Clinical characteristics of patients with myositis and autoantibodies to different fragments of the Mi-2 beta antigen

[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.

Complement membrane attack complex is related with immune-mediated necrotizing myopathy

This study is to investigate the expression of complement membrane attack complex (C5b-9) in the skeletal muscle of patients with necrotizing myopathy (NM), and to investigate the relationship between C5b-9 and NM. Thirteen patients with NM and control patients with polymyositis and muscular dystrophy were enrolled in this study. Examinations including creatine kinase (CK) and L-lactate dehydrogenase (LDH) in the serum, electromyogram and muscle pathological examination were performed. C5b-9 expression in the skeletal muscle was determined by immunohistochemistry and analyzed by Image Plus Pro 6.0. C5b-9 expression was particularly prominent in necrotic muscle fibers, and also positive in blood vessels. C5b-9 diffusely expressed in vascular endothelial cells and smooth muscle layer. But the intensity was not related with the elevated level of serum CK. So, C5b-9 is strongly expressed in the necrotic muscle fiber and blood vessels, and may contribute to the pathogenesis of NM.

Predictors of clinical improvement in rituximab-treated refractory adult and juvenile dermatomyositis and adult polymyositis

OBJECTIVE

To identify the clinical and laboratory predictors of clinical improvement in a cohort of myositis patients treated with rituximab.

METHODS

We analyzed data for 195 patients with myositis (75 with adult polymyositis [PM], 72 with adult dermatomyositis [DM], and 48 with juvenile DM) in the Rituximab in Myositis trial. Clinical improvement was defined as 20% improvement in at least 3 of the following 6 core set measures of disease activity: physician's and patient's/parent's global assessment of disease activity, manual muscle testing, physical function, muscle enzymes, and extramuscular disease activity. We analyzed the association of the following baseline variables with improvement: myositis clinical subgroup, demographics, myositis damage, clinical and laboratory parameters, core set measures, rituximab treatment, and myositis autoantibodies (antisynthetase, anti-Mi-2, anti-signal recognition particle, anti-transcription intermediary factor 1γ [TIF-1γ], anti-MJ, other autoantibodies, and no autoantibodies). All measures were univariately assessed for association with improvement using time-to-event analyses. A multivariable time-dependent proportional hazards model was used to evaluate the association of individual predictive factors with improvement.

RESULTS

In the final multivariable model, the presence of an antisynthetase, primarily anti-Jo-1 (hazard ratio [HR] 3.08, P < 0.01), anti-Mi-2 (HR 2.5, P < 0.01), or other autoantibody (HR 1.4, P = 0.14) predicted a shorter time to improvement compared to the absence of autoantibodies. A lower physician's global assessment of damage (HR 2.32, P = 0.02) and juvenile DM (versus adult myositis) (HR 2.45, P = 0.01) also predicted improvement. Unlike autoantibody status, the predictive effect of physician's global assessment of damage and juvenile DM diminished by week 20. Rituximab treatment did not affect these associations.

CONCLUSION

Our findings indicate that the presence of antisynthetase and anti-Mi-2 autoantibodies, juvenile DM subset, and lower disease damage strongly predict clinical improvement in patients with refractory myositis.

Dermatomyositis associated with hepatitis B virus-related hepatocellular carcinoma

Dermatomyositis is an idiopathic inflammatory myopathy with typical cutaneous manifestations. It has been proposed that dermatomyositis may be caused by autoimmune responses to viral infections. Previous studies have shown an association between dermatomyositis and malignant tumors such as ovarian cancer, lung cancer, and colorectal cancer. However, a chronic hepatitis B virus (HBV) infection associated with dermatomyositis and hepatocellular carcinoma (HCC) has been very rarely reported. Here, we report a rare case of dermatomyositis coinciding with HBV-associated HCC. A 55-year-old male was confirmed to have HCC and dermatomyositis based on proximal muscle weakness, typical skin manifestations, elevated muscle enzyme levels, and muscle biopsy findings. This case suggests that HCC and/or a chronic HBV infection may be factors in the pathogenesis of dermatomyositis through a paraneoplastic mechanism.

