A novel grey scale and Power Doppler ultrasonographic score for idiopathic inflammatory myopathies: Siena Myositis Ultrasound Grading Scale.

OBJECTIVES: No clear-cut guidelines exist on the use of diagnostic procedures for idiopathic inflammatory myopathies (IIM) and only minimal and conflicting data report the use of ultrasound (US). In this regard, we aimed to assess if grey-scale (GS) and Power Doppler (PD) US, graded with a 0-3-point scale, may be a reliable tool in a cohort of patients affected by IIM. METHODS: All patients underwent US examination of both thighs in axial and longitudinal scans. Oedema and atrophy, both assessed in GS and PD, were graded with a 0-3-point scale. Spearman's test was used to identify the correlations between US and clinical and serological variables. RESULTS: A total of 20 patients were included. Six and two patients were evaluated twice and three times, respectively. Muscle oedema was found to be directly correlated with physician global assessment (PhGA), serum myoglobin and PD and negatively with disease duration. PD score was positively correlated to PhGA and negatively to disease duration. Muscle atrophy directly correlated with Myositis Damage Index, disease duration and patient's age. The single-thigh sub-analysis evidenced a direct correlation between PD score and Manual Muscle Test. CONCLUSIONS: In our cohort, we found that oedema and PD are strictly related to early, active myositis, suggesting that an inflamed muscle should appear swollen, thickened and with Doppler signal. Conversely, muscle atrophy reflects the age of the patient and the overall severity of the disease. Such findings shed a new, promising, light on the role of US in diagnosis and monitoring of IIMs.

External validation of the EULAR/ACR idiopathic inflammatory myopathies classification criteria with a Japanese paediatric cohort.

OBJECTIVES: To assess the performance of the EULAR/ACR idiopathic inflammatory myopathies (IIMs) classification criteria to classify juvenile IIMs (JIIMs) in an Asian paediatric population. METHODS: Sixty-eight JIIM patients and 49 non-JIIM patients diagnosed at seven major paediatric rheumatology centres in Japan between 2008 and 2015 were enrolled. Retrospective data were collected, and each patient's data form was submitted. The expert group reviewed the forms and re-examined the diagnoses. The EULAR/ACR criteria were then applied and the probability of having JIIM was determined for each case. The sensitivity and specificity of the EULAR/ACR criteria were compared with those of other existing criteria. RESULTS: The sensitivity/specificity of the EULAR/ACR classification criteria were 92.1/100% with muscle biopsy data (n = 38); 86.7/100% without muscle biopsy data (n = 30) and 89.7/100% in our total cohort (n = 68). The sensitivity of Bohan and Peter's criteria and Tanimoto's criteria were 80.9 and 64.7% in our total cohort, respectively. Among 68 physician-diagnosed JIIM patients, seven cases (three JDM and four overlap myositis) were not classified as JIIM because the probability did not reach the cut-off point (55%). The three JDM patients all presented with only one of the three skin manifestations that are listed in the criteria: Gottron's sign. CONCLUSION: Our validation study with Japanese JIIM cases indicates that the EULAR/ACR classification criteria for IIM generally perform better than existing diagnostic criteria for myositis.

A network of core and subtype-specific gene expression programs in myositis.

Myositis comprises a heterogeneous group of skeletal muscle disorders which converge on chronic muscle inflammation and weakness. Our understanding of myositis pathogenesis is limited, and many myositis patients lack effective therapies. Using muscle biopsy transcriptome profiles from 119 myositis patients (spanning major clinical and serological disease subtypes) and 20 normal controls, we generated a co-expression network of 8101 dynamically regulated transcripts. This network organized the myositis transcriptome into a map of gene expression modules representing interrelated biological processes and disease signatures. Universally myositis-upregulated network modules included muscle regeneration, specific cytokine signatures, the acute phase response, and neutrophil degranulation. Universally myositis-suppressed pathways included a specific subset of myofilaments, the mitochondrial envelope, and nuclear isoforms of the anti-apoptotic humanin protein. Myositis subtype-specific modules included type 1 interferon signaling and titin (dermatomyositis), RNA processing (antisynthetase syndrome), and vasculogenesis (inclusion body myositis). Importantly, therapies exist to target influential proteins in many myositis-dysregulated modules, and nearly all modules contained understudied proteins and non-coding RNAs - many of which were extraordinarily dysregulated in myositis and may represent novel therapeutic targets. Finally, we apply our network to patient classification, finding that a deep learning algorithm trained on patient-level network "images" successfully assigned patients to clinical groups and further into molecular subclusters. Altogether, we provide a global resource to probe and contextualize differential gene expression in myositis.

Myositis-specific autoantibodies and their clinical associations in idiopathic inflammatory myopathies.

