Autoantibody profiles in the sera of European patients with myositis

Pulmonary complications of inflammatory myopathy

Pulmonary complications cause significant morbidity and mortality in the idiopathic inflammatory myopathies. Advances in biomarker discovery have facilitated clinical phenotyping, allowing investigators to better define at-risk patient subsets and to potentially gauge disease activity. This serologic characterization has complemented more traditional assessment tools. Pharmacologic management continues to rely on the use of corticosteroids, often in combination with additional immunosuppressive agents. The rarity of myositis-associated interstitial lung disease and lack of controlled trials have limited analyses of treatment efficacy, mandating the development of standardized outcome measures and improvement of data sharing between disciplines.

[Dermatomyositis-specific antibodies]

BACKGROUND

Idiopathic inflammatory myopathies are chronic systemic autoimmune diseases characterized by symmetrical proximal muscle weakness. The clinicopathological subdivision nowadays appears to be obsolete which is why the immunoserological classification has been developed.

OBJECTIVES

Dermatomyositis represents one the most important subsets of idiopathic inflammatory myopathy and dermatomyositis-specific autoantibodies play a significant role in this subset. The aim of this article was to present these autoantibodies with the help of the literature.

METHODS

This article presents the most important information about dermatomyositis including not only the classical anti-Mi-2 autoantibody but also the recently detected anti-TIF1γ, anti-NXP2, anti-SAE and anti-MDA5 autoantibodies. The focus is on the frequency of these autoantibodies, the associated symptoms in adult and juvenile dermatomyositis cases and some special aspects from the literature.

RESULTS

All of the studies confirmed that these autoantibodies are particularly detectable in dermatomyositis. The results from the literature have recently shown that the frequency of the autoantibodies detected in juvenile cases is higher than the frequency of traditional autoantibodies (e.g. anti-Jo-1, anti-Mi-2 and anti-SRP).

CONCLUSION

It is useful to detect these autoantibodies in order to be able to make a better assessment of the clinical symptoms and prognosis during the course of the disease.

Anti-signal recognition particle autoantibody ELISA validation and clinical associations

OBJECTIVE

The aim of this study was to develop and validate a quantitative anti-signal recognition particle (SRP) autoantibody serum ELISA in patients with myositis and longitudinal association with myositis disease activity.

METHODS

We developed a serum ELISA using recombinant purified full-length human SRP coated on ELISA plates and a secondary antibody that bound human IgG to detect anti-SRP binding. Protein immunoprecipitation was used as the gold standard for the presence of anti-SRP. Serum samples from three groups were analysed: SRP(+) myositis subjects by immunoprecipitation, SRP(-) myositis subjects by immunoprecipitation and non-myositis controls. The ELISA's sensitivity, specificity, positive predictive value and negative predictive value were evaluated. Percentage agreement and test-retest reliability were assessed. Serial samples from seven SRP immunoprecipitation-positive subjects were also tested, along with serum muscle enzymes and manual muscle testing.

RESULTS

Using immunoprecipitation, we identified 26 SRP(+) myositis patients and 77 SRP(-) controls (including 38 patients with necrotizing myopathy). Non-myositis control patients included SLE (n = 4) and SSc (n = 7) patients. Anti-SRP positivity by ELISA showed strong agreement (97.1%) with immunoprecipitation (κ = 0.94). The sensitivity, specificity, positive predictive value, and negative predictive value of the anti-SRP ELISA were 88, 100, 100 and 96, respectively. The area under the curve was 0.94, and test-retest reliability was strong (r = 0.91, P < 0.001). Serial samples showed that anti-SRP levels paralleled changes in muscle enzymes and manual muscle testing.

CONCLUSION

We developed a quantitative ELISA for detecting serum anti-SRP autoantibodies and validated the assay in myositis. Longitudinal assessment of SRP levels by ELISA may be a useful biomarker for disease activity.

Brief report: antisynthetase syndrome-associated myocarditis

BACKGROUND

The antisynthetase (AS) syndrome is characterized by autoimmune myopathy, interstitial lung disease, cutaneous involvement, arthritis, fever, and antibody specificity. We describe 2 patients with AS syndrome who also developed myocarditis, depressed biventricular function, and congestive heart failure.

