Myositis specific autoantibodies

Prevalence of cutaneous manifestations and myositis-specific antibodies in COVID-19 patients and Anti-PL7 antibodies association with pulmonary radiological severity: A retrospective study

BACKGROUND

Dermatomyositis (DM) is an idiopathic immune-mediated myopathy, and may involve many organs, including muscles, skin and lungs. Myositis-specific autoantibodies (MSAs) are a useful aid in diagnosis DM and identifying its clinical subtype. During the COVID-19 pandemic, several studies found clinical similarities regarding lung involvement in both COVID-19 and DM. Such similarities have prompted speculation of a common pathogenetic mechanism. Indeed, viral infections are well-known triggers of autoimmune diseases. This prompted us to investigate whether circulating MSAs could be markers of the severity of lung involvement and of clinical outcome in COVID-19 patients. Moreover, we investigated the presence of cutaneous signs of DM in COVID-19 patients.

METHODS

We conducted a retrospective cohort study on 178 hospitalized patients affected by COVID-19. The diagnosis was confirmed by naso-pharyngeal swab positivity for SARS-CoV-2. The severity of lung involvement was assessed by assigning to each patient a radiological score ranging from 1 to 4, based on chest imaging (chest X-rays or CT scans). Serum samples were tested for MSAs.

RESULTS

Anti-PL-7 antibodies were detected in 10.1% of patients and were found to be associated with an increased risk of severe pulmonary involvement (p = 0.019) and a worse prognosis in COVID-19 patients. Cutaneous lesions were observed in 26.4% of patients. However, none were cutaneous manifestations of DM.

CONCLUSIONS

The detection of anti-PL7 antibodies might predict severe pulmonary involvement and a worse prognosis in COVID-19 patients.

Enhanced immune complex formation in the lungs of patients with dermatomyositis

BACKGROUND

Interstitial lung disease is frequently comorbid with dermatomyositis and has a poor prognosis, especially in patients with the anti-melanoma differentiation-associated gene 5 (MDA5) autoantibody. However, the pathogenesis of dermatomyositis-related interstitial lung disease remains unclear.

METHODS

We examined 18 and 19 patients with dermatomyositis-related interstitial lung disease and idiopathic pulmonary fibrosis (control), respectively. Lung tissues obtained from these patients were semi-quantitatively evaluated by immunohistochemical staining with in-house anti-human MDA5 monoclonal antibodies, as well as anti-human immunoglobulin (Ig) G, IgM, IgA, and complement component 3(C3) antibodies. We established human MDA5 transgenic mice and treated them with rabbit anti-human MDA5 polyclonal antibodies, and evaluated lung injury and Ig and C3 expression.

RESULTS

MDA5 was moderately or strongly expressed in the lungs of patients in both groups, with no significant differences between the groups. However, patients with dermatomyositis-related interstitial lung disease showed significantly stronger expression of C3 (p < 0.001), IgG (p < 0.001), and IgM (p = 0.001) in the lungs than control. Moreover, lung C3, but IgG, IgA, nor IgM expression was significantly stronger in MDA5 autoantibody-positive dermatomyositis-related interstitial lung disease (n = 9) than in MDA5 autoantibody-negative dermatomyositis-related interstitial lung disease (n = 9; p = 0.022). Treatment with anti-MDA5 antibodies induced lung injury in MDA5 transgenic mice, and strong immunoglobulin and C3 expression was observed in the lungs of the mice.

CONCLUSION

Strong immunoglobulin and C3 expression in the lungs involve lung injury related to dermatomyositis-related interstitial lung disease. Enhanced immune complex formation in the lungs may contribute to the poor prognosis of MDA5 autoantibody-positive dermatomyositis-related interstitial lung disease.

Environmental factors associated with juvenile idiopathic inflammatory myopathy clinical and serologic phenotypes

BACKGROUND

Environmental exposures have been associated with the juvenile idiopathic inflammatory myopathies (JIIM). We undertook a questionnaire-based study to evaluate patient-reported exposures as possible risk factors for JIIM.

FINDINGS

One-hundred-seven patients with JIIM were enrolled in a myositis natural history protocol and completed environmental questionnaires. Frequencies of exposures in clinical and myositis-specific autoantibody (MSA) groups were examined. Patients with juvenile dermatomyositis (JDM) and juvenile connective tissue myositis (JCTM) more frequently received an immunization within 1 year of diagnosis compared to juvenile polymyositis (57.5 and 71.4% vs 0.0%, p ≤ 0.017). JCTM patients were more often underweight at diagnosis relative to JDM patients (42.9% vs 7.0%, p = 0.002). MSA-negative patients more frequently had gastroenteritis within a year of diagnosis compared to patients with anti-MDA5 autoantibodies (28.6% vs 0.0%, p = 0.032). Heavy exercise was more frequent in MSA-negative and anti-MDA5 groups compared to the anti-TIF-1 autoantibody group (42.9 and 35.3% vs. 9.0%, p ≤ 0.047). Medications received within 1 year of diagnosis were more frequent in MSA-negative patients relative to those with anti-MDA5 autoantibodies (92.9% vs. 52.8% p = 0.045). Being breastfed > 6 months was more frequent in MSA-negative patients (88.9%) compared to anti-TIF-1 and anti-MDA5 autoantibody groups (41.2 and 28.6%, p ≤ 0.036).

CONCLUSIONS

Certain environmental exposures prior to diagnosis differed among clinical and serologic subgroups of JIIM, suggesting additional exposures to be explored as possible risk factors for JIIM phenotypes.

