Clinical and serological characteristics of 125 Dutch myositis patients. Myositis specific autoantibodies aid in the differential diagnosis of the idiopathic inflammatory myopathies

Predictors of cardiac involvement in idiopathic inflammatory myopathies

Objectives

Idiopathic inflammatory myopathies (IIM) are a group of rare disorders that can affect the heart. This work aimed to find predictors of cardiac involvement in IIM.

Methods

Multicenter, open cohort study, including patients registered in the IIM module of the Rheumatic Diseases Portuguese Register (Reuma.pt/Myositis) until January 2022. Patients without cardiac involvement information were excluded. Myo(peri)carditis, dilated cardiomyopathy, conduction abnormalities, and/or premature coronary artery disease were considered.

Results

230 patients were included, 163 (70.9%) of whom were females. Thirteen patients (5.7%) had cardiac involvement. Compared with IIM patients without cardiac involvement, these patients had a lower bilateral manual muscle testing score (MMT) at the peak of muscle weakness [108.0 ± 55.0 vs 147.5 ± 22.0, p=0.008] and more frequently had oesophageal [6/12 (50.0%) vs 33/207 (15.9%), p=0.009] and lung [10/13 (76.9%) vs 68/216 (31.5%), p=0.001] involvements. Anti-SRP antibodies were more commonly identified in patients with cardiac involvement [3/11 (27.3%) vs 9/174 (5.2%), p=0.026]. In the multivariate analysis, positivity for anti-SRP antibodies (OR 104.3, 95% CI: 2.5-4277.8, p=0.014) was a predictor of cardiac involvement, regardless of sex, ethnicity, age at diagnosis, and lung involvement. Sensitivity analysis confirmed these results.

Conclusion

Anti-SRP antibodies were predictors of cardiac involvement in our cohort of IIM patients, irrespective of demographical characteristics and lung involvement. We suggest considering frequent screening for heart involvement in anti-SRP-positive IIM patients.

Cardiovascular Abnormalities in Juvenile Dermatomyositis: A Scoping Review for the Clinical Rheumatologists

Juvenile dermatomyositis (JDM) is a common form of inflammatory myositis in children. Vasculopathy and endothelial dysfunction play significant roles in the pathogenesis of JDM. Cardiac involvement in JDM is often underestimated, and it may be a potential indicator of poor prognosis. Cardiac dysfunction in JDM can occur both in the acute and chronic stages of the disease. Amongst the acute complications, acute congestive heart failure (CHF), myocarditis, arrhythmia, and complete heart block are common. However, these remain unrecognized due to a lack of overt clinical manifestations. Increased rates of cardiovascular abnormalities have been noted with anti-SRP and anti-Jo 1 auto-antibody positivity. Long-term follow-up studies in JDM have shown an increased prevalence of hypertension, atherosclerosis, coronary artery disease, and metabolic syndrome in adolescence and adulthood. Monitoring of body-mass index, blood pressure, and laboratory evaluation of fasting glucose and lipid profile may help in identifying metabolic syndrome in children with JDM. Steroid-sparing agents, daily exercise, and a healthy diet may reduce such long-term cardiac morbidities. Current use of multimodality imaging such as stress-echocardiography, contrast-enhanced echocardiography, cardiac magnetic resonance imaging, and positron emission tomography has increased the diagnostic yield of subclinical heart disease during acute and chronic stages of JDM. This review elaborates on different aspects of cardiac dysfunction in JDM. It also emphasizes the importance of cardiac screening in long-term follow-up of children with JDM.

A New Method for the Assessment of Myalgia in Interstitial Lung Disease: Association with Positivity for Myositis-Specific and Myositis-Associated Antibodies

In this study, it was found that myositis-specific and myositis-associated antibodies (MSAs and MAAs) improved the recognition of idiopathic inflammatory myopathies (IIMs) in interstitial lung disease (ILD) patients. The objective of this study is to propose a clinical method to evaluate myalgia in respiratory settings as a possible tool for the recognition of MSA/MAA positivity in ILD patients. We prospectively enrolled 167 ILD patients with suspected myositis, of which 63 had myalgia evoked at specific points (M+ILD+). We also enrolled in a 174 patients with only myalgia (M+ILD-) in a rheumatological setting. The patients were assessed jointly by rheumatologists and pulmonologists and were tested for autoantibodies. M+ILD+ patients were positive for at least one MAA/MSA in 68.3% of cases, as were M-ILD+ patients in 48.1% of cases and M+ILD- patients in 17.2% of cases (p = 0.01 and <0.0001, respectively). A diagnosis of IIM was made in 39.7% of M+ILD+ patients and in 23.1% of the M-ILD+ group (p = 0.02). Myalgia was significantly associated with positivity for MSA/MAAs in ILD patients (p = 0.01, X2: 6.47). In conclusion, myalgia in ILD patients with suspected myositis is associated with MSA/MAA positivity, and could support a diagnosis of IIM. A significant proportion of M+ILD- patients also had MSA/MAA positivity, a phenomenon warranting further study to evaluate its clinical meaning.

