Autoantibodies to a 140-kd protein in juvenile dermatomyositis are associated with calcinosis

Liquid-liquid phase separation in innate immunity

Intrinsic and innate immune responses are essential lines of defense in the body's constant surveillance of pathogens. The discovery of liquid-liquid phase separation (LLPS) as a key regulator of this primal response to infection brings an updated perspective to our understanding of cellular defense mechanisms. Here, we review the emerging multifaceted role of LLPS in diverse aspects of mammalian innate immunity, including DNA and RNA sensing and inflammasome activity. We discuss the intricate regulation of LLPS by post-translational modifications (PTMs), and the subversive tactics used by viruses to antagonize LLPS. This Review, therefore, underscores the significance of LLPS as a regulatory node that offers rapid and plastic control over host immune signaling, representing a promising target for future therapeutic strategies.

Identification of connective tissue disease autoantibodies and a novel autoantibody anti-annexin A11 in patients with "idiopathic" interstitial lung disease

BACKGROUND

Autoantibodies are a hallmark feature of Connective Tissue Diseases (CTD). Their presence in patients with idiopathic interstitial lung disease (ILD) may suggest covert CTD. We aimed to determine the prevalence of CTD autoantibodies in patients diagnosed with idiopathic ILD.

METHODS

499 patient sera were analysed: 251 idiopathic pulmonary fibrosis (IPF), 206 idiopathic non-specific interstitial pneumonia (iNSIP) and 42 cryptogenic organising pneumonia (COP). Autoantibody status was determined by immunoprecipitation.

RESULTS

2.4% of IPF sera had a CTD-autoantibody compared to 10.2% of iNSIP and 7.3% of COP. 45% of autoantibodies were anti-synthetases. A novel autoantibody targeting an unknown 56 kDa protein was found in seven IPF patients (2.8%) and two NSIP (1%) patients. This was characterised as anti-annexin A11.

CONCLUSION

Specific guidance on autoantibody testing and interpretation in patients with ILD could improve diagnostic accuracy. Further work is required to determine the clinical significance of anti-annexin A11.

Autoantibody evaluation in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), generally referred to as myositis is a heterogeneous group of diseases characterized by muscle inflammation and/or skin involvement, diverse extramuscular manifestations with variable risk for malignancy and response to treatment. Contemporary clinico-serologic categorization identifies 5 main clinical groups which can be further stratified based on age, specific clinical manifestations and/or risk for cancer. The serological biomarkers for this classification are generally known as myositis-specific (MSAs) and myositis-associated antibodies. Based on the use of these antibodies, IIM patients are classified into anti-synthetase syndrome, dermatomyositis, immune-mediated necrotizing myopathy, inclusion body myositis, and overlap myositis. The current classification criteria for IIM requires clinical findings, laboratory measurements, and histological findings of the muscles. However, the use MSAs and myositis-associated autoantibodies as an adjunct for disease evaluation is thought to provide a cost-effective personalized approach that may not only guide diagnosis but aid in stratification and/or prognosis of patients. This review provides a comprehensive overview of contemporary autoantibodies that are specific or associated myositis. In addition, it highlights possible pathways for the detection and interpretation of these antibodies with limitations for routine clinical use.

[Pulmonary involvement in idiopathic inflammatory myopathies]

Idiopathic inflammatory myopathies are rare systemic diseases with different types of pulmonary manifestations depending on the underlying aetiology; here, interstitial lung diseases (ILD) are the most frequently found patterns depending on the underlying disorder. There is a lack of sufficient prospective studies on this heterogeneous group of patients, particularly in case of ILD being involved. The diagnosis is based upon guideline recommendations for ILD and requires a multidisciplinary discussion within a team with specific expertise in this field. Myositis specific antibodies and myositis associated antibodies form an essential part of the diagnostic tools and may also be associated with a certain phenotype or disease progression. Anti-t-RNA-synthetase antibodies (Anti-ARS) and anti-melanoma differentiation-associated gene 5 antibodies (MDA5) play an important clinical role for treatment the estimation of response and prognosis. The most common ILD patterns are nonspecific interstitial pneumonia (NSIP) and organising pneumonia (OP) or a mixed pattern of both. Treatment is based on systemic steroids and early initiation of other immunosuppressant drugs. Evidence for this is, however, sparse, since most of the studies having investigated treatment modalities are of retrospective nature, even though some new prospective data may be useful for the establishment of treatment pathways in the future.

Severe gastrointestinal involvements in patients with adult dermatomyositis with anti-NXP2 antibody

OBJECTIVE

Gastrointestinal (GI) involvements were scarcely reported in adult anti-nuclear matrix protein 2 (NXP2) dermatomyositis (NXP2+DM). In this study, we investigated the clinical, pathological and molecular features as well as treatment options of this rare yet life-threatening disease.

METHODS

We retrospectively collected the data of the cohort of NXP2+ DM from 2012 to 2022 in our hospital. RNA sequencing was performed in intestinal samples of perforated patients compared with healthy controls data set.

RESULTS

A total of 56 patients with adult NXP2+DM were collected including 10 cases with GI involvements. Abdominal pain and melena were the initial manifestations for GI involvements with a median 10-month time lag after the diagnosis of NXP2+DM when myositis largely subsided. Within weeks, GI perforation occurred in 8 of 10 patients, while five patients underwent eight surgical interventions subsequently. The short-term mortality was observed in four patients. NXP2+DM with GI involvements presented with more extramuscular systemic manifestations such as interstitial lung disease and subcutaneous calcinosis. The GI pathological features encompassed vasculitis/vasculopathy with high MxA expression, intestinal smooth muscle necrosis and serosal calcinosis. Gene expression profile validated the type-I interferon activation and revealed that epithelial mesenchymal transition and focal adhesion pathway may also contribute. Finally, vedolizumab, an anti-α4β7-integrin monoclonal antibody, exhibited promising therapeutic signals which should be further investigated.