Biomarker und Histologie bei idiopathischen inflammatorischen Myopathien

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

Autoantibodies in Myositis. How to Achieve a Comprehensive Strategy for Serological Testing

Myopathies are a rare type of acquired, chronic autoimmune diseases of the skeletal muscles and affect both children and adults. The hallmark symptoms of idiopathic inflammatory myopathies (IIM) are muscle inflammation, proximal muscle weakness and disability, arthritis, cutaneous rashes, calcinosis, ulceration, malignancy and interstitial lung disease (ILD). Subforms of IIM include polymyositis, dermatomyositis, cancer-related myositis and sporadic inclusion body myositis. Autoantibodies function as biomarkers for diagnosis of IIM and can be used to delimit clinically distinguishable IIM subforms. To maximise the diagnostic information it is essential to perform comprehensive multiparametric serological testing including both screening and confirmation tests.

Differential Clinical Associations of Anti-Nuclear Matrix Protein 2 Autoantibodies in Patients With Idiopathic Inflammatory Myopathies

OBJECTIVE

To investigate the associations between anti-nuclear matrix protein 2 (anti-NXP-2) autoantibody levels and disease activity as well as calcinosis severity in patients with idiopathic inflammatory myopathies (IIMs).

METHODS

Serum levels of anti-NXP-2 autoantibodies were determined in 709 patients with IIMs and also serially measured in the patients' sera with an in-house enzyme-linked immunosorbent assay using MORC3 recombinant protein. Patients with anti-NXP-2 autoantibodies were divided into 2 subgroups: those with and those without calcinosis. Associations of anti-NXP-2 autoantibody levels with organ-specific disease activity (using 10-cm visual analog scale [VAS] scores), serum creatine kinase (CK) levels, and calcinosis severity were investigated in cross-sectional and longitudinal analyses.

RESULTS

A cross-sectional analysis of 56 IIM patients with anti-NXP-2 autoantibodies (38 without calcinosis and 18 with calcinosis) showed that in patients without calcinosis, the levels of anti-NXP-2 autoantibodies were positively correlated with the physician's global assessment of disease activity and muscle VAS scores and serum CK levels, whereas no such association was found in patients with calcinosis. Results of the longitudinal study revealed strong correlations of anti-NXP-2 antibody levels with the physician's global assessment and constitutional, cutaneous, gastrointestinal, and muscle VAS scores and serum CK levels in patients without calcinosis, but in patients with calcinosis, only a moderate correlation was observed between anti-NXP-2 antibody levels and the physician's global VAS and constitutional VAS scores. Of note, in patients without calcinosis, anti-NXP-2 autoantibodies were found to disappear during periods of clinical remission, but reappeared with disease relapse. No association between anti-NXP-2 antibody levels and the severity of calcinosis was observed.

CONCLUSION

These findings indicate that anti-NXP-2 autoantibodies serve as a useful marker for disease activity in patients with IIMs, especially in the absence of calcinosis. The differential associations observed between anti-NXP-2 autoantibody levels and disease activity suggest that there may be a phenotypic difference between patients with and those without calcinosis.

Idiopathic Inflammatory Myopathies and Malignancy: a Comprehensive Review

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of autoimmune diseases (collectively known as myositis) affecting the skeletal muscles as well as other organ systems such as skin, lungs, and joints. The primary forms of myositis include polymyositis (PM), dermatomyositis (PM), and immune-mediated necrotizing myopathy (IMNM). Patients with these diseases experience progressive proximal muscle weakness, have characteristic muscle biopsy findings, and produce autoantibodies that are associated with unique clinical features. One distinguishing feature of these patients is that they are also known to have an increased risk of cancer. Since the first description of the association in 1916, it has been extensively reported in the medical literature. However, there have been significant variations between the different studies with regard to the degree of cancer risk in patients with IIM. These discrepancies can, in part, be attributed to differences in the definition of malignancy-associated myositis used in different studies. In recent years, significant advances have been made in defining specific features of IIM that are associated with the development of malignancy. One of these has been myositis-specific antibodies (MSAs), which are linked to distinct clinical phenotypes and categorize patients into groups with more homogeneous features. Indeed, patients with certain MSAs seem to be at particularly increased risk of malignancy. This review attempts a systematic evaluation of research regarding the association between malignancy and myositis.

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

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

Antimelanoma differentiation-associated protein 5 antibody level is a novel tool for monitoring disease activity in rapidly progressive interstitial lung disease with dermatomyositis

BACKGROUND

Antimelanoma differentiation-associated protein (anti-MDA)5 antibodies are associated with rapidly progressive interstitial lung disease (RP-ILD) in patients with clinically amyopathic dermatomyositis (CADM) or dermatomyositis (DM).

OBJECTIVES

We aimed to evaluate the relevance of monitoring anti-MDA5 antibody levels for the management of RP-ILD in patients with CADM or DM.

METHODS

Twelve patients with CADM (n = 10) or DM (n = 2) accompanied by RP-ILD were included. Baseline characteristics and outcomes were recorded. Serial measurements of anti-MDA5 antibody levels were measured. All patients were treated with corticosteroids, tacrolimus and intravenous cyclophosphamide.

RESULTS

All patients achieved RP-ILD remission after combined immunosuppressive therapy for a mean of 6·8 months, with significant decreases noted in the mean anti-MDA5 antibody levels at remission. Six (50%) patients became anti-MDA5 antibody negative after therapy. After a mean follow-up of 31 months, RP-ILD relapse was observed in four (33%) patients in both the anti-MDA5 antibody sustained positive group and the negative conversion group. However, relapsed patients in the sustained positive group relapsed earlier than those in the negative conversion group. Thus, a decrease in anti-MDA5 antibody levels during remission was associated with longer remission. Relapses were associated with a reincrease of anti-MDA5 antibody levels in four of four (100%) patients. In contrast, none of the patients without reincrease in anti-MDA5 antibody exhibited symptoms of relapse during follow-up. Therefore, reincrease in anti-MDA5 antibody levels was associated with relapse.

CONCLUSIONS

The anti-MDA5 antibody level is a novel parameter for monitoring and a good predictor of RP-ILD relapse in patients with CADM or DM.