METHODS AND RESULTS

Both patients were diagnosed with AS syndrome based on clinical manifestations, detection of serum AS antibodies, and myositis confirmation with the use of skeletal muscle magnetic resonance imaging and skeletal muscle biopsy. In addition, myocarditis resulting in heart failure was confirmed with the use of cardiac magnetic resonance imaging and from endomyocardial biopsy findings. After treatment for presumed AS syndrome-associated myocarditis, one patient recovered and the other patient died.

CONCLUSIONS

AS syndrome is a rare entity with morbidity and mortality typically attributed to myositis and lung involvement. This is the first report of AS syndrome-associated myocarditis leading to congestive heart failure in 2 patients. Given the potentially fatal consequences, myocarditis should be considered in patients with AS syndrome presenting with heart failure.

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.

Exploring necrotizing autoimmune myopathies with a novel immunoassay for anti-3-hydroxy-3-methyl-glutaryl-CoA reductase autoantibodies

Introduction

Necrotizing autoimmune myopathies (NAM) have recently been defined as a distinct group of severe acquired myopathies, characterized by prominent myofiber necrosis without significant muscle inflammation. Because of the lack of appropriate biomarkers, these diseases have been long misdiagnosed as atypical forms of myositis. NAM may be associated to autoantibodies directed against signal recognition particle (SRP) or 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR). The objective of this work was to quantify anti-HMGCR autoantibodies in patients with suspicion of NAM through the development of a new addressable laser bead immunoassay (ALBIA).

Methods

Recombinant HMGCR C-domain was bound to fluorescent beads. After incubation with serum, autoantibodies were revealed using class- or subclass-specific anti-human immunoglobulin G (IgG) antibodies. Anti-HMGCR levels were assayed in 150 patients with suspicion of NAM, 142 controls with different inflammatory/autoimmune diseases and 100 healthy donors. Inhibition with free recombinant HMGCR and immunoprecipitation experiments confirmed test specificity. Reproducibility and repeatability were determined from sera with various levels of anti-HMGCR autoantibodies. A multiplex assay (ALBIA-NAM) was also developed to permit the simultaneous quantification of anti-HMGCR and anti-signal recognition particle autoantibodies.

Results

No controls scored positive. Of 150 patients with suspicion of NAM, 24% were positive for anti-HMGCR autoantibodies with levels ranging from 24 to 2,656 AU/mL. Anti-HMGCR positivity could be associated to a cytoplasmic pattern in immunofluorescence assay on HEp-2 cells. Anti-HMGCR-positive patients had high creatine kinase (CK) levels (mean 6,630 IU/L) and only 40% of them had been exposed to statins. Multiplex ALBIA-NAM was equally as effective as monoplex anti-HMGCR and anti-SRP ALBIA.

Conclusions

Both monoplex ALBIA-HMGCR and multiplex ALBIA-NAM reliably detect and quantify anti-HMGCR autoantibodies. A positive result allows ascribing patients with a necrotizing myopathy to an autoimmune form. Anti-HMGCR autoantibodies may be found in patients who have not taken statins.

The multicenter study of a new assay for simultaneous detection of multiple anti-aminoacyl-tRNA synthetases in myositis and interstitial pneumonia

OBJECTIVE

Autoantibodies to aminoacyl-tRNA synthetases (ARSs) are useful in the diagnosis of idiopathic inflammatory myopathy (IIM) with interstitial pneumonia (IP). We developed an enzyme-linked immunosorbent assay (ELISA) system using a mixture of recombinant ARS antigens and tested its utility in a multicenter study.

METHODS

We prepared six recombinant ARSs: GST-Jo-1, His-PL-12, His-EJ and GST-KS expressed in Escherichia coli, and His-PL-7 and His-OJ expressed in Hi-5 cells. After confirming their antigenic activity, with the exception of His-OJ, we developed our ELISA system in which the five recombinant ARSs (without His-OJ) were mixed. Efficiency was confirmed using the sera from 526 Japanese patients with connective tissue disease (CTD) (IIM n = 250, systemic lupus erythematosus n = 91, systemic sclerosis n = 70, rheumatoid arthritis n = 75, Sjögren's syndrome n = 27 and other diseases n = 13), 168 with idiopathic interstitial pneumonia (IIP) and 30 healthy controls collected from eight institutes. IIPs were classified into two groups; idiopathic pulmonary fibrosis (IPF) (n = 38) and non-IPF (n = 130). RESULTS were compared with those of RNA immunoprecipitation.

