Uncertainties in the pathogenesis of adult dermatomyositis

Novel therapeutic targets in dermatomyositis

Dermatomyositis (DM) is a systemic autoimmune disease with variable clinical presentations, including inflammation in the skin, muscle, lungs, and/or joints. Current therapeutic strategies in DM typically include broad immunosuppression; however, the currently used modalities are not universally effective and are associated with various side effects, including risk of infection. There is currently a highly unmet need for more effective and well-tolerated therapies. Recent years have witnessed increased interest in pharmaceutical development of new therapeutic strategies for DM. This review aims to summarize the landscape of therapies that are currently being tested or planned in patients with DM. These therapies have a wide variety of immunological targets, including T cells, B cells, inflammatory signaling pathways, type I interferons, autoantibodies, and other targets.

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

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

MecCog: A knowledge representation framework for genetic disease mechanism

MOTIVATION

Experimental findings on genetic disease mechanisms are scattered throughout the literature and represented in many ways, including unstructured text, cartoons, pathway diagrams, and network graphs. Integration and structuring of such mechanistic information greatly enhances its utility.

RESULTS

MecCog is a graphical framework for building integrated representations (mechanism schemas) of mechanisms by which a genetic variant causes a disease phenotype. A MecCog mechanism schema displays the propagation of system perturbations across stages of biological organization, using graphical notations to symbolize perturbed entities and activities, hyperlinked evidence tagging, a mechanism ontology, and depiction of knowledge gaps, ambiguities, and uncertainties. The web platform enables a user to construct, store, publish, browse, query, and comment on schemas. MecCog facilitates the identification of potential biomarkers, therapeutic intervention sites, and critical future experiments.

AVAILABILITY

The MecCog framework is freely available at http://www.meccog.org.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

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.

Skeletal Muscle Microvasculature: A Highly Dynamic Lifeline

Skeletal muscle is highly irrigated by blood vessels. Beyond oxygen and nutrient supply, new vessel functions have been identified. This review presents vessel microanatomy and functions at tissue, cellular, and molecular levels. Mechanisms of vessel plasticity are described during skeletal muscle development and acute regeneration, and in physiological and pathological contexts.

Innate immune-response mechanisms in dermatomyositis: an update on pathogenesis, diagnosis and treatment

Dermatomyositis (DM) is an autoimmune disease mainly affecting muscle and skin. Typical clinical and laboratory findings include muscle weakness with elevated muscle enzymes, characteristic skin lesions (e.g., Gottron papules, heliotrope erythema, Shawl sign), and specific serum autoantibodies. Recent studies have highlighted the activation of the innate immune system, including high expression of interferons (IFNs) and IFN-regulated proteins, as an important pathological hallmark of DM. These findings have changed our understanding of the disease fundamentally, since inappropriate activation of the innate immune system with secondary dysregulation of the adaptive immune response is now considered to be a central pathogenetic feature of DM. In this article, we review current guidelines and standards in diagnosis and treatment. We detail evidence-based and pathophysiology-based treatment strategies, with a focus on skin as well as on muscle lesions. Particularly, we discuss how the recent advances in the understanding of the pathomechanisms of DM have altered our conception of the mode of action of established drugs such as chloroquine and methotrexate. Finally, we outline possible future treatment strategies, with a focus on the innate immune system, e.g., targeting the IFN system with the anti-IFN-α antibody sifalimumab.

The role of type I interferons and other cytokines in dermatomyositis

Much work has been done to unveil the mechanisms behind the pathogenesis of dermatomyositis (DM) - mainly those involving certain pathogenic cytokines, termed "pathokines" as the principal cytokines involved. Recently, it has become clear that a group of cytokines known as type I interferons (IFN-Is) play a significant role in the development of DM. We review the literature published between 1946 and 2014 using an Ovid Medline database search to provide an update on the role of IFN-Is and other cytokines in the pathogenesis of DM. We provide information about the genes and proteins induced by IFN-Is and potential mechanisms by which these downstream products relate to clinical disease activity. We also explore findings of other autoimmune phenomena that may contribute to disease onset and activity including T-helper 17 (Th17) cells and associated interleukins, as well as autoantibodies. Finally, we provide a brief update on current treatment options for DM as well as some new immunomodulatory treatment modalities in development.