[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.

A new ELISA for dermatomyositis autoantibodies: rapid introduction of autoantigen cDNA to recombinant assays for autoantibody measurement

Advances in immunology, biochemistry, and molecular biology have enabled the development of a number of assays for measuring autoantibodies. ELISA has been widely used, because it can deal with relatively large numbers of serum samples more quickly than other immunologic methods, such as immunoblotting and immunoprecipitation. Recombinant autoantigens, which are generally produced in E. coli using the relevant cloned cDNA, are necessary for ELISA. Conventional clinical ELISA tests are limited in their ability to purify proteins free of bacterial contaminants, and the process is labor intensive. We recently developed new ELISA tests that utilize simple in vitro transcription and translation labeling of autoantigens in order to measure dermatomyositis- (DM-) specific autoantibodies, including autoantibodies to Mi-2, MDA5, NXP-2, TIF1-α, and TIF1-γ. This method may allow for the rapid conversion of cDNAs to a chemiluminescent ELISA to detect autoantibodies that are found not only in DM but also in other autoimmune diseases.

Classification, diagnosis, and management of idiopathic inflammatory myopathies

The detection and characterization of a large array of autoantibodies, including at least 8 different antisynthetase, anti-SRP, -200/100 (HMGCR), -Mi-2, -CADM-140 (MDA5), -SAE, -p155, -MJ (NXP-2), and -PMS1, frequently associated with distinct and well-defined clinicopathological features, allowed for significant improvement in the definition and diagnosis of idiopathic inflammatory myopathies (IIM). Classification remains difficult, with lingering divergence between the different specialties involved in IIM care, but several categories clearly stand out, including dermatomyositis (DM), overlap myositis (OM), polymyositis, necrotizing myositis, and sporadic inclusion body myositis (s-IBM). Biopsy and histological analysis remain crucial, particularly in the absence of autoantibodies, to accurately specify the diagnosis and rule out mimics such as muscular dystrophies and metabolic myopathies. Numerous infectious agents (in particular human immunodeficiency virus and human T cell lymphotrophic virus-1) and drugs (statins, tumor necrosis factor inhibitors, and proton pump inhibitors) can cause mimic IIM that must also be excluded. Pharmacological treatment, in addition to glucocorticoids and immunoglobulins, now includes mycophenolate mofetil and rituximab, which proved helpful in resistant cases, particularly rituximab in DM and OM. Exercise, initially seen as potentially deleterious, recently was shown to be efficacious and safe. IIM can thus be reasonably well controlled in most cases, although aggressive disease remains refractory to treatment, including some cases of necrotizing myopathy. Sporadic IBM still seems resistant to all medications tested to date.

Skeletal muscle degenerative diseases and strategies for therapeutic muscle repair

Skeletal muscle is a highly specialized, postmitotic tissue that must withstand chronic mechanical and physiological stress throughout life to maintain proper contractile function. Muscle damage or disease leads to progressive weakness and disability, and manifests in more than 100 different human disorders. Current therapies to treat muscle degenerative diseases are limited mostly to the amelioration of symptoms, although promising new therapeutic directions are emerging. In this review, we discuss the pathological basis for the most common muscle degenerative diseases and highlight new and encouraging experimental and clinical opportunities to prevent or reverse these afflictions.

Overlap connective tissue disease syndromes

Overlap Syndromes (OSs) have been defined as entities satisfying classification criteria of at least two connective tissue diseases (CTDs) occurring at the same or at different times in the same patient. CTDs include systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), polymyositis/dermatomyositis (PDM), and Sjögren syndrome (SS). Every combination between these disorders has been reported. In some OS a specific autoantibody has been indentified, supporting the hypothesis that these syndromes are not a mere association of two or more CTD in the same patient, but a well defined clinical entity with specific clinical characteristics. As an example, anti-t-RNA synthetase syndrome is characterized by the presence of anti-t-RNA synthetase antibodies. Notably, clinical manifestations observed in OS may be different from those observed in the single CTD. The treatment of OS is mainly based on the use of corticosteroids and immunosuppressants. Biologic drugs, i.e. anti-TNFα or anti-CD20 monoclonal antibodies, have been recently introduced as alternative treatments in refractory cases. Moreover, there are some concerns with the use of anti-TNF agents in patients with systemic autoimmune diseases due to the risk of triggering disease exacerbations. In this paper the most frequent OS are described with a special focus on the specific immunologic and clinical aspects. Furthermore, some personal data on anti-t-RNA synthetase syndrome and rhupus syndrome are reported.

