Immune mechanisms in polymyositis and dermatomyositis and potential targets for therapy

Peripheral Th17/Treg imbalance in Chinese patients with untreated antisynthetase syndrome associated interstitial lung disease

Interstitial lung disease (ILD) is a common and fatal manifestation of antisynthetase syndrome (ASS). The aim of this study was to provide new insight into investigate peripheral blood lymphocytes, CD4+ T cells, cytokine levels and their relation to the clinical profile of untreated patients with ASS-ILD. The retrospective study population included thirty patients diagnosed with ASS-ILD and 30 healthy controls (HCs). Baseline clinical and laboratory data were collected for all subjects, including peripheral blood lymphocyte, CD4+ T cell subsets measured by flow cytometry, and serum cytokine levels measured by multiple microsphere flow immunofluorescence. Their correlations with clinical and laboratory findings were analyzed by Pearson's or Spearman's correlation analysis. In addition, the Benjamini-Hochberg method was used for multiple correction to adjust the p-values. Patients with ASS-ILD had lower CD8+ T cells, higher proportion of Th17 cells and Th17/Treg ratio than HCs. Serum cytokine levels (IL-1β, IL-6, IL-12, IL-17, IL-8, IL-2, IL-4, IL-10, TNF-α and IFN-γ) were higher in patients with ASS-ILD than HCs. Moreover, Th17/Treg ratio was negatively correlated with diffusing capacity of carbon monoxide (DLCO)%. Our study demonstrated abnormalities of immune disturbances in patients with ASS-ILD, characterized by decreased CD8+ T cells and an increased Th17/Treg ratio, due to an increase in the Th17 cells. These abnormalities may be the immunological mechanism underlying the development of ILD in ASS.

Clinical implications and mechanism of complement C1q in polymyositis

Polymyositis (PM) is the most common autoimmune disease in neurology and among muscle disorders; it is of great significance to thoroughly understand the mechanism of PM to find new diagnosis and treatment methods. This research intends to elucidate the clinical implications and mechanisms of complement C1q in polymyositis (PM). One hundred fifteen PM patients (research group, RG) and 120 healthy subjects (control group, CG) who visited our hospital between March 2017 and March 2020 were selected. Peripheral blood C1q and creatine kinase (CK) levels of both groups were measured, and their correlations with clinical symptoms and prognostic recurrence of PM. Additionally, to further understand the mechanism of action of C1q in PM, we purchased BALB/c mice and grouped them as follows: control group with normal feeding, PM group with PM modeling, intervention group with PM modeling, and intraperitoneal injection of gC1qR monoclonal antibody 60.11, a C1q protein receptor. Inflammatory factors and muscle histopathology were detected in all groups of mice. Finally, rat macrophages (mø) were isolated, and changes in the biological behavior of mø were observed after silencing the expression of gC1qR. Serum C1q and CK were both higher in RG than in CG, with favorable diagnostic effects on PM (P < 0.05). C1q and CK increased in symptomatic anti-ribonuclear protein antibody (RNP)-positive patients but decreased in anti Jo-1 antibody (Jo-1)- and anti-neutrophil cytoplasmic antibody (ANCA)-positive patients (P < 0.05). PM mice were observed with elevated gC1qR, while model mice exhibited severe infiltration of inflammatory cells in muscle tissue, increased pro-IFs, and reduced anti-IFs, and the animals in the intervention group showed improved conditions (P < 0.05). Finally, it was found that CD68, CD86 protein, and invasion capacity of gC1qR-sh-transfected cells decreased, while CD206 and CD163 increased (P < 0.05). C1q is elevated in PM and is strongly linked to the pathological process of PM. Inhibition of gC1qR expression reduced inflammatory infiltration in PM mice.

Identification of common mechanisms and biomarkers for dermatomyositis and atherosclerosis based on bioinformatics analysis

BACKGROUND

Dermatomyositis (DM) manifests as an autoimmune and inflammatory condition, clinically characterized by subacute progressive proximal muscle weakness, rashes or both along with extramuscular manifestations. Literature indicates that DM shares common risk factors with atherosclerosis (AS), and they often co-occur, yet the etiology and pathogenesis remain to be fully elucidated. This investigation aims to utilize bioinformatics methods to clarify the crucial genes and pathways that influence the pathophysiology of both DM and AS.

METHOD

Microarray datasets for DM (GSE128470, GSE1551, GSE143323) and AS (GSE100927, GSE28829, GSE43292) were retrieved from the Gene Expression Omnibus (GEO) database. The weighted gene co-expression network analysis (WGCNA) was used to reveal their co-expressed modules. Differentially expression genes (DEGs) were identified using the "limma" package in R software, and the functions of common DEGs were determined by functional enrichment analysis. A protein-protein interaction (PPI) network was established using the STRING database, with central genes evaluated by the cytoHubba plugin, and validated through external datasets. Immune infiltration analysis of the hub genes was conducted using the CIBERSORT method, along with Gene Set Enrichment Analysis (GSEA). Finally, the NetworkAnalyst platform was employed to examine the transcription factors (TFs) responsible for regulating pivotal crosstalk genes.

RESULTS

Utilizing WGCNA analysis, a total of 271 overlapping genes were pinpointed. Subsequent DEG analysis revealed 34 genes that are commonly found in both DM and AS, including 31 upregulated genes and 3 downregulated genes. The Degree Centrality algorithm was applied separately to the WGCNA and DEG collections to select the 15 genes with the highest connectivity, and crossing the two gene sets yielded 3 hub genes (PTPRC, TYROBP, CXCR4). Validation with external datasets showed their diagnostic value for DM and AS. Analysis of immune infiltration indicates that lymphocytes and macrophages are significantly associated with the pathogenesis of DM and AS. Moreover, GSEA analysis suggested that the shared genes are enriched in various receptor interactions and multiple cytokines and receptor signaling pathways. We coupled the 3 hub genes with their respective predicted genes, identifying a potential key TF, CBFB, which interacts with all 3 hub genes.

CONCLUSION

This research utilized comprehensive bioinformatics techniques to explore the shared pathogenesis of DM and AS. The three key genes, including PTPRC, TYROBP, and CXCR4, are related to the pathogenesis of DM and AS. The central genes and their correlations with immune cells may serve as potential diagnostic and therapeutic targets.

