Similar topology of injury to keratinocytes and myofibres in dermatomyositis skin and muscle

Personalised medicine in juvenile dermatomyositis: From novel insights in disease mechanisms to changes in clinical practice

Juvenile dermatomyositis is characterized by childhood-onset chronic inflammation of the muscles and skin, with potential involvement of other organs. Patients are at risk for long-term morbidity due to insufficient disease control and steroid-related toxicity. Personalised treatment is challenged by a lack of validated tools that can reliably predict treatment response and monitor ongoing (subclinical) inflammation, and by a lack of evidence regarding the best choice of medication for individual patients. A better understanding of the involved disease mechanisms could reveal potential biomarkers and novel therapeutic targets. In this review, we highlight the most relevant immune and non-immune mechanisms, elucidating the effects of interferon overexpression on tissue alongside the interplay between the interferon signature, mitochondrial function, and immune cells. We review mechanism-based biomarkers that are promising for clinical implementation, and the latest advances in targeted therapy development. Finally, we discuss key steps needed for translating these discoveries into clinical practice.

Integrating the autoimmune connective tissue diseases for the medical student: A classification proposal based on pathogenesis and clinical phenotype

It is hard for medical students to recognize and understand the clinical presentation of systemic connective tissue diseases (SCTDs). In this study, we aimed to review the immune mechanisms of the main SCTDs and to propose a classification system focused on the student and based on each immune dysfunction's clinical phenotype. The search involved the MEDLINE database and included the terms "systemic lupus erythematosus," "antiphospholipid syndrome," "inflammatory myopathies," "rheumatoid arthritis," "Sjögren's syndrome" or "systemic sclerosis" and "pathogenesis," and "immunology" or "mechanism of disease." Systemic lupus erythematosus (SLE) is a prototypic immune-complex disease with a tendency toward vascular injury. Antiphospholipid syndrome (APS) is a diffuse immune-mediated thrombotic vasculopathy. In inflammatory myopathies (IMs), muscle inflammation leading to muscle weakness is the cardinal manifestation. Rheumatoid arthritis (RA) is a unique form of erosive and destructive polyarthritis. Sjögren's syndrome (SS) causes sicca symptoms due to infiltration of the exocrine glands. Disseminated fibrosis in systemic sclerosis (SSc) is caused by vascular injury with excessive fibroblast activation. After the review, we created a focus group involving all the authors to group the diseases according to their pathogenesis and clinical phenotype. Our group agreed that SCTDs can be divided in 3 groups based on the preferential clinical presentation and immune dysfunction: 1) vasculopathic features (SLE and APS), 2) tissue inflammation (IMs, RA, and SS), and 3) tissue fibrosis (SSc). In synthesis, we suggest that clustering SCTDs in groups based on clinical phenotype and presumptive immune dysfunction instead of ordering autoantibodies randomly can help students understand the diseases.

The role of interferons type I, II and III in myositis: A review

The classification of idiopathic inflammatory myopathies (IIM) is based on clinical, serological and histological criteria. The identification of myositis-specific antibodies has helped to define more homogeneous groups of myositis into four dominant subsets: dermatomyositis (DM), antisynthetase syndrome (ASyS), sporadic inclusion body myositis (sIBM) and immune-mediated necrotising myopathy (IMNM). sIBM and IMNM patients present predominantly with muscle involvement, whereas DM and ASyS patients present additionally with other extramuscular features, such as skin, lung and joints manifestations. Moreover, the pathophysiological mechanisms are distinct between each myositis subsets. Recently, interferon (IFN) pathways have been identified as key players implicated in the pathophysiology of myositis. In DM, the key role of IFN, especially type I IFN, has been supported by the identification of an IFN signature in muscle, blood and skin of DM patients. In addition, DM-specific antibodies are targeting antigens involved in the IFN signalling pathways. The pathogenicity of type I IFN has been demonstrated by the identification of mutations in the IFN pathways leading to genetic diseases, the monogenic interferonopathies. This constitutive activation of IFN signalling pathways induces systemic manifestations such as interstitial lung disease, myositis and skin rashes. Since DM patients share similar features in the context of an acquired activation of the IFN signalling pathways, we may extend underlying concepts of monogenic diseases to acquired interferonopathy such as DM. Conversely, in ASyS, available data suggest a role of type II IFN in blood, muscle and lung. Indeed, transcriptomic analyses highlighted a type II IFN gene expression in ASyS muscle tissue. In sIBM, type II IFN appears to be an important cytokine involved in muscle inflammation mechanisms and potentially linked to myodegenerative features. For IMNM, currently published data are scarce, suggesting a minor implication of type II IFN. This review highlights the involvement of different IFN subtypes and their specific molecular mechanisms in each myositis subset.

