD). Recently, anti-MDA5-Ab levels have been shown to correlate with disease activity in DM patients. Thus, B cells that are stimulated by excess B-cell activating factor (BAFF) play an important role in the pathogenesis of DM through auto-Ab production. In this study, we investigated the role of BAFF in DM patients. We measured the serum BAFF levels in 56 adult DM patients (14 with anti-ARS-Ab, 18 with anti-MDA5-Ab, seven with anti-Mi-2-Ab and 17 with anti-transcriptional intermediary factor-1γ-Ab) . For a longitudinal study, 130 serum specimens from 10 DM patients with anti-MDA5-Ab were analyzed. Serum BAFF levels were significantly higher in DM patients than in healthy controls. DM patients with elevated serum BAFF levels more frequently had ILD. In subgroup analysis, DM patients with anti-ARS-Ab and DM patients with anti-MDA5-Ab exhibited increased BAFF levels compared with controls, while DM patients with other MSA showed BAFF levels comparable with controls. In the longitudinal study, serum BAFF levels in DM patients with anti-MDA5-Ab were decreased after immunosuppressive therapy along with serum levels of anti-MDA5-Ab and ferritin, which are biomarkers of disease activity. These results suggest that BAFF plays an important role in the pathogenesis of ILD in DM patients with anti-ARS and anti-MDA5-Ab. Furthermore, serum BAFF level is associated with disease activity in DM patients with anti-MDA5-Ab.

Multispecialty approach for improving outcomes in juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is a pediatric rheumatic disease characterized by inflammation of the muscle and skin. Prognosis of JDM in children has improved in general owing to medical progress; however, pathogenesis and management of JDM in children and prognosis in refractory JDM remain challenging. For elucidation of JDM pathophysiology and establishment of appropriate treatment for JDM, pediatric rheumatologists need to adopt a multispecialty approach that involves experts in genetics, immunology, pathology, musculoskeletal medicine, dermatology, pulmonology, cardiology, hematology, gastroenterology, endocrinology, ophthalmology, psychology, radiology, pharmacology, physiotherapy, surgery, preventive medicine, and adult rheumatology. Such collaborations will potentially lead to improved outcomes in children with JDM.

Guidelines of the Brazilian Society of Rheumatology for the treatment of systemic autoimmune myopathies

BACKGROUND

Recommendations of the Myopathy Committee of the Brazilian Society of Rheumatology for the management and therapy of systemic autoimmune myopathies (SAM).

MAIN BODY

The review of the literature was done in the search for the Medline (PubMed), Embase and Cochrane databases including studies published until June 2018. The Prisma was used for the systematic review and the articles were evaluated according to the levels of Oxford evidence. Ten recommendations were developed addressing the management and therapy of systemic autoimmune myopathies.

CONCLUSIONS

Robust data to guide the therapeutic process are scarce. Although not proven effective in controlled clinical trials, glucocorticoid represents first-line drugs in the treatment of SAM. Intravenous immunoglobulin is considered in induction for refractory cases of SAM or when immunosuppressive drugs are contra-indicated. Consideration should be given to the early introduction of immunosuppressive drugs. There is no specific period determined for the suspension of glucocorticoid and immunosuppressive drugs when individually evaluating patients with SAM. A key component for treatment in an early rehabilitation program is the inclusion of strength-building and aerobic exercises, in addition to a rigorous evaluation of these activities for remission of disease and the education of the patient and his/her caregivers.

Systemic and Tissue Inflammation in Juvenile Dermatomyositis: From Pathogenesis to the Quest for Monitoring Tools