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

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

The Brazilian Society of Rheumatology recommendations on investigation and diagnosis of systemic autoimmune myopathies

BACKGROUND

This research is recommended by the Myopathy Committee of the Brazilian Society of Rheumatology for the investigation and diagnosis of systemic autoimmune myopathies. BODY: A systematic literature review was performed in the Embase, Medline (PubMed) and Cochrane databases, including studies published until October 2018. PRISMA was used for the review, and the articles were evaluated, based on the Oxford levels of evidence. Ten recommendations were developed addressing different aspects of systemic autoimmune myopathy investigation and diagnosis.

CONCLUSIONS

The European League Against Rheumatism/ American College of Rheumatology (EULAR/ACR) classification stands out for the diagnosis of systemic autoimmune myopathies. Muscular biopsy is essential, aided by muscular magnetic resonance images and electroneuromyography in complementary research. Analysis of the factors related to prognosis with the evaluation of extramuscular manifestations, and comorbidities and intense investigation regarding differential diagnoses are mandatory.

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.

Myositis-specific autoantibodies, a cornerstone in immune-mediated necrotizing myopathy

Over the past few years, myositis-specific autoantibodies played an increasing role in the inflammatory idiopathic myositis definition. They became the critical immunological marker for immune-mediated necrotizing myopathy diagnosis (IMNM) since the paradigm switch from histological to serological criteria. This review is focused on the key role of the anti-signal recognition particle (anti-SRP) and the anti-3-Hydroxy-3-MethylGlutaryl-Coenzyme A Reductase (anti-HMGCR) antibodies in immune-mediated necrotizing myopathy. Anti-SRP and anti-HMGCR antibodies are robust diagnostic tools in case of both the classical subacute form and the slowly progressive form of IMNM that may mimic muscular dystrophy. Anti-SRP and anti-HMGCR patients share clinical, biological and histological features with some antibody-associated specificity. Anti-SRP patients harbour more severe muscle weakness and atrophy with severe muscle damage on magnetic resonance imaging study. Approximately 10-20% of anti-SRP patients develop extramuscular symptoms, especially lung interstitial disease. Conversely, anti-HMGCR patients are often associated with statin exposure. In both cases, patients have a poor outcome with frequent relapse and the use of combined immunotherapy. Of note, various data suggest a direct pathogenic role of these antibodies reinforcing the interest in targeted therapeutic strategy.

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.

Immune-Mediated Necrotizing Myopathy

PURPOSE OF REVIEW

Immune-mediated necrotizing myopathy (IMNM) is a type of autoimmune myopathy characterized by relatively severe proximal weakness, myofiber necrosis with minimal inflammatory cell infiltrate on muscle biopsy, and infrequent extra-muscular involvement. Here, we will review the characteristics of patients with IMNM.

RECENT FINDINGS

Anti-signal recognition particle (SRP) and anti-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) autoantibodies are closely associated with IMNM and define unique subtypes of patients. Importantly, the new European Neuromuscular Centre criteria recognize anti-SRP myopathy, anti-HMGCR myopathy, and autoantibody-negative IMNM as three distinct subtypes of IMNM. Anti-SRP myopathy patients have more severe muscle involvement, have more common extra-muscular features, and may respond best to immunosuppressive regimens that include rituximab. In contrast, anti-HMGCR myopathy is often associated with statin exposure and intravenous immunoglobulin treatment may be an effective treatment, even as monotherapy. Both anti-SRP and anti-HMGCR myopathy tend to be most severe in younger patients. Furthermore, children with these forms of IMNM may present with dystrophy-like features which are potentially reversible with immunosuppressant treatment. IMNM patients with either autoantibody may experience fatty replacement of muscle soon after disease onset, suggesting that intense and early immunosuppressant therapy may provide the best chance to avoid long-term disability. IMNM is composed of anti-SRP myopathy, anti-HMGCR myopathy, and autoantibody-negative IMNM. Both anti-SRP and anti-HMGCR myopathy can cause severe weakness, especially in younger patients. Anti-SRP myopathy patients tend to have the most severe weakness and most prevalent extra-muscular features. Autoantibody-negative IMNM remains poorly described.

Autoantibody Specificities and Type I Interferon Pathway Activation in Idiopathic Inflammatory Myopathies

Myositis is a heterogeneous group of autoimmune diseases, with different pathogenic mechanisms contributing to the different subsets of disease. The aim of this study was to test whether the autoantibody profile in patients with myositis is associated with a type I interferon (IFN) signature, as in patients with systemic lupus erythematous (SLE). Patients with myositis were prospectively enrolled in the study and compared to healthy controls and to patients with SLE. Autoantibody status was analysed using an immunoassay system and immunoprecipitation. Type I IFN activity in whole blood was determined using direct gene expression analysis. Serum IFN-inducing activity was tested using peripheral blood cells from healthy donors. Blocking experiments were performed by neutralizing anti-IFNAR or anti-IFN-α antibodies. Patients were categorized into IFN high and IFN low based on an IFN score. Patients with autoantibodies against RNA-binding proteins had a higher IFN score compared to patients without these antibodies, and the IFN score was related to autoantibody multispecificity. Patients with dermatomyositis (DM) and inclusion body myositis (IBM) had a higher IFN score compared to the other subgroups. Serum type I IFN bioactivity was blocked by neutralizing anti-IFNAR or anti-IFN-α antibodies. To conclude, a high IFN score was not only associated with DM, as previously reported, and IBM, but also with autoantibody monospecificity against several RNA-binding proteins and with autoantibody multispecificity. These studies identify IFN-α in sera as a trigger for activation of the type I IFN pathway in peripheral blood and support IFN-α as a possible target for therapy in these patients.