RESULTS

Sensitivity and specificity of the ELISA were 97.1% and 99.8%, respectively when compared with the RNA immunoprecipitation assay. Anti-ARS antibodies were detected in 30.8% of IIM, 2.5% of non-myositis CTD, and 10.7% of IIP (5.3% of IPF and 12.3% of non-IPF). Anti-ARS-positive non-IPF patients were younger and more frequently treated with glucocorticoids and/or immunosuppressants than anti-ARS-negative patients.

CONCLUSION

A newly established ELISA detected anti-ARS antibodies as efficiently as RNA immunoprecipitation. This system will enable easier and wider use in the detection of anti-ARS antibodies in patients with IIM and IIP.

[Autoantibody profile in myositis]

Patients suffering from muscular symptoms or with an increase of creatine kinase levels may present a myopathy. In such situations, clinicians have to confirm the existence of a myopathy and determine if it is an acquired or a genetic muscular disease. In the presence of an acquired myopathy after having ruled out an infectious, a toxic agent or an endocrine cause, physicians must identify which type of idiopathic myopathy the patient is presenting: either a myositis including polymyositis, dermatomyositis, and inclusion body myositis, or an immune-mediated necrotizing myopathy. Histopathology examination of a muscle biopsy is determinant but detection of autoantibody is now also crucial. The myositis-specific antibodies and myositis-associated antibodies lead to a serologic approach complementary to the histological classification, because strong associations of myositis-specific antibodies with clinical features and survival have been documented. The presence of anti-synthetase antibodies is associated with an original histopathologic pattern between polymyositis and dermatomyositis, and defines a syndrome where interstitial lung disease drives the prognosis. Anti-MDA-5 antibody are specifically associated with dermatomyositis, and define a skin-lung syndrome with a frequent severe disease course. Anti-TIF1-γ is also associated with dermatomyositis but its presence is frequently predictive of a cancer association whereas anti-MI2 is associated with the classical dermatomyositis. Two specific antibodies, anti-SRP and anti-HMGCR, are observed in patients with immune-mediated necrotizing myopathies and may be very useful to distinguish acquired myopathies from dystrophic muscular diseases in case of a slow onset and to allow the initiation of effective therapy.

[Necrotizing myopathies: From genetic to acquired forms]

Necrotizing myopathies (NM) are defined by histological features. Muscle biopsy demonstrates marked muscle necrosis with regeneration, with little or an absence of inflammatory infiltrate. Histological pattern of NM is unspecific and can be encountered in diverse conditions as acquired myopathies and muscular dystrophies. Among acquired forms of NM, necrotizing autoimmune myopathy (NAM) is a recently recognized sub-group of the idiopathic inflammatory myopathies. Classically, patients present with a subacute severe proximal myopathy, associated with a markedly elevated creatine kinase level, usually greater than 10 times the upper limit of normal. Nevertheless, the clinical presentation can be misleading, with chronic course mimicking muscular dystrophy. Different forms of NAM can be distinguished with various underlying inciting conditions, including autoantibodies to the SRP, autoantibodies to the HMG-CoA reductase, association to connective tissue disease or underlying malignancy. Other associated conditions need yet to be identified. To confirm a diagnosis of NAM, other causes of NM should be excluded as toxic myopathies, muscular dystrophies and other inflammatory myopathies with a misleading histological pattern. NAM is a rare condition but is probably underdiagnosed. Both clinicoserologic and pathologic data must be taken into account to improve this diagnosis. We propose guidelines for diagnosis of NAM according to clinical course, to be used in clinical practice.

Common and specific associations of anti-SSA/Ro60 and anti-Ro52/TRIM21 antibodies in systemic lupus erythematosus

