Proposed immunologic models of the inflammatory myopathies and potential therapeutic implications

Type I interferon biomarker in idiopathic inflammatory myopathies: associations of Siglec-1 with disease activity and treatment response

OBJECTIVES

Novel biomarkers are needed to guide therapy in idiopathic inflammatory myopathies (IIM). Expression of Siglec-1, a type I interferon biomarker, was examined in adult patients with IIM in relation to disease activity and treatment response.

METHODS

We analysed PBMC samples from 19 newly diagnosed adult IIM patients who participated in a phase-2 pilot study on efficacy of intravenous immunoglobulin (IVIG) monotherapy, and from 9 healthy controls. Siglec-1 expression on monocytes was measured by flow cytometry before and after treatment, and was evaluated in relation to IIM subtype, physician global activity (PhGA) scores, manual muscle strength (MMT) and the Total Improvement Score (TIS).

RESULTS

Diagnoses included dermatomyositis (DM; n = 9), immune-mediated necrotizing myopathy (IMNM; n = 5), non-specific/overlap myositis (NSM/OM; n = 4), and antisynthetase syndrome (ASyS; n = 1). All patients showed increased Siglec-1 expression at baseline. Relative median fluorescence intensity of Siglec-1 was highest in patients with DM. After 9 weeks, follow-up samples were available for 15 patients of whom 10 patients showed a decline in Siglec-1 expression. In DM, Siglec-1 correlated with disease activity (MMT; rs = -0.603, p= 0.013 and PhGA; rs = 0.783, p< 0.001) and with the TIS (rs = -0.786, p= 0.036).

CONCLUSION

Siglec-1 was increased in treatment-naive IIM patients and showed a decline after IVIG monotherapy. In DM, Siglec-1 expression correlated with relevant clinical measures. This underlines the dynamic role of type I IFN in IIM and the biomarker potential of Siglec-1, in particular in DM. These findings should be further validated in larger cohorts with longer follow-up.

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

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

[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.

Immune-mediated lung diseases: A narrative review

The role of immunity in the pathogenesis of various pulmonary diseases, particularly interstitial lung diseases (ILDs), is being increasingly appreciated as mechanistic discoveries advance our knowledge in the field. Immune-mediated lung diseases demonstrate clinical and immunological heterogeneity and can be etiologically categorized into connective tissue disease (CTD)-associated, exposure-related, idiopathic, and other miscellaneous lung diseases including sarcoidosis, and post-lung transplant ILD. The immunopathogenesis of many of these diseases remains poorly defined and possibly involves either immune dysregulation, abnormal healing, chronic inflammation, or a combination of these, often in a background of genetic susceptibility. The heterogeneity and complex immunopathogenesis of ILDs complicate management, and thus a collaborative treatment team should work toward an individualized approach to address the unique needs of each patient. Current management of immune-mediated lung diseases is challenging; the choice of therapy is etiology-driven and includes corticosteroids, immunomodulatory drugs such as methotrexate, cyclophosphamide and mycophenolate mofetil, rituximab, or other measures such as discontinuation or avoidance of the inciting agent in exposure-related ILDs. Antifibrotic therapy is approved for some of the ILDs (e.g., idiopathic pulmonary fibrosis) and is being investigated for many others and has shown promising preliminary results. A dire need for advances in the management of immune-mediated lung disease persists in the absence of standardized management guidelines.

Thrombin generation potential is increased in patients with autoimmune inflammatory myopathies

PURPOSE

Dermatomyositis and polymyositis (DM/PM) are rare autoimmune inflammatory myopathies, characterized by an increased risk of cardiovascular and thromboembolic events, likely related to the prothrombotic plasma properties. The aim of this study was to assess the in vitro thrombin generation profile as a biomarker of plasma procoagulant properties in DM/PM patients.

METHODS

In 58 clinically stable DM/PM patients and 67 controls matched for sex, age, body mass index, we measured plasma thrombin generation potential using the Calibrated Automated Thrombinography (CAT) and analyzed its relationship with clinical disease characteristics, including autoantibodies profile.

RESULTS

Patients with DM/PM had a 21% increase in endogenous thrombin potential (ETP), 36% higher peak thrombin concentration, and 11% faster thrombin generation, compared to controls (p ​< ​0.001, all, also after adjustment for potential confounders). Interestingly, although both diseases did not differ in thrombin generation potential, heterogenous variables predicted elevated ETPs in both of them. In DM, that was higher fibrinogen, C-reactive protein, and total cholesterol, whereas in PM, presence of arthritis and increased blood platelet count. Surprisingly, thrombin formation capacity remained in a robust inverse relationship with serum troponin (r ​= ​-0.67, p ​< ​0.001) in the patient group.

CONCLUSIONS

DM/PM patients are characterized by an increased thrombin generation potential, suggesting prothrombotic plasma properties in both diseases. However, more studies are needed to verify its rationale and role in DM/PM clinical course and unfavorable clinical outcomes.

Possible future avenues for myositis therapeutics: DM, IMNM and IBM

Idiopathic inflammatory myopathies (IIMs) represent a heterogeneous group of systemic autoimmune diseases characterized by immune-mediated muscle injury. As insights into pathogenesis of IIM evolve, novel therapeutic strategies have become available to optimize outcomes. Herein, we summarize novel and emerging strategies in the management of dermatomyositis (DM), immunemediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM).