Simultaneous Combined Myositis, Inflammatory Polyneuropathy, and Overlap Myasthenic Syndrome

Immune-mediated neuromuscular disorders include pathologies of the peripheral nervous system, neuromuscular junction, and muscles. If overlap syndromes (or the association of almost two autoimmune disorders) are recognized, the simultaneous occurrence of several autoimmune neuromuscular disorders is rare. We describe two patients presenting the simultaneous occurrence of inflammatory neuropathy, myositis, and myasthenia gravis (with positive acetylcholine receptor antibodies). For each patient, we carried out a pathological analysis (nerve and muscle) and an electrophysiological study (and follow-up). To our knowledge, this is the first description of such a triple immune-mediated neuromuscular syndrome. We compared our observations with a few other cases of simultaneous diagnosis of two inflammatory neuromuscular disorders.

Scanning for Therapeutic Targets within the Cytokine Network of Idiopathic Inflammatory Myopathies

The idiopathic inflammatory myopathies (IIM) constitute a heterogeneous group of chronic disorders that include dermatomyositis (DM), polymyositis (PM), sporadic inclusion body myositis (IBM) and necrotizing autoimmune myopathy (NAM). They represent distinct pathological entities that, most often, share predominant inflammation in muscle tissue. Many of the immunopathogenic processes behind the IIM remain poorly understood, but the crucial role of cytokines as essential regulators of the intramuscular build-up of inflammation is undisputed. This review describes the extensive cytokine network within IIM muscle, characterized by strong expression of Tumor Necrosis Factors (TNFα, LTβ, BAFF), Interferons (IFNα/β/γ), Interleukins (IL-1/6/12/15/18/23) and Chemokines (CXCL9/10/11/13, CCL2/3/4/8/19/21). Current therapeutic strategies and the exploration of potential disease modifying agents based on manipulation of the cytokine network are provided. Reported responses to anti-TNFα treatment in IIM are conflicting and new onset DM/PM has been described after administration of anti-TNFα agents to treat other diseases, pointing to the complex effects of TNFα neutralization. Treatment with anti-IFNα has been shown to suppress the IFN type 1 gene signature in DM/PM patients and improve muscle strength. Beneficial effects of anti-IL-1 and anti-IL-6 therapy have also been reported. Cytokine profiling in IIM aids the development of therapeutic strategies and provides approaches to subtype patients for treatment outcome prediction.

B-cell survival factors in autoimmune rheumatic disorders

Autoimmune rheumatic disorders have complex etiopathogenetic mechanisms in which B cells play a central role. The importance of factors stimulating B cells, notably the B-cell activating factor (BAFF) and A proliferation inducing ligand (APRIL) axis is now recognized. BAFF and APRIL are cytokines essential for B-cell proliferation and survival from the immature stages to the development of plasma cells. Their levels are increased in some subsets of patients with autoimmune disorders. Several recent biologic drugs have been developed to block this axis, namely belimumab [already licensed for systemic lupus erythematosus (SLE) treatment], tabalumab, atacicept and blisibimod. Many clinical trials to evaluate the safety and efficacy of these drugs in several autoimmune disorders are ongoing, or have been completed recently. This review updates the information on the use of biologic agents blocking BAFF/APRIL for patients with SLE, rheumatoid arthritis, Sjögren's syndrome and myositis.

Disease specificity of autoantibodies to cytosolic 5'-nucleotidase 1A in sporadic inclusion body myositis versus known autoimmune diseases

OBJECTIVES

The diagnosis of inclusion body myositis (IBM) can be challenging as it can be difficult to clinically distinguish from other forms of myositis, particularly polymyositis (PM). Recent studies have shown frequent presence of autoantibodies directed against cytosolic 5'-nucleotidase 1A (cN-1A) in patients with IBM. We therefore, examined the autoantigenicity and disease specificity of major epitopes of cN-1A in patients with sporadic IBM compared with healthy and disease controls.

METHODS

Serum samples obtained from patients with IBM (n=238), PM and dermatomyositis (DM) (n=185), other autoimmune diseases (n=246), other neuromuscular diseases (n=93) and healthy controls (n=35) were analysed for the presence of autoantibodies using immunodominant cN-1A peptide ELISAs.

RESULTS

Autoantibodies directed against major epitopes of cN-1A were frequent in patients with IBM (37%) but not in PM, DM or non-autoimmune neuromuscular diseases (<5%). Anti-cN-1A reactivity was also observed in some other autoimmune diseases, particularly Sjögren's syndrome (SjS; 36%) and systemic lupus erythematosus (SLE; 20%).

CONCLUSIONS

In summary, we found frequent anti-cN-1A autoantibodies in sera from patients with IBM. Heterogeneity in reactivity with the three immunodominant epitopes indicates that serological assays should not be limited to a distinct epitope region. The similar reactivities observed for SjS and SLE demonstrate the need to further investigate whether distinct IBM-specific epitopes exist.