Little information exists about the association of anti-SSA/Ro60 and anti-Ro52/TRIM21 with systemic lupus erytematosus (SLE) features. In this work, we analysed the associations of both anti-Ro reactivities with clinical and immunological manifestations in 141 SLE patients. Photosensitivity and xerophtalmia/xerostomia were found to be positively associated with both anti-SSA/Ro60 (P = 0.024 and P = 0.019, resp.) and anti-Ro52/TRIM21 (P = 0.026 and P = 0.022, resp.). In contrast, a negative association was detected regarding anti-phospholipid antibodies, anti-SSA/Ro60 having a stronger effect (P = 0.014) than anti-Ro52/TRIM21. Anti-SSA/Ro60 showed a specific positive association with hypocomplementemia (P = 0.041), mainly with low C4 levels (P = 0.008), whereas anti-Ro52/TRIM21 was found to be positively associated with Raynaud's phenomenon (P = 0.026) and cytopenia (P = 0.048) and negatively associated with anti-dsDNA (P = 0.013). Lymphocytes are involved in the relationship between anti-Ro52/TRIM21 and cytopenia since positive patients showed lower cell levels than negative patients (P = 0.036). In conclusion, anti-SSA/Ro60 and anti-Ro52/TRIM21 showed both common and specific associations in SLE. These data thus increase evidence of the different associations of the two anti-Ro specificities even in a particular disease.

[Usefulness of autoantibodies for the diagnosis of autoimmune myopathies]

INTRODUCTION

Idiopathic myopathies are a group of acquired muscular diseases considered as autoimmune disorders. Characteristic histopathologic features allow the classification into myositis (polymyositis, dermatomyositis, and inclusion body myositis) and immune-mediated necrotizing myopathies. But overlapping histological features may be observed between different idiopathic myopathies and even between acquired and genetic muscular diseases. In the group of idiopathic myopathies important discrepancies can be observed concerning extra-muscular involvement and prognosis.

STATE OF ART

The discovery of myositis-specific antibodies and myositis-associated antibodies has led to a serologic approach complementary to histological classification, because striking associations of myositis-specific antibodies with clinical features and survival were observed. Here we reviewed the myositis-specific antibodies including autoantibodies directed against the aminoacyl tRNA-synthetase enzymes, the Mi-2 protein and the signal recognition particle, and the main myositis-associated autoantibodies, that can be tested in clinical practice.

PERSPECTIVES

We will also focus on newly described dermatomyositis-associated antibodies (directed against: transcription intermediary factor 1 family proteins, small ubiquitin-like modifier activating enzyme, and melanoma differentiation-associated gene 5), and immune-mediated necrotizing myopathy-associated antibodies (directed against HMGcoA-reductase).

CONCLUSION

Myositis-specific antibodies and myositis-associated antibodies are useful for the diagnosis of forms of autoimmune myopathies with distinct clinical features. They may help to define patients into clinical syndromes with specific outcomes and thus influence treatment strategies.

Idiopathic inflammatory myopathies

Inflammatory myopathies are chronic, immune-mediated diseases characterised by progressive proximal muscle weakness. They encompass a variety of syndromes with protean manifestations. The diagnosis is based on Bohan and Peter's classification criteria, which nowadays seem to be obsolete. Our increasing knowledge about the risk factors, genetic susceptibility and immunological pathways in the disease mechanism leads to the establishment of a new, immunogenetically and serologically validated diagnostic criteria system. The treatment of idiopathic inflammatory myopathy is also a complex task requiring much experience. The aims of therapy are to increase muscle strength, prevent the development of contractures and manage the systemic manifestations of the disease. The most important one is the early detection of diseases and patients' immunological control in special centres. Using the basis therapeutic drugs temporary or permanent remission can be achieved, which improves patientsG' quality of life and functional ability. Rehabilitation and physiotherapy in the remission period may significantly improve the outcome of patients with functional disorders. The introduction of new biological therapies further allows us to control the myositis patients' state more effectively. The aim of this review is to summarise our knowledge about clinical symptoms, pathomechanism, as well as genetic, serologic and environmental risk factors. We would also like to present the way to diagnosis and the latest research about diagnostic criteria system, proposed outcome measures and therapeutic possibilities.

Implications in the difference of anti-Mi-2 and -p155/140 autoantibody prevalence in two dermatomyositis cohorts from Mexico City and Guadalajara

Introduction

Autoantibodies and clinical manifestations in polymyositis/dermatomyositis (PM/DM) are affected by both genetic and environmental factors. The high prevalence of DM and anti-Mi-2 in Central America is thought to be associated with the high UV index of the area. The prevalences of autoantibodies and the clinical manifestations of PM/DM were evaluated comparing two cohorts in Mexico.