Pathophysiological Mechanisms and Treatment of Dermatomyositis and Immune Mediated Necrotizing Myopathies: A Focused Review

Idiopathic inflammatory myopathies (IIM), collectively known as myositis, are a composite group of rare autoimmune diseases affecting mostly skeletal muscle, although other organs or tissues may also be involved. The main clinical feature of myositis is subacute, progressive, symmetrical muscle weakness in the proximal arms and legs, whereas subtypes of myositis may also present with extramuscular features, such as skin involvement, arthritis or interstitial lung disease (ILD). Established subgroups of IIM include dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASyS), overlap myositis (OM) and inclusion body myositis (IBM). Although these subgroups have overlapping clinical features, the widespread variation in the clinical manifestations of IIM suggests different pathophysiological mechanisms. Various components of the immune system are known to be important immunopathogenic pathways in IIM, although the exact pathophysiological mechanisms causing the muscle damage remain unknown. Current treatment, which consists of glucocorticoids and other immunosuppressive or immunomodulating agents, often fails to achieve a sustained beneficial response and is associated with various adverse effects. New therapeutic targets have been identified that may improve outcomes in patients with IIM. A better understanding of the overlapping and diverging pathophysiological mechanisms of the major subgroups of myositis is needed to optimize treatment. The aim of this review is to report on recent advancements regarding DM and IMNM.

Rituximab in the treatment of immune-mediated necrotizing myopathy: a review of case reports and case series

Immune-mediated necrotizing myopathy (IMNM) is a group of immune-related myopathies characterized by progressive proximal muscle weakness, extremely high serum creatine kinase (CK) levels, and necrotic muscle fibers with a relative lack of inflammation. Treatment of IMNM is challenging, with most cases refractory to high-dose steroids in combination with multiple immunotherapies. The role of rituximab (RTX) for IMNM has been explored in isolated case reports and small series. The aim of this article was to perform a literature review of patients with IMNM treated with RTX and to evaluate RTX efficacy and safety. A total of 34 patients with IMNM were reviewed: 52.9% (18/34) with anti-signal recognition particle (SRP) antibodies and 47.1% (16/34) with anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibodies. Patient age at onset varied from 11 years to 81 years (mean 41 years). The majority of patients presented as a severe proximal muscle weakness and the peak level of CK varied from 3900 IU/L to 56,000 IU/L (mean 18,440 IU/L). Prior to RTX administration, all patients were treated with high-dose steroids and most were treated with multiple immunotherapies. The reason for initiating RTX was that 64.7% (22/34) of patients showed no improvement after previous treatments, and 35.3% (12/34) of patients relapsed when attempting to wean steroids or other immunosuppressive agents. With regard to RTX efficacy, 61.8% (21/34) of patients presented a response to RTX. Our data may support the use of RTX as an effective treatment strategy against IMNM resistant to steroids and multiple immunotherapies. Meanwhile, RTX as a first-line therapy could be a choice in IMNM, particularly in African Americans with anti-SRP antibody-positive subsets. ANA, antinuclear antibody; CK, creatine kinase; HMGCR, 3-hydroxy-3-methylglutaryl-CoA reductase; IMNM, immune-mediated necrotizing myopathy; MAC, membrane attack complex; MHC-I, major histocompatibility complex-I; RTX, rituximab; SRP, signal recognition particle.

Crosstalk Between Innate and T Cell Adaptive Immunity With(in) the Muscle

Growing evidence demonstrates a continuous interaction between the immune system and the skeletal muscle in inflammatory diseases of different pathogenetic origins, in dystrophic conditions such as Duchenne Muscular Dystrophy as well as during normal muscle regeneration. Although one component of the innate immunity, the macrophage, has been extensively studied both in disease conditions and during cell or gene therapy strategies aiming at restoring muscular functions, much less is known about dendritic cells and their primary immunological targets, the T lymphocytes. This review will focus on the dendritic cells and T lymphocytes (including effector and regulatory T-cells), emphasizing the potential cross talk between these cell types and their influence on the structure and function of skeletal muscle.

Severe Cutaneous Findings in a Woman with Dermatomyositis

Dermatomyositis is an inflammatory condition characterized by proximal muscle weakness and classic skin manifestations. The severity of these symptoms, however, can vary greatly. Here we present the case of a woman with a particularly severe form of the cutaneous signs. It is important to recognize the potential severity of this condition as the uncontrolled progression of this disease can lead to respiratory compromise and cardiac involvement.

Discovery of Key Genes in Dermatomyositis Based on the Gene Expression Omnibus Database

The aim of this study was to identify biomarkers of dermatomyositis (DM). The analysis was conducted by retrieving DM-related cDNA microarray data sets from public databases. Gene ontology, Kyoto encyclopedia of genes and genomes, and protein-protein interaction analyses were performed, together with quantitative PCR-based detection of biomarkers in muscle tissue after stimulation with serum from patients with DM or healthy controls. Our analysis of five microarray data sets identified 20 common differentially expressed genes that are closely associated with DM. PCR analysis showed that mRNAs of IFITM2, LY6E, DDX58, and IFI6 were expressed at significantly higher levels in the muscle tissue of patients with DM than in normal muscle tissues. These mRNAs were also upregulated in human skeletal muscle cells stimulated with the serum from patients with DM. The results of integrated analyses of the DM microarray data and the mRNA levels of genes showed significant differences between the muscle tissues of DM patients and controls, which could indicate key pathogenic genes and novel therapeutic targets for DM.

