Muscle Biopsy Findings in Combination With Myositis-Specific Autoantibodies Aid Prediction of Outcomes in Juvenile Dermatomyositis

Expert Perspective: Diagnostic Approach to Differentiating Juvenile Dermatomyositis From Muscular Dystrophy

Clinical tools that can aid in the diagnostic differentiation of juvenile dermatomyositis from muscular dystrophy.

Predictors of poor outcomes in juvenile dermatomyositis: what do we know? A narrative review

OBJECTIVE

Juvenile dermatomyositis (JDM) is a rare chronic systemic inflammatory disorder with a highly variable clinical course. It is important to identify the patients at risk of developing more severe disease. However, based on the existing literature, there is a lack of data regarding predictors of poor outcomes. Obtaining knowledge about clinical and laboratory risk factors for disease progression and severity at an earlier stage of the disease could potentially lead to a better long-term prognosis for patients with JDM.

METHODS

A narrative review to identify risk factors for poor outcomes in patients with JDM, such as death, severe disease, refractory disease, and functional impairment, was conducted. A total of 27 articles were included.

RESULTS

Certain clinical manifestations and immunology features appear to worsen the prognosis in children with JDM. The recognition of these risk factors is essential for all pediatric rheumatologists as it allows the earlier identification of patients with potentially worse outcomes. These patients should receive closer follow-up and aggressive and individualized therapy to reduce their morbimortality.

CONCLUSIONS

Additional research is needed not only to identify more predictors of worse outcomes but also more effective treatment approaches targeted toward these patients.

Recent Advances in Juvenile Dermatomyositis: Moving toward Integration of Myositis-Specific Antibody Clinical Phenotypes, IFN-Driven Pathogenesis, and Targeted Therapies

Juvenile dermatomyositis (JDM), the most common pediatric inflammatory myopathy, is associated with significant morbidity despite therapeutic advances. Distinct clinical phenotypes have emerged, which can correlate with myositis-specific antibodies. Because translational data solidify the role of type I IFNs in JDM disease pathogenesis, integration of clinical and molecular phenotyping may impact the choice of targeted therapy. This paper reviews clinical and molecular phenotyping in JDM and translational insights into immune pathogenesis that have created emerging options for targeted therapy.

Prevalence and Clinical Implications of Autoantibodies in Juvenile Dermatomyositis: A Single-Center Experience From India

OBJECTIVE

​​This study aimed to characterize the profile of myositis-specific and myositis-associated autoantibodies (MSAs/MAAs) in an Indian cohort of juvenile dermatomyositis (JDM) patients and correlate them with clinical features and outcomes.

METHODS

Forty-three children diagnosed with JDM were enrolled for this observational study. Clinical details (presentation, course, and outcome) were noted in a predesigned proforma. Serum samples were tested for 16 MSAs/MAAs by line immunoassay. MSAs/MAAs were correlated with clinical features and outcome (defined as a complete clinical response [≥6 months' disease inactivity on medication] or complete remission [≥6 months' inactivity off all drugs]).

RESULTS

Thirty-five subjects (81.4%) had at least 1 MSA/MAA detected. The most common antibodies were anti-NXP2 (n = 13, 30.2%), anti-TIF1γ (n = 10, 23.2%), and anti-MDA-5 (n = 8, 18.6%). No patient had anti-Ku, anti-Pm Scl-100, anti-PL-12, anti-EJ, anti-OJ, or anti-Ro52. Thirty-two patients (74.4%) attained a complete clinical response over a median follow-up duration of 14 months, among which 6 (13.9%) achieved complete remission over a median follow-up duration of 30 months. Anti-TIF1γ was associated with younger age at onset (≤3 years) (odds ratio [OR], 6.25; 95% confidence interval [CI], 1.15-34.12; p = 0.034) and disease flares after attaining complete response (OR, 10.18; 95% CI, 1.64-70.93; p = 0.013). Patients with anti-NXP2 had higher odds of severe muscular weakness (OR, 3.73; 95% CI, 0.95-14.59; p = 0.058) and truncal weakness (OR, 3.89; 95% CI, 0.97-15.64; p = 0.056). One child with anti-MDA-5 positivity had interstitial lung disease. We found no association between the MSA/MAA profile and the achievement of complete clinical response or remission.

CONCLUSIONS

MSAs/MAAs were identified in 81% of children with JDM in our study, which is higher than most other studies. The most frequently observed antibodies displayed a pattern consistent with other studies. Anti-TIF1γ was associated with a younger age at onset and disease flares even after attaining a complete clinical response. Anti-NXP2 had higher odds of severe muscular weakness. These observations suggest consistency in certain phenotypic associations observed across geographic boundaries.

Autoantibodies and damage in patients with idiopathic inflammatory myopathies: A longitudinal multicenter study from the MYONET international network

OBJECTIVE

To study the trajectories of changes in damage over time and explore associations with autoantibody defined subgroups using a large international cohort of patients with idiopathic inflammatory myopathies (IIM).

METHODS

Data from the MYONET registry, including patients who were tested for autoantibodies and had at least one assessment of damage using the Myositis Damage Index (MDI), were analyzed. Patients were sub-grouped according to their autoantibody profiles (myositis-specific, myositis-associated, or seronegative). The index date was defined as the time point for the first registered MDI assessment. The longitudinal trajectories of damage with autoantibody status as the main predictor were analyzed using linear mixed models.

RESULTS

A total of 757 adult patients were included in this study. Each year of disease duration since diagnosis had an estimated MDI score increase of 0.16 units for the seronegative group (reference). Compared with the seronegative group as reference, patients with dermatomyositis-specific autoantibodies developed less damage per year of follow-up since diagnosis (average 0.08 less score, P = 0.04), whereas patients with anti-PM/Scl autoantibodies developed more damage per year of follow-up since diagnosis (average 0.28 higher score, P = 0.03) independent of sex and age at diagnosis. The seronegative subgroup and the immune-mediated necrotizing myopathy autoantibody subgroup had the strongest correlation between severity of muscle damage and HAQ-DI scores at five years of follow-up, rho=0.84, P < 0.001 and rho=0.72, P < 0.001, respectively.

CONCLUSION

Our study is the first to describe patterns and trajectories of change in damage over time in relation to autoantibody defined subgroups in a large international multicenter cohort of patients with IIM. Patients with anti-PM/Scl scored a greater extent of damage, whereas patients with dermatomyositis-specific antibodies had less damage than seronegative patients. Severity in muscle damage had moderate to strong correlation with functional disability among the IMNM and seronegative subgroups with lower correlations for the other subgroups. These findings suggest that autoantibodies may be useful predictors of long-term damage.

Factors Associated With Complete Clinical Response and Remission in a Cohort of Romanian Children With Juvenile Dermatomyositis

OBJECTIVES

To describe a Romanian cohort of patients with juvenile dermatomyositis (JDM) and to identify factors associated with disease severity, complete clinical response, and sustained remission.

METHODS

We retrospectively reviewed data from 30 JDM patients from 2013 to 2022. The inactive disease state was defined as no active skin rash, muscle weakness, or elevated muscle enzymes. A complete clinical response implied a status of inactive disease maintained for six consecutive months while on medication and remission of inactive disease for at least six consecutive months after treatment. Association factors and predictors of time to complete clinical response and time to remission emerged from bivariate correlation (Pearson's coefficient) and univariate survival analysis (Kaplan-Meier analysis).

RESULTS

The median times to complete clinical response and time to remission for the entire cohort were 30.5 months (2.5 years) and 48.5 months (4.04 years), respectively. Nine patients (30%) had a severe disease course, while twenty-one patients (70%) had a mild/moderate course. The presence of calcinosis, time to corticosteroid discontinuation, history of treatment escalation in the first 18 months, and treatment with azathioprine or biologic DMARDs were strongly associated with a longer time to clinical remission (Pearson's > 0.5, p < 0.05). Seven patients (23%) achieved remission, and none of them relapsed during the subsequent median follow-up of 19 months.

Personalised medicine in juvenile dermatomyositis: From novel insights in disease mechanisms to changes in clinical practice

Juvenile dermatomyositis is characterized by childhood-onset chronic inflammation of the muscles and skin, with potential involvement of other organs. Patients are at risk for long-term morbidity due to insufficient disease control and steroid-related toxicity. Personalised treatment is challenged by a lack of validated tools that can reliably predict treatment response and monitor ongoing (subclinical) inflammation, and by a lack of evidence regarding the best choice of medication for individual patients. A better understanding of the involved disease mechanisms could reveal potential biomarkers and novel therapeutic targets. In this review, we highlight the most relevant immune and non-immune mechanisms, elucidating the effects of interferon overexpression on tissue alongside the interplay between the interferon signature, mitochondrial function, and immune cells. We review mechanism-based biomarkers that are promising for clinical implementation, and the latest advances in targeted therapy development. Finally, we discuss key steps needed for translating these discoveries into clinical practice.