Methods

Ninety-five Mexican patients with PM/DM (66 DM, 29 PM; 67 Mexico City, 28 Guadalajara) were studied. Autoantibodies were characterized by immunoprecipitation using ³⁵S-methionine labeled K562 cell extract. Clinical information was obtained from medical records.

Results

DM represented 69% of PM/DM and anti-Mi-2 was the most common autoantibody (35%), followed by anti-p155/140 (11%); however, anti-Jo-1 was only 4%. The autoantibody profile in adult-onset DM in Mexico City versus Guadalajara showed striking differences: anti-Mi-2 was 59% versus 12% (P = 0.0012) whereas anti-p155/140 was 9% versus 35% (P = 0.02), respectively. A strong association of anti-Mi-2 with DM was confirmed and when clinical features of anti-Mi-2 (+) DM (n = 30) versus anti-Mi-2 (-) DM (n = 36) were compared, the shawl sign (86% versus 64%, P < 0.05) was more common in the anti-Mi-2 (+) group (P = 0.0001). Levels of creatine phosphokinase (CPK) were higher in those who were anti-Mi-2 (+) but they responded well to therapy.

Conclusions

Anti-Mi-2 has a high prevalence in Mexican DM and is associated with the shawl sign and high CPK. The prevalence of anti-Mi-2 and anti-p155/140 was significantly different in Mexico City versus Guadalajara, which have a similar UV index. This suggests roles of factors other than UV in anti-Mi-2 antibody production.

[New aspects on the pathogenesis of myositis]

Idiopathic inflammatory myopathies (IIM) are chronic inflammatory diseases of muscle characterized by proximal muscle weakness. There are three main groups of diseases, dermatomyositis, polymyositis and inclusion body myositis. The muscle tissue is invaded by the humoral autoantibody producing immune system (B-cells) and by the cellular immune system with autoaggressive and inflammation modulating cells (e.g. dendritic cells, monocytes/macrophages, CD4 + and CD8 + T-cells and natural killer cells). The presence of specific or associated autoantibodies and inflammatory cellular infiltrates with cytotoxic and immune autoreactive properties are characteristic for IIM diseases. The pathogenesis is still unknown; nevertheless, there are several hints that exogenic factors might be involved in initiation and disease progression and bacterial, fungal and viral infections are thought to be possible initiators. Up to now information on prognostic markers to help with decision-making for individual treatment are limited. In addition, there has been only limited therapeutic success including conventional or novel drugs and biologicals and comparative validation studies are needed using similar outcome measurements. Moreover, to facilitate the use and development of novel therapies, elaboration of intracellular and cell-specific regulation could be useful to understand the etiopathogenesis and allow a better diagnosis, prognosis and possibly also a prediction for individualized subgroup treatment.

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.

Clinical features of inflammatory myopathies and their association with malignancy: a systematic review in asian population

Introduction. Idiopathic inflammatory myopathies (IIMs) are a group of chronic systemic autoimmune diseases that mainly affect the skeletal muscle. The common subtypes include adult dermatomyositis (DM), polymyositis (PM), and inclusion body myositis (IBM). Most of the earlier studies that described the clinical characteristics of IIM as well as their association with cancer were conducted in Western population. Our study is the first systematic review that summarizes the clinical data of DM/PM in Asian population. Methods. We identified 14 case series of DM/PM that met our eligibility criteria. We then compared this data with that from previous reports from Europe and North America. Results. Our systematic review included 2518 patients. Dermatomyositis is more common, with the ratio of dermatomyositis to polymyositis being 1.36 : 1. 69% of them were females with mean age of 45.5 years. Extramuscular manifestations, including arthritis/arthralgia, dysphagia, and interstitial lung disease, are found in one-third of the patients. Malignancy was found in 10% of patients, with lung and nasopharyngeal carcinomas being the most common malignancies associated with these myopathies. Conclusion. Clinical presentation of PM/DM appears to be similar in both Western and Asian populations. However, the type of associated malignancies in Asians differs from that in Caucasians. Ethnic background should be one of the factors that clinicians should consider while screening for malignancy.

Update: biomarkers for idiopathic inflammatory myopathies

PURPOSE OF REVIEW

Establishing diagnoses and distinguishing active disease from chronic injury remain significant clinical challenges in idiopathic inflammatory myopathies (IIM). Recent 'discovery' approaches utilizing novel genomic and proteomic techniques have revealed candidate molecular biomarkers to augment clinical and classical histological data.