Involvement of YKL-40-positive macrophages commonly identified in polymyositis and dermatomyositis in the pathogenesis of myositis: a retrospective study

YKL-40 is implicated in inflammation and tissue repair, but no reports have investigated its involvement in myositis in polymyositis (PM) and dermatomyositis (DM). Therefore, we aimed to investigate the relationship between YKL-40 and PM/DM. We retrospectively enrolled 35 patients diagnosed with PM/DM along with 26 healthy controls (HCs). Both PM and DM were diagnosed according to Bohan and Peter's criteria. Serum YKL-40 levels were measured, age-corrected to YKL-40 percentile values, and compared to HCs. Patients with myositis without interstitial lung disease were also enrolled and compared to HCs. Immunofluorescence staining was performed to identify YKL-40-positive inflammatory cells in muscle biopsy samples from two patients each with PM and DM. Age-corrected serum YKL-40 levels were significantly higher in patients with PM/DM compared to HCs with and without lung disease; however, these levels decreased significantly after treatment. Immunohistochemical analysis showed infiltration of YKL-40-positive inflammatory cells into the intramuscular sheath and perimuscular membrane. Immunofluorescence staining showed CD68 expression in YKL-40-positive inflammatory cells, suggesting that these cells were macrophages. To the best of our knowledge, this is the first study to demonstrate that YKL-40-positive macrophages are present in PM and DM, indicating that YKL-40 may be involved in PM/DM.

Transcriptome analysis of skeletal muscle in dermatomyositis, polymyositis, and dysferlinopathy, using a bioinformatics approach

Background

Polymyositis (PM) and dermatomyositis (DM) are two distinct subgroups of idiopathic inflammatory myopathies. Dysferlinopathy, caused by a dysferlin gene mutation, usually presents in late adolescence with muscle weakness, degenerative muscle changes are often accompanied by inflammatory infiltrates, often resulting in a misdiagnosis as polymyositis.

Objective

To identify differential biological pathways and hub genes related to polymyositis, dermatomyositis and dysferlinopathy using bioinformatics analysis for understanding the pathomechanisms and providing guidance for therapy development.

Methods

We analyzed intramuscular ribonucleic acid (RNA) sequencing data from seven dermatomyositis, eight polymyositis, eight dysferlinopathy and five control subjects. Differentially expressed genes (DEGs) were identified by using DESeq2. Enrichment analyses were performed to understand the functions and enriched pathways of DEGs. A protein-protein interaction (PPI) network was constructed, and clarified the gene cluster using the molecular complex detection tool (MCODE) analysis to identify hub genes.

Results

A total of 1,048, 179 and 3,807 DEGs were detected in DM, PM and dysferlinopathy, respectively. Enrichment analyses revealed that upregulated DEGs were involved in type 1 interferon (IFN1) signaling pathway in DM, antigen processing and presentation of peptide antigen in PM, and cellular response to stimuli in dysferlinopathy. The PPI network and MCODE cluster identified 23 genes related to type 1 interferon signaling pathway in DM, 4 genes (PDIA3, HLA-C, B2M, and TAP1) related to MHC class 1 formation and quality control in PM, and 7 genes (HSPA9, RPTOR, MTOR, LAMTOR1, LAMTOR5, ATP6V0D1, and ATP6V0B) related to cellular response to stress in dysferliniopathy.

Conclusion

Overexpression of genes related to the IFN1 signaling pathway and major histocompatibility complex (MHC) class I formation was identified in DM and PM, respectively. In dysferlinopathy, overexpression of HSPA9 and the mTORC1 signaling pathway genes was detected.

Patients with dermatomyositis shared partially similar transcriptome signature with COVID-19 infection

Dermatomyositis (DM) is an autoimmune disease that primarily affects the skin and skeletal muscle. Virus infection and type I interferon-related signaling pathways play an important role in the pathogenesis of dermatomyositis. In this study, we found that the skin of patients with DM and the skin of patients with COVID-19 have similar transcriptional profiles, and identified key genes involved in dermatomyositis based on bioinformatics analysis. These hub-genes might be served as potential biomarkers for the early diagnosis and therapy of DM, including MX1, ISG15, IFIT3, IFIT1, RSAD2, IFIT2, IFI6, XAF1, IRF9, MX2.

Type 1 interferon signature in peripheral blood mononuclear cells and monocytes of idiopathic inflammatory myopathy patients with different myositis-specific autoantibodies

Background

Myositis-specific autoantibodies (MSAs) are clinically used to diagnose and define idiopathic inflammatory myopathy (IIM) subsets. However, the underlying pathogenic mechanisms of patients with different MSAs remain unclear.

Methods

A total of 158 Chinese patients with IIM and 167 gender- and age-matched healthy controls (HCs) were enrolled. Transcriptome sequencing (RNA-Seq) was performed with peripheral blood mononuclear cells (PBMCs), followed by the identification of differentially expressed genes (DEGs) and analysis of gene set enrichment analysis, immune cell infiltration, and WGCNA. Monocyte subsets and related cytokines/chemokines were quantified. The expressions of interferon (IFN)-related genes were validated using qRT-PCR and Western blot in both PBMCs and monocytes. We also performed correlation analysis and ROC analysis to explore the potential clinical significance of the IFN-related genes.

Results

There were 1,364 genes altered in patients with IIM, including 952 upregulated and 412 downregulated genes. The type I interferon (IFN-I) pathway was remarkably activated in patients with IIM. Compared with patients with other MSAs, IFN-I signatures were significantly activated in patients with anti-melanoma differentiation-associated gene 5 (MDA5) antibodies. In total, 1,288 hub genes associated with IIM onset were identified using WGCNA, including 29 key DEGs associated with IFN signaling. The patients had more CD14brightCD16- classical, CD14brightCD16+ intermediate, and fewer CD14dimCD16+ non-classical monocyte subsets. Plasma cytokines like IL-6 and TNF and chemokines including CCL3 and MCPs increased. The validation of IFN-I-related gene expressions was consistent with the findings from RNA-Seq. The IFN-related genes were correlated with laboratory parameters and helpful for IIM diagnosis.

Conclusion

Gene expressions were remarkably altered in the PBMCs of IIM patients. Anti-MDA5+ IIM patients had a more pronounced activated IFN signature than others. Monocytes exhibited a proinflammatory feature and contributed to the IFN signature of IIM patients.

A protocol for single nucleus RNA-seq from frozen skeletal muscle

Single-cell technologies are a method of choice to obtain vast amounts of cell-specific transcriptional information under physiological and diseased states. Myogenic cells are resistant to single-cell RNA sequencing because of their large, multinucleated nature. Here, we report a novel, reliable, and cost-effective method to analyze frozen human skeletal muscle by single-nucleus RNA sequencing. This method yields all expected cell types for human skeletal muscle and works on tissue frozen for long periods of time and with significant pathological changes. Our method is ideal for studying banked samples with the intention of studying human muscle disease.

Spontaneous Pneumomediastinum and Subcutaneous Emphysema in Dermatomyositis: A Case Series and Literature Review

Background

Spontaneous pneumomediastinum and subcutaneous emphysema are rare and serious complications of dermatomyositis (DM).