Juvenile dermatomyositis with Anti-SAE antibodies in a Moroccan child associated with pseudo-angioedema: a case report

BACKGROUND

Juvenile Dermatomyositis (JDM) is the leading cause of non-infectious inflammatory myopathy in children. It is a heterogeneous group of autoimmune diseases characterized by a variable combination of muscular, dermatological, and visceral involvement. Myositis-specific autoantibodies help define homogeneous subgroups with common clinical characteristics and prognoses. Anti-SAE (small ubiquitin-like modifier 1 (SUMO-1) activating enzyme) antibodies are among the most recently discovered specific autoantibodies. The presence of these antibodies is very rare, making it challenging to define clinical features and prognosis in the juvenile form. We report the first case of an African patient with juvenile dermatomyositis and positive anti-SAE antibodies.

CASE REPORT

A 5-year-3-month-old Moroccan boy presented to the pediatric emergency department with dysphagia that had been evolving for two days, preceded two months earlier by facial erythema associated with fatigue, lower limb pain, difficulty walking, and progressive inflammatory polyarthralgia. On admission, the child had a heliotrope rash with predominant pseudo-angioedema on the lips, periungual telangiectasia, and Gottron's papules over the bilateral interphalangeal and metatarsophalangeal joints. The patient had a more pronounced proximal muscle weakness in the lower limbs. He had no urticaria, fever, arthritis, calcinosis, cutaneous ulcers, or lipodystrophy. The Joint examination was normal, as was the pleuropulmonary examination. The electroneuromyography showed myogenic changes in all four limbs. Laboratory findings showed elevated levels of creatine phosphokinase and lactate dehydrogenase and a mild inflammatory syndrome. The electrocardiogram was normal. The anti-SAE antibodies were positive. The boy was diagnosed with juvenile dermatomyositis. He received methylprednisolone bolus therapy followed by oral prednisone. The latter was gradually tapered in combination with weekly intramuscular methotrexate. As a result, dysphagia disappeared within 48 h. After two weeks, there was an improvement in the muscular score and a significant regression of facial pseudo-angioedema.

CONCLUSION

We report the first African patient with anti-SAE autoantibody-positive JDM. He had a typical dermatological manifestation of JDM associated with pseudo-angioedema predominant on the lips; a rarely reported sign in DM and JDM patients. The patient responded well to corticosteroid therapy and methotrexate.

Juvenile idiopathic inflammatory myositis: an update on pathophysiology and clinical care

The childhood-onset or juvenile idiopathic inflammatory myopathies (JIIMs) are a heterogenous group of rare and serious autoimmune diseases of children and young people that predominantly affect the muscles and skin but can also involve other organs, including the lungs, gut, joints, heart and central nervous system. Different myositis-specific autoantibodies have been identified that are associated with different muscle biopsy features, as well as with different clinical characteristics, prognoses and treatment responses. Thus, myositis-specific autoantibodies can be used to subset JIIMs into sub-phenotypes; some of these sub-phenotypes parallel disease seen in adults, whereas others are distinct from adult-onset idiopathic inflammatory myopathies. Although treatments and management have much improved over the past decade, evidence is still lacking for many of the current treatments and few validated prognostic biomarkers are available with which to predict response to treatment, comorbidities (such as calcinosis) or outcome. Emerging data on the pathogenesis of the JIIMs are leading to proposals for new trials and tools for monitoring disease.

Role of CD14+ monocyte-derived oxidised mitochondrial DNA in the inflammatory interferon type 1 signature in juvenile dermatomyositis

OBJECTIVES

To define the host mechanisms contributing to the pathological interferon (IFN) type 1 signature in Juvenile dermatomyositis (JDM).

METHODS

RNA-sequencing was performed on CD4+, CD8+, CD14+ and CD19+ cells sorted from pretreatment and on-treatment JDM (pretreatment n=10, on-treatment n=11) and age/sex-matched child healthy-control (CHC n=4) peripheral blood mononuclear cell (PBMC). Mitochondrial morphology and superoxide were assessed by fluorescence microscopy, cellular metabolism by 13C glucose uptake assays, and oxidised mitochondrial DNA (oxmtDNA) content by dot-blot. Healthy-control PBMC and JDM pretreatment PBMC were cultured with IFN-α, oxmtDNA, cGAS-inhibitor, TLR-9 antagonist and/or n-acetyl cysteine (NAC). IFN-stimulated gene (ISGs) expression was measured by qPCR. Total numbers of patient and controls for functional experiments, JDM n=82, total CHC n=35.

RESULTS

Dysregulated mitochondrial-associated gene expression correlated with increased ISG expression in JDM CD14+ monocytes. Altered mitochondrial-associated gene expression was paralleled by altered mitochondrial biology, including 'megamitochondria', cellular metabolism and a decrease in gene expression of superoxide dismutase (SOD)1. This was associated with enhanced production of oxidised mitochondrial (oxmt)DNA. OxmtDNA induced ISG expression in healthy PBMC, which was blocked by targeting oxidative stress and intracellular nucleic acid sensing pathways. Complementary experiments showed that, under in vitro experimental conditions, targeting these pathways via the antioxidant drug NAC, TLR9 antagonist and to a lesser extent cGAS-inhibitor, suppressed ISG expression in pretreatment JDM PBMC.

CONCLUSIONS

These results describe a novel pathway where altered mitochondrial biology in JDM CD14+ monocytes lead to oxmtDNA production and stimulates ISG expression. Targeting this pathway has therapeutical potential in JDM and other IFN type 1-driven autoimmune diseases.

Juvenile Dermatomyositis: what comes next? Long-term outcomes in childhood myositis from a patient perspective

BACKGROUND

To describe long-term outcomes in JDM using patient questionnaires and link to longitudinal, prospectively collected data for each patient within the Juvenile Dermatomyositis Cohort and Biomarker Study, UK and Ireland (JDCBS) to determine outcome predictors.  METHODS: JDCBS participants aged ≥ 16y completed the SF36, HAQ and a questionnaire regarding current disease features, medications, education and employment. Data collected from the JDCBS included disease subtype, demographics, clinical and laboratory features. Intensity indices were calculated for physician VAS, modified skin DAS, CMAS and MMT8 by dividing area under the curve (AUC) from longitudinal score trajectories by duration of study follow-up (y). Relationships between questionnaire and JDCBS clinical / laboratory data were investigated fitting statistical models appropriate for cross sectional and longitudinal data.

RESULTS

Of 190 questionnaires sent, 84 (44%) were returned. Average age of respondents was 20.6 years (SD 3.9), time since diagnosis was 12.4 years (SD 5.0), age at onset was 9.2 years (SD 4.3), female to male ratio 4.25:1. Forty-nine (59%) self-reported persistently active disease, 54 (65%) were still taking immunosuppressive medication. 14/32 at school/higher education reported myositis adversely affecting academic results. 18-24 year-olds were twice as likely to be unemployed compared the UK population (OR = 0.456, 95% CI 0.24, 0.84, p = 0.001). Participants ≥ 18 years were three times as likely to be living with a parent/guardian (OR = 3.39, p < 0.001). SF36 MCS and MMT8 intensity index scores were significantly correlated (ρ = 0.328, p = 0.007).

CONCLUSIONS

After 12.4 years, questionnaire responders reported self-perceived high rates of persistently active disease and medication use, reduced rates of employment and were more likely to live with a parent/guardian. Perceived persistently active muscle disease appeared to affect quality of life in these patients and was the most significant contributor to long-term outcomes. Our findings highlight the importance of including the patient perspective in the assessment of long term outcomes, so that that we can start to target initial management strategies more effectively based on a combination of clinical and patient-reported data.