Myofiber HLA-DR expression is a distinctive biomarker for antisynthetase-associated myopathy

Objectives

To assess the value of major histocompatibility complex (MHC) class II antigen (HLA-DR) expression to distinguish anti-synthetase myopathy (ASM) from dermatomyositis (DM).

Methods

Muscle biopsies from patients with ASM (n = 33), DM without anti-synthetase antibodies (ASAb) (n = 17), and normal muscle biopsy (n = 10) were first reviewed. ASAb included anti-Jo1 (26/33), anti-PL12 (4/33), anti-PL7 (2/33), and anti-EJ (1/33). Immunohistochemistry was performed for MHC-I/HLA-ABC, MHC-II/HLA-DR, membrane attack complex (C5b-9), neural cell adhesion molecule (NCAM)/CD56 expression, and inflammatory cell subsets. Twenty-four ASM and 12 DM patients from another center were added for HLA-DR evaluation.

Results

Ubiquitous myofiber HLA-ABC expression was equally observed in ASM and DM (93.9% vs 100%, NS). In contrast, myofiber HLA-DR expression was found in 27/33 (81.8%) ASM (anti-Jo1: 23/26, 88.5%; others: 5/7, 71.4%) vs 4/17 (23.5%) DM patients (p < 0.001). HLA-DR was perifascicular in ASM, a pattern not observed in DM. In addition, C5b-9 deposition was observed on sarcolemma of non-necrotic perifascicular fibers in ASM, while, in DM, C5b-9was mainly detected in endomysial capillaries. CD8 cells were more abundant in ASM than in DM (p < 0.05), and electively located in perimysium or in perifascular endomysium. HLA-DR expression correlated positively with the CD8+ cells infiltrates. Strictly similar observations were made in the confirmatory study.

Conclusion

ASM is characterized by strong myofiber MHC-II/HLA-DR expression with a unique perifascicular pattern, not described so far. HLA-DR detection must be included for routine myopathological diagnosis of inflammatory/dysimmune myopathies. HLA-DR expression in ASM may indicate a specific immune mechanism, possibly involving IFNγ.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0154-2) contains supplementary material, which is available to authorized users.

Clinical presentation and evaluation of dermatomyositis

Dermatomyositis (DM) is a chronic inflammatory disorder of the skin and muscles. Evidence supports that DM is an immune-mediated disease and 50–70% of patients have circulating myositis-specific auto-antibodies. Gene expression microarrays have demonstrated upregulation of interferon signaling in the muscle, blood, and skin of DM patients. Patients with classic DM typically present with symmetric, proximal muscle weakness, and skin lesions that demonstrate interface dermatitis on histopathology. Evaluation for muscle inflammation can include muscle enzymes, electromyogram, magnetic resonance imaging, and/or muscle biopsy. Classic skin manifestations of DM include the heliotrope rash, Gottron's papules, Gottron's sign, the V-sign, and shawl sign. Additional cutaneous lesions frequently observed in DM patients include periungual telangiectasias, cuticular overgrowth, “mechanic's hands”, palmar papules overlying joint creases, poikiloderma, and calcinosis. Clinically amyopathic DM is a term used to describe patients who have classic cutaneous manifestations for more than 6 months, but no muscle weakness or elevation in muscle enzymes. Interstitial lung disease can affect 35–40% of patients with inflammatory myopathies and is often associated with the presence of an antisynthetase antibody. Other clinical manifestations that can occur in patients with DM include dysphagia, dysphonia, myalgias, Raynaud phenomenon, fevers, weight loss, fatigue, and a nonerosive inflammatory polyarthritis. Patients with DM have a three to eight times increased risk for developing an associated malignancy compared with the general population, and therefore all patients with DM should be evaluated at the time of diagnosis for the presence of an associated malignancy. This review summarizes the immunopathogenesis, clinical manifestations, and evaluation of patients with DM.

Interferon and biologic signatures in dermatomyositis skin: specificity and heterogeneity across diseases

Background

Dermatomyositis (DM) is an autoimmune disease that mainly affects the skin, muscle, and lung. The pathogenesis of skin inflammation in DM is not well understood.