The role of interleukin-17 in immune-mediated inflammatory myopathies and possible therapeutic implications

The idiopathic inflammatory myopathies are a heterogeneous group of autoimmune muscle disorders with distinct clinical and pathological features and underlying immunopathogenic mechanisms. Traditionally, CD4(+) Th1 cells or CD8(+) cytotoxic effector T cells and type I/II interferons have been primarily implicated in the pathogenesis of the inflammatory myopathies. The presence of IL-17A producing cells in the inflamed muscle tissue of myositis patients and the results of in vitro studies suggest that IL-17A and the Th17 pathway may also have a key role in these diseases. The contribution of IL-17A to other chronic inflammatory and autoimmune diseases has been well established and clinical trials of IL-17A inhibitors are now at an advanced stage. However the precise role of IL-17A in the various forms of myositis and the potential for therapeutic targeting is currently unknown and warrants further investigation.

Inflammatory myopathy with anti-SRP antibodies: case series of a South Australian cohort

Myopathy associated with anti-signal recognition particle (SRP) antibodies is a rare form of myopathy, which is thought to be distinct from classic polymyositis. We sought to determine the demographic, clinical and histopathological features of patients with anti-SRP antibodies. Hence we undertook an audit of patients with histologically-confirmed myositis who had anti-SRP antibodies. Of 144 patients with inflammatory myositis tested for myositis-specific and myositis-associated antibodies between 2007 and 2011 inclusive, five with anti-SRP antibodies were identified. All five were male, four had severe proximal weakness, one was asymptomatic and three had dysphagia. None had cardiovascular involvement. All patients showed isolated anti-SRP positivity and absence of antinuclear antibodies. Muscle histopathology showed variable myofibre necrosis, and most had an inflammatory infiltrate. Majority showed a favorable response to combination immunosuppressive therapy. Myopathy associated with anti-SRP antibodies is clinically heterogeneous in presentation. Muscle histopathology shows a mixture of necrotic and inflammatory features.

Immune mechanisms in polymyositis and dermatomyositis and potential targets for therapy

PM and DM are characterized clinically by weakness and low endurance of skeletal muscle. Other organs are frequently involved, suggesting that idiopathic inflammatory myopathies (IIMs) are systemic inflammatory diseases. Involvement of immune mechanisms in IIMs is supported by the presence of T cells, macrophages and dendritic cells in muscle tissue, by the presence of autoantibodies and by HLA-DR being a strong genetic risk factor. T cells may have direct and indirect toxic effects on muscle fibres, causing muscle fibre necrosis and muscle weakness, but the target of the immune reaction is not known. A newly identified T cell subset, CD28(null) T cells, may have cytotoxic effects in the CD4(+) and CD8(+) T cell phenotype. These cells are apoptosis resistant and may contribute to treatment resistance. Several myositis-specific autoantibodies have been identified, but they are all directed against ubiquitously expressed autoantigens and the specificity of the T cell reactivity is not known. These autoantibodies are associated with distinct clinical phenotypes and some with distinct molecular pathways; e.g. sera from patients with anti-Jo-1 autoantibodies may activate the type I IFN system and these sera also contain high levels of B cell activating factor compared with other IIM subsets. The characterization of patients into subgroups based on autoantibody profiles seems to be a promising way to learn more about the specificities of the immune reactions. Careful phenotyping of infiltrating immune cells in muscle tissue before and after specific therapies and relating the molecular findings to clinical outcome measures may be another way to improve knowledge on specific immune mechanism in IIMs. Such information will be important for the development of new therapies.

Myositis-specific and myositis-associated autoantibody profiles and their clinical associations in a large series of patients with polymyositis and dermatomyositis

OBJECTIVE

To analyze the prevalence of myositis-specific and myositis-associated autoantibodies and their clinical correlations in a large series of patients with dermatomyositis/polymyositis.

METHOD

This cross-sectional study enrolled 127 dermatomyositis cases and 95 polymyositis cases. The disease-related autoantibody profiles were determined using a commercially available blood testing kit.

RESULTS

The prevalence of myositis-specific autoantibodies in all 222 patients was 34.4%, whereas myositis-associated autoantibodies were found in 41.4% of the patients. The most frequently found autoantibody was anti-Ro-52 (36.9%), followed by anti-Jo-1 (18.9%), anti-Mi-2 (8.1%), anti-Ku (4.1%), anti-SRP (3.2%), anti-PL-7 (3.2%), anti-PL-12 (2.7%), anti-PM/Scl75 (2.7%), and anti-PM/Scl100 (2.7%). The distributions of these autoantibodies were comparable between polymyositis and dermatomyositis, except for a higher prevalence of anti-Jo-1 in polymyositis. Anti-Mi-2 was more prevalent in dermatomyositis. Notably, in the multivariate analysis, anti-Mi-2 and anti-Ro-52 were associated with photosensitivity and pulmonary disorders, respectively, in dermatomyositis. Anti-Jo-1 was significantly correlated with pulmonary disorders in polymyositis. Moreover, anti-Ro-52 was associated with anti-Jo-1 in both diseases. No significant correlation was observed between the remaining autoantibodies and the clinical and/or laboratory findings.

CONCLUSIONS

Our data are consistent with those from other published studies involving other populations, although certain findings warrant consideration. Anti-Ro-52 and anti-Jo-1 were strongly associated with one another. Anti-Ro-52 was correlated with pulmonary disorders in dermatomyositis, whereas anti-Jo-1 was correlated with pulmonary alterations in polymyositis.