Juvenile Dermatomyositis (JDM) is a systemic immune-mediated disease of childhood, characterized by muscle weakness, and a typical skin rash. Other organ systems and tissues such as the lungs, heart, and intestines can be involved, but may be under-evaluated. The inflammatory process in JDM is characterized by an interferon signature and infiltration of immune cells such as T cells and plasmacytoid dendritic cells into the affected tissues. Vasculopathy due to loss and dysfunction of endothelial cells as a result of the inflammation is thought to underlie the symptoms in most organs and tissues. JDM is a heterogeneous disease, and several disease phenotypes, each with a varying combination of affected tissues and organs, are linked to the presence of myositis autoantibodies. These autoantibodies have therefore been extensively studied as biomarkers for the disease phenotype and its associated prognosis. Next to identifying the JDM phenotype, monitoring of disease activity and disease-inflicted damage not only in muscle and skin, but also in other organs and tissues, is an important part of clinical follow-up, as these are key determinants for the long-term outcomes of patients. Various monitoring tools are currently available, among which clinical assessment, histopathological investigation of muscle and skin biopsies, and laboratory testing of blood for specific biomarkers. These investigations also give novel insights into the underlying immunological processes that drive inflammation in JDM and suggest a strong link between the interferon signature and vasculopathy. New tools are being developed in the quest for minimally invasive, but sensitive and specific diagnostic methods that correlate well with clinical symptoms or reflect local, low-grade inflammation. In this review we will discuss the types of (extra)muscular tissue inflammation in JDM and their relation to vasculopathic changes, critically assess the available diagnostic methods including myositis autoantibodies and newly identified biomarkers, and reflect on the immunopathogenic implications of identified markers.

Aberrant activation of the type I interferon system may contribute to the pathogenesis of anti-melanoma differentiation-associated gene 5 dermatomyositis

BACKGROUND

Anti-melanoma differentiation-associated gene 5 (MDA5) dermatomyositis (DM) is a distinctive subtype of DM that carries a significant risk of interstitial lung disease (ILD). The mechanisms remain elusive.

OBJECTIVES

To explore the role of the type I interferon (IFN) system in the pathogenesis of anti-MDA5 DM.

METHODS

Twenty patients with anti-MDA5 DM were studied and compared with patients with anti-aminoacyl-tRNA synthetase (ARS) DM (n = 10) and autoantibody-negative patients with DM (n = 20). The levels of inflammatory cytokines, B-cell-activating factor (BAFF) and Krebs von den Lungen (KL)-6 in blood were tested by enzyme-linked immunosorbent assay and multiplex assays. Expressions of transcripts for IFN-associated sensors and type I IFN-inducible genes in peripheral blood mononuclear cells (PBMCs) were detected by real-time polymerase chain reaction. Expressions of the signal transducer and activator of transcription (STAT)1, interferon-stimulated gene (ISG)15 and MxA proteins in skin lesions were analysed by immunohistochemistry.

RESULTS

Plasma IFN-α levels were significantly increased in patients with anti-MDA5 DM. PBMCs from patients with anti-MDA5 DM showed significant upregulation of the TLR3, TLR7, IFIH1 and DDX58 genes, as well as serial IFN-inducible genes. Skin biopsies from patients with anti-MDA5 DM were characterized by strong expression of the STAT1, ISG15 and MxA proteins. In the patients with anti-MDA5 DM and ILD with high IFN-α production, there was a positive quantitative correlation between IFN-α and BAFF (r_s = 0·63, P = 0·044). In addition, the higher levels of BAFF paralleled the higher concentrations of KL-6 (r_s = 0·86, P = 0·0012).

CONCLUSIONS

Our data confirm the aberrant activation of the type I IFN system in anti-MDA5 DM. Overproduction of IFN-α linked with BAFF may be implicated in the development of ILD.

Serum levels of B-cell activating factor of the TNF family (BAFF) correlate with anti-Jo-1 autoantibodies levels and disease activity in patients with anti-Jo-1positive polymyositis and dermatomyositis

BACKGROUND

B-cell activating factor of the tumour necrosis factor family (BAFF) plays a role in autoantibody production and is elevated in dermatomyositis (DM) and anti-Jo-1-positive polymyositis (PM). We investigated the inter-relationships between serum levels of BAFF, anti-Jo-1 autoantibodies, and disease activity.