Methodology and Findings

We analyzed genome-wide expression data in DM skin and compared them to those from healthy controls. We observed a robust upregulation of interferon (IFN)-inducible genes in DM skin, as well as several other gene modules pertaining to inflammation, complement activation, and epidermal activation and differentiation. The interferon (IFN)-inducible genes within the DM signature were present not only in DM and lupus, but also cutaneous herpes simplex-2 infection and to a lesser degree, psoriasis. This IFN signature was absent or weakly present in atopic dermatitis, allergic contact dermatitis, acne vulgaris, systemic sclerosis, and localized scleroderma/morphea. We observed that the IFN signature in DM skin appears to be more closely related to type I than type II IFN based on in vitro IFN stimulation expression signatures. However, quantitation of IFN mRNAs in DM skin shows that the majority of known type I IFNs, as well as IFN g, are overexpressed in DM skin. In addition, both IFN-beta and IFN-gamma (but not other type I IFN) transcript levels were highly correlated with the degree of the in vivo IFN transcriptional response in DM skin.

Conclusions and Significance

As in the blood and muscle, DM skin is characterized by an overwhelming presence of an IFN signature, although it is difficult to conclusively define this response as type I or type II. Understanding the significance of the IFN signature in this wide array of inflammatory diseases will be furthered by identification of the nature of the cells that both produce and respond to IFN, as well as which IFN subtype is biologically active in each diseased tissue.

Rituximab treatment in patients with refractory inflammatory myopathies

OBJECTIVE

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

Pathogenic aspects of dermatomyositis, polymyositis and overlap myositis

Inflammatory myopathies (IMs) often have distinct histopathologic features suggesting humorally mediated involvement of the microcirculation in dermatomyositis (DM), including early capillary deposition of the complement C5b-9 membranolytic attack complex (MAC) and secondary ischaemic changes; and CD8 T-cell-mediated and MHC1-restricted autoimmune attack of myofibers in polymyositis (PM) and inclusion body myositis. Novel insights in these specific diseases include emerging evidence that capillary loss involves whole microvascular units in DM, and that regulatory T-cells strongly protect myofibers from experimental autotoxic attack in PM. However, all IMs do not exhibit pathophysiology-relevant histopathologic features of DM or PM. Autoimmune necrotizing myopathies (AINM) occur in the absence of endomysial inflammatory cells and may be specifically associated with anti-SRP autoantibodies. Moreover, IM histopathological features may be scarce, unspecific and overlapping. Therefore, increasing attention is paid to features shared by IMs regardless of their type, relevant to the innate immune response and to non-immune mechanisms. Innate immune responses to myodamage (and/or as yet unknown stimuli), involves release of chemokines, activation of specific Toll-like receptors (TLRs) and complex Th-1, Th-17 and other cytokine interplays; it triggers DC recruitment and maturation, and is associated with type 1 IFN signature (especially in DM where type 1 IFN-producing cells called plasmacytoid DCs are mainly detected). Non-immune mechanisms mainly include endoplasmic reticulum (ER) stress induced in myofibers by up-regulation of MHC-class I antigens (as typically observed in PM with a diffuse pattern and in DM with perifascicular predominance). ER stress may favour autoimmune reactions but may also be associated with myofiber damage and dysfunction in the absence of lymphocytes. Overlap myositis (OM) may be associated with other connective tissue diseases and a variety of autoantibodies, such as those directed against tRNA synthetase. Myositis specific autoantibodies are mainly expressed by regenerating myofibers, that may also express MHC-1 and endogenous ligand-binding TLRs, thus drawing a picture in which the regenerating myofiber plays a central pathophysiologic role.

Detection of the membrane attack complex as a diagnostic tool in dermatomyositis

BACKGROUND

Currently there is no reliable diagnostic marker to distinguish between the subgroups of idiopathic inflammatory myopathies (IIMs), i.e. dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Membrane attack complex (MAC) has been shown to be involved in the pathogenesis of dermatomyositis but its role as a diagnostic marker has not been evaluated.

AIM

To assess the diagnostic utility of MAC deposition in distinguishing dermatomyositis from other neuromuscular disorders.