Assessment of Thigh MRI Radiomics and Clinical Characteristics for Assisting in Discrimination of Juvenile Dermatomyositis

Magnetic resonance imaging (MRI) is an important non-invasive examination in the early diagnosis of juvenile dermatomyositis (JDM). We aimed to evaluate the feasibility of radiomics to establish a quantitative analysis of MRI images. Radiomics and machine learning were used to retrospectively analyze MRI T2 fat suppression sequences and relevant clinical data. The model associated with radiomics features was established using a cohort of patients who underwent thigh MRI at the children's hospital from June 2014 to September 2021. In total, 75 patients with JDM and 75 control children were included in the training cohort (n = 102) and validation cohort (n = 48). The independent factors including lower muscle strength (OR, 0.75; 95% CI, 0.59-0.90), higher creatine kinase (CK) level (OR, 1.65; 95% CI, 1.20-2.38), and higher radiomics score (OR, 2.30; 95% CI, 1.63-3.62) were associated with a clinical diagnosis of JDM. The combined model achieved good discrimination performance compared the radiomics score model under linear discriminant analyses in the training cohort (AUC, 0.949; 95% CI, 0.912-0.986 vs. AUC, 0.912; 95% CI, 0.858-0.967; p = 0.02) and in the validation cohort (AUC, 0.945; 95% CI, 0.878-1 vs. AUC, 0.905; 95% CI, 0.812-0.998; p = 0.03). The combined model showed the diagnostic value was not weaker than the biopsy (AUC, 0.950; 95% CI, 0.919-0.981, n = 150 vs. AUC, 0.952; 95% CI, 0.889-1, n = 72; p = 0.95) and electromyogram (EMG) (AUC, 0.950; 95% CI, 0.919-0.981 vs. AUC, 0.900; 95% CI, 0.852-0.948; p = 0.10) among all the patients. The combination of radiomics features extracted from the MRI and non-invasive clinical characteristics obtained a pronounced discriminative performance to assist in discriminating JDM.

Clinical and autoantibody phenotypes of juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is a heterogeneous autoimmune inflammatory myositis with symmetrical proximal muscle weakness and a characteristic rash. Juvenile dermatomyositis is characterized by variable presentation and phenotypes. Detection of myositis autoantibodies is useful in improving JDM diagnosis and predicting the prognosis. In this literature review based on case series we analyze clinical and autoantibody phenotypes of JDM in four patients who were hospitalized in one regional center in Ukraine during the last 3 years and three of them presented in the time of the COVID-19 pandemic. The reviewed literature showed the last updates for the JDM diagnosis and the role of myositis autoantibodies in the prediction of disease course, systemic involvement, and malignancy risk. The presence of anti-synthetase syndrome in all presented patients, mainly due to anti-PL-7 autoantibodies, encourages further study with more patients and with detection of other myositis-specific autoantibodies to identify or refute certain regional features.

Long-Term Outcomes and Prognosis Factors in Patients With Idiopathic Inflammatory Myopathies Based on Myositis-Specific Autoantibodies: A Single Cohort Study

OBJECTIVE

This study was undertaken to investigate the long-term survival rates and prognostic factors in patients with idiopathic inflammatory myopathies (IIMs) based on myositis-specific antibody (MSA) stratification.

METHODS

Exactly 628 patients with an IIM were included. Kaplan-Meier survival curves, univariate, and multivariate Cox regression were used to analyze the outcomes and risk factors.

RESULTS

The cumulative 1-, 5-, and 10-year survival rates for IIM patients overall were 91.4%, 82.8%, and 75.6%, respectively. The survival rate in the MSA subset was significantly different (P < 0.001). The 1- and 10-year survival rates in the anti-melanoma differentiation-associated protein 5 (anti-MDA-5)-positive subgroup were 79.5% and 58.5%, respectively, which were the lowest among all subgroups. The 10-year survival rate of anti-signal recognition particle (anti-SRP)-positive patients was the highest (96.4%). Independent risk factors that impacted the long-term prognosis for IIM patients included rapidly progressive interstitial lung disease (RP-ILD), malignancy, and elevated serum ferritin levels (hazard ratio [HR] 17.47, 20.36, and 9.15, respectively, P < 0.01), whereas disease duration was a protective factor (HR 0.27, P = 0.003). Among these subsets, the strongest independent risk factor for death in the anti-MDA-5-positive subgroup was RP-ILD (HR 3.4, P = 0.017). Malignancy was an independent risk factor in the anti-aminoacyl-tRNA synthetase antibody-positive, anti-transcription intermediary factor 1γ-positive, and MSA-negative subgroups (HR 46.69, 6.65, and 4.48, respectively; P < 0.001). RP-ILD was also a risk factor in the prognosis of individuals in the MSA-negative subgroup (HR 72.28, P < 0.001).

CONCLUSION

Despite favorable overall survival in patients with IIM, the anti-MDA-5-positive subgroup had the highest mortality rate among all MSA subgroups, highlighting the distinctive prognosis for patients with different MSAs. RP-ILD and malignancy are the most common causes of death in IIM patients.

Muscle biopsy in myositis: What the rheumatologist needs to know

The appropriate analysis of skeletal muscle tissues is a key element in many diagnostic procedures and can deliver valuable information about the organ that is affected. Although arguably the frequency of muscle biopsy may be declining in certain domains where genetic analysis is now the first line of diagnostic evaluation, it still has an important role in assessment of patients with neuromuscular disorders such as congenital myopathies, muscular dystrophies, metabolic and inflammatory diseases. Here, we have comprehensively discussed the aspects of a modern and fruitful approach to muscle biopsy histopathological studies in rheumatological disorders. We have focussed on the neuromuscular involvement in myositis and its differential diagnoses in both adult and paediatric settings. We have also covered the clinical indications for the biopsy, technical aspects and practical points relevant for the rheumatologists. Finally, we have critically discussed the current and future opportunities that a muscle biopsy may offer and its limitations.

Case Report: Simultaneously Developed Amyopathic Dermatomyositis and Autoimmune Sclerosing Cholangitis - a Coincidence or a Shared Immunopathogenesis?

Inflammatory rheumatic diseases (IRD) and autoimmune liver diseases (AILD) share many similarities regarding epidemiology, genetics, immunology and therapeutic regimens, so it is not surprising that approximately 20% of patients with AILD are diagnosed with an IRD as well. Clinical features and biochemical hallmarks of IRD and AILD often intertwine and cross diagnostic criteria. Therefore, the real distinction of underlying disorders in a patient with these comorbidities may be challenging. The present report is the first report of simultaneously developed juvenile dermatomyositis (JDM) and autoimmune sclerosing cholangitis (ASC) with both entities fulfilling the latest guidelines for a definite diagnosis. Both of these diagnoses are difficult to definitely establish since ASC has a similar serologic profile as autoimmune hepatitis and liver histological analysis is frequently non-specific, whereas clinically amyopathic JDM diagnosis depends mostly on classical dermatological symptoms, while the rest of the diagnostic criteria, including the necessity for skin or muscle biopsy and the presence of myositis specific antibodies, are still not uniformed. In spite of these challenges, our patient clearly met European League Against Rheumatism/American College of Rheumatology classification criteria for CAJDM and The European Society for Pediatric Gastroenterology, Hepatology and Nutrition diagnostic criteria for ASC. Since elevated serum transaminases, the presence of serum antinuclear antibodies and hypergammaglobulinemia could be explained as a part of both JDM and ASC, the underlying pathophysiology remains debatable. Intriguingly, JDM and ASC share genetic predisposition including human leukocyte antigen allele DRB1*0301 and tumor necrosis factor α 308A allele. Furthermore, both humoral and cellular components of the adaptive immune system contribute to the pathogenesis of JDM and ASC. Moreover, recent findings indicate that the loss of the CD28 expression on T-cells plays a significant role in their pathogenesis along with the Th17 immune pathway. Despite these common features that suggest shared autoimmunity, AILD and autoimmune myositis are traditionally studied and managed independently. The lack of therapies that target the underlying cause results in a high rate of adverse events due to unspecific immunosuppressive therapy. Shared autoimmunity is an ideal area to develop new, targeted immunotherapy that would hopefully be beneficial for more than one disease.

Juvenile Dermatomyositis

Die juvenile Dermatomyositis (JDM) ist die häufigste chronische entzündliche Myopathie des Kindesalters. In dieser Übersicht soll der aktuelle Kenntnisstand hinsichtlich der Diagnostik, Behandlung und Überwachung der JDM dargestellt werden. So liegen häufig myositis-spezifische Antikörper vor, die mit klinischen Phänotypen und dem Verlauf der Erkrankung korrelieren. Typ I Interferone spielen eine wichtige Rolle in der Pathogenese der Erkrankung. Möglicherweise kann diese Beobachtung in der Zukunft zu gezielten Therapien führen. Da langfristig schwerwiegende Komplikationen, wie z. B. Kalzinosen oder Lipodystrophie, drohen, besonders bei auf Dauer unzureichend kontrollierter Erkrankung, ist eine möglichst rasche und effektive Behandlung anzustreben. Zu diesem Zweck sollte eine intensive Remissionsinduktionstherapie, gefolgt von einer zielgerichteten Therapie angestrebt werden. Verschiedene validierte Messinstrumente stehen zur Verfügung, um den Verlauf der Erkrankung zu beurteilen. Die Pro-KIND-Initiative der Gesellschaft für Kinder- und Jugendrheumatologie hat Praxis- und Konsens-basiert in Deutschland sowohl eine diagnostische als auch eine Treat-to-Target-Behandlungsstrategie entwickelt. Im Rahmen nationaler und internationaler Kollaborationen soll sich die Behandlung der JDM in der Zukunft weiter verbessern.