RECENT FINDINGS

Whole blood and serum Type 1 interferons (IFN-1) and IFN-1 inducible genes are gaining traction as disease biomarkers in IIM. IFNβ is emerging as a disease activity marker specifically for dermatomyositis. Recently, molecules associated with innate immune-cell function, including TLR-3, high mobility group box (HMGB)-1, B7 Homolog 1, S100A4, and resistin have been detected in tissues of dermatomyositis patients. Serum Interleukin-17 (IL-17) and IL-23 correlate with active disease in early IIM. Antibodies recognizing the Survival Motor Neuron complex have been newly identified in a subset of patients with polymyositis. Protein aggregates are potential disease activity sensors for inclusion body myositis. Skin and lung harbor potential biomarkers for IIM.

SUMMARY

Recent advances in understanding the pathogenesis of IIM have led to discovery of molecules that are candidate biomarkers of disease activity. Type 1 interferon and myeloid-cell signatures are leading candidate markers for use in IIM activity monitoring.

Correlation of clinicoserologic and pathologic classifications of inflammatory myopathies: study of 178 cases and guidelines for diagnosis

The idiopathic inflammatory myopathies (IIM) are acquired muscle diseases characterized by muscle weakness and inflammation on muscle biopsy. Clinicoserologic classifications do not take muscle histology into account to distinguish the subsets of IIM. Our objective was to determine the pathologic features of each serologic subset of IIM and to correlate muscle biopsy results with the clinicoserologic classification defined by Troyanov et al, and with the final diagnoses. We retrospectively studied a cohort of 178 patients with clinicopathologic features suggestive of IIM with the exclusion of inclusion body myositis. At the end of follow-up, 156 of 178 cases were still categorized as IIM: pure dermatomyositis, n = 44; pure polymyositis, n = 14; overlap myositis, n = 68; necrotizing autoimmune myopathy, n = 8; cancer-associated myositis, n = 18; and unclassified IIM, n = 4. The diagnosis of IIM was ruled out in the 22 remaining cases. Pathologic dermatomyositis was the most frequent histologic picture in all serologic subsets of IIM, with the exception of patients with anti-Ku or anti-SRP autoantibodies, suggesting that it supports the histologic diagnosis of pure dermatomyositis, but also myositis of connective tissue diseases and cancer-associated myositis. Unspecified myositis was the second most frequent histologic pattern. It frequently correlated with overlap myositis, especially with anti-Ku or anti-PM-Scl autoantibodies. Pathologic polymyositis was rare and more frequently correlated with myositis mimickers than true polymyositis. The current study shows that clinicoserologic and pathologic data are complementary and must be taken into account when classifying patients with IIM patients. We propose guidelines for diagnosis according to both clinicoserologic and pathologic classifications, to be used in clinical practice.

Clinical and pathological roles of Ro/SSA autoantibody system

Anti-Ro/SSA antibodies are among the most frequently detected autoantibodies against extractable nuclear antigens and have been associated with systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). Although the presence of these autoantibodies is one of the criteria for the diagnosis and classification of SS, they are also sometimes seen in other systemic autoimmune diseases. In the last few decades, the knowledge of the prevalence of anti-Ro/SSA antibodies in various autoimmune diseases and symptoms has been expanded, and the clinical importance of these antibodies is increasing. Nonetheless, the pathological role of the antibodies is still poorly understood. In this paper, we summarize the milestones of the anti-Ro/SSA autoantibody system and provide new insights into the association between the autoantibodies and the pathogenesis of autoimmune diseases.

Clinical associations of anti-SSA/Ro60 and anti-Ro52/TRIM21 antibodies: Diagnostic utility of their separate detection