MATERIAL AND METHODS

Immunohistochemical detection of MAC deposition on endomysial microvessels was carried out on 127 muscle biopsies comprising of 21 cases of dermatomyositis, 42 other IIMs and 64 non-IIM neuromuscular diseases.

RESULTS

MAC deposition showed a high sensitivity (80.9%) and specificity (85%) to differentiate DM from other IIMs. Its specificity was higher (98.4%) in discriminating DM from non-IIM muscular diseases and IIM from non-IIMs.

CONCLUSION

MAC deposition can serve as a reliable marker to distinguish DM from other IIMs (i.e. PM and IBM) as well as from non-IIM diseases. It can also serve as a useful adjunct in diagnosis of IIMs when there is diagnostic dilemma with their morphologic similarities. These results provide further credence to the long-standing view that MAC-mediated capillary destruction is involved in the immunopathogenesis of DM.

Early-stage testicular cancer: a rare association with dermatomyositis

Dermatomyositis has a known association with malignancy. We report a case of dermatomyositis occurring in early-stage testicular cancer where the patient was in remission. It stresses the importance of considering testicular cancer as an association with dermatomyositis, as it is a potentially curable malignancy.

Innovative uses of rituximab in dermatology

Since its approval in 1997 by the US Food and Drug Administration, rituximab has been approved for use in certain B-cell lymphomas and treatment-resistant rheumatoid arthritis. Over the past 10 years, many published reports have suggested rituximab's efficacy in several inflammatory conditions in dermatology. This article includes a review of the mechanism of action, dosing, side-effect profile, and the current literature for various off-label uses of this CD20+ B-cell antagonist, rituximab.

Dermatomyositis and type 1 interferons

Dermatomyositis is a poorly understood multisystem disease predominantly affecting skin and muscle. This review focuses on the potential role of a group of related cytokines, the type 1 interferons, in the pathogenesis of dermatomyositis. Type 1 interferon-inducible transcripts and proteins are uniquely elevated in dermatomyositis muscle compared with all other muscle diseases studied to date. The endothelial cell tubuloreticular inclusions present in affected dermatomyositis muscle are biomarkers of type 1 interferon exposure. The cell-poor lichenoid reaction in skin with predominant involvement of the basal epidermal cell layer and its topologic equivalent in muscle, perifascicular atrophy, may be lesions that develop directly in response to type 1 interferon signaling.

Type 1 interferons and myositis

Recent studies suggest a mechanistic role for molecules induced by type 1 interferons in the pathogenesis of some forms of myositis. For dermatomyositis, evidence that these molecules injure myofibers seems especially strong. In the group of disorders known as polymyositis, the study of blood samples suggests a potential role. It is unknown what drives the sustained presence of type 1 interferon-inducible molecules in these diseases, as the type 1 interferons themselves have not been specifically detected along with their downstream biomarkers. Therapeutic development for blockade of IFNα is in progress aided by the identification of blood genomic biomarkers.

Muscle resident macrophages control the immune cell reaction in a mouse model of notexin-induced myoinjury

OBJECTIVE

Skeletal muscle may be the site of a variety of poorly understood immune reactions, particularly after myofiber injury, which is typically observed in inflammatory myopathies. This study was undertaken to explore both the cell dynamics and functions of resident macrophages and dendritic cells (DCs) in damaged muscle, using a mouse model of notexin-induced myoinjury to study innate immune cell reactions.

METHODS

The myeloid cell reaction to notexin-induced myoinjury was analyzed by microscopy and flow cytometry. Bone marrow (BM) transplantation studies were used to discriminate resident from exudate monocyte/macrophages. Functional tests included cytokine screening and an alloantigenic mixed leukocyte reaction to assess the antigen-presenting cell (APC) function. Selective resident macrophage depletion was obtained by injection of diphtheria toxin (DT) into CD11b-DT receptor-transgenic mice transplanted with DT-insensitive BM.