Autoimmune Myopathies: Updates on Evaluation and Treatment

The major forms of autoimmune myopathies include dermatomyositis (DM), polymyositis (PM), myositis associated with antisynthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). While each of these conditions has unique clinical and histopathological features, they all share an immune-mediated component. These conditions can occur in isolation or can be associated with systemic malignancies or connective tissue disorders (overlap syndromes). As more has been learned about these conditions, it has become clear that traditional classification schemes do not adequately group patients according to shared clinical features and prognosis. Newer classifications are now utilizing myositis-specific autoantibodies which correlate with clinical and histopathological phenotypes and risk of malignancy, and help in offering prognostic information with regard to treatment response. Based on observational data and expert opinion, corticosteroids are considered first-line therapy for DM, PM, ASS, and IMNM, although intravenous immunoglobulin (IVIG) is increasingly being used as initial therapy in IMNM related to statin use. Second-line agents are often required, but further prospective investigation is required regarding the optimal choice and timing of these agents.

Activated dendritic cells modulate proliferation and differentiation of human myoblasts

Idiopathic Inflammatory Myopathies (IIMs) are a heterogeneous group of autoimmune diseases affecting skeletal muscle tissue homeostasis. They are characterized by muscle weakness and inflammatory infiltration with tissue damage. Amongst the cells in the muscle inflammatory infiltration, dendritic cells (DCs) are potent antigen-presenting and key components in autoimmunity exhibiting an increased activation in inflamed tissues. Since, the IIMs are characterized by the focal necrosis/regeneration and muscle atrophy, we hypothesized that DCs may play a role in these processes. Due to the absence of a reliable in vivo model for IIMs, we first performed co-culture experiments with immature DCs (iDC) or LPS-activated DCs (actDC) and proliferating myoblasts or differentiating myotubes. We demonstrated that both iDC or actDCs tightly interact with myoblasts and myotubes, increased myoblast proliferation and migration, but inhibited myotube differentiation. We also observed that actDCs increased HLA-ABC, HLA-DR, VLA-5, and VLA-6 expression and induced cytokine secretion on myoblasts. In an in vivo regeneration model, the co-injection of human myoblasts and DCs enhanced human myoblast migration, whereas the absolute number of human myofibres was unchanged. In conclusion, we suggest that in the early stages of myositis, DCs may play a crucial role in inducing muscle-damage through cell–cell contact and inflammatory cytokine secretion, leading to muscle regeneration impairment.

Immune and myodegenerative pathomechanisms in inclusion body myositis

Inclusion Body Myositis (IBM) is a relatively common acquired inflammatory myopathy in patients above 50 years of age. Pathological hallmarks of IBM are intramyofiber protein inclusions and endomysial inflammation, indicating that both myodegenerative and inflammatory mechanisms contribute to its pathogenesis. Impaired protein degradation by the autophagic machinery, which regulates innate and adaptive immune responses, in skeletal muscle fibers has recently been identified as a potential key pathomechanism in IBM. Immunotherapies, which are successfully used for treating other inflammatory myopathies lack efficacy in IBM and so far no effective treatment is available. Thus, a better understanding of the mechanistic pathways underlying progressive muscle weakness and atrophy in IBM is crucial in identifying novel promising targets for therapeutic intervention. Here, we discuss recent insights into the pathomechanistic network of mutually dependent inflammatory and degenerative events during IBM.

Inflammatory myopathies: A new landscape

Greater accuracy in clinical descriptions combined with advances in muscle histology and immunology have established that inflammatory myopathies (IMs), similarly to inflammatory rheumatic diseases, constitute a highly heterogeneous group of conditions. The topographic distribution, severity, and tempo of onset of the myopathy vary widely, and the histological findings distinguish at least five different profiles, which may reflect different pathophysiological processes. Most IMs are connective tissue diseases that can affect multiple organs, among which the most common targets are the skin, joints, and lungs. The extramuscular manifestations may antedate the muscular involvement and should therefore suggest a diagnosis of IM even in the absence of obvious muscle disease. About 20 different autoantibodies have been identified in patients with IM. Some are mutually exclusive and associated with specific combinations of clinical manifestations. Following the model of antisynthetase syndrome, about 10 syndromes associated with autoantibodies specific of IM have been identified. Thus, polymyositis is now emerging as a rare entity that is often mistaken for more recently described patterns of IM. No consensus exists to date about the classification of IMs. Nevertheless, the clinical manifestations, autoantibody profile, and muscle histology can be used to distinguish patient subgroups with fairly homogeneous patterns of complications, treatment responses, and outcomes. These subgroups are also characterized by specific genetic and environmental factors. The advances made in the nosology of IMs have benefited the diagnosis, personalization of treatment strategies, and understanding of pathophysiological mechanisms. They can be expected to assist in the development of specific treatments.