Autoantibodies to cytosolic 5'-nucleotidase 1A in inclusion body myositis

OBJECTIVE

Sporadic inclusion body myositis (sIBM) is an inflammatory myopathy characterized by both degenerative and autoimmune features. In contrast to other inflammatory myopathies, myositis-specific autoantibodies had not been found in sIBM patients until recently. We used human skeletal muscle extracts as a source of antigens to detect autoantibodies in sIBM and to characterize the corresponding antigen.

METHODS

Autoantibodies to skeletal muscle antigens were detected by immunoblotting. The target antigen was immunoaffinity-purified from skeletal muscle extracts and characterized by mass spectrometry. A cDNA encoding this protein was cloned and expressed in vitro, and its recognition by patient sera was analyzed in an immunoprecipitation assay. Epitopes were mapped using microarrays of overlapping peptides.

RESULTS

An Mr 44,000 polypeptide (Mup44) was frequently targeted by sIBM autoantibodies. The target protein was purified, and subsequent mass spectrometry analysis revealed that Mup44 is the cytosolic 5'-nucleotidase 1A (cN1A). By immunoprecipitation of recombinant cN1A, high concentrations of anti-Mup44 autoantibodies were detected in 33% of sIBM patient sera, whereas their prevalence in dermatomyositis, polymyositis, and other neuromuscular disorders appeared to be rare (4.2%, 4.5%, and 3.2%, respectively). Low concentrations of anti-Mup44 antibodies were found in myositis as well as other neuromuscular disorders, but not in healthy controls. Three major autoepitope regions of cN1A were mapped by using microarrays containing a set of overlapping peptides covering the complete cN1A amino acid sequence.

INTERPRETATION

Anti-Mup44 autoantibodies, which are targeted to cN1A, represent the first serological biomarker for sIBM and may facilitate the diagnosis of this type of myositis.

Oxidative stress-induced modifications of histidyl-tRNA synthetase affect its tRNA aminoacylation activity but not its immunoreactivity

The aminoacyl-tRNA synthetases are ubiquitously expressed enzymes that catalyze the esterification of amino acids to their cognate tRNAs. Autoantibodies against several aminoacyl-tRNA synthetases are found in autoimmune polymyositis and dermatomyositis patients. Because necrosis is often found in skeletal muscle biopsies of these patients, we hypothesized that cell-death-induced protein modifications may help in breaking immunological tolerance. Since cell death is associated with oxidative stress, the effect of oxidative stress on the main myositis-specific autoantibody target Jo-1 (histidyl-tRNA synthetase; HisRS) was studied in detail. The exposure of Jurkat cells to hydrogen peroxide resulted in the detection of several oxidized methionines and one oxidized tryptophan residue in the HisRS protein, as demonstrated by mass spectrometry. Unexpectedly, the tRNA aminoacylation activity of HisRS appeared to be increased upon oxidative modification. The analysis of myositis patient sera did not lead to the detection of autoantibodies that are specifically reactive with the modified HisRS protein. The results of this study demonstrate that the Jo-1/HisRS autoantigen is modified under oxidative stress conditions. The consequences of these modifications for the function of HisRS and its autoantigenicity are discussed.

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.

Rituximab treatment in patients with refractory inflammatory myopathies

OBJECTIVE

To assess the efficacy of rituximab on disease activity and muscle strength in patients with inflammatory myopathies refractory to conventional therapy. METHODS; Thirteen patients were treated with rituximab 1000 mg i.v., twice, with a 2-week interval and followed for a median of 27 months. Primary outcomes were disease activity measured by creatine phosphokinase (CPK), lactate dehydrogenase (LDH) levels and muscle strength measured by hand-held dynamometry and manual muscle testing (MMT). Secondary outcomes were improvement in secondary laboratory measures, global assessment of general health, disease activity and pain, CS dose, functional ability, health-related quality of life and safety. Retreatment with rituximab was conducted if disease activity relapsed. RESULTS; The median levels of CPK and LDH were significantly reduced by 93.2 and 39.8%, respectively, compared with baseline after 34.6 months. The median muscle strength measured by hand-held dynamometry was significantly improved by 21.5% after 24 months. The median increase in muscle strength measured with MMT was 7.0% after 24 months of follow-up, although this did not reach statistical significance. Secondary outcomes improved as well. CONCLUSION; Rituximab is an effective treatment in refractory inflammatory myopathies, showing a decrease in CPK and LDH, an increase in muscle strength and improvement in scores of disease activity, general health, functional ability and health related quality of life with sustained effect during a median of 27.1 months of follow-up.

Observations on the classification of the inflammatory myopathies

This brief review considers historical approaches to the classification of the inflammatory myopathies. The last 25 years have seen advances in our knowledge of the underlying immune mechanism but the initial trigger for the idiopathic inflammatory myopathies remains unknown. Existing classifications have their limitations, but with the absence of a "gold standard" a definitive classification is not yet possible. Despite these problems, a working classification is possible that is valuable for everyday clinical practice.