METHODS

Serum levels of BAFF and anti-Jo-1 antibodies measured by enzyme-linked immunosorbent assay (ELISA) were compared to levels of myoglobin, creatine kinase (CK), aminotransferases (alanine (ALT) and aspartate (AST)), C-reactive protein (CRP), and disease activity assessed by the Myositis Disease Activity Assessment Tool in 63 anti-Jo-1 antibody-positive DM/PM patients. Serial serum samples collected at 2 (46 cases) and 3-5 time points (23 cases) were included. Relationships between BAFF, anti-Jo-1, disease activity, CRP, and their longitudinal changes were evaluated using correlation analysis, multiple regression (MR), path analysis (PA), and hierarchical linear models (HLM).

RESULTS

Cross-sectional assessment demonstrated significant correlations between the levels of BAFF and anti-Jo-1 antibodies which were associated with levels of CK, myoglobin, AST, and CRP, as well as multivariate associations between BAFF, anti-Jo-1 antibodies, and CK levels. PA revealed direct effects of anti-Jo-1 antibodies on CK (β = 0.41) and both direct (β = 0.42) and indirect (through anti-Jo-1 antibodies; β = 0.17) effects of BAFF on CK. Changes in levels of both BAFF and anti-Jo-1 between two time points (Δ) were associated with Δmyoglobin and Δaminotransferases and changes of BAFF correlated with ΔCK, Δcutaneous, Δmuscle, Δglobal, and Δskeletal disease activities. The longitudinal analysis showed a high intra-individual variability of serum levels of BAFF over time (97%) which could predict 79% of the variance in anti-Jo-1 levels. The anti-Jo-1 variability was explained by inter-individual differences (68%). The close longitudinal relationship between levels of BAFF, anti-Jo-1, and disease activity was supported by high proportions of their variance explained with serum levels of CK and CRP or pulmonary and muscle activities.

CONCLUSION

Our findings of associations between levels of BAFF and anti-Jo-1 antibodies in serum and myositis activity suggest a role of this cytokine in disease-specific autoantibody production as part of disease mechanisms, and support BAFF as a potential target for intervention in anti-Jo-1-positive myositis patients.

Update on outcome assessment in myositis

The adult and juvenile myositis syndromes, commonly referred to collectively as idiopathic inflammatory myopathies (IIMs), are systemic autoimmune diseases with the hallmarks of muscle weakness and inflammation. Validated, well-standardized measures to assess disease activity, known as core set measures, were developed by international networks of myositis researchers for use in clinical trials. Composite response criteria using weighted changes in the core set measures of disease activity were developed and validated for adult and juvenile patients with dermatomyositis and adult patients with polymyositis, with different thresholds for minimal, moderate and major improvement in adults and juveniles. Additional measures of muscle strength and function are being validated to improve content validity and sensitivity to change. A health-related quality of life measure, which incorporates patient input, is being developed for adult patients with IIM. Disease state criteria, including criteria for inactive disease and remission, are being used as secondary end points in clinical trials. MRI of muscle and immunological biomarkers are promising approaches to discriminate between disease activity and damage and might provide much-needed objective outcome measures. These advances in the assessment of outcomes for myositis treatment, along with collaborations between international networks, should facilitate further development of new therapies for patients with IIM.

Pulmonary manifestations of rheumatologic diseases

PURPOSE OF REVIEW

The present review intends to provide an overview of the diversity and complexity of pulmonary manifestations of rheumatologic diseases and gaps in knowledge to effectively manage them.

RECENT FINDINGS

Diffuse lung disease in children with rheumatologic diseases represents a heterogeneous group of autoimmune disorders. Despite their significant morbidity and mortality, we have limited understanding about their pathogenesis. Here, we provide an overview of the pathophysiology and current management approach of these disorders, highlighting tools which assist with diagnosis, risk stratification and therapy. In this context, we address the need to develop a standardized approach to diagnose at-risk patients with rheumatologic disease and to predict their progression and the need to develop robust studies which evaluate the factors and interventions that influence pulmonary disease outcome.

SUMMARY

Diffuse lung disease in children with rheumatologic diseases represents a heterogeneous group of severe autoimmune disorders. By adopting a collaborative research approach among multicenters to help diagnose, risk stratify, and understand disease progression, effective management decisions can be optimized to improve clinical outcome.