Guidelines on dermatomyositis--excerpt from the interdisciplinary S2k guidelines on myositis syndromes by the German Society of Neurology

The present guidelines on dermatomyositis (DM) represent an excerpt from the interdisciplinary S2k guidelines on myositis syndromes of the German Society of Neurology (available at www.awmf.org). The cardinal symptom of myositis in DM is symmetrical proximal muscle weakness. Elevated creatine kinase, CRP or ESR as well as electromyography and muscle biopsy also provide important diagnostic clues. Pharyngeal, respiratory, cardiac, and neck muscles may also be affected. Given that approximately 30% of patients also develop interstitial lung disease, pulmonary function tests should be part of the diagnostic workup. Although the cutaneous manifestations in DM are variable, taken together, they represent a characteristic and crucial diagnostic criterion for DM. Approximately 5-20% of individuals exhibit typical skin lesions without any clinically manifest muscle involvement (amyopathic DM). About 30% of adult DM cases are associated with a malignancy. This fact, however, should not delay the treatment of severe myositis. Corticosteroids are the therapy of choice in myositis (1-2 mg/kg). Additional immunosuppressive therapy is frequently required (azathioprine, for children methotrexate). In case of insufficient therapeutic response, the use of intravenous immunoglobulins is justified. The benefit of rituximab has not been conclusively ascertained yet. Acute therapeutic management is usually followed by low-dose maintenance therapy for one to three years. Skin lesions do not always respond sufficiently to myositis therapy. Effective treatment for such cases consists of topical corticosteroids and sometimes also calcineurin inhibitors. Systemic therapies shown to be effective include antimalarial agents (also in combination), methotrexate, and corticosteroids. Intravenous immunoglobulins or rituximab may also be helpful. UV protection is an important prophylactic measure.

Dysregulated innate immune function in the aetiopathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic muscle conditions that are believed to be autoimmune in nature. They have distinct pathological features, but the aetiopathogenesis of each subtype remains largely unknown. Recently, there has been increased interest in the complex role the innate immune system plays in initiating and perpetuating these conditions, and how this may differ between subtypes. This article summarises the traditional paradigms of IIM pathogenesis and reviews the accumulating evidence for disturbances in innate immune processes in these rare, but debilitating chronic conditions.

Transcriptomic profiling of long non-coding RNAs in dermatomyositis by microarray analysis

Long non-coding RNAs (lncRNAs) are prevalently transcribed in the genome and have been found to be of functional importance. However, the potential roles of lncRNAs in dermatomyositis (DM) remain unknown. In this study, a lncRNA + mRNA microarray analysis was performed to profile lncRNAs and mRNAs from 15 treatment-naive DM patients and 5 healthy controls. We revealed a total of 1198 lncRNAs (322 up-regulated and 876 down-regulated) and 1213 mRNAs (665 up-regulated and 548 down-regulated) were significantly differentially expressed in DM patients compared with the healthy controls (fold change>2, P < 0.05). Subgrouping DM patients according to the presence of interstitial lung disease and anti-Jo-1 antibody revealed different expression patterns of the lncRNAs. Pathway and gene ontology analysis for the differentially expressed mRNAs confirmed that type 1 interferon signaling was the most significantly dysregulated pathway in all DM subgroups. In addition, distinct pathways that uniquely associated with DM subgroup were also identified. Bioinformatics prediction suggested that linc-DGCR6-1 may be a lncRNA that regulates type 1 interferon-inducible gene USP18, which was found highly expressed in the perifascicular areas of the muscle fibers of DM patients. Our findings provide an overview of aberrantly expressed lncRNAs in DM muscle and further broaden the understanding of DM pathogenesis.

Critical review of the role of intravenous immunoglobulins in idiopathic inflammatory myopathies

OBJECTIVE

The aim of this review was to summarize key findings from the literature concerning the therapeutic role of intravenous immunoglobulins (IVIg) in idiopathic inflammatory myopathies (IIM), dissecting the evidence according to disease subtype and treatment indication, and to review the evidence relating to the mechanism of action of IVIg in IIM to ascertain rationale for continued research.

METHODS

Medline (Ovid) and Pubmed databases were searched from inception to July 2016 using relevant keywords. Original and review articles were retrieved for full-text review. Bibliographies of selected articles were also hand-searched for additional references. Data were summarized qualitatively and in tabular form.

RESULTS

The efficacy of IVIg in IIM is supported by 3 randomized controlled trials, involving dermatomyositis and polymyositis subjects, in refractory, relapsed, or steroid-dependent disease, as well as part of first-line therapy in elderly dermatomyositis subjects. Other indications for IVIg are supported by uncontrolled evidence only. Limitations of studies include open, uncontrolled or retrospective study designs, small and selected samples, short-term follow-up and ad hoc outcome measures. Despite the limited evidence, there is strong biological plausibility for the role of IVIg in IIM.

CONCLUSION

Robust, controlled evidence to support the use of IVIg using validated outcome measures is urgently required to guide therapeutic decision-making and maximize outcomes in IIM.

Immunotherapies for Immune-Mediated Myopathies: A Current Perspective

Until recently, the treatment of immune-mediated inflammatory myopathies has largely been empirical with glucocorticoids, steroid-sparing immunosuppressive drugs, and intravenous immunoglobulin. However, a proportion of patients are only partially responsive to these therapies, and there has been a need to consider alternative treatment approaches. In particular, patients with inclusion body myositis are resistant to conventional immunotherapies or show only a transient response, and remain a major challenge. With increasing recognition of the different subtypes of immune-mediated inflammatory myopathies, and improved understanding of their pathogenesis, more targeted treatments are now being trialled. The overall approach to treatment, and novel therapies targeting B cells, T cells, and specific cytokines are discussed in this review.