Case Presentation

Our article presents two clinically heterogeneous cases of DM who developed pneumomediastinum and subcutaneous emphysema. The first was a 24-year-old lady with a recently diagnosed DM. She developed rapidly progressive pneumonia, interstitial lung disease (ILD), pneumomediastinum, subcutaneous emphysema, and acute respiratory distress syndrome (ARDS). She died despite treatment with steroids and immunosuppressants (methotrexate and mycophenolate mofetil (MMF)). The second was a 30-year-old man diagnosed with amyopathic DM. He developed pneumomediastinum prior to ILD, which worsened over time, and subcutaneous emphysema evolved. However, he recovered completely after corticosteroid, MMF, and rituximab.

Conclusion

Spontaneous pneumomediastinum and subcutaneous emphysema may complicate DM. Corticosteroids, immunosuppressants, and respiratory support are the mainstay of management for these conditions. Though they were reported to carry a poor prognostic value, the course and outcome are highly variable among the cases.

Dermatomyositis Flare After a COVID-19 Infection Successfully Treated with Rituximab: A Case Report and Literature Review

INTRODUCTION

Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic, there has been a sudden surge in the incidence of several immune-mediated diseases, including dermatomyositis. The reported cases of COVID-19-related dermatomyositis are heterogeneous in their clinical presentation and implemented therapies.

CASE STUDY

We report a 23-year-old female patient diagnosed with a 3-year history of dermatomyositis. She has been well-controlled on maintenance therapy. However, 6 weeks after a mild COVID-19 infection, she developed a dermatomyositis flare. She improved only after aggressive treatment with pulse steroids, intravenous immunoglobulin, and rituximab.

CONCLUSION

Exacerbation of dermatomyositis can be encountered following a COVID-19 infection, even if the infection is mild. Aggressive therapy should be considered in such cases. The prognosis, however, is generally favorable.

Identification of hub biomarkers and immune cell infiltration characteristics of polymyositis by bioinformatics analysis

Background

Polymyositis (PM) is an acquirable muscle disease with proximal muscle involvement of the extremities as the main manifestation; it is a category of idiopathic inflammatory myopathy. This study aimed to identify the key biomarkers of PM, while elucidating PM-associated immune cell infiltration and immune-related pathways.

Methods

The gene microarray data related to PM were downloaded from the Gene Expression Omnibus database. The analyses using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes, gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) networks were performed on differentially expressed genes (DEGs). The hub genes of PM were identified using weighted gene co-expression network analysis (WGCNA) and least absolute shrinkage and selection operator (LASSO) algorithm, and the diagnostic accuracy of hub markers for PM was assessed using the receiver operating characteristic curve. In addition, the level of infiltration of 28 immune cells in PM and their interrelationship with hub genes were analyzed using single-sample GSEA.

Results

A total of 420 DEGs were identified. The biological functions and signaling pathways closely associated with PM were inflammatory and immune processes. A series of four expression modules were obtained by WGCNA analysis, with the turquoise module having the highest correlation with PM; 196 crossover genes were obtained by combining DEGs. Subsequently, six hub genes were finally identified as the potential biomarkers of PM using LASSO algorithm and validation set verification analysis. In the immune cell infiltration analysis, the infiltration of T lymphocytes and subpopulations, dendritic cells, macrophages, and natural killer cells was more significant in the PM.

Conclusion

We identified the hub genes closely related to PM using WGCNA combined with LASSO algorithm, which helped clarify the molecular mechanism of PM development and might have great significance for finding new immunotherapeutic targets, and disease prevention and treatment.

A glance into the future of myositis therapy

The idiopathic inflammatory myopathies are chronic diseases of the skeletal muscle that comprise various conditions, including dermatomyositis, polymyositis, immune-mediated necrotizing myopathy, and the antisynthetase syndrome. Although there are a number of distinguishing features, all these disorders are characterized by an immune and inflammatory response mainly directed against the muscle. Hence, therapy is geared toward curbing the autoimmune and inflammatory response. A quite wide range of medications are currently available to treat these disorders, but despite all therapeutic progress still a number of patients are unable to maintain a sustained remission. In this review article, we have marshaled a variety of potential therapeutic agents that may hold promise for the future treatment of the idiopathic inflammatory myopathies. It is to be expected that by increasing the therapeutic armamentarium with agents that have different mechanisms of action even challenging cases could be successfully managed, thus reducing disease burden and disability.

The SNPs of mitochondrial DNA displacement loop region and mitochondrial DNA copy number associated with risk of polymyositis and dermatomyositis

Oxidative damage-induced mitochondrial dysfunction may activate muscle catabolism and autophagy pathways to initiate muscle weakening in idiopathic inflammatory myopathies (IIMs). In this study, Single nucleotide polymorphisms (SNPs) in the mitochondrial displacement loop (D-loop) and mitochondrial DNA (mtDNA) copy number were assessed and their association with the risk of polymyositis and dermatomyositis (PM/DM) was evaluated. Excessive D-loop SNPs (8.779 ± 1.912 vs. 7.972 ± 1.903, p = 0.004) correlated positively with mtDNA copy number (0.602 ± 0.457 vs. 0.300 ± 0.118, p < 0.001). Compared with that of the controls, the mtDNA of PM/DM patients showed D-loop SNP accumulation. In addition, the distribution frequencies of 16304C (p = 0.047) and 16519C (p = 0.043) were significantly higher in the patients with PM/DM. Subsequent analysis showed that reactive oxygen species (ROS) generation was increased in PM/DM patients compared with that in the controls (18,477.756 ± 13,574.916 vs. 14,484.191 ± 5703.097, p = 0.012). Further analysis showed that the PM/DM risk-related allele 16304C was significantly associated with lower IL-4 levels (p = 0.021), while 16519C had a trend to be associated with higher IL-2 expression (p = 0.064). The allele 16519C was associated with a positive antinuclear antibody (ANA) status in PM/DM patients (p = 0.011). Our findings suggest that mitochondrial D-loop SNPs could be potential biomarkers for PM/DM risk and these SNPs associated with cytokine expression may be involved in the development of PM/DM. Further, mtDNA copy number-mediated mitochondrial dysfunction may precede the onset of PM/DM.

Low Circulating Monocytes Is in Parallel With Lymphopenia Which Predicts Poor Outcome in Anti-melanoma Differentiation-Associated Gene 5 Antibody-Positive Dermatomyositis-Associated Interstitial Lung Disease

Anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis (DM)-associated interstitial lung disease (ILD) may progress rapidly and lead to high mortality within 6 or 12 months. Except for reported prognostic factors, simple but powerful prognostic biomarkers are still in need in practice. In this study, we focused on circulating monocyte and lymphocyte counts and their variation tendency in the early stage of ILD. A total of 351 patients from two inception anti-MDA5 antibody-positive cohorts were included in this study, with various treatment choices. Lymphocyte count remained lower in the first month after admission in the non-survivor patients. Although baseline monocyte count showed no significant differences, average monocyte count in the following 4 weeks was also lower in the non-survivor group. Based on the C-index and analysis by the “survminer” R package in the discovery cohort, we chose 0.24 × 109/L as the cutoff value for Mono W0-2, 0.61 × 109/L as the cutoff value for lymph W0-2, and 0.78 × 109/L as the cutoff value for peripheral blood mononuclear cell (PBMC) W0-2, to predict the 6-month all-cause mortality. The Kaplan–Meier survival curves and adjusted hazard ratio with age, gender, and the number of immunosuppressants used all validated that patients with lower average monocyte count, lower average lymphocyte count, or lower average PBMC count in the first 2 weeks after admission had higher 6-month death risk, no matter in the validation cohort or in the pooled data. Furthermore, flow cytometry figured out that non-classical monocytes in patients with anti-MDA5 antibody-positive DM were significantly lower than healthy controls and patients with DM without anti-MDA5 antibodies. In conclusion, this study elucidated the predictive value of monocyte and lymphocyte counts in the early stage and may help rheumatologists to understand the possible pathogenesis of this challenging disease.