Autoantigens as Partners in Initiation and Propagation of Autoimmune Rheumatic Diseases

Systemic autoimmune diseases are characterized by specific targeting of a limited group of ubiquitously expressed autoantigens by the immune system. This review examines the mechanisms underlying their selection as immune targets. Initiation of autoimmune responses likely reflects the presentation of antigens with a distinct structure not previously encountered by the immune system, in a proimmune context (injury, malignancy, or infection). Causes of modified structure include somatic mutation and posttranslational modifications (including citrullination and proteolysis). Many autoantigens are components of multimolecular complexes, and some of the other components may provide adjuvant activity. Propagation of autoimmune responses appears to reflect a bidirectional interaction between the immune response and the target tissues in a mutually reinforcing cycle: Immune effector pathways generate additional autoantigen, which feeds further immune response. We propose that this resonance may be a critical principle underlying disease propagation, with specific autoantigens functioning as the hubs around which amplification occurs.

Signal recognition particle immunoglobulin g detected incidentally associates with autoimmune myopathy

Introduction: Paraneoplastic autoantibody screening of 150,000 patient sera by tissue‐based immunofluorescence incidentally revealed 170 with unsuspected signal recognition particle (SRP) immunoglobulin G (IgG), which is a recognized biomarker of autoimmune myopathy. Of the 77 patients with available information, 54 had myopathy. We describe the clinical/laboratory associations. Methods: Distinctive cytoplasm‐binding IgG (mouse tissue substrate) prompted western blot, enzyme‐linked immunoassay, and immunoprecipitation analyses. Available histories were reviewed. Results: The immunostaining pattern resembled rough endoplasmic reticulum, and mimicked Purkinje‐cell cytoplasmic antibody type 1 IgG/anti‐Yo. Immunoblotting revealed ribonucleoprotein reactivity. Recombinant antigens confirmed the following: SRP54 IgG specificity alone (17); SRP72 IgG specificity alone (3); both (32); or neither (2). Coexisting neural autoantibodies were identified in 28% (low titer). Electromyography revealed myopathy with fibrillation potentials; 78% of biopsies had active necrotizing myopathy with minimal inflammation, and 17% had inflammatory myopathy. Immunotherapy responsiveness was typically slow and incomplete, and relapses were frequent on withdrawal. Histologically confirmed cancers (17%) were primarily breast and hematologic, with some others. Conclusions: Autoimmune necrotizing SRP myopathy, both idiopathic and paraneoplastic, is underdiagnosed in neurological practice. Serological screening aids early diagnosis. Cancer surveillance and appropriate immunosuppressant therapy may improve outcome. Muscle Nerve53: 925–932, 2016

Development of autoantibodies against muscle-specific FHL1 in severe inflammatory myopathies

Mutations of the gene encoding four-and-a-half LIM domain 1 (FHL1) are the causative factor of several X-linked hereditary myopathies that are collectively termed FHL1-related myopathies. These disorders are characterized by severe muscle dysfunction and damage. Here, we have shown that patients with idiopathic inflammatory myopathies (IIMs) develop autoimmunity to FHL1, which is a muscle-specific protein. Anti-FHL1 autoantibodies were detected in 25% of IIM patients, while patients with other autoimmune diseases or muscular dystrophies were largely anti-FHL1 negative. Anti-FHL1 reactivity was predictive for muscle atrophy, dysphagia, pronounced muscle fiber damage, and vasculitis. FHL1 showed an altered expression pattern, with focal accumulation in the muscle fibers of autoantibody-positive patients compared with a homogeneous expression in anti-FHL1-negative patients and healthy controls. We determined that FHL1 is a target of the cytotoxic protease granzyme B, indicating that the generation of FHL1 fragments may initiate FHL1 autoimmunity. Moreover, immunization of myositis-prone mice with FHL1 aggravated muscle weakness and increased mortality, suggesting a direct link between anti-FHL1 responses and muscle damage. Together, our findings provide evidence that FHL1 may be involved in the pathogenesis not only of genetic FHL1-related myopathies but also of autoimmune IIM. Importantly, these results indicate that anti-FHL1 autoantibodies in peripheral blood have promising potential as a biomarker to identify a subset of severe IIM.

An overview of polymyositis and dermatomyositis

Polymyositis and dermatomyositis are inflammatory myopathies that differ in their clinical features, histopathology, response to treatment, and prognosis. Although their clinical pictures differ, they both present with symmetrical, proximal muscle weakness. Treatment relies mainly upon empirical use of corticosteroids and immunosuppressive agents. A deeper understanding of the molecular pathways that drive pathogenesis, careful phenotyping, and accurate disease classification will aid clinical research and development of more efficacious treatments. In this review we address the current knowledge of the epidemiology, clinical characteristics, diagnostic evaluation, classification, pathogenesis, treatment, and prognosis of polymyositis and dermatomyositis.

Distinctive cutaneous and systemic features associated with antitranscriptional intermediary factor-1γ antibodies in adults with dermatomyositis

BACKGROUND

Antibodies against transcriptional intermediary factor (TIF)-1γ are associated with malignancy in dermatomyositis (DM). Identification of clinical findings associated with anti-TIF-1γ antibodies in DM is a high priority for both patient diagnosis and risk assessment.

OBJECTIVE

We sought to define the clinical phenotype of patients with anti-TIF-1γ DM.

METHODS

Using a novel, sensitive, and specific assay for anti-TIF-1γ antibodies, we retrospectively tested plasma from 134 adult patients with DM and examined associations between anti-TIF-1γ antibodies and particular clinical and laboratory features.