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.

Paraneoplastic myalgias and myositis

There are several key observations on paraneoplastic myopathies: The risk of cancer associated with DM is very high, whereas risk of cancer associated with PM is mildly increased Most cancers develop within one year of the onset of myositis, although the risk remains high up to 5 years after diagnosis. The most common cancers associated with DM are adenocarcinoma, including lung, ovary, cervical, stomach, pancreas, colorectal and lymphoma, whereas PM is associated with a high risk of lymphoma. The clinical course of myopathy is closely linked with the course of cancer. Certain clinical features are associated with CAM including severe treatment resistant skin manifestations, severe muscle weakness, respiratory muscle weakness, and dysphagia, while some clinical features are protective such as arthritis, Raynaud, and ILD. Screening should be based on age, gender, ethnicity, and the geographic area of the patient; however, certain high-risk patients may require more extensive screening including tumor markers and thoracoabdominal–pelvic CT scans. Certain autoantibodies including anti-p155 and the absence of more common autoantibodies are associated with a higher risk of CAM, while the presence of antisynthetase autoantibodies lowers the risk for CAM. Although the pathogenesis of CAM is unclear, a plausible hypothesis is that immune responses generated against antigens commonly targeted in myositis are related to antitumor responses in affected individuals.

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.

Idiopathic inflammatory myopathies: definition and management of refractory disease

Adult idiopathic inflammatory myopathies, commonly referred to as myositis, are a heterogeneous group of diseases with an autoimmune etiology. In this review, the authors are going to focus on myositis excluding inclusion body myositis. They will review the prognostic factors (for mortality and response to steroids), define refractory disease, introduce a new concept (presumed refractory disease), analyze definitions of active disease, damage and improvement criteria, and summarize therapeutic alternatives for refractory patients, based on different disease phenotypes.

Pathogenesis and therapies of immune-mediated myopathies

The most common autoimmune muscle disorders include dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myositis (NAM) and sporadic inclusion body myositis (sIBM). DM is a complement-mediated microangiopathy leading to destruction of capillaries, hypoperfusion and inflammatory cell stress on the perifascicular regions. NAM is an increasingly recognized subacute myopathy triggered by statins, viral infections, cancer or autoimmunity with macrophages as the final effector cells causing fiber injury. PM and IBM are T cell-mediated disorders where cytotoxic CD8(+) T cells clonally expand in situ and invade major histocompatibility complex class I expressing muscle fibers. In sIBM, in addition to autoreactive T cells, there are degenerative features characterized by vacuolization and accumulation of stressor or amyloid-related misfolded proteins; an interrelationship between inflammatory and degeneration-associated molecules is prominent and enhances the cascade of pathogenic factors. These disorders are treatable, hence the need to make the correct diagnosis from the outset. The applied therapeutic strategies are outlined and the promising new agents are reviewed.