BACKGROUND: Myositis-specific autoantibodies (MSAs) have been found to be present predominantly in patients with idiopathic inflammatory myopathies (IIMs). This study aimed to investigate the prevalence of MSAs and their associated complications in a cohort of patients with IIMs. METHODS: This was a multicentered prospective study. Consecutive adult Chinese patients with IIMs in the regional hospitals in Hong Kong were followed up from July 2016 to January 2018. Clinical characteristics, treatment history, and disease complications were documented. A commercially available immunoblot assay was used to detect the MSAs. RESULTS: Out of the 201 patients studied, at least one MSA was found in 63.2% of patients. The most common among the identified MSAs were the anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5 Ab) and the anti-transcriptional intermediary factor 1-gamma antibody (anti-TIF1-γ Ab) (both 13.9%), followed by anti-Jo-1 antibody (12.4%). Anti-MDA5 was present exclusively in dermatomyositis (DM) and was strongly associated with digital ulcers, amyopathy, and rapidly progressive interstitial lung disease (RP-ILD). Anti-TIF1γ was strongly associated with refractory rash and malignancy. Independent risk factors of RP-ILD included anti-MDA5 (OR 14.5), clinically amyopathic DM (OR 13.9), and history of pulmonary tuberculosis (OR 12.2). Cox regression analysis showed that anti-TIF1γ (HR 3.55), DM (HR 3.82), and family history of cancer (HR 3.40) were independent predictors of malignancy. CONCLUSIONS: MSA testing enables dividing of patients with IIMs into phenotypically homogeneous subgroups and prediction of potentially life-threatening complications.

Teleconsultation experience with the idiopathic inflammatory myopathies: a prospective observational cohort study during the COVID-19 pandemic.

Teleconsultation has assumed a central role in the management of chronic and disabling rheumatic diseases, such as the idiopathic inflammatory myopathies (IIM), during COVID-19. However, the feasibility, challenges encountered, and outcomes remain largely unexplored. Here, we describe our teleconsultation experience in a prospectively followed cohort of adult and juvenile IIM. 250 IIM enrolled into the MyoCite cohort (2017-ongoing) were offered the option of audio/visual teleconsultation using WhatsApp during the nationwide lockdown. Clinical outcomes (major/minor relapse) and prescription changes were compared between IIM subsets. Socio-demographic and clinico-serological characteristics of those who sought teleconsultation were compared with those who did not. 151 teleconsultations were sought over a 93 day period by 71 (52.2%) of 136 IIM (median age 38 years, F:M 4.5:1). Nearly one-third (38%) consulted on an emergency basis, with voice consultations being the primary medium of communication. Over a quarter (26.8%) reported relapse (15.5% minor, 11.3% major), these being more common in JDM [71.4%, OR 8.9 (1.5-51)] as compared with adult IIM, but similar across various antibody-based IIM subtypes. Patients who relapsed required more consultations [2(2-3) vs 1(1-2), p 0.009]. The demographic and socioeconomic profile of the patients seeking consultation (n = 71) was not different from those who did not (n = 65). Voice-based teleconsultations may be useful to diagnose and manage relapses in IIM during the pandemic. Patient education for meticulous and timely reporting may be improve care, and larger multicentre studies may identify subsets of IIM that require greater care and early tele-triage for effective management of the condition.

Where are we moving in the classification of idiopathic inflammatory myopathies?

PURPOSE OF REVIEW: Discoveries of myositis-specific antibodies, transcriptomic signatures, and clinicoseropathological correlation support classification of idiopathic inflammatory myopathies (IIM) into four major subgroups: dermatomyositis, immune-mediated necrotizing myopathy (IMNM), antisynthetase syndrome (ASS), and inclusion body myositis (IBM) whereas leaving polymyositis as a historical nonspecific diagnosis of exclusion. This review summarizes and comments on recent knowledge regarding the major subgroup of IIM. RECENT FINDINGS: Type 1 interferon (IFN1) pathway activation is the most prominent in dermatomyositis whereas type 2 interferon (IFN2) pathway activation is high in IBM and ASS; neither pathway is distinct in IMNM. Myxovirus-resistant protein A, IFN1 surrogate marker, is now one of definite dermatomyositis muscle biopsy criteria in the new 2018 European Neuromuscular Centre classification of dermatomyositis; the classification emphasizes on different categorization with and without dermatomyositis-specific antibody result. Novel HLA loci associated with anti-TIF1-γ, anti-Mi-2, and anti-Jo-1 antibodies in Caucasian population are identified. Associations of chaperon-assisted selective autophagy (CASA) and complement-mediated autoimmunity in IMNM as well as highly differentiated T cells in IBM are discovered. SUMMARY: Current IIM classification requires integrated clinicoseropathological approaches. Additional information, such as transcriptomics, HLA haplotyping, and potential biomarkers help tailoring categorization that may have future diagnostic and therapeutic implications.

First external validation of sensitivity and specificity of the European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for idiopathic inflammatory myopathies with a Japanese cohort.