RESULTS

In all, 55 (41%) patients had autoantibodies to TIF-1γ. Anti-TIF-1γ positive patients were less likely to have systemic features including interstitial lung disease, Raynaud phenomenon, and arthritis/arthralgia. Patients with TIF-1γ autoantibodies had more extensive skin involvement, and some patients manifested characteristic findings including palmar hyperkeratotic papules, psoriasis-like lesions and a novel finding of hypopigmented and telangiectatic ("red on white") patches.

LIMITATIONS

This was a retrospective study from a single tertiary referral center.

CONCLUSION

TIF-1γ is the most commonly targeted DM-specific autoantigen in adults in a large US cohort. Although these patients tend to have less systemic involvement, their skin disease is often extensive and characteristic. Recognition of cutaneous findings in anti-TIF-1γ positive patients may allow more accurate and timely diagnosis and effective treatment of patients with DM.

[Risk factors for cancer in patients with myositis. Clinical, immunological characteristics and the role of the anti-p155/140 antibody]

INTRODUCTION

Idiopathic inflammatory myopathies are systemic autoimmune diseases characterized by progressive proximal muscle weakness. Cancer-associated myositis represents the worst prognostic group within this heterogeneous disease.

AIM

The aim of this study was to reveal factors which increase the risk factors for association of cancerous disease in patients with myositis. Furthermore, the authors explored the most common types of associated malignancies in their patients with myositis and characterize the clinical findings in a sub-group of anti-p155/140 positive patients.

METHOD

In this retrospective study, myositis patients with and without associated cancer were analysed (32 and 64 patients, respectively). In addition, anti-p155/140 positive and negative groups were compared, irrespective to the presence of associated malignancies.

RESULTS

The risk for associated malignancy was higher in patients with severe muscle and skin symptoms and those with dermatomyositis. Furthermore, increased risk for malignancy was noted in the presence of particular skin symptoms and the absence of systemic symptoms. The anti-p155/140 antibody was proved to be a feasible marker of an independent clinical sub-group which overlapped clinical characteristics with cancer-associated myositis.

CONCLUSIONS

These results may help the identification of patients with myositis with a higher risk for associated malignancy.

Anti-transcription intermediary factor 1-gamma autoantibody ELISA development and validation

OBJECTIVES

A quantitative anti-transcription intermediary factor 1-gamma (anti-TIF1-γ) ELISA may improve the detection of cancer-associated myositis (CAM). The aims of this study were the development and validation of a quantitative anti-TIF1-γ autoantibody ELISA in patients with myositis.

METHODS

We developed an ELISA using recombinant purified full-length human TIF1-γ. Patient serum was incubated with TIF1-γ-coated ELISA plates, and secondary antibody that bound human IgG was used to detect anti-TIF1-γ binding. Protein immunoprecipitation (IP) was used as the gold standard for the presence of anti-TIF1-γ. Serum samples from myositis patients with positive and negative anti-TIF1-γ by IP, from non-myositis autoimmune patients (SSc, SLE and RA) and from healthy controls were analysed. The ELISA's sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were evaluated. Agreement between the ELISA and IP results was determined using chi-squared and kappa tests. Test-retest reliability of the ELISA was assessed.

RESULTS

We identified 55 myositis patients with and 111 controls without anti-TIF1-γ by IP. Anti-TIF1-γ positivity by ELISA showed strong agreement (93.9%) with IP results (κ = 0.87). The sensitivity, specificity, PPV, NPV and overall accuracy of the anti-TIF1-γ ELISA were 91%, 96%, 93%, 95% and 94%, respectively. The area under the curve (AUC) of a receiver operating characteristic (ROC) curve was 0.938. Test-retest reliability was strong (Pearson r = 0.913, P < 0.001).

CONCLUSION

We developed a quantitative ELISA for detecting serum anti-TIF1-γ autoantibodies and validated the assay in myositis and other connective tissue disease patients. The availability of a validated, quantitative ELISA should improve the detection of anti-TIF1-γ autoantibodies and may improve the detection of CAM.

Functional redundancy of MyD88-dependent signaling pathways in a murine model of histidyl-transfer RNA synthetase-induced myositis

We have previously shown that i.m. administration of bacterially expressed murine histidyl-tRNA synthetase (HRS) triggers florid muscle inflammation (relative to appropriate control proteins) in various congenic strains of mice. Because severe disease develops even in the absence of adaptive immune responses to HRS, we sought to identify innate immune signaling components contributing to our model of HRS-induced myositis. In vitro stimulation assays demonstrated HRS-mediated activation of HEK293 cells transfected with either TLR2 or TLR4, revealing an excitatory capacity exceeding that of other bacterially expressed fusion proteins. Corresponding to this apparent functional redundancy of TLR signaling pathways, HRS immunization of B6.TLR2(-/-) and B6.TLR4(-/-) single-knockout mice yielded significant lymphocytic infiltration of muscle tissue comparable to that produced in C57BL/6 wild-type mice. In contrast, concomitant elimination of TLR2 and TLR4 signaling in B6.TLR2(-/-).TLR4(-/-) double-knockout mice markedly reduced the severity of HRS-induced muscle inflammation. Complementary subfragment analysis demonstrated that aa 60-90 of HRS were absolutely required for in vitro as well as in vivo signaling via these MyD88-dependent TLR pathways--effects mediated, in part, through preferential binding of exogenous ligands capable of activating specific TLRs. Collectively, these experiments indicate that multiple MyD88-dependent signaling cascades contribute to this model of HRS-induced myositis, underscoring the antigenic versatility of HRS and confirming the importance of innate immunity in this system.

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

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

NEFA/nucleobindin-2 is a target autoantigen of the anti-Wa antibody and is associated with transfer RNA

OBJECTIVES

The anti-Wa antibody found in systemic sclerosis patients reacts with a transfer RNA (tRNA)-associated 48-kDa protein and immunoprecipitates several tRNAs. We investigated the Wa antigen and its binding to tRNA species.