Clinical associations of anti-SSA/Ro60 and anti-Ro52/TRIM21 antibodies are not yet fully established. In order to analyse the diagnostic utility of their separate detection, we retrospectively revised the clinical data of 200 anti-SSA/Ro60 and/or anti-Ro52/TRIM21 positive patients identified by line immunoassay during ANA routine detection. Anti-SSA/Ro60 positive patients showed a significantly higher prevalence of autoimmune diseases (AIDs) independently on the presence of anti-Ro52/TRIM21 (OR 3.13, 95% CI 1.10-8.88, p = 0.032). Anti-SSA/Ro60 was independently associated with systemic lupus erythematosus (SLE) when comparing with Sjögren's syndrome (SS) and other systemic AIDs (OR 3.46, 95% CI 1.08-11.06, p = 0.036). The more frequent specificity found in cutaneous lupus erythematosus (CLE) was also anti-SSA/Ro60. In contrast, detection of isolated anti-Ro52/TRIM21 was characteristic of SS (7/35, 20.0%), diffuse cutaneous systemic sclerosis (dcSSc) (3/4, 75.0%), primary biliary cirrhosis (PBC) (4/5, 80.0%) and, specially, of polymyositis/dermatomyositis (PM/DM) (6/6, 100%). In fact, anti-Ro52/TRIM21 was the only antibody detected in 4 out of the 6 PM/DM patients. Malignancies mainly account for the observed high prevalence of mono-specific anti-Ro52/TRIM21 in patients with non-AIDs (10/15, 62.5%). In conclusion, this retrospective study supports the routine distinction of anti-SSA/Ro60 and anti-Ro52/TRIM21 due to their different clinical associations.

Autoantibodies produced at the site of tissue damage provide evidence of humoral autoimmunity in inclusion body myositis

Inclusion body myositis (IBM) belongs to a group of muscle diseases known as the inflammatory myopathies. The presence of antibody-secreting plasma cells in IBM muscle implicates the humoral immune response in this disease. However, whether the humoral immune response actively contributes to IBM pathology has not been established. We sought to investigate whether the humoral immune response in IBM both in the periphery and at the site of tissue damage was directed towards self-antigens. Peripheral autoantibodies present in IBM serum but not control serum recognized self-antigens in both muscle tissue and human-derived cell lines. To study the humoral immune response at the site of tissue damage in IBM patients, we isolated single plasma cells directly from IBM-derived muscle tissue sections and from these cells, reconstructed a series of recombinant immunoglobulins (rIgG). These rIgG, each representing a single muscle-associated plasma cell, were examined for reactivity to self-antigens. Both, flow cytometry and immunoblotting revealed that these rIgG recognized antigens expressed by cell lines and in muscle tissue homogenates. Using a mass spectrometry-based approach, Desmin, a major intermediate filament protein, expressed abundantly in muscle tissue, was identified as the target of one IBM muscle-derived rIgG. Collectively, these data support the view that IBM includes a humoral immune response in both the periphery and at the site of tissue damage that is directed towards self-antigens.

[Necrotizing autoimmune myopathy]

Idiopathic inflammatory myopathies are systemic autoimmune diseases characterized by symmetrical proximal muscle weakness. One of them is the subgroup of necrotizing autoimmune myopathy, which has recently been recognized as a separate entity. In addition to the typical symmetrical muscle weakness, it is characterized by very high creatine kinase levels, myopathic triad in the electromyography, and myocyte necrosis without significant inflammation. The paper aims to review this rare entity, which has to be diagnosed and treated quickly in every case.

Anti-PL-7 (anti-threonyl-tRNA synthetase) antisynthetase syndrome: clinical manifestations in a series of patients from a European multicenter study (EUMYONET) and review of the literature

Autoantibodies against several aminoacyl-transfer-RNA synthetases have been described in patients with myositis; anti-threonyl-tRNA synthetase (anti-PL-7) is one of the rarest. We describe the clinical and laboratory characteristics of a cohort of European anti-PL-7 patients, and compare them with previously reported cases. This multicenter study of patients positive for anti-PL-7, identified between 1984 and 2011, derives from the EUMYONET cohort. Clinical and serologic data were obtained by retrospective laboratory and medical record review, and statistical analyses were performed with chi-squared and Fisher exact tests. Eighteen patients, 15 women, were anti-PL-7 antibody positive. Median follow-up was 5.25 years (interquartile range, 2.8-10.7 yr), and 4 patients died. All patients had myositis (12 polymyositis, 5 dermatomyositis, and 1 amyopathic dermatomyositis), 10 (55.6%) had interstitial lung disease, and 9 (50%) had pericardial effusion. Occupational exposure to organic/inorganic particles was more frequent in patients with interstitial lung disease than in the remaining patients (5 of 10 vs. 1 of 7; p = 0.152), although the difference was not significant. Concurrent autoantibodies against Ro60 and Ro52 were seen in 8 of 14 (57%) patients studied. In the literature review the most common manifestations of anti-PL-7 antisynthetase syndrome were interstitial lung disease (77%), myositis (75%), and arthritis (56%). As in other subsets of the antisynthetase syndrome, myositis and interstitial lung disease are common features of the anti-PL-7 antisynthetase syndrome. In addition, we can add pericarditis as a possible manifestation related to anti-PL-7 antibodies.