CONCLUSIONS

GI involvement is a unique complication in patients with adult NXP2+DM. Timely recognition and targeted therapy may turn out to be lifesaving.

Macrophage activation syndrome in juvenile dermatomyositis: a case report and a comprehensive review of the literature

BACKGROUND

Macrophage activation syndrome (MAS) is a severe and life-threatening syndrome associated with autoimmune diseases. The coexistence of MAS and juvenile dermatomyositis (JDM) is not well reported. This report describes a case of JDM with MAS and summarizes the clinical characteristics and prognosis of MAS in patients with JDM.

CASE PRESENTATION

The patient was a 15-year-old female with JDM, presenting with heliotrope rash, muscle weakness, increased muscle enzyme, anti-nuclear matrix protein 2 (NXP2) antibody, and muscle biopsy consistent with JDM. The patient developed fever, cytopenia, and hyperferritinemia three months after the first manifestations. Hemophagocytosis was found in the bone marrow. The final diagnosis was JDM combined with MAS. Despite intensive treatment, the patient died of MAS. By reviewing the literature, we found 17 similar cases. Together with the present case, 18 patients were identified, the median age of disease onset was 13.5 years, and male to female ratio was 1.25: 1. Nine out of 16 (56.3%) patients were complicated with interstitial lung disease (ILD). The median time interval between JDM onset and MAS diagnosis was 9 weeks. At the onset of MAS, all (100%) patients had elevated levels of ferritin and serum liver enzymes. Among 18 patients, 14 (77.8%) had fever, 14/17 (82.4%) had cytopenia, 11/11 (100%) had hepatosplenomegaly, and 13/14 (92.9%) had hemophagocytosis. Five (27.8%) patients showed central nervous system (CNS) involvement. The mortality of MAS rate of in patients with JDM was 16.7%, despite various treatment methods.

CONCLUSION

. The coexistence of JDM and MAS is underestimated with increased mortality. Hepatosplenomegaly and increased serum levels of ferritin in patients with JDM should raise clinical suspicion for MAS.

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.

Calcinosis Cutis and Calciphylaxis in Autoimmune Connective Tissue Diseases

Calcinosis represents a severe complication of several autoimmune disorders. Soft-tissue calcifications have been classified into five major types: dystrophic, metastatic, idiopathic, iatrogenic, and calciphylaxis. Autoimmune diseases are usually associated with dystrophic calcifications, including calcinosis cutis, occurring in damaged or devitalized tissues in the presence of normal serum levels of calcium and phosphate. In particular, calcinosis cutis has been described in dermatomyositis, polymyositis, juvenile dermatomyositis, systemic sclerosis, systemic lupus erythematosus, primary Sjögren's syndrome, overlap syndrome, mixed connective tissue disease, and rheumatoid arthritis. Calciphylaxis, a severe and life-threatening syndrome presenting with vascular calcifications and thrombosis, has also been associated with some autoimmune conditions. Due to the potentially disabling character of calcinosis cutis and calciphylaxis, physicians' awareness about the clinical presentation and management of these diseases should be increased to select the most appropriate treatment option and avoid long-term complications. In this review, we aim to analyze the clinical features of calcinosis cutis and calciphylaxis associated with autoimmune diseases, and the main treatment strategies evaluated up to now for treating this potentially disabling disease.

Inflammatory Myopathies

PURPOSE OF REVIEW

This article outlines the salient clinical, serologic, electrophysiologic, imaging, and histopathologic findings and treatment options for the idiopathic inflammatory myopathies, including those related to immune checkpoint inhibitors and SARS-CoV-2.

RECENT FINDINGS

The classification of idiopathic inflammatory myopathies has improved with the integration of myositis-specific antibodies and histopathologic findings. Characteristic features of immune checkpoint inhibitor-related myositis have been identified, allowing early recognition and treatment of the syndrome. The COVID-19 pandemic has had a profound impact on the care of patients with idiopathic inflammatory myopathies, and several mechanisms of virus-related muscle injury have been proposed.

SUMMARY

A comprehensive evaluation including clinical examination, EMG, imaging, antibody testing, muscle biopsy, and cancer screening, when appropriate, can lead to an earlier accurate diagnosis and an individualized treatment approach for patients with idiopathic inflammatory myopathies.

VI Brazilian consensus guidelines for detection of anti-cell autoantibodies on HEp-2 cells

BACKGROUND

The VI Brazilian Consensus on Autoantibodies against HEp-2 cells for determination of autoantibodies against cellular constituents on HEp-2 cells was held on September, 2019, in Fortaleza (CE, Brazil). The guidelines in this edition were formulated by the group of Brazilian experts discussing the classification of complex patterns, the classification of the nuclear discrete dots (few and multiple), the identification of the discrete fine speckled pattern (AC-4a) and improvements on the ANA report.

MAINBODY

Sixteen Brazilian researchers and experts from universities and clinical laboratories representing the various geographical regions of Brazil participated in the meeting. Four main topics were discussed: (1) How to classify patterns with fluorescence in more than one cell compartment considering three relevant categoris: composite patterns, mixed patterns and multiple patterns; (2) The splitting of the discrete nuclear dots pattern into the multiple discrete nuclear dots (AC-6) and few discrete nuclear dots (AC-7) patterns, respectively; (3) Inclusion of a novel nuclear pattern characterized by discrete fine speckled pattern highly associated with antibodies to SS-A/Ro60, classified as AC-4a. In addition, adjustments on the Brazilian Consensus nomenclature were implemented aiming to harmonize the designation of some patterns with the International Consensus on ANA Patterns (ICAP). Furthermore, the designations of the PCNA-like pattern (AC-13), CENP-F-like pattern (AC-14) and Topo I-like pattern (AC-29) were adjusted in accordance to ICAP. Finally, there was a recommendation for adjustment in the test report in order to address the status of nuclear envelope staining. For all topics, the aim was to establish specific guidelines for laboratories and clinicians. All recommendations were based on consensus among participants. All recommendations from the V Consensus were maintained and there was relevant progress in the BCA/HEp-2 guidelines and further harmonization with ICAP.