METHODS

We performed molecular cloning of the Wa antigen and made its recombinant protein. To investigate Wa antigen distribution in the cell, we performed an indirect immunofluorescence study. To determine the Wa-bound tRNA species, we performed a reverse transcription (RT)-polymerase chain reaction (PCR) using the RNAs immunoprecipitated by anti-Wa antibody as templates, and synthetic primers of mammalian tRNA sequences. To clarify the tissue expression of Wa antigen, we performed quantitative and semi-quantitative PCR of the cDNA.

RESULTS

We demonstrated that the Wa antigen was identical to NEFA (DNA binding/EF-hand/acidic amino acid rich region), otherwise known as nucleobindin-2. A full-length and an alternative splice variant cDNA lacking exon 11 were isolated by cloning NEFA cDNA. Anti-Wa-positive sera stained both the nucleus and cytoplasm of HEp-2 cells. RT-PCR suggested that Wa binds at least six tRNA species. In human tissues, NEFA is expressed predominantly in exocrine glands.

CONCLUSIONS

We have demonstrated that the Wa antigen is NEFA or nucleobindin-2, which binds specific tRNA species, and is distributed in specific human tissues.

Inflammatory myopathy and severe rhabdomyolysis induced by leuprolide acetate therapy for prostate cancer: a case report

Introduction

Leuprolide acetate is a synthetic analog of gonadotropin-releasing hormone used for the treatment of prostate cancer. Its side effects are hot flashes, nausea, and fatigue. We report a case of a patient with proximal inflammatory myopathy accompanied by severe rhabdomyolysis and renal failure following the second application of leuprolide acetate. Drug withdrawal and steroid therapy resulted in remission within six weeks of the diagnosis. To the best of our knowledge, our case report describes the second case of leuprolide acetate-induced inflammatory myopathy and the first case of severe leuprolide acetate-induced rhabdomyolysis and renal failure in the literature.

Case presentation

A 64-year-old Swiss Caucasian man was admitted to the hospital because of progressive proximal muscle weakness, dyspnea, and oliguria. He had been treated twice with leuprolide acetate in monthly doses. We performed a muscle biopsy, which excluded other causes of myopathy. The patient's renal failure and rhabdomyolysis were treated with rehydration and steroid therapy.

Conclusion

The aim of our case report is to highlight the rare but severe side effects associated with leuprolide acetate therapy used to treat patients with inflammatory myopathy: severe rhabdomyolysis and renal failure.

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.

Analysis of dermatomyositis-specific autoantibodies and clinical characteristics in Japanese patients

Dermatomyositis (DM) is an idiopathic systemic inflammatory disease that is often accompanied by interstitial lung disease (ILD) or internal malignancy. New autoantibodies, anti-clinically amyopathic dermatomyositis 140 (anti-CADM-140) antibody (Ab) and anti-155/140 Ab, as well as anti-aminoacyl-tRNA synthetase (anti-ARS) Ab and anti-Mi-2 Ab, have been discovered and their utility indicated. However, the association between these autoantibodies and the clinical characteristics of DM is not fully understood, and it is unclear whether anti-155/140 Ab is "specific" to DM patients with internal malignancy. Therefore, we analyzed 55 DM patients and 18 non-DM patients with malignancy to evaluate the clinical characteristics, especially skin manifestations, in association with DM-specific autoantibodies detected by immunoprecipitation. Six patients (11%) had anti-CADM-140 Ab, nine (16%) had anti-155/140 Ab, eight (15%) had anti-ARS Ab and six (11%) had anti-Mi-2 Ab. The frequency of DM patients positive for any type of autoantibody was 53%. Among the 20 DM patients with ILD, three (15%) had both anti-CADM-140 Ab and rapidly progressive ILD, and required intensive therapy (P < 0.05). ILD found in anti-ARS Ab-positive patients did not progress rapidly. The prevalence of muscle involvement in patients with anti-CADM-140 Ab was 83%. Among the 18 DM patients with internal malignancy, four (22%) had anti-155/140 Ab, and internal malignancy was found in four cases (44%) of nine anti-155/140 Ab-positive patients. None of the non-DM patients with malignancy were positive for anti-155/140 Ab. In conclusion, the results of the present study indicate that anti-155/140 Ab is specific to DM patients with internal malignancy and that we may be able to predict prognosis of ILD and the presence of malignancy to some extent, suggesting that examination of autoantibodies in DM patients is clinically very useful. However, further investigation is needed because several findings differ from those of previous reports.

Autoimmune myopathies: autoantibodies, phenotypes and pathogenesis

The different autoimmune myopathies-for example, dermatomyositis, polymyositis, and immune-mediated necrotizing myopathies (IMNM)-have unique muscle biopsy findings, but they also share specific clinical features, such as proximal muscle weakness and elevated serum levels of muscle enzymes. Furthermore, around 60% of patients with autoimmune myopathy have been shown to have a myositis-specific autoantibody, each of which is associated with a distinct clinical phenotype. The typical clinical presentations of the autoimmune myopathies are reviewed here, and the different myositis-specific autoantibodies, including the anti-synthetase antibodies, dermatomyositis-associated antibodies, and IMNM-associated antibodies, are discussed in detail. This Review also focuses on a newly recognized form of IMNM that is associated with statin use and the production of autoantibodies that recognize 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the pharmacological target of statins. The contribution of interferon signaling to the development of dermatomyositis and the potential link between malignancies and the initiation of autoimmune myopathies are also assessed.

Pancreatic adenocarcinoma-associated polymyositis treated with corticosteroids along with cancer specific treatment: case report

BACKGROUND

Adenocarcinoma of the pancreas only rarely is associated with inflammatory myopathy. In this setting, polymyositis may be treated with glucocorticoids in combination with cancer specific treatment.