Role of Toll-like receptors and retinoic acid inducible gene I in endogenous production of type I interferon in dermatomyositis

To explore the possible mechanisms implicated in the endogenous production of type I interferons within the muscle tissue of dermatomyositis (DM) patients. We detected the co-localization of plasmacytoid dendritic cells (pDCs) with Toll-like receptors (TLRs) and retinoic acid inducible gene (RIG)-I by immunohistochemistry and immunofluorescence. Western blotting confirmed the expression of TLRs and RIG-I. TLR-3 and RIG-I was preferentially expressed in the perifascicular atrophy fibers of DM. TLR-7 was only in inflammatory infiltrates of a few DM patients. TLR-4 and TLR-9 was expressed mainly in inflammatory infiltrates. Immunofluorescence showed extensive co-localization of BDCA-2 with TLR-9 and little co-localization with TLR-7. Western blotting showed upregulation of expression of TLRs and RIG-I in DM compared with the controls. Our findings indicate that endogenous production of type I IFN in DM is generated by pDCs, mainly through the TLR-9 pathway and in part by TLR-7. TLR-3 and RIG-I are implicated in the formation of perifascicular atrophy in DM.

Fibrinogen reduction and bleeding complications in plasma exchange, immunoadsorption and a combination of the two

BACKGROUND

Immunoadsorption (IAS) and therapeutic plasma exchange (TPE) are considered safe although fibrinogen is removed. To date no comparison of fibrinogen reduction and associated risk of bleeding in apheresis exists.

METHODS

Retrospective analysis of TPE, three IAS adsorbers, and combined TPE/IAS regarding fibrinogen reduction and bleeding incidence in 67 patients (1,032 treatments).

RESULTS

TPE and TPE/IAS reduced fibrinogen by 64 ± 11% and 58 ± 9%, leading to concentrations <100 mg/dl in 20 and 17% of treatments, respectively. IAS decreased fibrinogen less than TPE (26 ± 6%, p < 0.0001), resulting in fibrinogen concentrations <100 mg/dl in 1% of treatments. The processed volume correlated with reduction in TPE (r = 0.64, p < 0.01), but not in IAS. Bleeding occurred in 1.3% (IAS), 2.3% (TPE) and 3.1% (TPE/IAS) of treatments.

CONCLUSION

Hypofibrinogenemia occurs in 20% of patients after TPE and TPE/IAS, but rarely after IAS. IAS removes fibrinogen independently of volume processed. Overall, bleeding is rare in apheresis.

Inhibition of myogenic microRNAs 1, 133, and 206 by inflammatory cytokines links inflammation and muscle degeneration in adult inflammatory myopathies

OBJECTIVE

The molecular basis of inflammatory myopathies such as dermatomyositis (DM), polymyositis, and inclusion body myositis, which share the characteristics of chronic muscle inflammation and skeletal muscle wasting, are poorly understood. As such, effective targeted treatments for these diseases are lacking, resulting in critical unmet medical needs for these devastating diseases. The purpose of this study was to identify possible new targets for drug development by exploring the mechanism by which inflammation may play a role in the pathology of the inflammatory myopathies.

METHODS

We compared expression levels of inflammatory cytokines and microRNAs (miRNAs) between muscle biopsy samples from patients with inflammatory myopathies and those from donors without myositis. In vitro human and mouse model systems were then used to characterize the role of these cytokines and microRNAs on myoblast-to-myocyte differentiation.

RESULTS

We observed increased expression of inflammatory cytokines, including tumor necrosis factor α (TNFα), interferon-α (IFNα), IFNβ, and interleukin-1β, in different subtypes of inflammatory myopathies. We observed decreased expression of microRNA-1 (miR-1), miR-133a, and miR-133b in all of the inflammatory myopathy subtypes we evaluated, as well as decreased expression of miR-206 in DM; these miRNAs are essential for adult skeletal muscle differentiation and maintenance. TNFα was significantly inversely correlated with decreased myogenic miRNA expression in the inflammatory myopathy subtypes. In mechanistic studies, TNFα inhibited the expression of myogenic miRNAs and suppressed the differentiation of C2C12 myoblasts to myocytes/myotubes in an NF-κB-dependent manner. This block in differentiation by TNFα was relieved by overexpression of miR-1, miR-206, or miR-133a/b.

CONCLUSION

Taken together, these results provide a new mechanistic link between the action of proinflammatory cytokines and the degenerative pathology of inflammatory myopathies, and suggest therapeutic approaches for these diseases.

Polymyositis Associated with Hepatitis B Virus Cirrhosis and Advanced Hepatocellular Carcinoma

Polymyositis (PM) is an inflammatory condition of skeletal muscle and is believed to be a paraneoplastic syndrome associated with various types of cancer. PM associated with chronic hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) is very rare. We report a case of advanced HCC with chronic HBV cirrhosis that presented with proximal muscle weakness. Further investigation showed elevation of muscle enzymes, myopathic pattern of electromyography (EMG), and evidence of myositis compatible with PM. Lamivudine and 1 mg/kg of oral prednisolone were given. Two sessions of transcatheter arterial chemoembolization (TACE) were performed and sorafenib was started. Muscle enzymes normalized after 6 weeks of treatment. Unfortunately, 5 months after treatment, patient was readmitted and died of severe bacterial pneumonia.