Biomimetic sponges improve muscle structure and function following volumetric muscle loss

Skeletal muscle is inept in regenerating after traumatic injuries such as volumetric muscle loss (VML) due to significant loss of various cellular and acellular components. Currently, there are no approved therapies for the treatment of muscle tissue following trauma. In this study, biomimetic sponges composed of gelatin, collagen, laminin-111, and FK-506 were used for the treatment of VML in a rodent model. We observed that biomimetic sponge treatment improved muscle structure and function while modulating inflammation and limiting the extent of fibrotic tissue deposition. Specifically, sponge treatment increased the total number of myofibers, type 2B fiber cross-sectional area, myosin: collagen ratio, myofibers with central nuclei, and peak isometric torque compared to untreated VML injured muscles. As an acellular scaffold, biomimetic sponges may provide a promising clinical therapy for VML.

Rituximab for Inflammatory Myopathies in a Colombian Cohort

INTRODUCTION/OBJECTIVES

Rituximab (RTX) is a treatment for refractory inflammatory myopathies, such as dermatomyositis (DM) and polymyositis (PM). This study describes the characteristics of patients receiving RTX for myositis in our institution to evaluate its efficacy.

METHOD

We collected demographic data from all patients diagnosed with DM or PM who received RTX between 2011 and 2018. Clinical and serological variables (including creatine phosphokinase [CPK] levels) were analyzed. Remission of disease was defined as no evidence of disease activity (active myositis) for longer than a 6-month continuous period while undergoing myositis therapy or no medication.

RESULTS

Eighteen patients who had received first-line immunosuppressants were included. Fifteen (83%) had DM, 2 (11%) had PM, 1 had juvenile dermatomyositis, and 14 (77%) were women. All patients received glucocorticoids. Three patients (16.6%) were treated with RTX as monotherapy, and 15 (83.3%) were treated with RTX combined with other immunosuppressants. On average, there were 2 RTX treatment cycles. Improved muscular weakness was found in 13 cases (72%), and improved serum CPK levels were found in 15 cases (83%). Twelve patients (66%) achieved remission.

CONCLUSIONS

Most patients experienced an objective improvement, as reflected in their serum CPK values and degree of muscular weakness. This suggests that RTX could be helpful in treating refractory myositis.

Functional electrical stimulation as a promising intervention for polymyositis-related weakness: a case report

Background/aims

Polymyositis is an inflammatory myopathy characterised by chronic and progressive muscle weakness. This case report discusses a 61-year-old African-American man with polymyositis. Even though pharmacological and physical therapy interventions had previously been prescribed, they had not been beneficial. This case report examined the effects of a functional electric stimulation-assisted exercise programme.

Methods

The patient was treated in an outpatient clinic two times a week and performed exercises three times a week on alternating days for 36 weeks. In the clinic, he received functional electrical stimulation-assisted strengthening to quadriceps, hamstrings and gluteus maximus while performing activities such as sit to stand, squats, bridging and cycling. For endurance training, he ambulated on the clinic track with a neuroprosthetic to assist with dorsiflexion in the swing phase of gait. At home, he performed lower extremity and core strengthening exercises. Measures to evaluate the intervention included the Manual Muscle Test, functional mobility (Timed Up and Go Test), balance (Berg Balance Scale, Activities of Balance Confidence Scale), endurance (Six-Minute Walk Test with a modified Borg scale) and gait speed (10-Metre Walk Test).

Results

After 36 weeks of treatment, the patient had made gains in strength in all muscle groups in his bilateral lower extremities except hip extensors. Timed Up and Go time decreased by 14.01 seconds. The patient changed from a medium fall risk to low fall risk on the Berg Balance Scale and his confidence increased by 46.2% on the Activities of Balance Confidence Scale. Furthermore, he gained endurance as exhibited by his increased distance of 289 feet on the Six-Minute Walk Test and his modified Borg score decreased from 4 out of 10 to 2 out of 10. The patient made subjective and objective gains in gait speed, increasing from 0.18 metres per second at his initial examination to 0.50 metres per second.

Conclusions

This case study demonstrates that functional electrical stimulation-assisted exercise, conducted in an outpatient setting, can improve strength and functional mobility in an individual with polymyositis without detrimental effects.

Investigating genetic drivers of juvenile dermatomyositis pathogenesis using bioinformatics methods

Juvenile dermatomyositis (JDM) is a chronic autoimmune disease. The pathogenic mechanisms remain ill-defined. The purpose of this study was to identify key genes related to JDM. Microarray datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEG) were identified. Then, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, and protein-protein interaction (PPI) network were carried out. In addition, the hub genes were selected by cytoHubba. The expression profile and diagnostic capacity (receiver-operator curve [ROC]) of interested hub genes were verified. Gene set enrichment analysis (GSEA) was also carried out. Moreover, the signature of hub genes was then used as a search query to explore the Connectivity Map (CMAP). A total of 128 DEG were identified. The enriched functions and pathways of the DEG include response to virus, negative regulation of cell migration, cadmium ion transmembrane transport, defense response to Gram-negative bacterium, positive regulation of megakaryocyte differentiation, and negative regulation of angiogenesis. Twenty-one hub genes were identified. The expression levels of the interested genes were also confirmed. ROC analysis confirmed that the expression of these genes can distinguish JDM from controls. GSEA showed that these genes are mainly related to "inflammatory response", "complement", "interferon-α response", "IL6/JAK/STAT3 signaling", "TGF-β signaling", "IL2/STAT5 signaling" and "TNF-α signaling via NF-κB". The CMAP research found some compounds with the potential to counteract the effects of the dysregulated molecular signature in JDM. In this study, bioinformatics methods were used to identify DEG, which helps us understand the molecular mechanisms of JDM and provide candidate targets for diagnosis and treatment of JDM.