CASE PRESENTATION

We present the case of a 52-year-old man with stage IIA pancreatic tail adenocarcinoma who underwent surgical treatment and six months into therapy with gemcitabine he developed symmetrical, painful, proximal muscle weakness with peripheral oedema. Re-evaluation with imaging modalities, muscle histology and biochemistry conferred the diagnosis of polymyositis associated with pancreatic cancer progression. The patient was treated with glucocorticoids along with gemcitabine and erlotinib which resulted in complete remission within six months. He remained in good health for a further six months on erlotinib maintenance therapy when a new computer tomography scan showed pancreatic cancer relapse and hence prompted 2nd line chemotherapy with gemcitabine.

CONCLUSIONS

Polymyositis associated with pancreatic cancer may respond to glucocorticoids along with cancer specific treatment.

The pulmonary histopathologic manifestations of the anti-Jo-1 tRNA synthetase syndrome

Of the idiopathic inflammatory myopathies, the anti-aminoacyl tRNA synthetase syndrome has the greatest association with interstitial lung disease (ILD). We reviewed 13 open surgical lung biopsies, four autopsies, and three native lungs resected at transplantation, for pulmonary ILD associated with the presence of anti-histidyl tRNA synthetase (anti-Jo-1) autoantibodies. Fifty percent (N=10) of patients presented with an acute decompensation of pulmonary function manifested as diffuse alveolar damage, although in five patients (25%) this marked diminution in function was superimposed on an underlying chronic interstitial pneumonia (usual interstitial pneumonia (three); nonspecific interstitial pneumonia(two)). Seven (35%) patients had usual interstitial pneumonia and two (10%) had nonspecific interstitial pneumonia exclusively, whereas one patient presented with an organizing pneumonia (5%). This study is the first to highlight the high biopsy incidence of diffuse alveolar damage in this patient population both de novo and superimposed on underlying chronic ILD, and also shows that usual interstitial pneumonia remains a significant pattern of interstitial injury in this autoimmune group. On the basis of coexisting patterns of lung injury, this study also suggests that nonspecific interstitial pneumonia in connective tissue disorders may progress over time to a usual interstitial pneumonia pattern of fibrosis, an observation that could be better assessed with future inclusion of autopsy and transplanted native lungs in study groups.

Cancer risks of dermatomyositis and polymyositis: a nationwide cohort study in Taiwan

Introduction

The association of idiopathic inflammatory myositis (IIM) and malignancies has been reported, but rarely in Asian countries. Our aim was to investigate the risk of cancer among IIM patients without a prior history of malignancies, in Taiwan.

Methods

We conducted a nationwide cohort study of 1,012 patients with dermatomyositis (DM) and 643 patients with polymyositis (PM), but without prior history of malignancies, utilizing the National Health Insurance Database from 1997 to 2007. Standardized incidence ratios (SIRs) of cancers were analyzed.

Results

A total of 95 cancers (9.4%) in DM and 33 cancers (4.4%) in PM were identified. Overall cancer risk was significantly elevated in DM patients (SIR = 5.11, 95% confidence interval [CI] = 5.01 to 5.22) and PM patients (SIR = 2.15, 95% CI = 2.08 to 2.22). Most cancers were detected in the first year of observation. The risk of cancer decreased with observation time, yet remained elevated compared with the general population in both study groups after 5 years of follow-up. DM was associated with sustained elevated risk of cancers in every age group, whereas the risk of cancer in PM was highest in younger patients and decreased with age. DM patients were at the greatest risk of cancers of the nasopharynx, lungs and hematopoietic malignancies.

Conclusions

Patients with IIM are at increased risk for cancer and should receive age-appropriate and gender-appropriate malignancy evaluations, with additional assessment for nasopharyngeal, lung and hematologic malignancy following diagnosis, and with continued vigilance for development of cancers in follow-up.

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.

Juvenile dermatomyositis: advances in pathogenesis, evaluation, and treatment

Juvenile dermatomyositis (JDM) is a rare, presumably autoimmune illness that causes proximal muscle weakness and a variety of typical cutaneous features. The study of this illness has been hampered by its rarity but, in recent years, important developments have increased our understanding of JDM. Genetic factors are likely important in the pathogenesis of JDM. These include several Human Leukocyte Antigen alleles, in particular those associated with the 8.1 ancestral haplotype and the tumor necrosis factor-alpha gene 308 polymorphism. Microchimerism, activation of plasmacytoid dendritic cells, and upregulation of type-1 interferon inducible genes also appear to play an important role in the pathogenesis of JDM. The study of JDM has also been limited by a lack of validated assessment tools. Recent work has validated the Childhood Myositis Assessment Scale and the Childhood Health Assessment Questionnaire as measures of muscle strength and function, and the Cutaneous Assessment Tool as a measure of skin disease activity and damage. Development of core sets of tools that should be used in all JDM studies has also been an important step. The use of magnetic resonance imaging and novel laboratory assessments (such as type-1 interferon inducible gene products, peripheral blood B cell and natural killer cell numbers, and myositis-associated and myositis-specific autoantibodies) are also playing an increasing role in the diagnosis and assessment of JDM. Current treatment is with corticosteroids, frequently in combination with other medications such as methotrexate or intravenous gammaglobulin. Newer therapies, such as anti-tumor necrosis factor agents and rituximab are currently being evaluated; it is not clear what role these medications will have in the future.

Characterization and peripheral blood biomarker assessment of anti-Jo-1 antibody-positive interstitial lung disease

OBJECTIVE

Using a combination of clinical, radiographic, functional, and serum protein biomarker assessments, this study was aimed at defining the prevalence and clinical characteristics of interstitial lung disease (ILD) in a large cohort of patients with anti-Jo-1 antibodies.