RESULTS

The connective tissue surrounding mouse muscle/fascicle tissue (the epimysium/perimysium) after deep muscle injury displayed a resident macrophage population of CD11b+F4/80+CD11c-Ly-6C-CX3CR1- cells, which concentrated first in the epimysium. These resident macrophages were being used by leukocytes as a centripetal migration pathway, and were found to selectively release 2 chemokines, cytokine-induced neutrophil chemoattractant and monocyte chemoattractant protein 1, and to crucially contribute to massive recruitment of neutrophils and monocytes from the blood. Early epimysial inflammation consisted of a predominance of Ly-6C(high)CX3CR1(low)CD11c- cells that were progressively substituted by Ly-6C(low)CX3CR1(high) cells displaying an intermediate, rather than high, level of CD11c expression. These CD11c(intermediate) cells were derived from circulating CCR2+ monocytes, functionally behaved as immature APCs in the absence of alloantigenic challenge, and migrated to draining lymph nodes while acquiring the phenotype of mature DCs (CD11c+Ia+CD80+ cells, corresponding to an inflammatory DC phenotype).

CONCLUSION

The results in this mouse model show that resident macrophages in the muscle epimysium/perimysium orchestrate the innate immune response to myoinjury, which is linked to adaptive immunity through the formation of inflammatory DCs.

Dermatomyositis-like muscle pathology in patients with chronic graft-versus-host disease

Myositis is a rare complication of chronic graft-versus-host disease (cGVHD) following hematopoietic stem cell transplantation (HSCT). Almost all such patients have been reported to have polymyositis (PM). We describe clinical, pathologic, and molecular studies of 3 patients with cGVHD following allogeneic HSCT who developed myopathy. In each case, perifascicular atrophy, the pathognomonic histologic feature of dermatomyositis (DM), was observed.

[Myositides]

Idiopathic inflammatory myopathies (IIM) are diseases that are potentially amenable to immunomodulatory therapy. The challenge for the neuropathologist consists in distinguishing these myopathies from secondary inflammatory myopathies, especially in the context of some muscular dystrophies and metabolic diseases that may also show inflammatory infiltrates. There are generalized IIMs (dermatomyositis, polymyositis, sporadic inclusion body myositis) and focal ones (e.g., proliferative myositis, macrophagic myofasciitis). This review provides diagnostic criteria for each of these and includes pathogenetic mechanisms where available.

Ultrasound in the inflammatory myopathies

Dermato- or polymyositis must be diagnosed or ruled out early because early immunosuppressive therapy prevents irreversible muscle degeneration. Acute poly- and dermatomyositis are accompanied by normal or increased size, low echogenicity, and elevated perfusion of affected muscles, whereas in chronic poly- and dermatomyositis, the size and perfusion of affected muscles are reduced and echogenicity is increased. Although magnetic resonance imaging is more sensitive in detecting edema-like muscular changes and thereby acute myositis, contrast-enhanced ultrasound with its capability of measuring perfusion has become a useful diagnostic tool in diagnosing acute inflammation in poly- and dermatomyositis.

[Elevated serum aldolase activity in a patient of non-eosinophilic myofasciitis and synovitis with perifascicular atrophy]

A 35-year-old man suffered from myalgia and joint pain on walking for 5 months. Physical and neurological examinations revealed dermal sclerosis, skin swelling, redness of forearms, Raynaud's phenomenon, joint pain, myalgia and muscle weakness. Eosinophilia was not found and serum creatine kinase activity was normal, while aldolase was markedly elevated. Abnormal signals suggesting synovitis and myofasciitis were found on MRI images. Biopsy of the fascia of quadriceps femoris showed perivascular mononuclear cell infiltration. A muscle biopsy showed mononuclear cell infiltration mainly in the perimysium extending to the endmysium. Eosinophilic cells were not found, Perifascicular atrophy was observed. Corticosteroid therapy improved clinical symptoms and serum aldolase level. We diagnosed him as non-eosinophilic myofasciitis and synovitis with perifascicular atrophy. The serum aldolase activity is usuful for diagnosis and for monitoring the disease activity.

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.

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.

Type I interferon-inducible gene expression in blood is present and reflects disease activity in dermatomyositis and polymyositis

OBJECTIVE

To apply gene expression profiling to the study of peripheral blood mononuclear cells from patients with inflammatory myopathies, in order to provide insight into disease pathogenesis and identify potential biomarkers associated with disease activity.