The Role of Immune Cells in the Pathogenesis of Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies (IIMs) are chronic autoimmune disorders involving multiple organs, such as the muscle, skin, lungs and joints. Although the detailed pathogenesis of IIMs remains unclear, immune mechanisms have long been recognised as of key importance. Immune cells contribute to many inflammatory processes via intercellular interactions and secretion of inflammatory factors, and many studies have demonstrated the participation of a variety of immune cells, such as T cells and B cells, in the development of IIMs. Here, we summarise the current knowledge regarding immune cells in IIM patients and discuss their potential roles in IIM pathogenesis.

Prevalence of interstitial lung disease in polymyositis and dermatomyositis: A meta-analysis from 2000 to 2020

OBJECTIVE

Interstitial lung disease (ILD) is the most important prognostic factor for mortality in patients with polymyositis (PM) and dermatomyositis (DM), but the prevalence of ILD in PM/DM may vary between countries. The aim of this study was to determine the overall prevalence of ILD in global patients with PM/DM.

METHODS

We performed a systematic literature review of studies published from Jan 1, 2000 to April 30, 2020 on ILD and PM/DM. We extracted data and pooled the prevalence by using a random-effect model due to high heterogeneity. Heterogeneity was assessed by subgroup analysis and sensitivity analysis.

RESULTS

A total of 34 studies with 10,130 patients were included in our meta-analysis. Pooled data demonstrated that the global prevalence of ILD in patients with PM/DM was 0.41 (95% confidence interval [CI] 0.35-0.48). However, this prevalence varied with geographical locations and time trends. The prevalence of ILD in PM/DM was 0.5 (95% CI 0.42-0.57) in Asia, 0.23 (95% CI 0.15-0.31) in America, and 0.26 (95% CI 0.18-0.34) in Europe. A higher prevalence of ILD was reported in studies published in 2011-2015 (0.43, 95% CI 0.34-0.52) and 2016-2020 (0.45, 95% CI 0.35-0.54), compared with those published in 2000-2010 (0.27, 95% CI 0.16-0.39). The pooled prevalence of ILD in patients with DM, PM, and clinically amyopathic dermatomyositis subtype was 0.42 (95% CI 0.35-0.49), 0.35 (95% CI 0.27-0.42), and 0.53 (95% CI 0.32-0.74), respectively. Patients with anti-Jo-1 and anti-melanoma differentiation-associated gene 5 antibodies were more likely to develop ILD than other myositis-specific autoantibodies.

CONCLUSION

The global prevalence of ILD in patients with PM/DM was approximately 41% and the condition was predominant in Asians. This highlights potential genetic and environmental differences in the pathogenesis of ILD in patients with PM/DM. More studies are required to elucidate the specific associations.

The altered metabolism profile in pathogenesis of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are a group of heterogeneous autoimmune diseases characterized by muscle weakness, muscle inflammation and extramuscular manifestations. Despite extensive efforts, the mechanisms of IIMs remain largely unknown, and treatment is still a challenge for physicians. Metabolism changes have emerged as a crucial player in autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). However, little is known about metabolism changes in IIMs. In this review, we focus on the alteration of metabolism profile in IIMs, and the relationships with clinical information. We highlight the potential roles of metabolism in the pathogenesis of IIMs and discuss future perspectives for metabolic checkpoint-based therapeutic interventions.

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.

Aberrant expansion of circulating CD4+ CXCR5+ CCR7lo PD1hi Tfh precursor cells in idiopathic inflammatory myopathy

OBJECTIVE

To determine circulating follicular T helper (Tfh) cell precursor and its relationship with clinical characteristics in idiopathic inflammatory myopathy (IIM).

METHODS

The study population included 47 patients with IIM and 30 healthy controls. Circulating CD4⁺ CXCR5⁺ CCR7^lo PD-1^hi T cells and intracellular interleukin (IL)-21 were assessed by flow cytometry. Serum IL-21 levels were measured by enzyme-linked immunosorbent assay. The disease activity was evaluated using myositis disease activity assessment visual analog scales (VAS) as well as muscle and physician global assessment (PGA).

RESULTS

The percentage of the CCR7^lo PD-1^hi subset cells within CD4⁺ CXCR5⁺ T cells was significantly increased in patients with IIM compared to that in healthy controls (14.3 ± 6.5 vs 11.4 ± 2.6, P = .009). Patients with higher percentages of CCR7^lo PD-1^hi subsets presented with higher PGA VAS (P = .000), muscle VAS (P = .000), as well as serum creatinine kinase (CK) levels (P = .000) than those with lower percentages of CCR7^lo PD-1^hi subsets. IL-21 expression significantly increased in CD4⁺ CXCR5⁺ CCR7^lo PD-1^hi T cells in patients with IIM compared to that in healthy controls (26.07 ± 7.38 vs 19.25 ± 5.67, P = .001). Meanwhile, both the CCR7^lo PD-1^hi subset and intracellular IL-21 expression in IIM patients showed significantly positive correlation with PGA VAS, muscle VAS and serum CK levels. Circulating CD4⁺ CXCR5⁺ CCR7^lo PD-1^hi T cells and intracellular IL-21 decreased significantly when disease was improved (P = .018; P = .028).

CONCLUSION

The percentage of circulating CCR7^lo PD-1^hi subset among total CD4⁺ CXCR5⁺ T cells and intracellular IL-21 expression expanded and showed significant correlation with disease activity in IIM. The circulating follicular helper T cell precursor may be involved in the pathogenesis, especially muscle injury in IIM.

Risk of major autoimmune diseases in female breast cancer patients: A nationwide, population-based cohort study

BACKGROUND

Breast cancer is one of the most common malignancies among women. However, there remains no consensus in current literature on the incidence of autoimmune diseases among breast cancer patients. The purpose of this study was to evaluate the risks of major autoimmune diseases (MAD) including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren's syndrome (SS) and dermatomyositis (DMtis)/polymyositis (PM) in female breast cancer patients.

METHODS

Using the Taiwanese National Health Insurance Research Database (NHIRD) records from 2003 to 2013, we identified newly-diagnosed female breast cancer patients and randomly selected females without breast cancer in the period 2007 to 2013 into a control group. We matched the two cohorts using a 1:4 ratio based on age, and the year of index date for comparison of the risk of major autoimmune diseases. We estimated and compared the relative risks of autoimmune diseases in female breast cancer patients and females without breast cancer.

RESULTS

A total of 54,311 females with breast cancer and 217,244 matched females without breast cancer were included in this study. For SLE, the incidence rates were 2.3 (breast cancer group) vs. 10.0 (control group) per 100,000 women years; for RA rates were 19.3 (breast cancer group) vs. 42.7 (control group) per 100,000 women years; and for SS rates were 20.5 (breast cancer group) vs. 38.2 (control group) per 100,000 women years. After adjusting for potential confounders, the hazard ratios (95% confidence intervals) for female breast cancer patients vs. control group were 0.04 (0.01-0.24) for SLE; 0.03 (0.02-0.04) for RA; and 0.21 (0.09-0.48) for SS.