CONCLUSION

The VI BCA/HEp-2 edition was successful in establishing important recommendations regarding the classification of complex patterns, in supporting the identification of a novel pattern within the AC-4 group and in the harmonization process with the ICAP terminology.

An Italian Multicenter Study on Anti-NXP2 Antibodies: Clinical and Serological Associations

The identification of anti-NXP2 antibodies is considered a serological marker of dermatomyositis (DM), with calcinosis, severe myositis and, in some reports, with cancer. Historically, these associations with anti-NXP2 antibodies have been detected by immunoprecipitation (IP), but in the last few years commercial immunoblotting assays have been released. The aim of this collaborative project was to analyse the clinical features associated to anti-NXP2 antibodies, both with commercial line blot (LB) and IP. Myositis-specific and myositis-associated autoantibodies were detected in single centres by commercial line blot (LB); available sera were evaluated in a single centre by protein and RNA immunoprecipitation (IP), and IP-Western blot. Sixty patients anti-NXP2+ (NXP2+) positive by LB were compared with 211 patients anti-NXP2 negative with idiopathic inflammatory myositis (IIM). NXP2+ showed a younger age at IIM onset (p = 0.0014), more frequent diagnosis of dermatomyositis (p = 0.026) and inclusion-body myositis (p = 0.009), and lower rate of anti-synthetase syndrome (p < 0.0001). As for clinical features, NXP2+ more frequently develop specific skin manifestations and less frequently features related with overlap myositis and anti-synthetase syndrome. IP confirmed NXP2 positivity in 31 of 52 available sera (62%). Most clinical associations were confirmed comparing NXP2 LB+/IP+ versus NXP2-negative myositis, with the following exceptions: inclusion-body myositis diagnosis was not detected, whilst dysphagia and myositis were found more frequently in NXP2 LB+/IP+ patients. The 21 LB+ /IP-myositis patients did not show differences in clinical features when compared with the NXP2-myositis patients and more frequently displayed multiple positivity at LB. Risk of developing cancer-associated myositis was similar between NXP2-positive and NXP2-negative myositis patients, either when detected by LB or IP. Protein-IP confirmed NXP2 antibodies in nearly 60% of sera positive for the same specificity with commercial assay. Double-positive cases rarely occurred in myositis patients with a clinical diagnosis other than dermatomyositis. Patients only positive by LB (LB+/IP-) did not display clinical features typical of NXP2. NXP2 positivity by LB should be confirmed by other methods in order to correctly diagnose and characterize patients affected by idiopathic inflammatory myositis.

Reliability of antinuclear matrix protein 2 antibody assays in idiopathic inflammatory myopathies is dependent on target protein properties

A line blotting assay (LB) is currently used to detect myositis-specific autoantibodies (MSAs) in patients with idiopathic inflammatory myopathies (IIMs), because of its simplicity; however, the sensitivity and specificity of this assay is low. The aim of this study is to evaluate the accuracy of the commercial LB in detection of antinuclear matrix protein 2 (NXP2) antibody. Seventy-seven serum samples from patients with IIMs, in which anti-NXP2 antibodies were detected through immunoprecipitation and western blotting (IP-WB) using K562 cell lysate, were enrolled. All samples were assessed by LB and IP-WB using recombinant human NXP2 whole protein (rNXP2) produced by insect cells, and the positive rates of each assay were compared. Thirty-two samples (41.6%) showed false-negativity by LB, which includes 11 samples with negative results by IP-WB using rNXP2. Relative intensities of IP-WB using cell lysate were significantly higher in the samples with positive results by both LB and IP-WB using rNXP2, compared to samples with positive by IP-WB using rNXP2 but negative by LB. Three of 11 samples with negative results by both LB and IP-WB using rNXP2 revealed high antibody titers. Further, differences in post-transcriptional SUMOylation were observed between recombinant and natural NXP2 proteins. In conclusion, the LB showed low sensitivity for detection of anti-NXP2 antibody, an effect exacerbated at low titers of anti-NXP2 antibodies. Moreover, there appears to be differences in the reactivities of antibodies to recombinant and natural NXP2 proteins with different post-transcriptional modifications.

Idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), also known as myositis, are a heterogeneous group of autoimmune disorders with varying clinical manifestations, treatment responses and prognoses. Muscle weakness is usually the classical clinical manifestation but other organs can be affected, including the skin, joints, lungs, heart and gastrointestinal tract, and they can even result in the predominant manifestations, supporting that these are systemic inflammatory disorders. Different myositis-specific autoantibodies have been identified and, on the basis of clinical, histopathological and serological features, IIMs can be classified into several subgroups — dermatomyositis (including amyopathic dermatomyositis), antisynthetase syndrome, immune-mediated necrotizing myopathy, inclusion body myositis, polymyositis and overlap myositis. The prognoses, treatment responses and organ manifestations vary among these groups, implicating different pathophysiological mechanisms in each subtype. A deeper understanding of the molecular pathways underlying the pathogenesis and identifying the autoantigens of the immune reactions in these subgroups is crucial to improve outcomes. New, more homogeneous subgroups defined by autoantibodies may help define disease mechanisms, and will also be important in future clinical trials to develop targeted therapies and in identifying biomarkers to guide treatment decisions for the individual patient.

Idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), also known as myositis, are a heterogeneous group of autoimmune disorders with varying clinical manifestations, treatment responses and prognoses. Muscle weakness is usually the classical clinical manifestation but other organs can be affected, including the skin, joints, lungs, heart and gastrointestinal tract, and they can even result in the predominant manifestations, supporting that IIM are systemic inflammatory disorders. Different myositis-specific auto-antibodies have been identified and, on the basis of clinical, histopathological and serological features, IIM can be classified into several subgroups - dermatomyositis (including amyopathic dermatomyositis), antisynthetase syndrome, immune-mediated necrotizing myopathy, inclusion body myositis, polymyositis and overlap myositis. The prognoses, treatment responses and organ manifestations vary among these groups, implicating different pathophysiological mechanisms in each subtype. A deeper understanding of the molecular pathways underlying the pathogenesis and identifying the auto-antigens of the immune reactions in these subgroups is crucial to improving outcomes. New, more homogeneous subgroups defined by auto-antibodies may help define disease mechanisms and will also be important in future clinical trials for the development of targeted therapies and in identifying biomarkers to guide treatment decisions for the individual patient.

Myositis-Specific Antibodies and Myositis-Associated Antibodies in Patients With Idiopathic Inflammatory Myopathies From the PANLAR Myositis Study Group

BACKGROUND

Dermatomyositis (DM) and polymyositis (PM) are forms of idiopathic inflammatory myopathies (IIMs), which are associated with the production of autoantibodies that are useful in the diagnosis and prognosis of the disease.

OBJECTIVE

The aim of this study was to determine the frequency of antinuclear autoantibodies (ANAs), myositis-specific autoantibodies (MSAs), and myositis-associated autoantibodies (MAAs) in 6 Latin American countries.

METHODS

Two hundred ten patients with IIM were included in this cross-sectional study from 2014 to 2017: 112 from Mexico, 46 from Colombia, 20 from Peru, 16 from the Dominican Republic, 10 from Argentina, and 6 from Guatemala. Antinuclear autoantibodies were detected by indirect immunofluorescence on HEp-2 cells. MSAs and MAAs were tested by a line immunoassay method. Mann-Whitney U and χ2 tests were used for statistical analysis.

RESULTS

Of the 210 IIM patients, 139 (66.2%) had DM, 59 (28%) PM, and 12 (5.7%) juvenile DM. The mean age was 43.5 (6-79 years); 158 (75.2%) were female, and 52 (24.8%) were male. The overall frequency of ANA was 60%. The most frequent patterns were fine speckled (AC-4) (78.3%) and cytoplasmic (AC-19) (6.45%). The most frequent MSA were anti-Mi-2 (38.5%) and anti-Jo-1 (11.9%). Anti-Mi-2 was more frequent in patients from Colombia (40.1%). The MAA more frequent were anti-Ro-52/TRIM21 (17.6%) and anti-PM-Scl75 (7.5%).

CONCLUSIONS

This is the first study of ANA, MSA, and MAA in patients from 6 countries from the Panamerican League against Rheumatism myositis study group. We observed a general prevalence of 60% of ANA. In relation to MSA and MAA, anti-Mi-2 was the more frequent (38.5%).

The Significance of Autoantibodies in Juvenile Dermatomyositis

Juvenile dermatomyositis is a chronic and rare autoimmune disorder classified into the spectrum of idiopathic inflammatory myopathies. Although this entity is mainly characterized by the presence of pathognomonic cutaneous lesions and proximal muscle weakness, the clinical manifestation can be highly heterogeneous; thus, diagnosis might be challenging. Current treatment recommendations for juvenile dermatomyositis, based mainly upon case series, include the use of corticosteroids, immunomodulatory, and immunosuppressive agents. Recently, several specific autoantibodies have been shown to be associated with distinct clinical phenotypes of classic dermatomyositis. There is a need to further evaluate their relevance in the formation of various clinical features. Furthermore, while providing more personalized treatment strategies, one should consider diversity of autoantibody-related subgroups of juvenile dermatomyositis.

MORC protein family-related signature within human disease and cancer

The microrchidia (MORC) family of proteins is a highly conserved nuclear protein superfamily, whose members contain common domain structures (GHKL-ATPase, CW-type zinc finger and coiled-coil domain) yet exhibit diverse biological functions. Despite the advancing research in previous decades, much of which focuses on their role as epigenetic regulators and in chromatin remodeling, relatively little is known about the role of MORCs in tumorigenesis and pathogenesis. MORCs were first identified as epigenetic regulators and chromatin remodelers in germ cell development. Currently, MORCs are regarded as disease genes that are involved in various human disorders and oncogenes in cancer progression and are expected to be the important biomarkers for diagnosis and treatment. A new paradigm of expanded MORC family function has raised questions regarding the regulation of MORCs and their biological role at the subcellular level. Here, we systematically review the progress of researching MORC members with respect to their domain architectures, diverse biological functions, and distribution characteristics and discuss the emerging roles of the aberrant expression or mutation of MORC family members in human disorders and cancer development. Furthermore, the illustration of related mechanisms of the MORC family has made MORCs promising targets for developing diagnostic tools and therapeutic treatments for human diseases, including cancers.

Biomarker und Histologie bei idiopathischen inflammatorischen Myopathien

Die idiopathischen inflammatorischen Myopathien (IIM) sind eine Gruppe entzündlicher Muskelerkrankungen für deren Diagnosestellung, Verlaufsbeurteilung, Prognoseabschätzung und Risikostratifizierung Biomarker eine jeweils essentielle Rolle spielen. Biomarker in diesem Kontext können sowohl „herkömmliche“ serologische Marker wie Muskelenzyme oder Autoantikörper, histologische Marker wie entitätsspezifische inflammatorische Muster, aber auch genomische und genetische Marker sein. Der vorliegende Artikel gibt einen Überblick über bewährte und innovative Marker.

Identification and prediction of novel classes of long-term disease trajectories for patients with juvenile dermatomyositis using growth mixture models

Objectives

Uncertainty around clinical heterogeneity and outcomes for patients with JDM represents a major burden of disease and a challenge for clinical management. We sought to identify novel classes of patients having similar temporal patterns in disease activity and relate them to baseline clinical features.

Methods

Data were obtained for n = 519 patients, including baseline demographic and clinical features, baseline and follow-up records of physician’s global assessment of disease (PGA), and skin disease activity (modified DAS). Growth mixture models (GMMs) were fitted to identify classes of patients with similar trajectories of these variables. Baseline predictors of class membership were identified using Lasso regression.