METHODS

A review of clinical records, pulmonary function test results, and findings on imaging studies determined the existence of ILD in anti-Jo-1 antibody-positive individuals whose data were accumulated in the University of Pittsburgh Myositis Database from 1982 to 2007. Multiplex enzyme-linked immunosorbent assays (ELISAs) for serum inflammation markers, cytokines, chemokines, and matrix metalloproteinases in different patient subgroups were performed to assess the serum proteins associated with anti-Jo-1 antibody-positive ILD.

RESULTS

Among the 90 anti-Jo-1 antibody-positive individuals with sufficient clinical, radiographic, and/or pulmonary function data, 77 (86%) met the criteria for ILD. While computed tomography scans revealed a variety of patterns suggestive of underlying usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia, a review of the histopathologic abnormalities in a subset of patients undergoing open lung biopsy or transplantation or whose lung tissue was obtained at autopsy (n = 22) demonstrated a preponderance of UIP and diffuse alveolar damage. Analysis by multiplex ELISA yielded statistically significant associations between anti-Jo-1 antibody-positive ILD and elevated serum levels of C-reactive protein (CRP), CXCL9, and CXCL10, which distinguished this disease entity from idiopathic pulmonary fibrosis and anti-signal recognition particle antibody-positive myositis. Recursive partitioning further demonstrated that combinations of these and other serum protein biomarkers can distinguish these disease subgroups at high levels of sensitivity and specificity.

CONCLUSION

In this large cohort of anti-Jo-1 antibody-positive individuals, the incidence of ILD approached 90%. Multiplex ELISA demonstrated disease-specific associations between anti-Jo-1 antibody-positive ILD and serum levels of CRP as well as the interferon-gamma-inducible chemokines CXCL9 and CXCL10, highlighting the potential of this approach to define biologically active molecules contributing to the pathogenesis of myositis-associated ILD.

[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.

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

OBJECTIVE

The identification of novel autoantibodies in juvenile dermatomyositis (DM) may have etiologic and clinical implications. The aim of this study was to describe autoantibodies to a 140-kd protein in children recruited to the Juvenile DM National Registry and Repository for UK and Ireland.

METHODS

Clinical data and sera were collected from children with juvenile myositis. Sera that recognized a 140-kd protein by immunoprecipitation were identified. The identity of the p140 autoantigen was investigated by immunoprecipitation/immunodepletion, using commercial monoclonal antibodies to NXP-2, reference anti-p140, and anti-p155/140, the other autoantibody recently described in juvenile DM. DNA samples from 100 Caucasian children with myositis were genotyped for HLA class II haplotype associations and compared with those from 864 randomly selected UK Caucasian control subjects.

RESULTS

Sera from 37 (23%) of 162 patients with juvenile myositis were positive for anti-p140 autoantibodies, which were detected exclusively in patients with juvenile DM and not in patients with juvenile DM-overlap syndrome or control subjects. No anti-p140 antibody-positive patients were positive for other recognized autoantibodies. Immunodepletion suggested that the identity of p140 was consistent with NXP-2 (the previously identified MJ autoantigen). In children with anti-p140 antibodies, the association with calcinosis was significant compared with the rest of the cohort (corrected P < 0.005, odds ratio 7.0, 95% confidence interval 3.0-16.1). The clinical features of patients with anti-p140 autoantibodies were different from those of children with anti-p155/140 autoantibodies. The presence of HLA-DRB1*08 was a possible risk factor for anti-p140 autoantibody positivity.

CONCLUSION

This study has established that anti-p140 autoantibodies represent a major autoantibody subset in juvenile DM. This specificity may identify a further immunogenetic and clinical phenotype within the juvenile myositis spectrum that includes an association with calcinosis.

Newly identified autoantibodies: relationship to idiopathic inflammatory myopathy subsets and pathogenesis

PURPOSE OF REVIEW

There is increasing evidence that patients with polymyositis and dermatomyositis have specific clinico-serological profiles. Myositis-specific autoantibodies target intracellular proteins involved in key processes such as translocation and nuclear transcription, and are closely linked to patterns of disease expression. This review highlights the recent work on novel myositis-specific autoantibodies, their autoantigen targets, the relationship to clinical subsets and potential role in pathogenesis.

RECENT FINDINGS

During the annual review period novel autoantibodies have been described in adult-onset dermatomyositis (anti-SAE autoantibodies) and juvenile dermatomyositis (anti-p155/140 autoantibodies) (anti-MJ or anti-p140 autoantibodies). These findings are important because the function of the autoantigen targets may point to shared pathogenic pathways. Studies highlighting the potential role of autoantigen-driven responses and autoantibody production in disease initiation and propagation are discussed, as well as further evidence on the relationship between autoantigens and corresponding target tissues.

SUMMARY

Considerable progress has been made emphasizing the striking association between genotype, serotype and clinical phenotype in the myositis disease spectrum. Further characterization of the identity and function of autoantigen systems in target tissues will greatly facilitate investigation of models of autoimmunity in this disease.

A case of polymyositis associated with papillary thyroid cancer: a case report

Differentiated thyroid cancer is rarely associated with paraneoplastic events. Polymyositis, an autoimmune inflammatory myopathy, can be manifested as a paraneoplastic syndrome (PS). We report a case of a young woman who developed progressive proximal muscle weakness one and a half year after a total thyroidectomy for papillary thyroid cancer. Clinical features, laboratory results and muscle biopsy led us to the diagnosis of polymyositis, possibly related to her previous malignancy. A search for recurrence of the thyroid carcinoma or other underlying malignancy was fruitless. The patient improved slowly but almost completely after about 6 months of immunosupressive therapy, which she is still receiving.