CONCLUSION

Female breast cancer patients had lower risks of SLE, RA and SS when compared to female individuals without breast cancer. However, there was no significant difference in the risk of developing DMtis/PM between both groups.

Rituximab in systemic autoimmune rheumatic diseases: indications and practical use

Objectives: To review the therapeutic option of Rituximab, a chimeric anti-CD20 antibody, in systemic autoimmune rheumatic diseases (SARDs) such as systemic lupus erythematosus, systemic sclerosis, primary Sjögren syndrome and idiopathic inflammatory myopathy. Methods: A non-systematic review was conducted. Results: The specific role and indication of rituximab in SARDs has been the subject of multiple trials in recent years. Evidence supports the use of rituximab in moderate-to-severe refractory systemic lupus erythematosus, diffuse skin involvement in systemic sclerosis and systemic involvement in primary Sjögren syndrome. Several guidelines have adopted these indications. In addition, there is a consensus about the use of rituximab in refractory myositis. The role of rituximab in interstitial lung disease associated with these SARDs needs to be further explored. Conclusion: Rituximab is a treatment option in several SARDs. Upcoming trials, use in daily practice and the safety profile are elaborated on.

Myositis and neuromuscular side-effects induced by immune checkpoint inhibitors

AIM

To characterise clinical presentation, laboratory and histopathologic characteristics and assess the treatment and outcome of neuromuscular side-effects of checkpoint therapy.

METHODS

The side-effect registry and the institutional database from ten skin cancer centres were queried for reports on myositis and neuromuscular side-effects induced by checkpoint inhibitors. In total, 38 patients treated with ipilimumab, tremelimumab, nivolumab and pembrolizumab for metastatic skin cancer were evaluated and characterised.

RESULTS

Myositis was the most frequent neuromuscular adverse event. In 32% of cases, myositis was complicated by concomitant myocarditis. Furthermore, cases of isolated myocarditis, myasthenia gravis, polymyalgia rheumatica, radiculoneuropathy and asymptomatic creatine kinase elevation were reported. The onset of side-effects ranged from the first week of treatment to 115 weeks after the start of therapy. Most of the cases were severe (49% grade III-IV Common Terminology Criteria for Adverse Events), and there were two fatalities (5%) due to myositis and myositis with concomitant myocarditis. Only half of the cases (50%) completely resolved, whereas the rest was either ongoing or had sequelae. Steroids were given in 80% of the resolved cases and in 40% of the unresolved cases.

CONCLUSION

Immune-mediated neuromuscular side-effects of checkpoint inhibitors greatly vary in presentation and differ from their idiopathic counterparts. These side-effects can be life threatening and may result in permanent sequelae. Occurrence of these side-effects must be taken into consideration for patient information, especially when considering adjuvant immunotherapy with anti-programmed cell-death protein 1 (PD-1) antibodies and monitoring, which should include regular surveillance of creatine kinase.

Pathological Issues in Dystrophinopathy in the Age of Genetic Therapies

Dystrophinopathy is a class of genetic skeletal muscle disease characterized by myofiber degeneration and regeneration due to insufficient levels or functioning of dystrophin. Pathological evaluation for dystrophinopathy includes the identification of dystrophic skeletal muscle pathology and the immunohistochemical evaluation of dystrophin epitopes, but biopsies have become rare in recent years. However, the evaluation of dystrophin expression in the research setting has become critically important due to recent advances in genetic therapies, including exon skipping and gene therapy. Given the number of these therapies under evaluation in patients, it is likely that the traditional methods of evaluating dystrophinopathy will need to evolve in the near future. This review discusses current muscle biopsy diagnostic practices in dystrophinopathy and further focuses on how these practices have evolved in the context of therapeutic interventions for dystrophinopathy.

Elevated serum YKL-40 correlates with clinical characteristics in patients with polymyositis or dermatomyositis

Background

Serum YKL-40 has been proved to be a promising biomarker for estimating the disease activity of several autoimmune diseases. However, its utility in polymyositis or dermatomyositis has not been established. The aim of this study was to investigate the utility of YKL-40 in patients with polymyositis/dermatomyositis.

Method

Patients with definite polymyositis/dermatomyositis who visited the Second People’s Hospital of Wuxi between April 2016 and March 2017 were prospectively enrolled. Eighty-seven healthy individuals were set as a control. Serum YKL-40 of all participants was determined using ELISA. The associations between YKL-40 and clinical characteristics of polymyositis/dermatomyositis were analysed using the Student’s t-test, Mann-Whitney test and receiver operating characteristic curve analysis.

Results

A total of 99 patients with polymyositis/dermatomyositis were enrolled. The patients with polymyositis/dermatomyositis had significantly higher serum YKL-40 concentration. Patients with interstitial lung disease had significantly higher YKL-40 concentration than those without. Serum YKL-40 was positively correlated with myositis disease activity assessment visual analogue scale, C-reactive protein, erythrocyte sedimentation rate and ferritin. The area under receiver operating characteristic curve of YKL-40 for identifying interstitial lung disease was 0.82.

Conclusions

Serum YKL-40 is a useful biomarker for estimating disease activity or severity of polymyositis/dermatomyositis.

DNA immunization site determines the level of gene expression and the magnitude, but not the type of the induced immune response

Optimization of DNA vaccine delivery improves the potency of the immune response and is crucial to clinical success. Here, we inquired how such optimization impacts the magnitude of the response, its specificity and type. BALB/c mice were DNA-immunized with two model immunogens, HIV-1 protease and reverse transcriptase by intramuscular or intradermal injections with electroporation. DNA immunogens were co-delivered with DNA encoding luciferase. Delivery and expression were monitored by in vivo bioluminescence imaging (BLI). The endpoint immune responses were assessed by IFN-γ/IL-2 FluoroSpot, multiparametric flow cytometry and antibody ELISA. Expression and immunogenicity were compared in relation to the delivery route. Regardless of the route, protease generated mainly IFN-γ, and reverse transcriptase, IL-2 and antibody response. BLI of mice immunized with protease- or reverse transcriptase/reporter plasmid mixtures, demonstrated significant loss of luminescence over time. The rate of decline of luminescence strongly correlated with the magnitude of immunogen-specific response, and depended on the immunogenicity profile and the immunization route. In vitro and in vivo BLI-based assays demonstrated that intradermal delivery strongly improved the immunogenicity of protease, and to a lesser extent, of reverse transcriptase. Immune response polarization and epitope hierarchy were not affected. Thus, by changing delivery/immunogen expression sites, it is possible to modulate the magnitude, but not the type or fine specificity of the induced immune response.

Association of Serum Soluble CD163 with Polymyositis and Dermatomyositis, Especially in Anti-MDA5 Antibody–positive Cases

Objective.

We elucidated the association of serum soluble CD163 (sCD163) with rapidly progressive interstitial lung disease (RP-ILD), autoantibody profiles, and serum ferritin in patients with polymyositis (PM), classic dermatomyositis (DM), and clinical amyopathic dermatomyositis (CADM).