Recent Advances in Pharmacological Treatments of Adult Dermatomyositis

PURPOSE OF THE REVIEW

Dermatomyositis (DM) is an uncommon autoimmune disease that primarily affects the skin, muscle, and/or lungs, and remains a therapeutic challenge. We discuss recent studies evaluating efficacy of conventional treatments for clinically amyopathic DM (CADM), DM-associated interstitial lung (ILD) disease, and classic DM (CDM). We highlight several emerging new therapies with a focus on clinical trials, systematic reviews, and case series in the last 5 years.

RECENT FINDINGS

Recent studies report a significant number of patients remain refractory to antimalarials and require second- and third-line agents. Effective treatment for DM-associated ILD can vary based on patient specific antibodies. CDM requires oral glucocorticoids; recent studies have evaluated the benefits of adjunctive therapies including methotrexate and calcineurin inhibitors. New therapies target cell populations or cytokines thought to drive disease pathogenesis. Dermatomyositis is an autoimmune disease that remains challenging to treat. Many patients are refractory to conventional therapies, warranting the development and evaluation of new treatments.

Myalgia in Patients with Dermatomyositis and Polymyositis Is Attributable to Fasciitis Rather Than Myositis: A Retrospective Study of 32 Patients who Underwent Histopathological Examinations

OBJECTIVE

To determine the association between fasciitis and the clinical variables in patients with dermatomyositis (DM) and polymyositis (PM).

METHODS

We retrospectively reviewed the medical records of 32 patients (24 DM, 8 PM) with newly diagnosed DM and PM and in whom fascia and muscle specimens were histopathologically examined. The relationship between fasciitis and the clinical variables was statistically analyzed. These included age, sex, myalgia, muscle weakness, creatine kinase (CK) and aldolase activities, anti-Jo1 antibody, interstitial lung disease, and malignancy.

RESULTS

Twenty (62.5%) of the 32 patients who underwent the histopathological examination of a fascia specimen had fasciitis, including 18 (75%) of 24 patients with DM and 2 (25%) of 8 patients with PM. The frequency of fasciitis was significantly higher among the patients with DM than among the patients with PM (p < 0.05). Histopathologically, fasciitis in PM was very mild in comparison to that in DM. The frequency of myalgia in patients with fasciitis was significantly higher than that in patients without fasciitis (p < 0.05). However, myalgia was not associated with myositis. There were no significant differences in the patients with and without fasciitis in age, sex, manual muscle test 8 scores, CK or aldolase activities, or the presence of anti-Jo1 antibodies and malignancy.

CONCLUSION

The frequency of fasciitis was significantly higher among patients with DM than among those with PM. Fasciitis, rather than myositis, was associated with myalgia.

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.

Sustained autoimmune mechanisms in dermatomyositis

Dermatomyositis is an autoimmune disease predominantly affecting skin and muscle. Its poorly understood pathogenesis is increasingly being linked to the overproduction of type 1 interferon-inducible gene transcripts and proteins. Mechanisms have been identified by which chronic sustained accumulation of these proteins might occur and thereby injure tissue in dermatomyositis.

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.

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.

Interferon-stimulated gene 15 (ISG15) conjugates proteins in dermatomyositis muscle with perifascicular atrophy

OBJECTIVE

We investigated interferon-stimulated gene 15 (ISG15), a poorly understood ubiquitin-like modifier, and its enzymatic pathway in dermatomyositis (DM), an autoimmune disease primarily involving muscle and skin.

METHODS

We generated microarray data measuring transcript abundance for approximately 18,000 genes in each of 113 human muscle biopsy specimens, and studied biopsy specimens and cultured skeletal muscle using immunohistochemistry, immunoblotting proteomics, real-time quantitative polymerase chain reaction, and laser-capture microdissection.

RESULTS

Transcripts encoding ISG15-conjugation pathway proteins were markedly upregulated in DM with perifascicular atrophy (DM-PFA) muscle (ISG15 339-fold, HERC5 62-fold, and USP18 68-fold) compared with 99 non-DM samples. Combined analysis with publicly available microarray datasets showed that >50-fold ISG15 transcript elevation had 100% sensitivity and specificity for 28 biopsies from adult DM-PFA and juvenile DM patients compared with 199 muscle samples from other muscle diseases. Free ISG15 and ISG15-conjugated proteins were only found on immunoblots from DM-PFA muscle. Cultured human skeletal muscle exposed to type 1 interferons produced similar transcripts and ISG15 protein and conjugates. Laser-capture microdissection followed by proteomic analysis showed deficiency of titin in DM perifascicular atrophic myofibers.

INTERPRETATION

A large-scale microarray study of muscle samples demonstrated that among a diverse group of muscle diseases DM was uniquely associated with upregulation of the ISG15 conjugation pathway. Exposure of human skeletal muscle cell culture to type 1 interferons produced a molecular picture highly similar to that seen in human DM muscle. Perifascicular atrophic myofibers in DM were deficient in a number of skeletal muscle proteins including titin.