METHODS

We used Affymetrix whole-genome microarrays to measure the expression of approximately 38,500 genes in 65 blood and 15 muscle samples from 44 patients with dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), myasthenia gravis, or genetically determined myopathies and from 12 healthy volunteers. In 9 patients, 2 samples were obtained at different time points, when disease was either active or improving, and these paired blood samples were also compared. Bioinformatics techniques were used to identify genes with significant differential expression among diagnostic categories and in relation to disease activity. We corroborated the microarray data with quantitative real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Most patients with active DM or PM, but not patients with IBM, had significant and high up-regulation of the type I interferon-alpha/beta (IFNalpha/beta)-inducible genes in blood. Furthermore, the up-regulation of these genes correlated with disease activity in DM and PM, with down-regulation occurring when disease was controlled with treatment.

CONCLUSION

DM and PM are diseases characterized by the systemic overexpression of IFNalpha/beta-inducible genes. The magnitude of the overexpression of these genes is higher in DM and correlates with disease activity in both disorders. Although PM and IBM have been modeled as having similar immunologic processes occurring within muscle, there are substantial differences in the expression of IFNalpha/beta-inducible genes in blood in these diseases.

Advances in the immunopathophysiology of the idiopathic inflammatory myopathies: Not as simple as suspected

In the past three decades, not much has changed in the pathophysiologic concepts of dermatomyositis and polymyositis. However, in the past couple of years, many changes have occurred reflecting the extremely complex nature of the immune response in general. New pathophysiologic models are needed, but at present, none of them encompasses all the recent findings. The changing concepts of dermatomyositis and polymyositis offer new opportunities for unraveling these diseases and developing better strategies for prevention and treatment. This article discusses the most important developments and their methodologic short-comings.

Treatment of Susac's syndrome

Susac's syndrome (SS) is an immune-mediated endotheliopathy that affects the microvasculature of the brain, retina, and inner ear. SS responds well to immunosuppressive therapies when treatment is prompt, aggressive, and sustained. Striking similarities exist between SS and dermatomyositis (DM), regarding immunopathogenesis, natural history, and treatment needs. We apply lessons learned from study of DM to SS, and offer our current treatment protocol for SS. Since these treatment guidelines are based mainly on anecdotal evidence, they represent only preliminary recommendations.

Off-label uses of biologics in dermatology: Rituximab, omalizumab, infliximab, etanercept, adalimumab, efalizumab, and alefacept (Part 2 of 2)

Recently, dermatologists have witnessed a revolution in our therapeutic armamentarium with the development of several novel biologic immunomodulators. Although psoriasis remains the only condition in dermatology for which the use of biologic immunomodulators has been approved by the Food and Drug Administration, these drugs have the potential to significantly impact the treatment of several inflammatory conditions in dermatology. This article includes a review of the mechanism of action, dosing, and side-effect profile, as well as a review of the current literature on off-label uses of the CD20-positive B-cell antagonist rituximab, the IgE antagonist omalizumab, the tumor necrosis factor-alpha antagonists infliximab, etanercept, and adalimumab, and the T-cell response modifiers efalizumab and alefacept.

Contrast-enhanced Ultrasound in Dermatomyositis- and Polymyositis

OBJECTIVE

To evaluate prospectively contrast-enhanced ultrasound (CEUS) in patients suspected of having dermatomyositis or polymyositis.

METHODS

In 35 patients (23 women, 12 men; mean age, 51 years+/-16 years) who were suspected of having dermatomyositis or polymyositis, perfusion in clinically affected skeletal muscles was quantified with contrast-enhanced intermittent power Doppler ultrasound. By applying a modified model that analyzed the replenishment kinetics of microbubbles, the perfusion-related parameters blood flow, local blood volume and blood flow velocity were measured. Findings were compared with muscle biopsy appearances and with the results of MRI that was performed with a 1.5-Tesla unit. Receiver operating characteristic analysis was performed and optimum thresholds for diagnosis of myositis were determined.

RESULTS

Eleven patients had histologically confirmed dermatomyositis or polymyositis and showed significantly higher blood flow velocity (P=.01 for dermato- and P<.001 for polymyositis), blood flow (P<.001 for dermato- and polymyositis), and blood volume (P=.007 for dermato- and P<.001 for polymyositis) on contrast-enhanced ultrasound than those who did not have myositis. An increase in signal intensity on T2-weighted MR images was found in all patients with myositis. MRI had a sensitivity, specificity, positive (PPV), and negative predicting values (NPV) of 100%, 88%, 77%, and 100% for diagnosis of myositis, respectively. CEUS blood flow was the best ultrasound measure for diagnosis of dermato- or polymyositis with sensitivity, specificity, PPV, and NPV of 73%, 91%, 80%, and 88%, respectively.