Methods.

Serum sCD163 levels were retrospectively measured by ELISA in patients with PM, classic DM, and CADM, as well as in healthy controls (HC). Repeat sera samples were obtained posttreatment from available patients. The associations between serum sCD163 levels and clinical information were analyzed.

Results.

Serum sCD163 levels in patients with PM/classic DM/CADM were significantly higher than those in HC (n = 72, 56, 34, and 68, respectively; p < 0.001 for all comparisons). No significant difference was observed between serum sCD163 levels in patients with and without ILD (p = 0.16) or between those with RP-ILD and chronic ILD (p = 0.21). Serum sCD163 levels were significantly higher in patients with anti-MDA5 antibodies (n = 27) than in those without (p = 0.001). Serum sCD163 levels were weakly correlated with serum ferritin levels in the patients with PM, classic DM, and CADM (r = 0.21). Serum sCD163 levels decreased significantly following treatment in all patient groups (p = 0.003).

Conclusion.

The present results suggest an association of serum sCD163 with PM, classic DM, and CADM, especially in anti-MDA5 antibody–positive cases. However, serum sCD163 levels were not specifically associated with ILD or RP-ILD.

Paradoxical development of polymyositis-like autoimmunity through augmented expression of autoimmune regulator (AIRE)

Autoimmunity is prevented by the function of the autoimmune regulator [AIRE (Aire in mice)], which promotes the expression of a wide variety of tissue-restricted antigens (TRAs) from medullary thymic epithelial cells (mTECs) and from a subset of peripheral antigen-presenting cells (APCs). We examined the effect of additive expression of human AIRE (huAIRE) in a model of autoimmune diabetes in NOD mice. Unexpectedly, we observed that mice expressing augmented AIRE/Aire developed muscle-specific autoimmunity associated with incomplete maturation of mTECs together with impaired expression of Aire-dependent TRAs. This led to failure of deletion of autoreactive T cells together with dramatically reduced production of regulatory T cells in the thymus. In peripheral APCs, expression of costimulatory molecules was augmented. We suggest that levels of Aire expression need to be tightly controlled for maintenance of immunological tolerance. Our results also highlight the importance of coordinated action between central tolerance and peripheral tolerance under the common control of Aire.

Polymyositis with elevated serum IgG4 levels and abundant IgG4+ plasma cell infiltration: A case report and literature review

INTRODUCTION

Polymyositis (PM) is a type of autoimmune, inflammatory myopathy. IgG4-related disease (IgG4-RD) is a recently recognized disease entity characterized by elevated serum IgG4 levels and IgG4 plasma-cell infiltration of various organs. However, several reports have described cases of other diseases that present with those features, suggesting the importance of careful differential diagnosis. Herein, we report the first case of PM with elevated serum IgG4 levels and IgG4 plasma cells in the muscles, mimicking IgG4-RD.A 73-year-old woman visited our hospital because of proximal muscle weakness of both thighs. Her blood test showed high levels of serum creatinine kinase, aldolase, and IgG4. Magnetic resonance imaging of the thighs showed muscle edema. Needle electromyography showed findings typical of myositis. Histological analysis of her left quadriceps revealed infiltration of IgG4 plasma cells as well as CD8 T cells. Scattered necrotic and regenerating muscle fibers with no specific findings for IgG4-RD (storiform fibrosis and obliterative phlebitis) were typical for PM. We diagnosed her condition as PM and treated her with 40 mg/day of prednisolone that decreased levels of muscle enzymes and improved muscle weakness.

CONCLUSION

Our case indicated that PM could present with high serum IgG4 levels and IgG4 plasma-cell infiltration, mimicking IgG4-RD. Although the mechanism of IgG4 elevation in such PM is unclear, our case highlights the necessity to recognize that high serum IgG4 levels and IgG4 plasma-cell infiltration in organs are not specific for IgG4-RD.

3-n-Butylphthalide reduces the oxidative damage of muscles in an experimental autoimmune myositis animal model

3-n-Butylphthalide (NBP) protects the mitochondria and reduces apoptosis in multiple disease models. However, it remains to be determined whether NBP can protect muscle cells from oxidative stress, lipid peroxidation and apoptosis in myositis. In the present study, a myosin immunization protocol was applied to induce experimental autoimmune myositis (EAM) in guinea pigs. After 4 weeks, a low- or high-dose NBP solution was injected intraperitoneally into the guinea pigs, with saline solution serving as the negative control. After 10 days, the guinea pigs were sacrificed and muscle cells were isolated for analysis. The results revealed that NBP increased the superoxide dismutase and catalase activity, and reduced malondialdehyde activity in the EAM model. Furthermore, NBP enhanced ATPase activity in muscle mitochondrial membranes and muscle fiber membranes, reduced the number of apoptotic cells, and differentially regulated the Bcl-2, Bax and BAD mRNA and protein expression levels in muscle tissues and sera. NBP directly protects muscle mitochondria and muscle cells from oxidative damage. Notably, NBP reduced muscle cell apoptosis. Thus, it is speculated that, as an antioxidant treatment, NBP may benefit individuals with myopathy.

Potential role of autophagy in T‑cell survival in polymyositis and dermatomyositis

Peripheral blood T lymphocytopenia has previously been identified in polymyositis/dermatomyositis (PM/DM) patients. Therefore, the present study aimed to examine the potential role of autophagy in peripheral blood T cell survival in PM/DM patients. Transmission electron microscopy was used to detect the formation of autophagosomes of peripheral blood cluster of differentiation (CD)3+ T cells obtained from 24 patients with PM/DM and 21 healthy controls. Protein and mRNA expression levels of autophagy‑related molecules were examined by western blot analysis and reverse transcription‑quantitative polymerase chain reaction, respectively. The number of peripheral blood CD3+ T cells decreased significantly in PM/DM patients. The median percentage of apoptosis of CD3+ T cells in PM/DM patients was significantly increased compared with healthy controls. Furthermore, the number of autophagosomes and the expression of the autophagy markers microtubule‑associated protein 1A/1B‑light chain 3 (LC3) and Beclin‑1 were significantly reduced in the circulating CD3+ T cells of PM/DM patients compared with those of healthy controls. LC3 and Beclin‑1 protein levels correlated negatively with apoptosis rates in circulating CD3+ T cells in patients with PM/DM. CD3+ T cells from PM/DM patients treated with rapamycin increased autophagy and decreased apoptosis compared with untreated cells (P<0.05). In conclusion, these results suggested that autophagy may serve a potential protective role in the peripheral blood T cells of patients with PM/DM.