Efficacy and tolerance of corticosteroids and methotrexate in patients with juvenile dermatomyositis: a retrospective cohort study

OBJECTIVES

To assess the efficacy and tolerance of the conventional first-line treatment by methotrexate (MTX) and corticosteroids (CS) in patients with juvenile dermatomyositis (JDM) regardless of severity.

METHODS

We conducted a monocentric retrospective study of patients with newly-diagnosed JDM treated with MTX and CS from 2012 to 2020. Proportion of clinically inactive disease (CID) within six months of MTX initiation was evaluated using both PRINTO criteria (evaluating muscle inactive disease) and Disease Activity Score (evaluating skin inactive disease). We compared responders and non-responders using univariate analyses.

RESULTS

Forty-five patients with JDM, out of which thirty (67%) severe JDM, were included. After six months of treatment with MTX and CS, complete CID, muscle CID and skin CID were achieved in 14/45 (31%), 19/45 (42%) and 15/45 (33%) patients respectively. The absence of myositis-specific (MSA) or myositis-associated autoantibodies (MAA) at diagnosis was associated with a better overall, cutaneous and muscular therapeutic response, compared with antibody-positive forms (p< 0.01). Requirement for ICU (p= 0.029) and cutaneous ulcerations (p= 0.018) were associated to a less favorable muscle response. MTX was stopped due to intolerance in six patients (13%) before month 6.

CONCLUSION

Conventional first-line treatment with MTX was not efficient in a large subset of JDM patients, especially in patients with MSA-positive forms, and in patients with severe JDM. Larger multicentre cohorts are required to confirm these data and to identify new predictive biomarkers of MTX response, in order to treat patients with JDM as early as possible with appropriate targeted drugs.

Autoantibody Profile of Children with Juvenile Dermatomyositis

OBJECTIVE

To study autoantibody profile in juvenile dermatomyositis (JDM) and to look for phenotypic associations of these autoantibodies, if any.

METHODS

Thirty-four children with JDM with a minimum follow-up duration of 24 mo were enrolled. Clinical findings and investigations at the time of diagnosis were noted from the clinic records. At inclusion, they were clinically evaluated for residual disease, disease activity and complications. All the enrolled patients were tested for antinuclear antibodies (ANA), muscle specific antibodies (MSA) and myositis associated autoantibodies (MAA).

RESULTS

ANA positivity was seen in 14/34 children. At least one MSA or MAA was present in 8/34 children. Anti-SRP, anti-MDA-5, and anti-Mi-2 antibodies were present in 4, 3, and 1 patient, respectively. Anti-SSA/Ro52 antibody was positive in 1 child. All four children with anti-SRP antibody were girls, who had polycyclic course. Two of them developed calcinosis. Prominent skin involvement with less severe muscle involvement and monocyclic course were seen in patients with anti-MDA-5 antibody. Two of them had arthritis/arthralgia at initial presentation. The only patient with anti-Mi-2 had normal muscle strength at enrollment. None of the patients had anti-synthetase antibodies (anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ), anti-Ku, anti-Scl-70, anti-NXP-2 or anti-HMG CoA.

CONCLUSION

Eight patients tested positive for at least one MSA or MAA. The prevalence of autoantibodies was low. Positivity for anti-SRP, anti-MDA-5, anti-Mi-2 and anti-SSA/Ro52 antibodies was seen in 4, 3, 1 and 1 patients, respectively. Ethnic differences and testing for autoantibodies during/after therapy could be responsible for the low positivity rate for autoantibodies.

Clinical features and diagnostic tools in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are rare autoimmune disorders affecting primarily muscles, but other organs can be involved. This review describes the clinical features, diagnosis and treatment for IIMs, namely polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (sIBM), immune-mediated necrotizing myopathy (IMNM), and myositis associated with antisynthetase syndrome (ASS). The diagnostic approach has been updated recently based on the discovery of circulating autoantibodies, which has enhanced the management of patients. Currently, validated classification criteria for IIMs allow clinical studies with well-defined sets of patients but diagnostic criteria to guide the care of individual patients in routine clinical practice are still missing. This review analyzes the clinical manifestations and laboratory findings of IIMs, discusses the efficiency of modern and standard methods employed in their workup, and delineates optimal practice for clinical care. Α multidisciplinary diagnostic approach that combines clinical, neurologic and rheumatologic examination, evaluation of electrophysiologic and morphologic muscle characteristics, and assessment of autoantibody immunoassays has been determined to be the preferred approach for effective management of patients with suspected IIMs.

Dermatomyositis With Anti-MDA5 Antibodies: Bioclinical Features, Pathogenesis and Emerging Therapies

Anti-MDA5 dermatomyositis is a rare systemic autoimmune disease, historically described in Japanese patients with clinically amyopathic dermatomyositis and life-threatening rapidly progressive interstitial lung disease. Subsequently, the complete clinical spectrum of the disease was enriched by skin, articular and vascular manifestations. Depending on the predominance of these symptoms, three distinct clinical phenotypes with different prognosis are now defined. To date, the only known molecular component shared by the three entities are specific antibodies targeting MDA5, a cytosolic protein essential for antiviral host immune responses. Several biological tools have emerged to detect these antibodies, with drawbacks and limitations for each of them. However, the identification of this highly specific serological marker of the disease raises the question of its role in the pathogenesis. Although current knowledge on the pathogenic mechanisms that take place in the disease are still in their enfancy, several lines of evidence support a central role of interferon-mediated vasculopathy in the development of skin and lung lesions, as well as a possible pathogenic involvement of anti-MDA5 antibodies. Here, we review the clinical and biological evidences in favor of these hypothesis, and we discuss the contribution of emerging therapies that shed some light on the pathogenesis of the disease.

Updates on Juvenile Dermatomyositis from the Last Decade: Classification to Outcomes

Juvenile dermatomyositis (JDM) is a heterogeneous disease with new classification criteria and updates in myositis-specific autoantibody and myositis-associated antibody groups. There are many validated assessment tools for assessing disease activity in JDM. Future studies will optimize these tools and improve feasibility in clinical and research contexts. Genetic and environmental risk factors, mechanisms of muscle pathology, role of interferon, vascular markers, and changes in immune cells provide insights to JDM pathogenesis. Outcomes have improved, but chronic disease, damage, and mortality highlight the need for better outcome predictors and treatments. Increased collaboration of stakeholders may help overcome research barriers and improve JDM treatment.

JAK inhibitors: a potential treatment for JDM in the context of the role of interferon-driven pathology

Juvenile Idiopathic Inflammatory Myopathies (IIM) are a group of rare diseases that are heterogeneous in terms of pathology that can include proximal muscle weakness, associated skin changes and systemic involvement. Despite options for treatment, many patients continue to suffer resistant disease and lasting side-effects. Advances in the understanding of the immunopathology and genetics underlying IIM may specify new therapeutic targets, particularly where conventional treatment has not achieved a clinical response. An upregulated type I interferon signature is strongly associated with disease and could be a prime target for developing more specific therapeutics. There are multiple components of the IFN pathway that could be targeted for blockade therapy.Downstream of the cytokine receptor complexes are the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway, which consists of JAK1-3, TYK2, and STAT1-6. Therapeutic inhibitors have been developed to target components of this pathway. Promising results have been observed in case studies reporting the use of the JAK inhibitors, Baricitinib, Tofacitinib and Ruxolitinib in the treatment of refractory Juvenile Dermatomyositis (JDM). There is still the question of safety and efficacy for the use of JAK inhibitors in JDM that need to be addressed by clinical trials. Here we review the future for the use of JAK inhibitors as a treatment for JDM.

Juvenile dermatomyositis in Thai children: Retrospective review of 30 cases from a tertiary care center

BACKGROUND

Juvenile dermatomyositis is a rare condition, but it is the most common idiopathic inflammatory myopathy in pediatric patients.

AIM

To study the clinical manifestations, investigations, treatment, clinical course, and outcomes of juvenile dermatomyositis in Thai children.

METHOD

This retrospective study included juvenile dermatomyositis patients treated at Siriraj Hospital, a 2,300-bed national tertiary referral center in Bangkok, Thailand, from 1994 to 2019.