Results

GMM analysis of PGA identified two classes of patients. Patients in class 1 (89%) tended to improve, while patients in class 2 (11%) had more persistent disease. Lasso regression identified abnormal respiration, lipodystrophy and time since diagnosis as baseline predictors of class 2 membership, with estimated odds ratios, controlling for the other two variables, of 1.91 for presence of abnormal respiration, 1.92 for lipodystrophy and 1.32 for time since diagnosis. GMM analysis of modified DAS identified three classes of patients. Patients in classes 1 (16%) and 2 (12%) had higher levels of modified DAS at diagnosis that improved or remained high, respectively. Patients in class 3 (72%) began with lower DAS levels that improved more quickly. Higher proportions of patients in PGA class 2 were in DAS class 2 (19%, compared with 16 and 10%).

Conclusion

GMM analysis identified novel JDM phenotypes based on longitudinal PGA and modified DAS.

Anti-nuclear matrix protein 2 antibody-positive inflammatory myopathies represent extensive myositis without dermatomyositis-specific rash

OBJECTIVES

Myositis-specific autoantibodies (MSAs) define distinct clinical subsets of idiopathic inflammatory myopathies (IIMs). The anti-nuclear matrix protein 2 (NXP2) antibody, a MSA detected in juvenile/adult IIMs, has been reported to be associated with a high risk of subcutaneous calcinosis, subcutaneous oedema, and internal malignancies. The study aimed to clarify the clinical features of anti-NXP2 antibody-positive IIMs in detail.

METHODS

This multi-centre retrospective observational study on 76 anti-NXP2 antibody-positive patients. The antibody was detected via a serological assay using immunoprecipitation and western blotting. The patients were selected from 162 consecutive Japanese patients with IIMs.

RESULTS

The cohort of anti-NXP2 antibody-positive IIMs included 29 juvenile patients and 47 adult patients. Twenty-seven (35.5%) patients presented with polymyositis phenotype without dermatomyositis-specific skin manifestations (heliotrope rash or Gottron sign/papules); this was more common in the adults than children (48.9% vs. 15.8%, P < 0.01). Nine (11.8%) patients had subcutaneous calcinosis, and 20 (26.3%) patients had subcutaneous oedema. In addition, the proportion of patients with muscle weakness extending to the distal limbs was high (36 patients [47.4%]) in this cohort. Adult patients had a higher prevalence of malignancy than the general population (age-standardised incidence ratio of malignancies: 22.4).

CONCLUSION

Anti-NXP2 antibody-positive IIMs, which include dermatomyositis sine dermatitis, are characterised by atypical skin manifestations and extensive muscular involvement.

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.

Covert clues: the non-hallmark cutaneous manifestations of dermatomyositis

Dermatomyositis (DM) is a strikingly heterogenous disease characterized by a broad and ever-evolving spectrum of cutaneous manifestations that transcend the classic “hallmarks” defined by Peter and Bohan in 1975. Despite the increasing preponderance and ubiquity of autoantibody, radiologic, and electrophysiologic testing, the diagnosis of DM still hinges largely on prompt detection of cutaneous manifestations of this condition. While pathognomonic cutaneous features of DM are more readily recognizable, many patients present with subtle and/or atypical skin manifestations, and diagnosis of DM may require clinician identification of these cutaneous clues. In this review, we highlight several of the lesser-known skin manifestations of DM, specifically, panniculitis, diffuse subcutaneous edema, erythroderma, calcinosis, ulceration, flagellate erythema, Wong-type DM, gingival telangiectasias, and the ovoid palatal patch. We describe the clinical and histopathologic presentation of these cutaneous findings. While manifesting less frequently than the heliotrope rash, Gottron’s papules, and Gottron’s sign, these cutaneous clues are equally important for clinicians to recognize in order to facilitate timely diagnosis and early intervention.

Treatment of Calcinosis in Juvenile Dermatomyositis

PURPOSE OF REVIEW

Juvenile dermatomyositis (JDM) is a rare autoimmune disease characterised by muscle and skin involvement. Calcinosis is a debilitating complication of JDM which is difficult to treat and may cause long-term morbidity. The purpose of this review is to provide an update for the treatment of JDM-associated calcinosis based on previously published studies.

RECENT FINDINGS

Evidence-based studies are lacking for the management of calcinosis, and current treatment modalities have been largely based on case reports, case series, cohort studies, limited controlled studies and anecdotal clinical experience. The use of early aggressive therapy for resistant cases is strongly suggested to halt persistent disease activity which may help in reducing steroid use and their associated complications. Recent insights into disease pathogenesis, myositis-specific antibodies and genetic associations have led to identification of novel therapeutic targets such as Janus kinase (JAK) 1/2. Different treatment regimens with variable outcomes are in use for the treatment of refractory calcinosis; nevertheless, the level of evidence is not sufficient to propose specific guidelines. Recently, JAK 1/2 inhibitors have shown to be effective as an emerging therapeutic option highlighting that translational and clinical research is crucial to develop targeted treatment for JDM-associated calcinosis.

Clinical characteristics and poor predictors of anti-NXP2 antibody-associated Chinese JDM children

BACKGROUND

Juvenile dermatomyositis (JDM) is a rare and sometimes fatal disease in children. The anti-NXP2 antibody is one of the most common antibodies and muscle ischaemia associated with NXP2 autoantibodies was a severe subtype of JDM. Further information is needed regarding clinical characteristics and factors associated with poor prognosis. But there are no reports about clinical characteristics and high risk factor of poor prognosis. For the first time, we introduced the clinical characteristics and poor predictors of anti-NXP2 antibody-associated juvenile dermatomyositis in Chinese children.

METHODS

Twenty-six patients with anti-NXP2 antibody-related JDM from 85 JDM Chinese patients were diagnosed from January 2016 to November 2019. Logistic regression was used to analyze the risk factors for refractory cases and mortality.