Dermatomyositis as a complication of interferon-α therapy: a case report and review of the literature

Autoimmune disorder is one of the important side effects of interferon-α therapy. Some polymyositis cases as complication of interferon-α therapy were reported, but dermatomyositis were rarely. We report a case of dermatomyositis as a complication of interferon-α therapy for hepatitis C. A 52-year-old Japanese man was treated by combination therapy with pegylated interferon-α-2b and ribavirin for hepatitis C. Three months after the initiation of therapy, he showed erythema in the posterior cervical to dorsal and anterior cervical to thoracic regions, weight loss, general malaise, muscle pain, and severe increase in levels of muscle enzymes. We made a diagnosis of dermatomyositis according to these clinical features, proximal muscle-predominant myogenic change on electromyography, and infiltration of monocytes and CD4+-dominant lymphocytes on skin biopsy, although myositis-associated antibodies were absent. He was successfully treated with intravenous immunoglobulin and tacrolimus in addition to glucocorticoid. This is a very rare case of dermatomyositis associated with interferon-α therapy. We reviewed several similar published cases and the association of dermatomyositis and type I interferon.

Skeletal muscle microvasculature in the diagnosis of neuromuscular disease

Blood vessels are often overlooked in analyses of skeletal muscle biopsies. However, there are many vascular features in skeletal muscle biopsies that, when interpreted in the context of other histologic patterns and clinical history, provide useful information that allows muscle pathologists to narrow their differential diagnoses and provide more accurate guidance to treating physicians. Here, we provide a review of normal skeletal muscle vasculature with details of the ultrastructure of vessel walls. We discuss the vascular effects of factors common to many patients undergoing muscle biopsy, for example, diabetes mellitus, hypertension, and aging. We then discuss vascular findings relevant to diagnostic muscle biopsy evaluation, with current theories of pathogenesis and detailed descriptions of the important features.

Cytosolic 5'-nucleotidase 1A autoimmunity in sporadic inclusion body myositis

OBJECTIVE

We previously identified a circulating autoantibody against a 43 kDa muscle autoantigen in sporadic inclusion body myositis (IBM) and demonstrated the feasibility of an IBM diagnostic blood test. Here, we sought to identify the molecular target of this IBM autoantibody, understand the relationship between IBM autoimmunity and muscle degeneration, and develop an IBM blood test with high diagnostic accuracy.

METHODS

IBM blood samples were screened using mass spectrometry and a synthetic human peptidome. Plasma and serum samples (N=200 patients) underwent immunoblotting assays, and results were correlated to clinical features. Muscle biopsy samples (n=30) were examined by immunohistochemistry and immunoblotting. Exome or whole genome sequencing was performed on DNA from 19 patients.

RESULTS

Both mass spectrometry and screening of a 413,611 human peptide library spanning the entire human proteome identified cytosolic 5'-nucleotidase 1A (cN1A; NT5C1A) as the likely 43 kDa IBM autoantigen, which was then confirmed in dot blot and Western blot assays using recombinant cN1A protein. Moderate reactivity of anti-cN1A autoantibodies was 70% sensitive and 92% specific, and high reactivity was 34% sensitive and 98% specific for the diagnosis of IBM. One to 3 major cN1A immunodominant epitopes were identified. cN1A reactivity by immunohistochemistry accumulated in perinuclear regions and rimmed vacuoles in IBM muscle, localizing to areas of myonuclear degeneration.

INTERPRETATION

Autoantibodies against cN1A are common in and highly specific to IBM among muscle diseases, and may provide a link between IBM's dual processes of autoimmunity and myodegeneration. Blood diagnostic testing is feasible and should improve early and reliable diagnosis of IBM.

Longitudinal Peripheral Blood Lymphocyte Subsets Correlate with Decreased Disease Activity in Juvenile Dermatomyositis

Objective:

To determine the clinical characteristics and subsets of peripheral blood lymphocytes (PBL), which correlate with decreased disease activity in patients with juvenile dermatomyositis (JDM).

Methods.

Peripheral blood mononuclear cells from 24 patients with JDM were collected at Mayo Clinic Rochester between 2007 and 2011. These were analyzed using fluorescence-activated cell sorting and flow cytometry. Clinical disease activity was determined by visual analog scales (VAS) collected in 2 consecutive visits and correlated with PBL subsets.

Results.

The change in CD3+CD69+ T cells correlated with the change in global VAS scores. The change in HLA-DR- CD11c+ myeloid dendritic cells also correlated with the change in extramuscular VAS scores. There were trends toward decreased levels of HLA-DR- CD11c+ cells with decreased muscle and global VAS scores, but these did not reach significance. The change in HLA-DR- CD123+ plasmacytoid dendritic cells negatively correlated with the change in muscle VAS scores. Although not statistically significant, decreased levels of CD3-CD16- CD56+ natural killer (NK) cells and HLA-DR- CD86+ myeloid dendritic cells, and increased levels of CD16+CD56- NK cells, correlated with decreased VAS scores.

Conclusion.

Changes in CD3+CD69+ T cells, HLA-DR- CD11c+ myeloid dendritic cells, and HLA-DR- CD123+ plasmacytoid dendritic cells are associated with improved clinical course in JDM and could be used as markers for disease activity, but findings need to be verified in a larger, independent cohort. Lack of significant differences among most of our PBL subsets suggests that lymphocyte phenotyping may be difficult to definitively correlate with disease activity in JDM.

Classification and Diagnostic Investigation in Inflammatory Myopathies: A Study of 99 Patients

Objective.

Insights into the pathogenesis of inflammatory myopathies have led to new diagnostic methods. The aims of our study were (1) to evaluate the consequences of using the classification of Amato/European Neuromuscular Centre Workshop (ENMC) compared to that of Bohan and Peter; and (2) to evaluate any diagnostic benefit in using an extended pathological investigation.

Methods.