Myositis-specific autoantibodies: detection and clinical associations

In recent years, the detection and characterization of (novel) autoantibodies is becoming increasingly important for the early diagnosis of autoimmune diseases. The idiopathic inflammatory myopathies (IIM, also indicated with myositis) are a group of systemic autoimmune disorders that involve inflammation and weakness of skeletal muscles. One of the hallmarks is the infiltration of inflammatory cells in muscle tissues. A number of myositis-specific autoantibodies have been identified and these may be associated with distinct IIM subclasses and clinical symptoms. Here, we review all myositis-specific autoantibodies identified today as well as their target proteins, together with their clinical associations in IIM patients. Post-translational modifications that might be associated with the generation of autoantibodies and the development of the disease are discussed as well. In addition, we describe well established autoantibody detection techniques that are currently being used in diagnostic laboratories, as well as novel multiplexed methods. The latter techniques provide great opportunities for the simultaneous detection of distinct autoantibodies, but may also contribute to the identification of novel autoantibody profiles, which may have additional diagnostic and prognostic value. The ongoing characterization of novel autoantibody specificities emphasizes the complexity of processes involved in the development of such autoimmune diseases.

Diagnostic performance and validation of autoantibody testing in myositis by a commercial line blot assay

OBJECTIVE

Serological testing for myositis-specific or associated autoantibodies [myositis-specific antibody (MSA) and myositis-associated antibody (MAA)] is useful for the diagnosis of idiopathic inflammatory myopathies (IIMs). However, available assays are neither standardized nor validated. The objective is to evaluate the accuracy of a commercial line blot assay for myositis diagnosis.

METHODS

IgG antibodies against Jo-1, PL-7, PL-12, PM/Scl, Ku, Mi-2 and Ro52 antigens were detected by a line blot and in-house RNA immunoprecipitation or immunoblot. We tested sera from 208 IIM patients, 50 healthy subjects and 180 control patients (11 non-autoimmune myopathy, 23 muscular dystrophy, 11 UCTD, 68 SLE, 36 SSc, 22 SS and 9 arthropathy).

RESULTS

MSAs or MAAs were detected in 98 (47%) out of the 208 IIM patients by line blot: anti-Jo-1 in 43 (21%), anti-PL-7 or anti-PL-12 in 8 (4%), anti-Mi-2 in 9 (4%), anti-PM/Scl in 9 (4%), anti-Ku in 10 (5%) and anti-Ro52 in 49 (24%). Overall specificity was: 100% for anti-Jo-1, anti-PL-7 or PL-12 and anti-PM/Scl; 96% for anti-Ku; 98% for anti-Mi-2; and 76% for anti-Ro52. In-house testing confirmed line blot results regarding anti-Jo-1, anti-PM/Scl and anti-Ku, while it was more accurate than line blot in detecting anti-Mi-2 (7 vs 4% sensitivity, 100 vs 98% specificity), and anti-aminoacyl-tRNA synthetase (anti-ARS) non-Jo-1 antibodies (11 vs 4% sensitivity, 97 vs 99% specificity).

CONCLUSIONS

Line blot could be a suitable serological test in the diagnostic workup for myositis, and it represents a reliable alternative to more time-consuming procedures. Continuous effort is recommended in order to improve its accuracy.

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

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

Dermatomyositis and polymyositis: Clinical presentation, autoantibodies, and pathogenesis

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

Paraneoplastic myopathy

PURPOSE OF REVIEW

It has been recognized for some time now, that compared with the normal population, patients with idiopathic inflammatory myopathies (IIM) live with an increased risk of developing malignancy. In the majority of these patients, cancer-associated myositis appears to have some paraneoplastic features. The aim of the present review is to describe new data that explain the connection between myositis and malignant diseases, as well as to highlight its value in the current management of these patients.

RECENT FINDINGS

Antigen expressions and patterns shared by regenerating muscle and cancers raise questions about whether myositis cases without clinically observable cancer may represent a fully successful antitumor immune response with bystander damage to regenerating muscle. The discovery of anti-155/140 autoantibody may aid in the better diagnosis of adult IIM patients with a higher risk of malignancy. It also may help the better understanding of paraneoplastic myositis.

SUMMARY

Cancer-associated myositis differs from primary myositis in many aspects. Prognosis and life-expectancy are determined by the underlying malignancy. Therefore, patient-specific examinations for detection of an underlying cancer are important in the management of patients. Recent clinical findings and new possibilities in immunoserological testing may result in the elaboration of an evidence-based recommendation for cancer screening programs in patients with IIM in the future.