RESULTS

The ratio of male to female was 1:1.9. The median age of onset was 4.5 (1-13) years. Twenty-four cases (92.3%) had rash and muscle weakness. Treatments included glucocorticoids, immunosuppressive agents, biological agents (7 cases), plasma exchange, Janus kinase inhibitor (7 cases) and autologous stem cell transplant (1 case). Refractory JDM patients (11/26, 42.3%) were associated with edema, skin ulcer, muscle strength<=grade 3, CD4/CD8 ratio < 1.4 and ferritin > 200μg/ml. Among 6 cases (6/26, 23.1%) with severe gastrointestinal involvement, 5 cases died and 1 case survived after autologous stem cell transplant (ASCT). The risk factors for gastrointestinal involvement and mortality were edema, skin ulcer, severe muscle weakness (dysphagia/ hoarseness/ soft voice), BMI < 15 and ANA positive.

CONCLUSIONS

Edema, skin ulcer and severe muscle weakness predicted refractory disease, GI involvement, and mortality in anti-NXP2 antibody-positive JDM of Chinese children. Decreased CD4/CD8 ratio and high ferritin related with refractory cases, and very low BMI and ANA (+) are probably, associated with gastrointestinal involvement and mortality.

TRIAL REGISTRATION

http://www.chictr.org.cn/showproj.aspx?proj=49846 .

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.

Clinical characteristics and prognostic analysis of Chinese dermatomyositis patients with malignancies

Although a strong association between idiopathic inflammatory myositis (IIM) and malignancy has been widely reported, few studies have solely focused on the concurrence of dermatomyositis (DM) and malignancies (DM-malignancy).We conducted a retrospective analysis of 37 DM-malignancy cases among 363 DM patients admitted to our hospital between January 2012 and December 2017.(1) The mean age at DM diagnosis was higher for DM-malignancy patients than for DM-non-malignancy patients [(54.76 ± 9.77) years vs (48.57 ± 12.82) years, t = 2.84, P = .005]. (2) Gynecological malignancies (35.90%/14 cases) were the most common malignancies. Malignancies were diagnosed before DM for 7 DM-malignancy patients. The interval between the DM and malignancy diagnoses for the remaining 32 DM-malignancy patients was less than 6 months for 18 patients (46.15%), less than 1 years for 23 patients (58.9%), and less than 2 years for 29 patients (74.26%). (3) There was no significant difference either in antinuclear antibody or anti-Ro-52 positivity between the 2 groups (P > .05). (4) Multivariate analysis demonstrated that DM onset age ≥50 years and concurrence with ILD increased the risk of death for DM patients [hazard ratio (HR): 1.62 and 2.72; 95% confidence interval (CI): (1.08-2.43) and (1.47-5.02); P = .02 and 0.001, respectively], and male gender decreased the risk of death [HR 0.66, 95% CI (0.44-0.98), P = .04]. DM-malignancy patients were older than DM-non-malignancy patients. Gynecological malignancies were the most common malignancies among these patients. A DM onset age ≥50 years, female sex and the presence of ILD were independent risk factors for death.

Assessment of diagnostic utility, clinical phenotypic associations, and prognostic significance of anti-NXP2 autoantibody in patients with idiopathic inflammatory myopathies: a systematic review and meta-analysis

The objectives of this study are to analyze the association between anti-nuclear matrix protein 2 (NXP2) autoantibody and idiopathic inflammatory myopathies (IIMs) and to assess the diagnostic and prognostic relevance of anti-NXP2 autoantibody in patients with IIMs. A systematic search was performed in PubMed, Web of Science, EMBASE, the Cochrane Library, and Scopus to identify studies published as of February 29, 2020. Data was analyzed using Stata 12.0 and Meta-DiSc 1.4. Twenty-eight studies (4764 patients with IIMs and 1981 controls) were included in the meta-analysis. Anti-NXP2 autoantibody showed a significant association with IIMs (odds ratio (OR) = 26.36, 95% confidence interval (CI): 12.05-57.67, P < 0.001), especially juvenile IIMs (OR = 62.48, 95% CI: 16.97-229.98, P < 0.001). The pooled sensitivity, specificity, and area under the curve were 0.19 (95% CI = 0.16-0.21), 1.00 (95% CI = 1.00-1.00), and 0.95 for patients with juvenile IIMs versus controls. Anti-NXP2 autoantibody was associated with an increased risk of developing five characteristics (edema, muscle weakness, myalgia/myodynia, dysphagia, and calcinosis) and reduced risk of interstitial lung disease (ILD) (P < 0.001). Anti-NXP2 autoantibody showed no association with increased risk of death in IIMs (P = 0.463). These findings suggest that anti-NXP2 autoantibody is specially related to IIMs and is related to edema, muscle weakness, myalgia/myodynia, dysphagia, calcinosis, and ILD in patients with IIMs. However, there is no evidence to suggest that the presence of anti-NXP2 autoantibody confers a poor prognosis with respect to overall survival. Key Points • This study summarized the diagnostic and prognostic accuracies of anti-NXP2 autoantibody for patients with IIMs. Anti-NXP2 autoantibody is related to edema, muscle weakness, myalgia/myodynia, dysphagia, calcinosis, and ILD in patients with IIMs.

Calcinosis Biomarkers in Adult and Juvenile Dermatomyositis

Dermatomyositis (DM) is a rare idiopathic inflammatory myopathy characterized by muscle weakness and cutaneous manifestations in adults and children. Calcinosis, a complication of DM, is the abnormal deposition of insoluble calcium salts in tissues, including skin, subcutaneous tissue, tendons, fascia, and muscle. Calcinosis is more commonly seen in juvenile DM (JDM), but also develops in adult DM. Although the mechanism of calcinosis remains unclear, several pathogenic hypotheses have been proposed, including intracellular accumulation of calcium secondary to an alteration of the cellular membrane by trauma and inflammation, local vascular ischemia, dysregulation of mechanisms controlling the deposition and solubility of calcium and phosphate, and mitochondrial damage of muscle cells. Identifying calcinosis biomarkers is important for early disease detection and risk assessment, and may lead to novel therapeutic targets for the prevention and treatment of DM-associated calcinosis. In this review, we summarize myositis autoantibodies associated with calcinosis in DM, histopathology and chemical composition of calcinosis, genetic and inflammatory markers that have been studied in adult DM and JDM-associated calcinosis, as well as potential novel biomarkers.