From a consecutive retrospective database, we evaluated 99 patients for classification. Patients with inclusion body myositis (IBM) were classified according to Griggs,et al. In addition to routine stainings and immunohistochemistry, a multilevel serial sectioning procedure was performed on paraffin-embedded material, to identify scarce pathological findings.

Results.

Classification according to Bohan and Peter could be performed for 83 of the 99 patients, whereas only 60 patients met the Amato/ENMC criteria, the latter resulting in the following diagnostic groups: IBM (n = 18), nonspecific myositis (n = 14), polymyositis (n = 12), dermatomyositis (n = 10), dermatomyositis sine dermatitis (n = 5), and immune-mediated necrotizing myopathy (n = 1). Most of the Amato/ENMC diagnostic groups harbored patients from several of the Bohan and Peter groups, which included a substantial group lacking proximal muscle weakness. The serial sectioning procedure was essential for classification of 9 patients (15%), and led to a more specific diagnosis for 13 patients (22%) according to Amato/ENMC.

Conclusion.

The classification of Amato/ENMC was more restrictive, forming groups based on clinical criteria and specified myopathological findings, which clearly differed from the groups of the Bohan and Peter classification. An extended pathological investigation increased the diagnostic yield of a muscle biopsy and highlights the quantity and specificity of certain pathological findings.

Pathogenesis and therapy of inclusion body myositis

PURPOSE OF REVIEW

Inclusion body myositis (IBM) is a poorly understood progressive muscle disease of middle and later life. Its dual pathologies of autoimmunity and unexplained myofiber degeneration and loss have been enigmatic since its earliest descriptions over 40 years ago. No reliable effective therapy currently exists for IBM. This review provides an update of current issues in the pathogenesis and therapy of IBM.

RECENT FINDINGS

Recent studies have further defined the clinical features of IBM, including natural history, pattern of muscle involvement, and role of MRI imaging. Further potential immune mediators have been identified. An autoantibody directed against a muscle antigen appears to have high specificity for IBM among muscle diseases. Further evidence for myonuclear degeneration has been reported.

SUMMARY

IBM remains a poorly understood muscle disease, although understanding of the pathophysiological mechanisms continues to expand and is supporting new therapeutic approaches.

Idiopathic inflammatory myopathies: current trends in pathogenesis, clinical features, and up-to-date treatment recommendations

Recently, there have been important advances in the understanding of the pathophysiologic features, assessment, and management of patients with a newly diagnosed idiopathic inflammatory myopathy (IIM). Myositis-specific autoantibodies have been identified to define patient subgroups and offer prognostic implications. Similarly, proinflammatory cytokines, such as interleukin 6 and type 1 interferon-dependent genes, may serve as potential biomarkers of disease activity in adult and juvenile patients with dermatomyositis (DM). Moreover, magnetic resonance imaging has become an important modality for the assessment of muscle inflammation in adult IIM and juvenile DM. Immune-mediated necrotizing myopathies also are being recognized as a subset of IIM triggered by medications such as statins. However, confusion exists regarding effective management strategies for patients with IIM because of the lack of large-scale, randomized, controlled studies. This review focuses primarily on our current management and treatment algorithms for IIM including the care of pediatric patients with juvenile DM. For this review, we conducted a search of PubMed and MEDLINE for articles published from January 1, 1970, to December 1, 2011, using the following search terms: idiopathic inflammatory myopathies, dermatomyositis, polymyositis, juvenile dermatomyositis, sporadic inclusion body myositis, inclusion body myositis, inflammatory myositis, myositis, myopathies, pathogenesis, therapy, and treatment. Studies published in English were selected for inclusion in our review as well as additional articles identified from bibliographies.

Fascin-expressing Dendritic Cells Dominate in Polymyositis and Dermatomyositis

Objective.

Dendritic cells (DC) have been reported among inflammatory infiltrating cells in muscle tissue in idiopathic inflammatory myopathies (IIM), but to our knowledge no studies concerning the expression of langerin (CD207) or fascin (markers of immature and mature DC, respectively) in IIM have been published.

Methods.

Immunohistochemical analyses of langerin and fascin expression were performed on specimens from normal muscles, as well as those affected by polymyositis (PM) and dermatomyositis (DM). The results were analyzed by Mann-Whitney U test.

Results.

In PM and DM, fascin-positive cells were numerous in the majority of the studied samples in perimysial, endomysial, and perivascular cellular infiltrates. Sporadic langerin-positive cells were detected.

Conclusion.

Fascin-positive DC predominance in inflammatory infiltrates in myositic muscles confirms the prevalence of mature forms and indicates that there are conditions stimulating DC maturation in both PM and DM. The induction of immunological tolerance by inhibiting DC maturation may be a promising direction for studies of myositis treatment.

Knee extensor strength exhibits potential to predict function in sporadic inclusion-body myositis

INTRODUCTION

In this study we address the challenging issue of potential use of muscle strength to predict function in clinical trials. This has immediate relevance to translational studies that attempt to improve quadriceps strength in sporadic inclusion-body myositis (sIBM).

METHODS

Maximum voluntary isometric contraction testing as a measure of muscle strength and a battery of functional outcomes were tested in 85 ambulatory subjects with sIBM.

RESULTS

Marked quadriceps weakness was noted in all patients. Strength was correlated with distance walked at 2 and 6 minutes. Additional correlations were found with time to get up from a chair, climb stairs, and step up on curbs.