Role of non-immune mechanisms of muscle damage in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) comprise a group of autoimmune diseases that are characterized by symmetrical skeletal muscle weakness and muscle inflammation with no known cause. Like other autoimmune diseases, IIMs are treated with either glucocorticoids or immunosuppressive drugs. However, many patients with an IIM are frequently resistant to immunosuppressive treatments, and there is compelling evidence to indicate that not only adaptive immune but also several non-immune mechanisms play a role in the pathogenesis of these disorders. Here, we focus on some of the evidence related to pathologic mechanisms, such as the innate immune response, endoplasmic reticulum stress, non-immune consequences of MHC class I overexpression, metabolic disturbances, and hypoxia. These mechanisms may explain how IIM-related pathologic processes can continue even in the face of immunosuppressive therapies. These data indicate that therapeutic strategies in IIMs should be directed at both immune and non-immune mechanisms of muscle damage.

Clinical significance of antibodies to Ro52/TRIM21 in systemic sclerosis

INTRODUCTION

Autoantibodies to Ro52 recently identified as TRIM21 are among the most common autoantibodies in systemic autoimmune rheumatic diseases, but their clinical association remains poorly understood. We undertook this study to determine the clinical and serologic associations of anti-Ro52/TRIM21 antibodies in patients with systemic sclerosis (SSc).

METHODS

Detailed clinical data and sera from 963 patients with SSc enrolled in a multicenter cohort study were collected and entered into a central database. Antibodies to Ro52/TRIM21 and other autoantibodies were detected with an addressable laser-bead immunoassay and different enzyme-linked immunosorbent assay (ELISA) systems. Associations between anti-Ro52/TRIM21 antibodies and clinical and other serologic manifestations of SSc were investigated.

RESULTS

Anti-Ro52/TRIM21 antibodies were present in 20% of SSc patients and overlapped with other main SSc-related antibodies, including anti-centromere (by immunofluorescence and centromere protein (CENP)-A and CENP-B ELISA), anti-topoisomerase I, anti-RNA polymerase III, and anti-Pm/Scl antibodies. Anti-Ro52/TRIM21 antibodies were strongly associated with interstitial lung disease (odds ratio (OR), 1.53; 95% confidence interval (CI), 1.11 to 2.12; P = 0.0091) and overlap syndrome (OR, 2.06; 95% CI, 1.01 to 4.19; P = 0.0059).

CONCLUSIONS

Anti-Ro52/TRIM21 antibodies were the second most common autoantibodies in this SSc cohort. In SSc, anti-Ro52/TRIM21 antibodies may be a marker of interstitial lung disease and overlap syndrome.

Cutting edge issues in polymyositis

Skeletal muscle is the target tissue of immunoflogistic processes in patients affected with idiopathic inflammatory myopathies (IIM). IIM are classified into three major forms: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis. Recent data suggest that, in the major subsets of myositis, antigens in muscles drive a B-cell antigen-specific immune response. Moreover, some non-immunological mechanisms have been advocated. In this regard, an increased expression of Jo-1 and Mi-2 in muscle biopsies from PM and DM patients compared to normal muscle has been demonstrated; these candidate autoantigens in myositis are expressed at high levels in regenerating muscle cells rather than in mature myotubes. Myositis autoantigen upregulation has also been observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Myositis-specific autoantibodies (MSA) are disease markers and target intracellular proteins involved in key processes such as translocation and nuclear transcription. Myositis target antigens encompass aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, the signal recognition particle ribonucleoprotein, together with novel target antigens including p155/140, CADM-140, and SAE. Despite their high specificity for autoimmune myositis, MSA target non-muscle restricted proteins ubiquitary to all cell types, making the specific muscle involvement difficult to explain. Non-immunological mechanisms also seem to contribute to the pathogenesis of IIM; activation of endoplasmic reticulum stress response due to muscle regeneration and inflammation but independent to MHC-1 up-regulation has been recently reported in patients with myositis.