Expression of the dermatomyositis autoantigen Mi-2 in regenerating muscle

OBJECTIVE

Autoantibodies against the chromatin remodeler Mi-2 are found in a distinct subset of patients with dermatomyositis (DM). Previous quantitative immunoblotting experiments demonstrated that Mi-2 protein levels are up-regulated in DM muscle. This study was undertaken to define the population of cells expressing high levels of Mi-2 in DM muscle and to explore the regulation and functional role of Mi-2 during muscle regeneration.

METHODS

The expression of Mi-2 was analyzed by immunofluorescence microscopy in human muscle biopsy specimens. In an experimental mouse model, cardiotoxin was used to induce muscle injury and repair, and expression of Mi-2 during muscle regeneration was studied in this model by immunofluorescence and immunoblotting analyses. In addition, a cell culture system of muscle differentiation was utilized to artificially modulate Mi-2 levels during proliferation and differentiation of myoblasts.

RESULTS

In human DM muscle tissue, increased Mi-2 expression was found preferentially in the myofibers within fascicles affected by perifascicular atrophy, particularly in the centralized nuclei of small perifascicular muscle fibers expressing markers of regeneration. In injured mouse muscle tissue, Mi-2 levels were dramatically and persistently up-regulated during muscle regeneration in vivo. Premature silencing of Mi-2 with RNA interference in vitro resulted in accelerated myoblast differentiation.

CONCLUSION

Expression of Mi-2 is markedly up-regulated during muscle regeneration in a mouse model of muscle injury and repair. It is also up-regulated in human DM myofibers expressing markers of regeneration. Results of the in vitro studies indicate that this protein may play a role in modulating the kinetics of myoblast differentiation. Our findings thus suggest that high levels of Mi-2 expression in muscle biopsy tissue from patients with DM reflect the presence of incompletely differentiated muscle cells.

[Myopathies and malignancy]

There is a greater risk of developing cancer among patients with inflammatory myositis, specifically dermatomyositis. This relationship was first described in 1916 by Sterz and has been corroborated in population based studies. This chapter describes clinical and serological characteristics of patients with myositis and cancer, as well as the most common malignancies and diagnostic and prognostic considerations in this group of patients.

[Dermatomyositis]

Dermatomyositis is a form of idiopathic inflammatory myopathy that involves skeletal muscle and skin. The objectives of this review are to briefly describe the cutaneous manifestations of the disease, to raise some questions still debated about amyopathic dermatomyositis, and to reflect current knowledge of an interesting aspect in dermatomyositis as it is the risk to develop malignancy. Although clear evidence for a significant dermatomyositis-cancer association exists, optimal clinical or biological factors that predict an association with cancer have not been identified. Recently, some specific autoantibodies in dermatomyositis have been shown to be associated with internal malignancy. They open up the possibility to have available serological markers for detecting cancer-associated myositis in the near future.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies are a group of systemic autoimmune syndromes characterized by striated muscle inflammation. Here, we discuss the clinical features of this group of conditions and review the recent developments in the understanding of the pathogenesis and immunogenetics of the idiopathic inflammatory myopathies. The role of myositis-specific autoantibodies and their clinical significance and an overview of management are also provided.

Developments in the scientific and clinical understanding of inflammatory myopathies

The idiopathic inflammatory myopathies are chronic autoimmune disorders sharing the clinical symptom of muscle weakness and, in typical cases, inflammatory cell infiltrates in muscle tissue. During the last decade, novel information has accumulated supporting a role of both the innate and adaptive immune systems in myositis and suggesting that different molecular pathways predominate in different subsets of myositis. The type I interferon activity is one such novel pathway identified in some subsets of myositis. Furthermore, nonimmunological pathways have been identified, suggesting that factors other than direct T cell-mediated muscle fibre necrosis could have a role in the development of muscle weakness.