Cardiological features in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) represent a heterogeneous group of autoimmune systemic diseases characterized by chronic muscle weakness and inflammatory cell infiltrates in skeletal muscle. The most frequent IIMs, such as adult-onset polymyositis and dermatomyositis, display a wide range of clinical manifestations other than myositis, including skin changes, Raynaud's phenomenon and interstitial lung disease. Cardiac involvement is now well recognized as a clinically important manifestation in patients with polymyositis or dermatomyositis, although its actual frequency is still uncertain. Cardiovascular complications represent one of the most frequent causes of death in myositis, apart from cancer and lung involvement. Despite the fact that clinical manifestations are relatively rare, asymptomatic cardiovascular features are frequently reported in patients with polydermatomyositis and dermatomyositis. They are characterized by isolated electrocardiographic changes, valve disease, coronary vasculitis, ischemic abnormalities, heart failure and myocarditis. Chronic inflammation producing myocyte degeneration, tissues fibrosis and vascular alterations can explain the majority of reported cardiac features in myositic patients. Although previous works reported an association between heart involvement and some myositis-specific autoantibodies (namely anti-signal recognition particle), electrocardiography, echocardiography and, where necessary, heart magnetic resonance remain the mainstay for diagnosing and monitoring myocardial inflammation in these diseases. Anyway, a complete multiorgan assessment and a careful analysis of autoantibodies should be performed in every patient in order to define any possible distinct disease entities with different prognosis within the spectrum of IIMs.

Clinical cardiac involvement in idiopathic inflammatory myopathies: a systematic review

BACKGROUND

Idiopathic inflammatory myopathies (IIM) presenting with diffuse skeletal muscular inflammation and cardiac involvement is one of the major causes of clinical deterioration. Our purpose was to observe the frequency of various reported clinical cardiac afflictions, cardiovascular mortality and its most important contributors in the IIM population.

METHODS

MEDLINE database was searched from 1977 through 2009. Articles reporting objective evidence of cardiac involvement were assessed. Patients were included if they satisfied Bohan and Peter criteria for definite or probable diagnosis of IIM. The review conforms to the criteria of the new PRISMA statement of preferred reporting items for systematic reviews and meta-analyses.

RESULTS

Thirty-three out of 90 articles reported cardiac data. Twelve were case reports, while 21 articles were either cohort studies or case series. Angina was reported in 7% of cumulative prospective cohort. Dysrhythmias were seen in 31.8% of electrocardiograms. Diastolic dysfunction was the most common echocardiographic finding. Congestive heart failure was reported in 5.6% of the prospective cohort and was the most common cause of death accounting for 21% of total cardiac mortality. Myocarditis was the most common feature in reported pathology literature (38%), followed by focal myocardial fibrosis (22%).

CONCLUSION

Cardiac involvement is an important cause of morbidity and mortality in patients with IIM. Myocardial fibrosis puts the patient at risk for systolic or diastolic heart failure and dysrhythmias. This review, therefore, suggests the importance of early and comprehensive cardiac evaluation in IIM population. Confirmation of these findings will require prospective studies of consecutive patients with long-term follow-up.

[How can we diagnose and better understand inflammatory myopathies? The usefulness of auto-antibodies]

The inflammatory myopathies are a group of quite proteiform, systemic auto-immune diseases which include polymyositis, dermatomyositis and inclusion body myopathies. To facilitate the diagnosis, classification criteria (Bohan and Peter, 1975) have been proposed, based essentially on clinical criteria. In addition, over the past fifteen years, auto-antibodies characterizing certain forms of inflammatory myopathy have been identified. One distinguishes schematically: auto-antibodies specific for myositis and auto-antibodies sometimes associated with myositis. Concerning the myositis specific auto-antibodies (MSA), schematically there are a dozen specificities which are classed according to the cellular distribution of the auto-antigen. The most characteristic are certainly the auto-antibodies directed against cytoplasmic antigens: the anti-tRNA synthetases (anti-Jo-1 (PL-1), anti-PL-7, PL-12, EJ, OJ, JS, KS, ZO, YRS), anti-SRP (signal recognition particle), anti-Mas and anti-KJ, anti-Fer (eEF1), anti-Wa and anti-CADM p140. Other auto-antibodies are directed against nuclear auto-antigens: the anti-Mi-2, anti-PMS (PMS1, PMS2) and related antibodies (MLH1, DNA PKcs…), anti-56 kDa, anti-MJ (NXP-2), anti-SAE and anti-p155/p140 (TIF-1γ). Concerning the auto-antibodies sometimes associated with myositis (myositis associated auto-antibodies or MAA), they can also be observed in other auto-immune diseases. These auto-antibodies are directed against nuclear or nucleolar auto-antigens: the anti-PM-Scl, anti-Ku, anti-RNP (U1 RNP and U2 RNP, U4/U6 RNP and U5 RNP), anti-Ro 52 kDa and more rarely, anti-Ro 60 kDa and anti-La. The auto-antibodies related to myositis are biological tools which are of interest in two main ways. They have allowed us to sort out the nosology of these inflammatory myopathies, in particular by defining anti-tRNA synthetase syndrome. It now remains to determine how they might be employed to complement the classical clinico-biological diagnostic criteria. In this perspective, it will be indispensable first of all to diffuse and standardize the methods of detection. The latter are at the moment very heterogeneous as they use techniques and above all antigenic preparations which are extremely diverse. These antibodies are also very interesting "physiopathological" tools to try to better understand myositis. The example of anti-tRNA synthetases is a particularly original model of auto-immunization, which allows one to establish a link between an initial, probably poorly specific muscular lesion and the appearance of auto-antibodies which maintain and aggravate the muscular disease.