RESULTS

Thirty patients (22 females and 8 males) were included with a female to male ratio of 2.7:1. Median age at diagnosis was 5.1 years (range, 2.6-14.8 years). Median duration of illness before diagnosis was 6.5 months (range, 0.3-84.0 months). Acute and subacute onset occurred in the majority of patients. Presenting symptoms included muscle weakness in 27/30 (90%), skin rash in 26/30 (86.7%), muscle pain in 17/26 (65.4%), and arthralgia in 4/18 (22.2%) of patients. Dermatologic examination revealed Gottron's rash, heliotrope rash, and periungual telangiectasia in 25/30 (83.3%), 21/30 (70.0%), and 15/24 (62.5%) of patients, respectively. Interestingly, scalp dermatitis was found in 8/21 (38.1%) of patients. The most commonly used treatment regimen in this series was a combination of prednisolone and methotrexate. During the median follow-up of 3.1 years (range, 0.0-18.5 years), only one-third of patients were seen to have monocyclic disease. Extraskeletal osteosarcoma at a previous lesion of calcinosis cutis was observed in one patient at 12 years after juvenile dermatomyositis onset.

LIMITATIONS

This was a retrospective single-center study, and our results may not be generalizable to other healthcare settings. Prospective multicenter studies are needed to confirm the findings of this study.

CONCLUSION

juvenile dermatomyositis usually poses a diagnostic and therapeutic challenge, which can be compounded by the ethnic variations in the clinical presentation, as observed in this study. Asian patients tend to present with acute or subacute onset of disease, and arthralgia and/or arthritis are less common than in Caucasian patients. Scalp dermatitis is not uncommon in pediatric juvenile dermatomyositis patients. An association between juvenile dermatomyositis and malignancy, though rare, can occur.

Corticosteroid discontinuation, complete clinical response and remission in juvenile dermatomyositis

OBJECTIVE

A North American registry of JDM patients was examined for frequency of and factors associated with corticosteroid discontinuation, complete clinical response and remission.

METHODS

We evaluated probability of achieving final corticosteroid discontinuation, complete clinical response and remission in 307 JDM patients by Weibull time-to-event modelling; conditional probability of complete clinical response and remission using Bayesian network modelling; and significant predictors with multivariable Markov chain Monte-Carlo Weibull extension models.

RESULTS

The probability of corticosteroid discontinuation was 56%, complete clinical response 38% and remission 30% by 60 months after initial treatment in 105 patients. The probability of remission was conditional on corticosteroid discontinuation and complete clinical response. Photosensitivity, contractures and a longer time to complete clinical response were predictive of the time to final corticosteroid discontinuation. Anti-MJ (NXP2) autoantibodies and a Northwest residential geoclimatic zone were predictive of shorter time to complete clinical response, while dysphonia, contractures, an increase in medications within 24 months and a longer time to corticosteroid discontinuation were associated with longer time to complete clinical response. Anti-p155/140 (TIF1) autoantibodies, an increase in medications within 12-24 months, or longer times to corticosteroid discontinuation and complete clinical response were associated with longer time to remission.

CONCLUSION

JDM patients achieve favourable outcomes, including corticosteroid discontinuation, complete clinical response and remission, although timelines for these may be several years based on time-dependent analyses. These outcomes are inter-related and strong predictors of each other. Selected clinical features and myositis autoantibodies are additionally associated with these outcomes.

Geographical Latitude Remains as an Important Factor for the Prevalence of Some Myositis Autoantibodies: A Systematic Review

The idiopathic inflammatory myopathies (IIM) are characterized by muscular weakness, cutaneous manifestations, muscle damage revealed by increase of muscular enzymes, muscle biopsy, electromyography and changes on magnetic resonance imaging. However, the hallmark of these IIM, is the development of myositis specific antibodies (MSA) or myositis associated antibodies (MAA). The theories about their presence in the serum of IIM is not known. Some studies have suggested that some of these MSA, such as anti-Mi-2 increases according to the intensity of UV radiation. There is scarce information about the environmental factors that might contribute in order to be considered as triggering factors as UV radiation might be. In this review, we analyzed the reported prevalence of MSAs and MAAs regarding to their geographical location and the possible relation with UV radiation. We collected the prevalence data of fifteen MSA and thirteen MAA from 22 countries around the world and we were able to observe a difference in prevalence between countries and continents. We found differences in anti-PL7, anti-Ro52, anti-La and anti-Ku prevalence according to UV radiation level. Otherwise, we observed that anti-Mi-2 prevalence increases near to the Equator meanwhile anti-MJ/NXP2 and anti-ARS prevalence had an opposite behavior increasing their prevalence in the geographical locations farther to the Equator. Our results highlighted the importance to include the UV radiation and other environmental factors in IIM studies, in order to clarify its association with MSA and MAA prevalence as well as its possible role in the immunopathogenesis of these diseases.

Anti-SAE autoantibody-positive Japanese patient with juvenile dermatomyositis complicated with interstitial lung disease - a case report

BACKGROUND

Clinical phenotypes and outcomes in juvenile dermatomyositis (JDM) have been defined by various myositis-specific autoantibodies (MSAs). One of the recently described MSAs associated with DM is targeted against the small ubiquitin-like modifier 1 activating enzyme (SAE). We report an anti-SAE autoantibody-positive JDM patient complicated with interstitial lung disease (ILD).

CASE PRESENTATION

An 8-year-8-month-old Japanese girl presented with bilateral eyelid edema and facial erythema. At 8 years 4 months, she had dry cough and papules with erythema on the dorsal side of the interphalangeal joints of both hands. Her facial erythema gradually worsened and did not improve with topical steroids. At the first visit to our department at 8 years 8 months of age, she had a typical heliotrope rash and Gottron's papules, with no fever or weight loss, and a chest computed tomography scan showed ground-glass opacity under visceral pleura. There was no clinical evidence of myositis, muscle weakness, myalgia, or muscle magnetic resonance imaging (MRI) findings. She had mild dry cough, without any signs of respiratory distress. Laboratory tests showed no elevated inflammatory markers. She had a normal serum creatine kinase level with a slightly elevated aldolase level, and serum anti-SAE autoantibody was detected by immunoprecipitation-western blotting. She was diagnosed with juvenile amyopathic DM complicated by ILD and received two courses of methylprednisolone pulse therapy followed by oral corticosteroid and cyclosporin A. We gradually reduced the corticosteroid dose as her skin rash improved after treatment initiation. There was no progression of muscle symptoms, dysphagia, or disease flare during a 24-month follow-up period.

CONCLUSIONS

We report a patient with anti-SAE autoantibody-positive JDM complicated by interstitial pneumonia. This patient had no progression of muscle symptoms and dysphagia during a 24-month follow-up period, which differs from previous reports in adult patients with MSAs. There have been no previous reports of pediatric patients with SAE presenting with ILD. However, ILD seen in this case was not rapidly progressive and did not require cytotoxic agents. To prevent overtreatment, appropriate treatment choices are required considering the type of ILD.

Dermatomyositis autoantibodies: how can we maximize utility?

The past 15 years has seen significant advances in the characterization of myositis-specific autoantibodies (MSAs) and their associated phenotypes in patients with dermatomyositis (DM). As more careful studies are performed, it is clear that unique combinations of clinical and pathological phenotypes are associated with each MSA, despite the fact that there is considerable heterogeneity within antibody classes as well as overlap across the groups. Because risk for interstitial lung disease (ILD), internal malignancy, adverse disease trajectory, and, potentially response to therapy differ by DM MSA group, a deeper understanding of MSAs and validation and standardization of assays used for detection are critical for optimizing diagnosis and treatment. Like any test, the diagnostic sensitivity and specificity of assays for various MSAs is not perfect. Currently tests for MSAs are helpful at minimum for a clinician to assess relative risk or contribute to diagnosis and perhaps counsel the appropriate patient about what to expect. With international standardization and larger studies it is likely that more antibody tests will make their way into formal schemata for diagnosis and actionable risk assessment in DM. In this review, we summarize key considerations for interpreting the clinical and pathologic associations with MSA in DM and identify critical gaps in knowledge and practice that will maximize their clinical utility and utility for understanding disease pathogenesis.

Pathologic Features of Anti-Mi-2 Dermatomyositis

OBJECTIVE

To identify the characteristic pathologic features of dermatomyositis (DM) associated with anti-Mi-2 autoantibodies (anti-Mi-2 DM).

METHODS

We reviewed 188 muscle biopsies from patients (1) pathologically diagnosed with DM through the sarcoplasmic expression for the myxovirus-resistant protein A and (2) serologically positive for 1 of 5 DM-specific autoantibodies (DMSAs) (anti-Mi-2, n = 30; other DMSAs, n = 152) or negative for all 5 DMSAs (n = 6). We then compared the histopathologic and immunohistochemical features of patients with anti-Mi-2 DM to those with non-Mi-2 DM and patients with anti-synthetase syndrome (ASS) (n = 212) using the t test, Fisher exact test, and a logistic regression model.