CONCLUSIONS

Increased skeletal muscle perfusion measured by CEUS could serve as an additional measurer for the diagnosis of an inflammatory myopathy.

Rationale for T Cell Inhibition by Cyclosporin A in Major Autoimmune Diseases

T cells exert a fundamental role in different autoimmune chronic inflammatory diseases. The low-affinity autoreactive T cell clones provide the first amplification loop after the antigen (AgX) presentation, and if not counterregulated by the T regulatory cells (Treg), they maintain the inflammation and predispose to organ damage. Interrupting the T cell amplification loop through calcineurin antagonists leads to maintenance of the whole process under the autoimmune threshold.

Interferon-α/β-mediated innate immune mechanisms in dermatomyositis

Dermatomyositis has been modeled as an autoimmune disease largely mediated by the adaptive immune system, including a local humorally mediated response with B and T helper cell muscle infiltration, antibody and complement-mediated injury of capillaries, and perifascicular atrophy of muscle fibers caused by ischemia. To further understand the pathophysiology of dermatomyositis, we used microarrays, computational methods, immunohistochemistry and electron microscopy to study muscle specimens from 67 patients, 54 with inflammatory myopathies, 14 with dermatomyositis. In dermatomyositis, genes induced by interferon-alpha/beta were highly overexpressed, and immunohistochemistry for the interferon-alpha/beta inducible protein MxA showed dense staining of perifascicular, and, sometimes all myofibers in 8/14 patients and on capillaries in 13/14 patients. Of 36 patients with other inflammatory myopathies, 1 patient had faint MxA staining of myofibers and 3 of capillaries. Plasmacytoid dendritic cells, potent CD4+ cellular sources of interferon-alpha, are present in substantial numbers in dermatomyositis and may account for most of the cells previously identified as T helper cells. In addition to an adaptive immune response, an innate immune response characterized by plasmacytoid dendritic cell infiltration and interferon-alpha/beta inducible gene and protein expression may be an important part of the pathogenesis of dermatomyositis, as it appears to be in systemic lupus erythematosus.

The Effects of Meditation and Visual Imagery on an Immune System Disorder: Dermatomyositis

OBJECTIVE

To analyze the relationship between a patient's "spontaneous recovery" from dermatomyositis and her practice of transcendental meditation and visual imagery without confounding effects of conventional therapies.

DESIGN

Study of time-varying relationships between (1) measures of arm strength and skin condition (rash and pain) and (2) mind-body interventions-controlling for psychologic stress-in a patient with dermatomyositis, using regression analysis to determine half-lives of treatments and stress.

SETTING

Institutional referral center.

INTERVENTION

Transcendental meditation and visual imagery (no drugs).

OUTCOME MEASURES

Daily measurements of arm strength and skin condition over 294 days. Events producing psychologic stress were also rated using a numerical scale.

RESULTS

The patient recovered, which is a low-probability event without conventional therapy. Regression analysis of time dependence between measures of arm strength, rash, and pain and application of mind-body treatments revealed statistically significant relationships for both meditation (p values 0.02 to 0.001) and visual imagery (p values 0.02 to 0.002). Stress had a significant negative impact on skin symptoms but not arm strength. Beneficial effects of meditation had half-lives of 48-59 days for skin condition and no detectable decay for arm strength. Benefits of visual imagery were more transient (half-lives 4-18 days). The effects of stress had half-lives of only 1-3 days.

CONCLUSIONS

The results demonstrate a statistically significant relationship between mind-body therapies and the patient's recovery from dermatomyositis, possibly mediated by influences on the humoral immune system. A key factor in the recovery was the slower decay rate of meditation and visual imagery compared to stress. As dermatomyositis is a humorally mediated immune microvasculopathy, the benefits of meditation and imagery in our patient comport with a growing body of evidence showing that these techniques influence immune system function.