Autoantibody Biomarkers in Rheumatic Diseases

Autoantibodies encountered in patients with systemic rheumatic diseases bear clinical significance as a biomarker to help or predict diagnosis, clinical phenotypes, prognosis, and treatment decision-making. Furthermore, evidence has accumulated regarding the active involvement of disease-specific or disease-associated autoantibodies in the pathogenic process beyond simple association with the disease, and such knowledge has become essential for us to better understand the clinical value of autoantibodies as a biomarker. This review will focus on the current update on the autoantibodies of four rheumatic diseases (rheumatoid arthritis, myositis, systemic sclerosis, and anti-neutrophil cytoplasmic antibody associated vasculitis) where there has been a tremendous progress in our understanding on their biological effects and clinical use.

A Clinically and Biologically Based Subclassification of the Idiopathic Inflammatory Myopathies Using Machine Learning

OBJECTIVE

Published predictive models of disease outcomes in idiopathic inflammatory myopathies (IIMs) are sparse and of limited accuracy due to disease heterogeneity. Computational methods may address this heterogeneity by partitioning patients based on clinical and biological phenotype.

METHODS

To identify new patient groups, we applied similarity network fusion (SNF) to clinical and biological data from 168 patients with myositis (64 adult polymyositis [PM], 65 adult dermatomyositis [DM], and 39 juvenile DM [JDM]) in the Rituximab in Myositis trial. We generated a sparse proof-of-concept bedside classifier using multinomial regression and identified characteristics that distinguished these groups. We conducted χ² tests to link new patient groups with the myositis subtypes.

RESULTS

SNF identified five patient groups in the discovery cohort that subdivided the myositis subtypes. The sparse multinomial regressor to predict patient group assignments (areas under the receiver operating characteristic curve = [0.78, 0.97]; areas under the precision-recall curve = [0.55, 0.96]) found that autoantibody enrichment defined four of these groups: anti-Mi-2, anti-signal recognition peptide (SRP), anti-nuclear matrix protein 2 (NXP2), and anti-synthetase (Syn). Depletion of immunoglobulin M (IgM) defined the fifth group. Each group was associated with one subtype, with adult DM being associated with anti-Mi-2 and anti-Syn autoantibodies, JDM being associated with anti-NXP2 autoantibodies, and adult PM being associated with IgM depletion and anti-SRP autoantibodies. These associations enabled us to further resolve the current myositis subtypes.

CONCLUSION

Using unsupervised machine learning, we identified clinically and biologically homogeneous groups of patients with IIMs, forming the basis of an integrated disease classification based on both clinical and biological phenotype, thus validating other approaches and what has been previously described.

Inflammatory muscle disease - An update

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of inflammatory myopathies whose common feature is immune-mediated muscle injury. There are distinct subgroups including dermatomyositis (DM), polymyositis (PM), inclusion body myositis, and immune-mediated necrotizing myopathy. Antisynthetase syndrome is also emerging as a distinct subgroup with its unique muscle histopathological characteristic of perifascicular necrosis. While the newly updated EULAR/ACR Classification Criteria for IIM have brought advancements in diagnosis and the exclusion of mimickers, the use of only one autoantibody in the derivation of the schema limits its use. Similarly, while the advent of multiple novel therapeutics in the treatment of myositis has been exciting, it has also highlighted the scarcity of validated outcome measures. The purpose of our review is to highlight the updated classification criteria of myositis, newly reported clinical phenotypes associated with myositis autoantibodies, the measurement of outcomes, and emerging treatments in the field.

Clinical practice guidance for juvenile dermatomyositis (JDM) 2018-Update

Juvenile dermatomyositis is the most common type of juvenile idiopathic inflammatory myopathy mainly affecting the skin and proximal muscles. We have published the Japanese version of 'Clinical practice guidance for juvenile dermatomyositis (JDM) 2018 'consisting of a review of articles in the field and evidence-informed consensus-based experts' opinion on the treatment strategy in collaboration with The Pediatric Rheumatology Association of Japan and The Japan College of Rheumatology under the financial support by 'Research on rare and intractable diseases, Health and Labor Sciences Research Grants'. This article is a digest version of the Japanese guidance.

Juvenile dermatomyositis: advances in clinical presentation, myositis-specific antibodies and treatment

BACKGROUND

Juvenile dermatomyositis (JDM) is a chronic autoimmune disease characteristic by inflammation of small vessels within the skin, muscle and vital organs. But the clinical features and treatment of JDM have not been fully clarified.

DATA SOURCES

Databases underwent through PubMed for articles about the clinical features, myositis-specific antibodies of JDM and its treatment, and we selected publications written in English which were relevant to the topic of this review.

RESULTS

Clinical features and myositis-specific antibodies may predict the severity and prognosis of disease. Although the mortality rate has been lower with traditional treatments, such as corticosteroid, intravenous immunoglobulin, and disease-modifying anti-rheumatic drugs such as methotrexate, their usages are variable. Novel biological therapies seem to be effective for refractory JDM patients, but more clinical trials are necessary.

CONCLUSIONS

JDM is a sever disease of childhood. We need to better understand recent advances of JDM in the context of clinical features including skin manifestations, muscle weakness and organ damage, myositis-specific antibodies and their associated outcomes and the treatment of disease.

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.