RESULTS

Patients with anti-Mi-2 DM showed significantly higher severity scores in muscle fiber and inflammatory domains than non-Mi-2 DM patients. The presence of perifascicular necrosis, increased perimysial alkaline phosphatase activity, and sarcolemmal membrane attack complex deposition was more frequent in patients with anti-Mi-2 DM (p < 0.01). After Bonferroni correction, there were no significant differences in the percentages of the features mentioned above between the patients with anti-Mi-2 DM and those with ASS (p > 0.01).

CONCLUSION

Perifascicular necrosis and perimysial pathology, features previously reported in ASS, are common in patients with anti-Mi-2 DM. Our findings not only assist in differentiating anti-Mi-2 DM from other DM subtypes but also suggest the possibility of an overlapping mechanism between anti-Mi-2 DM and ASS.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that the muscle biopsies of DM patients with anti-Mi-2 autoantibodies are more likely to demonstrate higher severity scores in muscle fiber and inflammatory domains.

Anti-MDA5 juvenile idiopathic inflammatory myopathy: a specific subgroup defined by differentially enhanced interferon-α signalling

OBJECTIVES

JDM and juvenile overlap myositis represent heterogeneous subtypes of juvenile idiopathic inflammatory myopathy (JIIM). Chronic evolution can occur in up to 60% of cases, and morbidity/mortality is substantial. We aimed to describe the clinical, biological, histological and type I IFN status in JIIM associated with anti-melanoma differentiation-associated protein 5 (anti-MDA5) autoantibodies at presentation (group 1) in comparison with other JIIM (group 2).

METHODS

This was a retrospective and prospective study of patients with JIIM ascertained from three French paediatric rheumatology reference centres between 2013 and 2019. Muscle biopsies were reviewed. Type I interferon pathway activity was assessed by dosage of IFNα serum protein and the expression of IFN-stimulated genes.

RESULTS

Sixty-four patients were included, 13 in group 1 (54% JDM and 46% juvenile overlap myositis) and 51 in group 2 (76% JDM and 24% juvenile overlap myositis). Group 1 patients demonstrated more arthritis, skin ulcerations, lupus features and interstitial lung disease, and a milder muscular involvement. Serum IFNα levels were higher in group 1 than 2, and decreased after treatment or improvement in both groups. Outcome was similar in both groups. Unconventional treatment (more than two lines) was required in order to achieve remission, especially when skin ulceration was reported.

CONCLUSION

This study indicates a higher frequency of arthritis, skin ulcerations and interstitial lung disease, but milder muscular involvement, in JIIM with positive anti-MDA5 autoantibodies compared with other JIIM. Our data support an important role of systemic IFNα in disease pathology, particularly in the anti-MDA5 auto-antibody-positive subgroup. In severe and refractory forms of JIIM, IFNα may represent a therapeutic target.

Gastrointestinal perforation in anti-NXP2 antibody-associated juvenile dermatomyositis: case reports and a review of the literature

BACKGROUND

To summarize the characteristics of gastrointestinal (GI) perforation in anti-nuclear matrix protein 2 (NXP2) antibody-associated juvenile dermatomyositis (JDM).

METHODS

Five patients with GI perforation from a JDM cohort of 120 cases are described. Relevant literature was reviewed.

RESULTS

Five patients, including four females and one male, were included in the study. The age of onset of these patients ranged from 3.3 to 9.5 years with the median age of 5.0 years. When these patients were complicated by GI perforation, childhood myositis assessment score (CMAS) ranged from 1 to 5 with the median score of 2. Myositis-specific antibody (MSA) spectrum analysis indicated that the five patients were anti-NXP2 antibody positive. The initial symptoms of GI perforation were progressive abdominal pain and intermittent fever. Two patients also presented with ureteral calculus with hydronephrosis and ureteral stricture. Surgery was performed in four patients. One patient failed to undergo a repair as the perforation was high in position. For the other three patients, perforation repair was successful, of which two patients failed due to recurrent perforation. At 24 months postoperative follow-up, one patient was in complete remission on prednisone (Pred) and methotrexate (MTX) treatment, and her ureteral stricture had disappeared. The other four patients died. Adding these cases with 16 other patients described in the literature, the symptom at onset was progressive abdominal pain, which often occurred within 10 months after JDM was diagnosed. Perforation most commonly occurred in the duodenum, although it also occurred at multiple sites or was recurrent. The mortality rate of GI perforation in JDM was 38% (8/21).

CONCLUSIONS

All the five perforation cases in our study subjected to MSA analysis were anti-NXP2 antibody positive. The symptom at onset was abdominal pain. The most common site of perforation was the duodenum in the retroperitoneum, and the lack of acute abdominal manifestations prevented early diagnosis. GI perforation may be a fatal complication in JDM, and early diagnosis is very important. More research is needed to determine the pathogenesis and predictive factors of GI perforation in JDM.

Clinical features, muscle biopsy scores, myositis specific antibody profiles and outcome in juvenile dermatomyositis

INTRODUCTION

Juvenile dermatomyositis (JDM) is the most common inflammatory myopathy of childhood.

OBJECTIVE

To analyze clinical features, paraclinical examinations, MSAs, treatment response and long-term outcome in a JDM cohort METHODS: 58 patients (35F, 23 M) from a tertiary referral center in the last two decades are included.

RESULTS

Mean age at onset was 8.1 ± 4.3, with a mean follow-up period of 5.66±3.59 years. Dermatological manifestations (91%) and muscle weakness (76%) were the key diagnostic elements. Elevated serum creatine kinase levels (86%), electromyography (23/25), muscle MRI (12/15), and muscle biopsy (n = 35) were compatible with the diagnosis. Out of 46 patients tested, 34 (76%) had autoantibodies, with NXP2 (21.7%), followed by TIF1g (17.4%), MDA5 (8.7%), and Mi-2 (8.7%). Presence of TIF1g and NXP2 indicated a severe course; and Ku a much severe course compared to previous studies. Corticosteroids (100%) combined with methotrexate (93%) was the initial treatment. Biological disease modifying anti-rheumatic drugs (DMARDs) were used in 22% of the cohort. Calcinosis (36%) was the most common long-term complication, associated with disease onset ≤6 years, higher muscle biopsy scores and MDA5 positivity. Complete remission was achieved in 65.5% of the patients in a median 24 (IQR 11.8-42.5) months with a relapse rate of 26.3%. 43.9% of NXP2 and 33.3% of TIF-1 g positive patients had a relapse. Course was monophasic (31%), polyphasic (17.2%), chronic (51.8%) without mortality.

CONCLUSION

Integration of clinical features with laboratory and biopsy findings may help to predict prognosis and guide treatment in JDM. In our cohort calcinosis was associated with age, MDA5 autoantibodies, and muscle biopsy scores.

Insights into the knowledge, attitude and practices for the treatment of idiopathic inflammatory myopathy from a cross-sectional cohort survey of physicians

The idiopathic inflammatory myopathies (IIM) are heterogeneous and lead to high morbidity and mortality. Knowledge deficits among healthcare professionals could be detrimental to clinical care. Identifying areas of deficient Knowledge, Attitude and Practice (KAP) of IIM can improve physician education and patient outcomes. To assess the proportion of physicians treating IIM with poor KAP and identify the key areas of deficit. An anonymised and validated e-survey (57 questions) was circulated among physicians treating IIM (purposive sampling). Responses were evaluated using the Likert scale for good (> 70% correct response), poor (> 20% chose > 2 answers) and the rest as intermediate consensus. Descriptive statistics were used. Intergroup comparisons were done using non-parametric tests. Of 80 (9.1% of 883) respondents, 90% were rheumatologists and 37.5% academicians. The knowledge base of treating physicians was good in specific domains such as triggers (80-90%), clinical presentation (MDA5, statin myositis, steroid myopathy, anti-synthetase syndrome) (82-92%), IIM mimics (41-89%), investigations (23-92%) and risk of osteoporosis in IIM (79%). There is also an intermediate knowledge base/consensus for outcome measures (30-56%) and response criteria (30-53%). There was poor knowledge and consensus on trials (27-34%), EULAR/ACR criteria (31%) and exercise-based interventions (17-62%). While 90% agree on the need for muscle biopsy to diagnose polymyositis, only one-third advocated it for juvenile and adult DM. Physicians have a good understanding of the triggers, clinical presentation and mimics of IIM. Poor to intermediate knowledge and consensus exists regarding muscle biopsy, outcome measures, response criteria and exercise-based interventions, which could be addressed through future focussed educational initiatives.