Dermatomyositis and polymyositis: Clinical presentation, autoantibodies, and pathogenesis

Dermatomyositis (DM) and polymyositis (PM) are autoimmune myopathies characterized clinically by proximal muscle weakness, muscle inflammation, extramuscular manifestations, and frequently, the presence of autoantibodies. Although there is some overlap, DM and PM are separate diseases with different pathophysiological mechanisms. Furthermore, unique clinical phenotypes are associated with each of the myositis-specific autoantibodies (MSAs) associated with these disorders. This review will focus on the clinical features, pathology, and immunogenetics of PM and DM with an emphasis on the importance of autoantibodies in defining unique phenotypes and, perhaps, as clues to help elucidate the mechanisms of disease.

Myositis-specific and myositis-associated antibodies in overlap myositis in comparison to primary dermatopolymyositis: Relevance for clinical classification: retrospective study of 169 patients

OBJECTIVE

The current study was performed in order to determine the prevalence of different myositis-specific and myositis-associated antibodies, as well as their association with clinical characteristics, disease course and response to therapy in 169 Hungarian patients with idiopathic inflammatory myopathy.

METHODS

Sera of 130 primary and 39 overlap myositis including systemic sclerosis (13), rheumatoid arthritis (12), systemic lupus erythematosus (5) and Sjögren's syndrome (9) cases were analyzed. Antinuclear antibody, scleroderma-associated antibodies (anti-centromere, anti-topoisomerase I), anti-Jo-1, anti-PL-7, anti-PL-12, anti-Mi-2, anti-SRP and anti-PM-Scl, anti-Ku, anti-SS-A, anti-SS-B, anti-U1snRNP were tested. Autoantibody results were compared with clinical characteristics, disease course of overlap versus primary myositis patients, as well as with response to therapy.

RESULTS

Associated connective tissue disease occurred in 23.1% of the patients. Myositis-associated antibodies were found in 8.5% of primary myositis patients, indicating that 11 additional primary myositis patients (23% vs. 29.6%) can be classified as overlap in all cohort according to the newly proposed diagnostic criteria. Polymyositis was found to be the most common myositis form in overlap myositis (87.2%), while scleroderma was the most common disease associated (33.3%). ANA was positive in 25.4% of primary and in 61.5% of overlap myositis cases. Altogether 39.6% of myositis patients (n=67) had autoantibodies, most commonly anti Jo-1 (18.3%) correlating with a polycyclic disease course.

CONCLUSION

Inclusion of myositis-specific and associated antibodies into the newly proposed diagnostic criteria for inflammatory myopathies is of great importance in order to determine subclasses and to introduce adequate therapy in time.

[Myositis-specific autoantibodies]

BACKGROUND

Myositis-specific antibodies (MSA) are autoantibodies that are almost exclusively detected in idiopathic inflammatory myopathies (IIM). This article provides an overview of these autoantibodies and how they can be used clinically to identify subgroups of IIM.

MATERIAL AND METHODS

The article is based on a non-systematic literature review and our own experience.

RESULTS

MSA can be detected in up to 50 % of patients with IIM. Patients with anti-synthetase antibodies have a constellation of clinical findings termed "the anti-synthetase syndrome", in which interstitial lung disease dominates the clinical picture. Anti-Mi2 antibodies is another myositis-specific antibody. Patients with anti-Mi2 antibodies often have classical dermatomyositis, while the anti-SRP antibody identifies patients with severe myopathy, poor response to treatment with corticosteroids and histological findings of muscle cell necrosis - often lacking inflammatory infiltrates. The newly detected anti-CADMp140 appears to be associated with amyopathic or hypomyopathic dermatomyositis, previously called dermatomyositis sine myositis. Anti-p155 antibodies are most often found in patients who also have cancer.

INTERPRETATION

Myositis-specific antibodies may be useful for identification of clinical subgroups of IIM and can thereby affect the choice of medical treatment.

Clinical implications of autoantibody screening in patients with autoimmune myositis

OBJECTIVE

To evaluate the clinical usefulness of serum autoantibody profiling in patients with autoimmune myositis.

METHODS

We retrospectively studied 74 consecutive patients: 68 had definite or probable myositis according to Bohan-Peter criteria, six suffered from antisynthetase syndrome with subclinical myopathy. Myositis specific antibodies (MSA) (anti-ARS, -SRP, -Mi-2) were determined by RNA immunoprecipitation or immunoblot, myositis associated antibodies (MAA) (anti-RoRNP, -U1RNP, -PM/Scl, -Ku) by immunoblot.

RESULTS

Forty-three patients (58%) were positive for MSA: anti-Jo-1 in 15/27 polymyositis (PM) (55%), 4/33 dermatomyositis (DM) (12%), 1/8 overlap (12%) and 2/6 antisynthetase syndrome (33%); anti-ARS non-Jo-1 in 1/27 PM (4%), 2/33 DM (6%) and 4/6 antisynthetase syndrome (67%); anti-Mi-2 in 1/27 PM (4%) and 11/33 DM (33%); anti-SRP in 3/27 PM (11%) and 1/33 DM (3%). One patient was anti-Jo-1/Mi-2 positive, one anti-Jo-1/SRP positive. Moreover, 27 patients (36%) were positive for MAA: anti-Ro/SSA in 8/27 PM (30%), 7/33 DM (21%), 1/8 overlap (12%), and 3/6 antisynthetase syndrome (50%); anti-U1RNP in 1/27 PM (3.7%), 1/33 DM (3%), and 2/8 overlap (25%); anti-PM/Scl in 2/8 overlap (25%), anti-Ku in 2/8 overlap (25%). Anti-Jo-1 was predominantly associated with PM, anti-Mi-2 was almost exclusively found in DM patients. Anti-ARS antibodies were closely associated with interstitial lung disease and polyarthritis; notably, anti-ARS non-Jo-1 was more frequent in patients without overt muscle alterations. Anti-Ro/SSA antibody was not associated with any disease subset, but significantly more frequent in antisynthetase syndrome.