Idiopathic Inflammatory Myopathies: A Review of the Classification and Impact of Pathogenesis

Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune muscle diseases with significant morbidity and mortality. This review details and updates the pathogenesis and emerging importance of myositis-specific antibodies in the development of IIMs. An increase in the understanding of how these myositis-specific antibodies play a role in IIMs has led to the further categorization of IIMs from the traditional polymyositis versus dermatomyositis, to additional subcategories of IIMs such as necrotizing autoimmune myositis (NAM). The diagnosis of IIMs, including manual muscle testing, laboratory studies, and non-invasive imaging have become important in classifying IIM subtypes and for identifying disease severity. Treatment has evolved from an era where glucocorticoid therapy was the only option to a time now that includes traditional steroid-sparing agents along with immunoglobulin therapy and biologics, such as rituximab.

The Immune Response and the Pathogenesis of Idiopathic Inflammatory Myositis: a Critical Review

The pathogenesis of idiopathic inflammatory myositis (IIMs, including polymyositis and dermatomyositis) remains largely enigmatic, despite advances in the study of the role played by innate immunity, adaptive immunity, genetic predisposition, and environmental factors in an orchestrated response. Several factors are involved in the inflammatory state that characterizes the different forms of IIMs which share features and mechanisms but are clearly different with respect to the involved sites and characteristics of the inflammation. Cellular and non-cellular mechanisms of both the immune and non-immune systems have been identified as key regulators of inflammation in polymyositis/dermatomyositis, particularly at different stages of disease, leading to the fibrotic state that characterizes the end stage. Among these, a special role is played by an interferon signature and complement cascade with different mechanisms in polymyositis and dermatomyositis; these differences can be identified also histologically in muscle biopsies. Numerous cellular components of the adaptive and innate immune response are present in the site of tissue inflammation, and the complexity of idiopathic inflammatory myositis is further supported by the involvement of non-immune mechanisms such as hypoxia and autophagy. The aim of this comprehensive review is to describe the major pathogenic mechanisms involved in the onset of idiopathic inflammatory myositis and to report on the major working hypothesis with therapeutic implications.

Dermatomyositis Associated with Sarcoidosis: Two Cases

Dermatomyositis (DM) and sarcoidosis are two idiopathic systemic disorders. Reports of patients with both conditions are extremely rare. Here we describe two patients who presented with DM and DM-associated antibodies, and later developed biopsy-proven sarcoidosis. There are increasing reports of the occurrence of sarcoidosis in the context of autoimmune diseases. These observations might imply similarities in the pathogenetic mechanisms.

The NKG2D-IL-15 signaling pathway contributes to T-cell mediated pathology in inflammatory myopathies

NKG2D is an activating receptor on T cells, which has been implicated in the pathogenesis of autoimmune diseases. T cells are critically involved in idiopathic inflammatory myopathies (IIM) and have been proposed as specific therapeutic targets. However, the mechanisms underlying T cell-mediated progressive muscle destruction in IIM remain to be elucidated. We here determined the involvement of the NKG2D – IL-15 signaling pathway. Primary human myoblasts expressed NKG2D ligands, which were further upregulated upon inflammatory stimuli. In parallel, shedding of the soluble NKG2D ligand MICA (sMICA) decreased upon inflammation potentially diminishing inhibition of NKG2D signaling. Membrane-related expression of IL-15 by myoblasts induced differentiation of naïve CD8⁺ T cells into highly activated, cytotoxic CD8⁺NKG2D^high T cells demonstrating NKG2D-dependent lysis of myoblasts in vitro. CD8⁺NKG2D^high T cell frequencies were increased in the peripheral blood of polymyositis (PM) patients and correlated with serum creatinine kinase concentrations, while serum sMICA levels were not significantly changed. In muscle biopsy specimens from PM patients expression of the NKG2D ligand MICA/B was upregulated, IL-15 was expressed by muscle cells, CD68⁺ macrophages as well as CD4⁺ T cells, and CD8⁺NKG2D⁺ cells were frequently detected within inflammatory infiltrates arguing for a local signaling circuit in the inflammatory muscle milieu. In conclusion, the NKG2D – IL-15 signaling pathway contributes to progressive muscle destruction in IIM potentially opening new therapeutic avenues.

Elevated risk of venous thromboembolic events in patients with inflammatory myopathies

Venous thromboembolism (VTE) is a multifactorial disease manifesting as either deep vein thrombosis or pulmonary embolism. Its prevalence makes VTE a significant issue for both the individual – as a negative factor influencing the quality of life and prognosis – and the society due to economic burden. VTE is the third most common vascular disorder in Western countries, after myocardial infarction and stroke, making it a major cause of in-hospital mortality, responsible for 5%–10% of hospital deaths. Despite many studies conducted, only 50%–60% provoking factors have been identified, while the remaining 40%–50% have been classified as idiopathic or unprovoked. Chronic inflammatory disorders, with their underlying prothrombotic state, reveal an increased risk of VTE (six to eight times) compared with the general population. Among the inflammatory disorders, we can identify inflammatory myopathies – a group of rare, chronic diseases featuring weakness and inflammation of muscles with periods of exacerbation and remission; their main classes are polymyositis and dermatomyositis. The objective of this review is to emphasize the need of VTE prophylaxis in individuals with inflammatory myopathies in order to reduce morbidity and mortality rates among those patients and improve their quality of life and prognosis.

Cell death, clearance and immunity in the skeletal muscle

The skeletal muscle is an immunologically unique tissue. Leukocytes, virtually absent in physiological conditions, are quickly recruited into the tissue upon injury and persist during regeneration. Apoptosis, necrosis and autophagy coexist in the injured/regenerating muscles, including those of patients with neuromuscular disorders, such as inflammatory myopathies, dystrophies, metabolic and mitochondrial myopathies and drug-induced myopathies. Macrophages are able to alter their function in response to microenvironment conditions and as a consequence coordinate changes within the tissue from the early injury throughout regeneration and eventual healing, and regulate the activation and the function of stem cells. Early after injury, classically activated macrophages ('M1') dominate the picture. Alternatively activated M2 macrophages predominate during resolution phases and regulate the termination of the inflammatory responses. The dynamic M1/M2 transition is increasingly felt to be the key to the homeostasis of the muscle. Recognition and clearance of debris originating from damaged myofibers and from dying stem/progenitor cells, stromal cells and leukocytes are fundamental actions of macrophages. Clearance of apoptotic cells and M1/M2 transition are causally connected and represent limiting steps for muscle healing. The accumulation of apoptotic cells, which reflects their defective clearance, has been demonstrated in various tissues to prompt autoimmunity against intracellular autoantigens. In the muscle, in the presence of type I interferon, apoptotic myoblasts indeed cause the production of autoantibodies, lymphocyte infiltration and continuous cycles of muscle injury and regeneration, mimicking human inflammatory myopathies. The clearance of apoptotic cells thus modulates the homeostatic response of the skeletal muscle to injury. Conversely, defects in the process may have deleterious local effects, guiding maladaptive tissue remodeling with collagen and fat accumulation and promoting autoimmunity itself. There is strong promise for novel treatments based on new knowledge of cell death, clearance and immunity in the muscle.