Heterogeneity of autoantibodies in 100 patients with autoimmune myositis: insights into clinical features and outcomes

The objective of this study was to determine the prevalence, mutual associations, clinical manifestations, and diagnoses associated with serum autoantibodies, as detected using recently available immunoassays, in patients with autoimmune myositis (AIM). Sera and clinical data were collected from 100 patients with AIM followed longitudinally. Sera were screened cross-sectionally for 21 autoantibodies by multiplex addressable laser bead immunoassay, line blot immunoassay, immunoprecipitation of in vitro translated recombinant protein, protein A assisted immunoprecipitation, and enzyme-linked immunosorbent assay. Diagnoses were determined using the Bohan and Peter classification as well as recently proposed classifications. Relationships between autoantibodies and clinical manifestations were analyzed by multiple logistic regression. One or more autoantibodies encompassing 19 specificities were present in 80% of the patients. The most common autoantibodies were anti-Ro52 (30% of patients), anti-Ku (23%), anti-synthetases (22%), anti-U1RNP (15%), and anti-fibrillarin (14%). In the presence of autoantibodies to Ku, synthetases, U1RNP, fibrillarin, PM-Scl, or scleroderma autoantigens, at least one more autoantibody was detected in the majority of sera and at least two more autoantibodies in over one-third of sera. The largest number of concurrent autoantibodies was six autoantibodies. Overall, 44 distinct combinations of autoantibodies were counted. Most autoantibodies were unrestricted to any AIM diagnostic category. Distinct clinical syndromes and therapeutic responses were associated with anti-Jo-1, anti-fibrillarin, anti-U1RNP, anti-Ro, anti-Ro52, and autoantibodies to scleroderma autoantigens. We conclude that a significant proportion of AIM patients are characterized by complex associations of autoantibodies. Certain myositis autoantibodies are markers for distinct overlap syndromes and predict therapeutic outcomes. The ultimate clinical features, disease course, and response to therapy in a given AIM patient may be linked to the particular set of associated autoantibodies. These results provide a rationale for patient profiling and its application to therapeutics, because it cannot be assumed that the B-cell response is the same even in the majority of patients in a given diagnostic category.

Chest CT findings in patients with inflammatory myopathy and Jo1 antibodies

Thoracic high-resolution computed tomography scans (HRCT) of 17 patients with inflammatory muscle disorders (IMD) and positive Jo1 antibodies were retrospectively reviewed regarding presence, extension, and distribution of pathological findings. Abnormal findings were found in 14 (82.3%) patients. The predominant CT abnormality was ground glass attenuation, which was present in seven patients (41.1%), having a bilateral and diffuse distribution. In general, lesions tended to appear in the lower lobes and more specifically in the lung bases. Interlobular septal thickening was found in six patients (35.3%); it was seen in the upper and lower lobes with peripheral distribution and bilateral localization in five out of six patients. Bronchiectases, reticular opacities, and honeycombing were found in six patients (35.3%). Air space consolidation was seen in about 17% of the patients. Lung involvement is a frequent feature of IMD patients with positive Jo1 antibodies and its most common radiological pattern is that of nonspecific interstitial pneumonia.

Mechanisms of disease: autoantigens as clues to the pathogenesis of myositis

Autoimmune inflammatory myopathies, referred to as myositis, comprise a heterogeneous group of chronic inflammatory muscle diseases that present with various clinical phenotypes, histologic changes and autoantibodies, resulting in progressive inflammatory muscle damage and weakness. In up to 20% of myositis patients, particularly those with dermatomyositis, there is an association with cancer that is most frequently diagnosed within 1 year of presentation of myositis. Accumulating data show that autoantibodies in myositis target a specific group of intracellular molecules that are not muscle-specific in their expression. The striking association between autoantibodies recognizing ubiquitously expressed molecules and distinct clinical phenotypes suggests that the target tissues themselves might regulate and shape the phenotype-specific immune response in myositis. Studies indicate that changes in phenotype-specific autoantigens, such as altered structure, enhanced expression, and acquisition of adjuvant properties during various forms of cellular stress, apoptosis, and transformation, might be mechanistically important in this regard. This Review discusses these developments and highlights a central role of autoantigens themselves as a critical partner in driving autoimmune diseases, and the potential for their therapeutic manipulation. In addition, we will highlight insights that the cancer-autoimmunity interface in this group of diseases provides into the relationship between the anticancer immune response and autoimmune diseases.