Inflammatory milieu of muscle biopsies in juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is an inflammatory myopathy which causes severe morbidity and high mortality if untreated. In this study, we aimed to define the T-helper cell profile in the muscle biopsies of JDM patients. Muscle biopsies of twenty-six patients (50% female) were included in the study. Immunohistochemical expression of CD3, CD20, CD138, CD68, IL-17, Foxp3, IFN-ɣ, IFN-alpha and IL-4 was studied and muscle biopsies were scored using the JDM muscle biopsy scoring tool. Inflammatory cells were in small clusters in perimysium and perivascular area or scattered throughout the endomysium in most biopsies; however in 2 biopsies, lymphoid follicle-like big clusters were observed, and in one, there was a very dense and diffuse inflammatory infiltration nearly destroying all the muscle architecture. Seventy-three per cent of the biopsies had T cells, 88% had B cells, 57% had plasma cells, and all had macrophages. As for T-helper cell subtypes, 80% of the biopsies were Th1 positive, 92% Th17 positive and 30% Treg positive. No IL-4 positive inflammatory cell was detected, and only 2 biopsies showed IFN-alpha positivity. The mean JDM biopsy score was 17.6, meaning moderate to severe muscular involvement. Visual analogue score of the pathologist was strongly correlated with histopathological features. B cells, macrophages, plasma cells and T cells constitute the inflammatory milieu of the JDM muscle biopsies. As for T cells, JDM is a disease mainly related with Th1 and Th17 T-helper cell subtypes and to some extend Treg. Th2 cells are not involved in the pathogenesis.

Distinct tissue injury patterns in juvenile dermatomyositis auto-antibody subgroups

INTRODUCTION

Juvenile dermatomyositis (JDM) can be classified into clinical serological subgroups by distinct myositis-specific antibodies (MSAs). It is incompletely understood whether different MSAs are associated with distinct pathological characteristics, clinical disease activities, or response to treatment.

METHODS

We retrospectively reviewed clinicopathological data from consecutive JDM patients followed in the pediatric rheumatology clinic at a single center between October 2016 and November 2018. Demographics, clinical data, and laboratory data were collected and analyzed. Detailed muscle biopsy evaluation of four domains (inflammation, myofiber, vessels, and connective tissue) was performed, followed by statistical analysis.

RESULTS

Of 43 subjects included in the study, 26 (60.5%) had a detectable MSA. The most common MSAs were anti-NXP-2 (13, 30.2%), anti-Mi-2 (7, 16.3%), and anti-MDA-5 (5, 11.6%). High titer anti-Mi-2 positively correlated with serum CK > 10,000 at initial visit (r = 0.96, p = 0.002). Muscle biopsied from subjects with high titer anti-Mi-2 had prominent perifascicular myofiber necrosis and perimysial connective tissue damage that resembled perifascicular necrotizing myopathy, but very little capillary C5b-9 deposition. Conversely, there was no positive correlation between the levels of the anti-NXP-2 titer and serum CK (r = - 0.21, p = 0.49). Muscle biopsies from patients with anti-NXP-2 showed prominent capillary C5b-9 deposition; but limited myofiber necrosis. Only one patient had anti-TIF1γ autoantibody, whose muscle pathology was similar as those with anti-NXP2. All patients with anti-MDA-5 had normal CK and near normal muscle histology.

CONCLUSIONS

Muscle biopsy from JDM patients had MSA specific tissue injury patterns. These findings may help improve muscle biopsy diagnosis accuracy and inform personalized treatment of JDM.

Using peripheral blood immune signatures to stratify patients with adult and juvenile inflammatory myopathies

OBJECTIVE

The inflammatory idiopathic myopathies (IIM) are a group of rare autoimmune diseases defined by muscle weakness and characterized by pro-inflammatory infiltrates in muscle. Little is known about the immunological profile in peripheral blood of these patients and how this relates to IIM subtypes. This study aimed to stratify adult and juvenile-onset IIM patients according to immune cell profile.

METHODS

Peripheral blood mononuclear cells from 44 patients with adult myositis (AM), 15 adolescent-onset juvenile dermatomyositis (a-JDM), and 40 age-matched healthy controls were analysed by flow cytometry to quantify 33 immune cell subsets. Adult myositis patients were grouped according to myositis subtype; DM and polymyositis; and also autoantibody specificity. Disease activity was determined by the myositis disease activity assessment tool and clinicians' decision on treatment.

RESULTS

Unique immune signatures were identified for DM, polymyositis and a-JDM compared with healthy controls. DM patients had a T-cell signature comprising increased CD4+ and TH17 cell frequencies and increased immune cell expression of IL-6. Polymyositis patients had a B-cell signature with reduced memory B cells. A-JDM had decreased naïve B cells and increased CD4+T cells. All patient groups had decreased CD8+central memory T-cell frequencies. The distinct immune signatures were also seen when adult myositis patients were stratified according to auto-antibody expression; patients with anti-synthetase-antibodies had reduced memory B cells and patients with autoimmune rheumatic disease overlap had an elevated Th17 profile.

CONCLUSION

Unique immune signatures were associated with adult vs juvenile disease. The Th17 signature in DM patients supports the potential use of IL-17 inhibitors in treatment of IIMs.

Long-term outcomes in Juvenile Myositis patients

OBJECTIVE

Juvenile idiopathic inflammatory myopathies (JIIM) are rare, chronic autoimmune muscle diseases of childhood, with the potential for significant morbidity. Data on long-term outcomes is limited. In this study we investigate correlations between clinical and demographic features with long-term outcomes in a referral population of adult patients with JIIM.

METHODS

Forty-nine adults with JIIM were assessed at two referral centers between 1994 and 2016. Features of active disease and damage at a cross-sectional assessment were obtained. Regression modeling was used to examine factors associated with long-term outcomes, defined by the presence of calcinosis or a higher adjusted Myositis Damage Index (MDI) score. A multivariable model of MDI was constructed using factors that were statistically significant in bivariate models.

RESULTS

At a median of 11.5 [IQR 4.5-18.9] years following diagnosis, median American College of Rheumatology (ACR) functional class was 2 [1.5-3.0], Health Assessment Questionnaire (HAQ) score was 0.4 out of 3.0 [0.0-1.0], and manual muscle testing (MMT) score was 229 out of 260 [212.6-256.8]. Median MDI score was 6.0 [3.5-8.9], with the most commonly damaged organ systems being cutaneous and musculoskeletal. Factors associated with an elevated MDI score were the presence of erythroderma and other cutaneous manifestations, disease duration, and ACR functional class. Calcinosis was present in 55% of patients. The strongest predictors of calcinosis were disease duration, periungual capillary changes, and younger age at diagnosis.

CONCLUSION

In a tertiary referral population, long-term functional outcomes of JIIM are generally favorable, with HAQ scores indicative of mild disability. Although most patients had mild disease activity and virtually all had significant disease damage, severe or systemic damage was rare. Certain clinical features are associated with long-term damage and calcinosis.

Juvenile Dermatomyositis-Clinical Phenotypes

PURPOSE OF REVIEW

Juvenile dermatomyositis is a heterogeneous disease with variable clinical outcomes. Here, we describe the recognised subtypes of idiopathic inflammatory myositis which occur in children, with particular reference to disease-associated autoantibodies.

RECENT FINDINGS

Large cohort studies have demonstrated that myositis autoantibodies are common in juvenile dermatomyositis and can be found in the majority of patients. They identify homogenous clinical subgroups and inform prognosis, particularly the risks of developing interstitial lung disease. Descriptions of immune-mediated necrotising myositis in juvenile patients have highlighted a rare but important clinical subset typically associated with severe muscle disease and treatment resistance. It is increasingly apparent that autoantibodies can provide detailed information on prognosis and the likely disease associations in those with juvenile dermatomyositis. Further work is needed to establish how this knowledge should influence our approach to treatment.

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.

Muscle Expression of Type I and Type II Interferons Is Increased in Juvenile Dermatomyositis and Related to Clinical and Histologic Features

OBJECTIVE

To evaluate the expression of type I interferon (IFNα/β)- and type II IFN (IFNγ)-inducible genes in muscle biopsy specimens from patients with juvenile dermatomyositis (DM) and to correlate their expression levels with histologic and clinical features.

METHODS

Expression levels of IFN-inducible genes and proinflammatory cytokines were assessed by quantitative polymerase chain reaction in muscle biopsy specimens from patients with juvenile DM (n = 39), patients with Duchenne's muscular dystrophy (DMD), and healthy controls. Muscle biopsy sections were stained and scored for severity of histopathologic features. The charts of patients with juvenile DM were reviewed for clinical features at the time of sampling and long-term outcomes.