CONCLUSIONS

Searching for MSA and MAA in patients with autoimmmune myositis is recommended because of its diagnostic and clinical value. Anti-ARS non-Jo-1 antibodies seem to preferentially target patients with pulmonary fibrosis without overt myopathy.

Myopathy associated with anti-signal recognition peptide antibodies: clinical heterogeneity contrasts with stereotyped histopathology

We report three patients with anti-signal recognition particle antibodies who had different presenting clinical pictures, mimicking acute polymyositis, limb-girdle muscular dystrophy, and acute rhabdomyolysis. Muscle biopsies typically showed necrotizing myopathy with little or no inflammation and deposits of membrane attack complex (C5b-9) in endomysial capillaries. The clinical course was severe in two patients and mild in one. The combination of corticosteroid with either an immunosuppressive agent or intravenous immunoglobulins was required to improve the condition of these patients.

Contribution of autoantibodies to the diagnosis and nosology of inflammatory muscle disease

The myositides are systemic autoimmune conditions of which the most important are polymyositis, dermatomyositis, and inclusion body myositis. In addition to the classic clinical diagnostic criteria, myositis-specific autoantibodies were identified about 15 years ago. Among the dozen or so myositis-specific autoantibodies reported to date, the most characteristic are directed against cytoplasmic antigens, such as tRNA synthetase (Jo-1 or PL-1, PL-7, PL-12, EJ, OJ, JS, and KS), signal-recognition particle (SRP), Mas, KJ, Fer (eEF1), and Wa. Antibodies to nuclear antigens include anti-Mi-2, anti-PMS (PMS1, and PMS2), and related antibodies (MLH1, DNA protein kinase catalytic subunit (DNA PKCS)...), and anti-56 kDa. Myositis-associated antibodies are not specific but may be found in patients with myositis. They are directed to nuclear or nucleolar antigens such as PM-Scl, Ku, RNP (U1-RNP and U2-RNP, U4/U6-RNP, and U5-RNP), Ro 52 kDa and, more rarely, Ro 60 kDa and La. Myositis-specific antibodies have proved useful on two fronts. They have improved the diagnosis of myositis by leading to the identification of characteristic clinical patterns, such as anti-synthetase syndrome. The place of autoantibodies alongside classic clinical and laboratory criteria remains to be determined, however. First, standardized assays will have to be developed to replace current detection methods, which use widely variable techniques and antigen preparations. Myositis-specific antibodies have also shed light on the pathogenesis of myositis. For instance, the development of antibodies to tRNA synthetases constitutes an original autoimmunity model that shows how muscle damage, probably of a nonspecific nature, can lead to the production of autoantibodies that perpetuate and aggravate the muscle lesions.

Myositis-specific and myositis-associated antibodies in a series of eighty-eight Mediterranean patients with idiopathic inflammatory myopathy

OBJECTIVE

To determine the prevalence of myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs) and their clinical and immunogenetic correlations in Mediterranean patients with idiopathic inflammatory myopathies.

METHODS

Sera from 88 patients were studied for MSAs and MAAs by RNA and protein immunoprecipitation. HLA typing was performed by sequence-specific primer- and sequence-specific oligonucleotide-polymerase chain reaction and serology. Statistical analyses were performed with Student's t-test and Fisher's exact test. Cumulative survival probabilities were estimated by the Kaplan-Meier method and Cox regression analysis.

RESULTS

Twenty-eight patients (30%) had MSAs, most commonly antisynthetase antibodies (23.9%). Six patients (7.5%) had anti-Mi-2 antibodies. No anti-signal recognition particles were found. Arthritis, mechanic's hands, interstitial lung disease, and sicca syndrome were more prevalent in patients with antisynthetase antibodies. Dysphagia and the need for more treatment courses were more frequent in patients who were anti-Mi-2 positive. Forty-three patients (48%) had MAAs, 20 (22%) with anti-Ro 60 and 18 (20.4%) with anti-Ro 52. Ten patients (11.4%) were positive for anti-PM-Scl, 6 (6.8%) for anti-RNP, and 1 for anti-Ku antibodies. Patients with PM-Scl, RNP, or Ro antibodies were more often classified as having overlap syndrome. Immunogenetic studies found a significant association between HLA-DR3 and the presence of antisynthetase antibodies (P = 0.049), anti-PM-Scl antibodies (P = 0.017), and interstitial lung disease (P = 0.03). No statistically significant differences in mortality, survival, or clinical course were observed between patients positive for MSAs or MAAs and the remaining patients.

CONCLUSION

These results are consistent with those from other published series, although some differences warrant consideration. Autoantibody studies may be useful for defining more homogeneous groups of patients with idiopathic inflammatory myopathies.