Dermatomyositis

Dermatomyositis (DM) is a chronic inflammatory disorder of the skin and muscles. Although thought to be autoimmune in origin, many questions remain as to the etiopathogenesis of this disease. DM has classically been considered a humorally mediated disease. Current evidence, however, seems to increasingly support alternative (though not mutually exclusive) mechanisms of pathogenesis, including cell-mediated and innate immune system dysfunction. Pathologic findings of DM in muscle include infarcts, perifascicular atrophy, endothelial cell swelling and necrosis, vessel wall membrane attack complex deposition, and myocyte-specific MHC I upregulation. As for the skin, histopathologic findings include hyperkeratosis, epidermal basal cell vacuolar degeneration and apoptosis, increased dermal mucin deposition, and a cell-poor interface dermatitis. Autoantibodies, particularly those that bind nuclear or cytoplasmic ribonucleoprotein antigens, are also commonly found in DM, although their importance in pathogenesis remains unclear. Defective cellular clearance, genetic predilection and environmental exposures, such as viral infection, may also play an important role in the pathogenesis of DM. The seminal work regarding the pathogenesis of DM is reviewed and an update on the recent basic and molecular advances in the field is provided.

Inflammatory muscle disease: clinical presentation and assessment of patients

Muscle weakness and muscle fatigue are the most common manifestations in patients with idiopathic inflammatory myopathies (ie, myositis), but other organs are frequently involved such as skin, lungs, joints, and the heart. These could occur before, simultaneously with, or after the onset of muscle symptoms. One tool to structure outcome measure is the International Classification of Functioning, Disability, and Health. Measures of "disability" can be divided into impairment and activity limitation/participation restriction. Most of the available outcome measures for myositis could be classified as measures of impairment, such as muscle strength, serum levels of muscle enzymes, and pulmonary function tests. Measures of activity limitation/participation restriction are also important, such as the myositis activities profile, the visual analog scale to assess impact on general well-being, and the generic short form-36 to capture impact on health-related quality of life.

The diagnostic utility of myositis autoantibody testing for predicting the risk of cancer-associated myositis

OBJECTIVES

There is a known association between myositis and cancer. The risk is greater in dermatomyositis (DM) than polymyositis (PM), although reliable methods to predict cancer risk in specific patients with myositis are not presently available. This study was undertaken to determine whether risk of developing cancer in myositis can be predicted by antibody profiling.

METHODS

A cross-sectional study of UK Caucasian adults with PM (n = 109), DM (n = 103) and connective tissue disease overlap (myositis/CTD-overlap, n = 70). Patients were tested for a comprehensive range of myositis-specific/associated autoantibodies. Sensitivity and specificity analyses were performed for the optimal identification of cancer risk.

RESULTS

Sixteen patients had cancer-associated myositis (CAM) (15 DM, 1 myositis/CTD-overlap). CAM patients were older at disease onset, and patients without myositis-specific/associated autoantibodies on "routine" laboratory testing (negative for anti-Jo-1, anti-PM-Scl, anti-U1-RNP, anti-U3-RNP, anti-Ku antibodies) had a significantly increased risk of CAM. Possession of the antibody against 155 kDa and 140 kDa protein specificities (anti-155/140 antibody) represented a significant risk factor for CAM, and was found exclusively in DM. A positive anti-155/140 antibody result proved highly specific, moderately sensitive, with high negative predictive value for CAM. A "negative routine myositis antibody panel" result was highly sensitive, with high negative predictive value for CAM. The combination of these two approaches was 94% sensitive, detecting 15 of 16 CAM, with 100% sensitivity and negative predictive value in DM.

CONCLUSIONS

These results may help clinicians predict which patients with myositis are at greater risk of developing cancer, thus identifying those requiring aggressive diagnostic evaluation and intensive cancer surveillance at myositis onset and follow-up.