Polymyositis and dermatomyositis - challenges in diagnosis and management

Polymyositis (PM) and dermatomyositis (DM) are different disease subtypes of idiopathic inflammatory myopathies (IIMs). The main clinical features of PM and DM include progressive symmetric, predominantly proximal muscle weakness. Laboratory findings include elevated creatine kinase (CK), autoantibodies in serum, and inflammatory infiltrates in muscle biopsy. Dermatomyositis can also involve a characteristic skin rash. Both polymyositis and dermatomyositis can present with extramuscular involvement. The causative factor is agnogenic activation of immune system, leading to immunologic attacks on muscle fibers and endomysial capillaries. The treatment of choice is immunosuppression. PM and DM can be distinguished from other IIMs and myopathies by thorough history, physical examinations and laboratory evaluation and adherence to specific and up-to-date diagnosis criteria and classification standards. Treatment is based on correct diagnosis of these conditions.

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Challenges of diagnosis and management influences the clinical research and practice of Polymyositis and dermatomyositis.

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Diagnostic criteria have been updated and novel therapies have been developed in PM/DM.

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Pathogenesis investigation and diagnosis precision improvement may help to guide future treatment strategies.

MORC3 Forms Nuclear Condensates through Phase Separation

Phase separation can produce local structures with specific functionality in the cell, and in the nucleus, this can lead to chromatin reorganization. Microrchidia 3 (MORC3) is a human ATPase that has been implicated in autoimmune disorders and cancer. Here, we show that MORC3 forms phase-separated condensates with liquid-like properties in the cell nucleus. Fluorescence live-cell imaging reveals that the MORC3 condensates are heterogeneous and undergo dynamic morphological changes during the cell cycle. The ATPase activity of MORC3 drives its phase separation in vitro and requires DNA binding and releasing the MORC3 CW domain-dependent autoinhibition through association with histone H3. Our findings suggest a mechanism by which the ATPase function of MORC3 mediates MORC3 nuclear compartmentalization.

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MORC3 forms nuclear condensates with liquid-like characteristics

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Morphology of the MORC3 condensates changes during the cell cycle

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Phase separation depends on the MORC3 ATPase activity and DNA binding

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CW impedes the ability of MORC3 to form condensates

Mechanism for autoinhibition and activation of the MORC3 ATPase

Microrchidia 3 (MORC3) is a human protein linked to autoimmune disorders, Down syndrome, and cancer. It is a member of a newly identified family of human ATPases with an uncharacterized mechanism of action. Here, we elucidate the molecular basis for inhibition and activation of MORC3. The crystal structure of the MORC3 region encompassing the ATPase and CW domains in complex with a nonhydrolyzable ATP analog demonstrates that the two domains are directly coupled. The extensive ATPase:CW interface stabilizes the protein fold but inhibits the catalytic activity of MORC3. Enzymatic, NMR, mutational, and biochemical analyses show that in the autoinhibited, off state, the CW domain sterically impedes binding of the ATPase domain to DNA, which in turn is required for the catalytic activity. MORC3 autoinhibition is released by disrupting the intramolecular ATPase:CW coupling through the competitive interaction of CW with histone H3 tail or by mutating the interfacial residues. Binding of CW to H3 leads to a marked rearrangement in the ATPase-CW cassette, which frees the DNA-binding site in active MORC3 (on state). We show that ATP-induced dimerization of the ATPase domain is strictly required for the catalytic activity and that the dimeric form of ATPase-CW might cooperatively bind to dsDNA. Together, our findings uncovered a mechanism underlying the fine-tuned regulation of the catalytic domain of MORC3 by the epigenetic reader, CW.

Clinical phenotypes and biologic treatment use in juvenile dermatomyositis-associated calcinosis

BACKGROUND

Few risk factors have been identified for the development of calcinosis among patients with Juvenile Dermatomyositis, and currently no clinical phenotype has been associated with its development. We analyzed a large database of patients to further elucidate any relationships among patients with and without calcinosis.

METHOD

The CARRA legacy registry recruited pediatric rheumatology patients from 55 centers across North America from 2010 through 2014, including over 650 subjects with Juvenile Dermatomyositis. We compared the demographic characteristics, clinical disease features and treatment histories of those with and without calcinosis using univariate and multivariate logistic regression.

RESULTS

Of the 631 patients included in the analysis, 84 (13%) had a current or prior history of calcinosis. These patients were statistically more likely to have longer durations of disease prior to diagnosis and treatment, have lipodystrophy and joint contractures, and to have received intravenous immune globulin or rituximab as treatments.

CONCLUSIONS

Calcinosis is found more often in patients with prolonged active disease, severe disease, and certain clinical features such as lipodystrophy and joint contractures. When these factors are combined with other known associations and predictors, groups of at-risk patients can be more effectively identified, treated and studied to improve overall outcomes.

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.

Clinical significance of myositis-specific autoantibodies

To date, increasing numbers of myositis-specific autoantibodies (MSAs) have been reported and their clinical significance has been elucidated. Anti-aminoacyl-tRNA synthetase (ARS) and anti-melanoma-differentiation associated gene 5 (MDA5) are strongly associated with interstitial lung disease (ILD); however, the clinical course of ILD is different depending on which autoantibody is present. Anti-ARS is associated with chronic and repetitive ILD and anti-MDA5 is associated with rapidly progressive ILD. Anti-MDA5, anti-transcriptional intermediary factor (TIF) 1-γ, anti-nuclear matrix protein (NXP) 2 and anti-Mi-2 antibodies are dermatomyositis specific. Anti-TIF1-γ and anti-NXP-2 antibodies are associated with malignancy, and anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies are associated with immune-mediated necrotizing myopathy (IMNM). Prognosis is also different among MSA-positive patient groups. Thus, MSAs are of great use for predicting disease course, prognosis, and determining therapeutic strategy as well as the diagnosis of idiopathic inflammatory myopathy (IIM) patients. Investigation of the pathogenic role of MSAs and their corresponding autoantigens will help us to understand the pathophysiology of IIM and identify new therapeutic targets.