CONCLUSIONS

Quadriceps (knee extensor) strength correlated with performance in this large cohort of sIBM subjects, which demonstrated its potential to predict function in this disease. These data provide initial support for use of muscle strength as a surrogate for function, although validation in a clinical trial is required.

Inclusion body myositis

PURPOSE OF REVIEW

Sporadic inclusion body myositis (sIBM) is a poorly understood immune and degenerative disease of skeletal muscle. Here, current opinion of the nature of this disease is summarized.

RECENT FINDINGS

Recent findings for sIBM include further characterization of muscle involvement through magnetic resonance imaging, the role of muscle as a host for immune cells, progress in the role of extranuclear TDP-43 in causing cellular injury, and the discovery of a new sIBM autoantibody.

SUMMARY

sIBM understanding continues to advance, with progress regarding the mechanism of this disease.

Mechanisms of action of intravenous immunoglobulin in inflammatory muscle disease

Intravenous immunoglobulin (IVIG) is a unique immune-modulating therapy that has a wide range of effects on the immune system at multiple levels. This allows it to be used successfully in a variety of immune-mediated, systemic, and neurological disorders, including the inflammatory myopathies. It is likely that the specific action of IVIG varies depending on the underlying pathogenesis of a given disease. In dermatomyositis (DM), IVIG has been shown to diminish the activity of complement and deposition of membrane attack complex on capillaries and muscle fibers, the expression of adhesion molecules, and cytokine production. IVIG also appears to modify gene expression in the muscle of DM patients. The mechanism by which IVIG affects muscle in polymyositis and inclusion body myositis has not been well-studied. However, it may work via suppression of T-cell activation (including cytotoxic T cells) and migration into muscle tissue and alterations in cytokine production. IVIG generally yields the greatest therapeutic benefit in DM and is often of marginal utility in inclusion body myositis. It is generally considered as second-line or adjunctive therapy in the inflammatory myopathies.

Therapeutic advances and future prospects in immune-mediated inflammatory myopathies

THE INFLAMMATORY MYOPATHIES INCLUDE THREE DISTINCT ENTITIES: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). A T-cell-mediated cytotoxic process in PM and IBM and a complement-mediated microangiopathy in DM are the hallmarks of the underlying autoimmune processes. The most consistent therapeutic problem remains the distinction of PM from the difficult-to-treat mimics such as s-IBM, necrotizing myopathies and inflammatory dystrophies. This review provides a step-by-step approach to the treatment of inflammatory myopathies, highlights the common pitfalls and mistakes in therapy, and identifies the emerging new therapies. In uncontrolled studies, PM and DM respond to prednisone to some degree and for some period of time, while a combination with one immu-nosuppressive drug (azathioprine, cyclosporine, mycophenolate, methotrexate) offers additional benefit or steroid-sparing effect. In contrast, IBM is resistant to most of these therapies, most of the time. Controlled studies have shown that IVIg is effective and safe for the treatment of DM, where is used as a second, and at times first, line therapy. IVIg seems to be also effective in the majority of patients with PM based on uncontrolled series, but it offers transient help to a small number of patients with IBM especially those with dysphagia. Bona fide patients with PM and DM who become resistant to the aforementioned therapies, may respond to rituximab, tacrolimus or rarely to an tumor necrosis factor alpha inhibitor. For IBM patients, experience with alemtuzumab, a T-cell-depleting monoclonal antibody, is encouraging.

Juvenile dermatomyositis: immunopathogenesis, role of myositis-specific autoantibodies, and review of rituximab use

Juvenile dermatomyositis (JDM) is an autoimmune disease of the skin and muscle that affects children. The etiology is poorly understood, but genetic susceptibility, environmental triggers, and abnormal immune responses are each thought to play a part. T cells have traditionally been implicated in the immunopathogenesis of JDM, but dendritic cells, B cells, and microchimerism are increasingly associated. Additionally, myositis-specific autoantibodies (MSA) can be present in the sera of affected patients and may correlate with distinct clinical phenotypes. Given the role of humoral immunity and MSA, there has been recent interest in the use of rituximab to treat JDM. Early results are mixed, but it is hoped that a prospective clinical trial will shed light on the issue in the near future.

Autoantibodies against a 43 KDa muscle protein in inclusion body myositis

Background

Inclusion body myositis (IBM) is a poorly understood and refractory autoimmune muscle disease. Though widely believed to have no significant humoral autoimmunity, we sought to identify novel autoantibodies with high specificity for this disease.

Methodology/Principal Findings

Plasma autoantibodies from 65 people, including 25 with IBM, were analyzed by immunoblots against normal human muscle. Thirteen of 25 (52%) IBM patient samples recognized an approximately 43 kDa muscle protein. No other disease (N = 25) or healthy volunteer (N = 15) samples recognized this protein.

Conclusions

Circulating antibodies against a 43-kDa muscle autoantigen may lead to the discovery of a novel biomarker for IBM. Its high specificity for IBM among patients with autoimmune myopathies furthermore suggests a relationship to disease pathogenesis.

Essential muscle pathology for the rheumatologist

This review introduces/refreshes some basic histopathologic methods and findings of skeletal muscle biopsies with emphasis on those diseases commonly encountered in a rheumatologist's practice. The 3 general areas of myopathology discussed are metabolic myopathies, toxic myopathies, and inflammatory myopathies. The authors, neuropathologists, hope to provide in this article what they think are some commonalities and disease-specific methods in their pathologic workup as well as a practical approach to the collaboration that pathologists undertake with their rheumatology colleagues to come to a working diagnosis.