RESULTS

Muscle expression levels of IFNα/β-inducible genes (type I IFN score), IFNγ, IFNγ-inducible genes (type II IFN score), and tumor necrosis factor (TNF) were significantly higher in juvenile DM patients not receiving glucocorticoid therapy before muscle biopsy (n = 27) compared to DMD patients (n = 24) (type I IFN score, P < 0.0001; type II IFN score, P < 0.001; TNF, P < 0.05) and healthy controls (n = 4) (type I IFN score, P < 0.01; type II IFN score, P < 0.01; TNF, P < 0.05). Immunofluorescence staining of muscle biopsy sections from untreated juvenile DM patients showed increased immunoreactivity for IFNγ and HLA class II molecules compared to controls. Type I and type II IFN scores were correlated with typical histopathologic features of juvenile DM muscle biopsy samples, such as infiltration of endomysial CD3+ cells (type I IFN score, r = 0.68; type II IFN score, r = 0.63), perimysial CD3+ cells (type I IFN score, r = 0.59; type II IFN score, r = 0.66), CD68+ cells (type II IFN score, r = 0.46), and perifascicular atrophy (type I IFN score, r = 0.61; type II IFN score, r = 0.77). Juvenile DM patients with a high type I IFN score, a high type II IFN score, and high TNF expression levels showed more severe disease activity at biopsy (P < 0.05). In addition, juvenile DM patients with a high type II IFN score at biopsy reached clinically inactive disease significantly later than patients with low type II IFN score (log rank chi-square value 13.53, P < 0.001).

CONCLUSION

The increased expression of IFN-inducible genes in the muscle in juvenile DM patients and their association with histologic and clinical features further support a pathogenic role for both type I and type II IFNs in juvenile DM.

Interferon Chemokine Score and Other Cytokine Measures Track With Changes in Disease Activity in Patients With Juvenile and Adult Dermatomyositis

Objective

Our aim was to identify cytokines and chemokines in patients with adult dermatomyositis (DM) and juvenile dermatomyositis (JDM) that predict changes in disease activity.

Methods

Multiplexed immunoassays (Meso Scale Discovery) enabled simultaneous measurement of interferon (IFN)‐regulated chemokines and other pro‐ and anti‐inflammatory cytokines specific to differentiation of specific T‐cell and innate pathways. Cytokine scores were computed for IFNCK (IP‐10, MCP‐1), Th1 (IFNɣ, TNFα, and IL2), Th2 (IL4, IL10, IL12, and IL 13), Th17 (IL6, IL17, IL1β), macrophage (MIP‐1α, MIP‐1β, IL8), and regulatory (IL10, TNFα) factors. Spearman correlation and mixed models were used to examine whether cytokines at a previous visit predict change in disease activity at the next visit.

Results

The study included 36 patients (16 DM and 20 JDM) with at least two visits (87 patient intervals between two visits). Mean age (SD) at inclusion was 56.9 (18.4) years for DM and 10.8 (6.6) years in JDM, 67% of patients were female, 89% Caucasian. The mean (SD) physician global, muscle and extra‐muscular disease activity Visual Analog Scale scores at inclusion were 41 (26), 36 (30), and 34 (21) mm, respectively. The change in IFN score from one visit to the next was associated with the change in physician global (P = 0.010) and extramuscular (P < 0.001) disease activity scores. Preliminary results revealed significant correlations of previous IFNCK score and IL‐6 with subsequent disease activity measures, but after adjustment for multiple visits per patient, these associations did not reach statistical significance.

Conclusion

There is a potential relationship between IFNCK and other cytokine scores seen in adult and juvenile DM with future disease states.

Histological heterogeneity in a large clinical cohort of juvenile idiopathic inflammatory myopathy: analysis by myositis autoantibody and pathological features

Aim

Juvenile idiopathic inflammatory myopathies have been recently reclassified into clinico‐serological subgroups. Myopathological correlates of the subgroups are incompletely understood.

Methods

We studied muscle biopsies from 101 children with clinically and serologically defined juvenile idiopathic inflammatory myopathies from the UK JDM Cohort and Biomarker Study by applying the international JDM score tool, myopathological review and C5b‐9 complement analysis.

Results

Autoantibody data were available for 90/101 cases with 18/90 cases positive for anti‐TIF1γ, 15/90 anti‐NXP2, 11/90 anti‐MDA5, 5/90 anti‐Mi2 and 6/90 anti‐PmScl. JDM biopsy severity scores were consistently low in the anti‐MDA5 group, high in the anti‐Mi2 group, and widely distributed in the other groups. Biopsies were classified histologically as perifascicular atrophy (22/101), macrophage‐rich necrosis (6/101), scattered necrosis (2/101), clustered necrosis (2/101), inflammatory fibre invasion (2/101), chronic myopathic change (1/101), diffuse endomysial macrophage infiltrates (40/101) and minimal change (24/101). MDA5 cases segregated with the minimal change group and showed no capillary C5b‐9‐deposition. The Mi2 group displayed high severity scores and a tendency towards sarcolemmal complement deposition. NXP2 and TIF1γ groups showed a variety of pathologies with a high proportion of diffuse endomysial macrophage infiltrates and a high proportion of capillary C5b‐9 deposition.

Conclusion

We have shown that juvenile idiopathic inflammatory myopathies have a spectrum of histopathological phenotypes and show distinct complement attack complex deposition patterns. Both correlate in some cases with the serological subtypes. Most cases do not show typical histological features associated with dermatomyositis (e.g. perifascicular atrophy). In contrast, more than half show relatively mild histopathological changes.

B Cells as a Therapeutic Target in Paediatric Rheumatic Disease

B cells carry out a central role in the pathogenesis of autoimmune disease. In addition to the production of autoantibodies, B cells can contribute to disease development by presenting autoantigens to autoreactive T cells and by secreting pro-inflammatory cytokines and chemokines which leads to the amplification of the inflammatory response. Targeting both the antibody-dependent and antibody-independent function of B cells in adult rheumatic disease has led to the advent of B cell targeted therapies in clinical practice. To date, whether B cell depletion could also be utilized for the treatment of pediatric disease is relatively under explored. In this review, we will discuss the role of B cells in the pathogenesis of the pediatric rheumatic diseases Juvenile Idiopathic Arthritis (JIA), Juvenile Systemic Lupus Erythematosus (JSLE) and Juvenile Dermatomyositis (JDM). We will also explore the rationale behind the use of B cell-targeted therapies in pediatric rheumatic disease by highlighting new case studies that points to their efficacy in JIA, JSLE, and JDM.

French expert opinion for the management of juvenile dermatomyositis

A guideline group consisting of a pediatric rheumatologist, internists, rheumatologists, immunologists, a physiotherapist and a patient expert elaborated guidelines related to the management of juvenile dermatomyositis on behalf of the rare autoimmune and autoinflammatory diseases network FAI2R. A systematic search of the literature published between 2000 and 2015 and indexed in PubMed was undertaken. Here, we present the expert opinion for diagnosis and treatment in juvenile dermatomyositis.

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.

Serum biomarkers of glucocorticoid response and safety in anti-neutrophil cytoplasmic antibody-associated vasculitis and juvenile dermatomyositis

Glucocorticoids are standard of care for many chronic inflammatory conditions, including juvenile dermatomyositis (JDM) and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). We sought to define pharmacodynamic biomarkers of therapeutic efficacy and safety concerns of glucocorticoid treatment for these two disorders. Previous proteomic profiling of patients with Duchenne muscular dystrophy (DMD) and inflammatory bowel disease (IBD) treated with glucocorticoids identified candidate biomarkers for efficacy and safety concerns of glucocorticoids. Serial serum samples from patients with AAV (n = 30) and JDM (n = 12) were obtained during active disease, and after treatment with glucocorticoids. For AAV, 8 of 11 biomarkers of the anti-inflammatory response to glucocorticoids were validated (P-value ≤0.05; CD23, macrophage-derived cytokine, interleukin-22 binding protein, matrix metalloproteinase-12, T lymphocyte surface antigen Ly9, fibrinogen gamma chain, angiopoietin-2 [all decreased], and protein C [increased]), as were 5 of 7 safety biomarkers (P-value ≤0.05; afamin, matrix metalloproteinase-3, insulin growth factor binding protein-5, angiotensinogen, leptin [all increased]). For JDM, 10 of 11 efficacy biomarkers were validated (P-value ≤0.05; all proteins except fibrinogen gamma chain) and 6 of 7 safety biomarkers (P-value ≤0.05; AAV proteins plus growth hormone binding protein). The identified efficacy biomarkers may be useful as objective outcome measures for early phase proof-of-concept studies when assessing novel anti-inflammatory drugs in JDM and AAV, and likely in other inflammatory disorders. Similarly, safety biomarkers may also be helpful assessing toxicity of alternatives to glucocorticoids.