Autoantibodies and their significance in myositis

Myositis autoantibodies continue to be the subject of substantial interest, with several significant recent developments. Recent studies have emphasized that anti-Jo-1 or other antisynthetases can be associated with interstitial lung disease, even in the absence of myositis. Anti-Jo-1 autoantibody levels were shown to correlate with disease activity over time. Immunization of mice with anti-Jo-1 led to muscle and lung inflammation, reminiscent of human disease. The complexity of the antibody picture in myositis continues to increase. Several new autoantibodies have been described or better characterized. Among these were a new antisynthetase reactive with phenylalanyl-transfer RNA synthetase (anti-Zo); an autoantibody that immunoprecipitates 155- and 140-kD proteins and was common in children but seemed to be associated with malignancy in adults; and an autoantibody to a small ubiquitin-like modifier--activating enzyme associated with dermatomyositis and interstitial lung disease. These findings have significant clinical implications and suggest promising areas of further research.

Rituximab for the treatment of juvenile dermatomyositis: a report of four pediatric patients

OBJECTIVE

Juvenile dermatomyositis (DM) is a chronic inflammatory myopathy of childhood primarily affecting the muscles and skin. Treatment for juvenile DM is often difficult, and conventional therapies include corticosteroids and other immune suppressants. We reviewed the records of 4 patients with juvenile DM who received the B cell-depleting anti-CD20 monoclonal antibody rituximab to determine whether this therapy resulted in improved control of their juvenile DM.

METHODS

This is a retrospective review of 4 pediatric patients ages 10-17 years with juvenile DM who were treated with rituximab. All patients were tested for myositis autoantibodies and received weekly rituximab infusions for a total of 4 doses. Two patients received repeat courses of rituximab 1 year after their first dose. Patients were followed up between 12 and 24 months after their first course of rituximab, and their strength, muscle enzymes, and rash were reviewed.

RESULTS

One patient was positive for a myositis-specific antibody, anti-Mi-2, and demonstrated striking reductions in her muscle enzyme levels for 1 year after rituximab therapy. Following a second course of rituximab, this patient remained disease free for 14 months before requiring a third course of rituximab. Two myositis antibody-negative patients showed clinical improvement and tolerated lower doses of corticosteroids following treatment with rituximab. Finally, 1 patient had worsening of her disease following rituximab.

CONCLUSION

These cases highlight the potential for anti-B cell therapies in the treatment of juvenile DM in both myositis-specific autoantibody-positive and -negative patients.

Identification of a novel autoantibody directed against small ubiquitin-like modifier activating enzyme in dermatomyositis

OBJECTIVE

Myositis-specific autoantibodies (MSAs) are directed against cell machinery proteins such as aminoacyl-transfer RNA synthetases, signal recognition particle, Mi-2, and CADM-140. Because serologic subsets can define patients with specific clinical manifestations, the identification of further MSAs may help to identify additional disease subsets within the myositis spectrum.

METHODS

Sera from 20 adult patients with dermatomyositis (DM) were screened for autoantibodies. Two patients were further characterized due to the presence of the same novel immunoprecipitation (IP) pattern on sodium docecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and similar clinical manifestations. Both patients presented with cutaneous disease, followed by proximal myositis 6 months later. Both patients had associated nonspecific interstitial pneumonia but no signs of malignancy. The novel targets were identified using a combination of IP, SDS-PAGE, and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry.

RESULTS

Indirect HEp-2 immunofluorescence on sera from both patients displayed a diffuse, coarse, speckled, nucleolar-sparing pattern. IP revealed the presence of previously uncharacterized bands at approximately 40 kd and approximately 90 kd in both patients. The novel targets were identified as the small ubiquitin-like modifier 1 (SUMO-1) activating enzyme A subunit and SUMO-1 activating enzyme B subunit.

CONCLUSION

These findings reveal previously uncharacterized autoantibodies directed against a protein involved in posttranslational modification, the SUMO activating enzyme, in 2 patients with DM who had similar clinical features, including severe skin disease and interstitial pneumonia.

Clinical and immunogenetic features of patients with autoantibodies to asparaginyl-transfer RNA synthetase

OBJECTIVE

We have previously described anti-KS autoantibodies and provided evidence that they are directed against asparaginyl-transfer RNA (tRNA) synthetase (AsnRS). The aim of the present study was to identify patients with anti-AsnRS autoantibodies and elucidate the clinical significance of this sixth antisynthetase antibody. In particular, we studied whether it was associated with the syndrome of myositis (polymyositis or dermatomyositis [DM]), interstitial lung disease (ILD), arthritis, and other features that had been previously associated with the 5 other anti-aminoacyl-tRNA synthetase autoantibodies.

METHODS

More than 2,500 sera from patients with connective tissue disease (including myositis and ILD) and controls were examined for anti-AsnRS autoantibodies by immunoprecipitation (IP). Positive and control sera were tested for the ability to inhibit AsnRS by preincubation of the enzyme source with the serum. The HLA class II (DRB1, DQA1, DQB1, DPB1) alleles were identified from restriction fragment length polymorphism of polymerase chain reaction-amplified genomic DNA.

RESULTS

Anti-AsnRS antibodies were identified in the sera of 8 patients (5 Japanese, 1 American, 1 German, and 1 Korean) by IP of the same distinctive set of tRNA and protein that differed from those precipitated by the other 5 antisynthetases, and these antibodies showed specific inhibition of AsnRS activity. Two of these patients had DM, but 7 of 8 (88%) had ILD. Four patients (50%) had arthritis, and 1 had Raynaud's phenomenon. This antisynthetase was very rare among myositis patients (present in 0% of Japanese myositis patients), but it was found in 3% of Japanese ILD patients. Thus, most patients with anti-AsnRS had chronic ILD with or without features of connective tissue disease. Interestingly, all 4 Japanese patients tested had DR2 (DRB1*1501/1502), compared with 33% of healthy controls.

CONCLUSION

These results indicate that anti-AsnRS autoantibodies, like anti-alanyl-tRNA synthetase autoantibodies, have a stronger association with ILD than with myositis and may be associated with the DR2 phenotype.