OBJECTIVE: To externally validate the performance of the new European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria set for idiopathic inflammatory myopathies (IIM) with a Japanese cohort. METHODS: This study included 420 IIM and 402 non-IIM cases. Probability of having IIM in each patient was calculated using the collected data set. The cut-off probability was set at 55%, as recommended by EULAR/ACR. Patients classified as IIM by the criteria were further subclassified with classification trees. RESULTS: When the probability cut-off was set at 55%, the sensitivity/specificity of the new criteria to diagnose IIM were 89.3%/91.0% in the total cohort, 88.1%/95.1% without muscle biopsy data and 90.4%/65.5% with biopsy data. The cohort included 12 overlap syndrome patients with biopsy data, who were included as non-IIM cases in accordance with traditional Japanese methods. When they were included in the IIM cases, the specificity in patients with biopsy increased to 74.4%. The sensitivity/specificity of the new criteria to diagnose polymyositis/dermatomyositis (PM/DM) plus juvenile and amyopathic DM in the Japanese cohort was 87.4%/92.4%, which were greater than those of the Tanimoto's criteria revised to enable classification of amyopathic DM (ADM) (71.2%/87.8%) and were comparable with those of Bohan & Peter's criteria to diagnose those diseases except for ADM (88.4%/88.3%). CONCLUSIONS: Our study externally validated high specificity of the new criteria for the first time, although with several limitations, including low percentage of child patients. The new criteria have higher sensitivity and/or specificity in classification of PM/DM than the previously reported criteria, demonstrating its usefulness for interethnic patients.

Trends in idiopathic inflammatory myopathies: cross-sectional data from the German National Database.

OBJECTIVE: To describe trends in outcomes among patients with idiopathic inflammatory myopathies (IIM) over two decades. METHODS: From 1997 to 2017, a total of 1079 IIM patients were documented in the National Database of the German Collaborative Arthritis Centers. Annual cross-sectional data on treatment, disease activity, patient-reported outcomes, hospitalization and employment were compared across the years. Information on phenotypes, organ manifestations and autoantibodies was collected for a subset to compare the assessment of global health, pain, fatigue and sleeping disorders. RESULTS: In 2017, significantly more IIM patients were assessed to be in low disease activity (94%) than in 1997 (59%), p < 0.01. Pain (p = 0.001), global health (p = 0.049), fatigue (p = 0.03) and sleeping disorders (p = 0.01) also improved since recording. Glucocorticoid use decreased from 84 to 58% (p < 0.01). Employment in patients < 65 years remained unchanged (53%), while early retirement (23-9%), hospitalization/year (34-18%) and sick leave (52-24%) decreased. A total of 186 patients with information on subtypes were classified as polymyositis (44%), dermatomyositis (33%), anti-synthetase syndrome (10%), overlapping-myositis (8%), inclusion body myositis (2%), necrotizing myositis (0.5%) and unspecific (3%). The most frequently reported symptoms were limitations in global health (60%), fatigue (57%) and sleeping disorders (51%), and all of them were most frequent in overlap-myositis. Pulmonary hypertension and cardiomyopathy were associated with poor outcomes regarding global health, daily activities and fatigue. CONCLUSION: IIM patients report better outcomes than 20 years ago, along with good physician-reported disease control. Global health, fatigue and sleeping disorders are relevant patient-reported domains in IIM.

Analysis of myositis autoantibodies in Chinese patients with cancer-associated myositis.

BACKGROUND: Cancer-associated myositis (CAM) has poor prognosis and causes higher mortality. In general, myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs) have been shown to be useful biomarkers for its diagnosis. METHODS: In the present study, focus was given in assessing the presence, prevalence, and diagnostic values of myositis autoantibodies in Chinese patients diagnosed with CAM. The sera collected from 49 CAM patients, 108 dermatomyositis/polymyositis (DM/PM) patients without cancer, 105 disease controls, and 60 healthy controls were detected for the presence of 16 autoantigens (Jo-1, OJ, EJ, PL-7, PL-12, MDA5, TIF1γ, Mi-2α, Mi-2ß, SAE1, NXP2, SRP, Ku, PM-Scl75, PM-Scl100, and Ro-52) using a commercial Euroline assay. RESULTS: The frequency of anti-TIF1γ was significantly higher in CAM patients than in DM/PM patients without cancer (46.9% vs 14.8%, P < .001). Importantly, the sensitivity and specificity for this MSA were 46.9% and 85.2%, respectively. These helped to differentiate CAM patients from DM/PM patients without cancer. However, there was no difference in other MSAs and MAAs between CAM and DM/PM patients without cancer. CONCLUSION: The present study indicates that anti-TIF1γ levels can serve as important biomarkers for CAM diagnosis and help in distinguishing between CAM and DM/PM patients without cancer.

Classification of idiopathic inflammatory myopathies: pathology perspectives.

PURPOSE OF REVIEW: Idiopathic inflammatory myopathies (IIM) are rare diseases with heterogenous clinicopathological features. In recent years, new classification systems considering various combinations of clinical, serological, and pathological information have been proposed. This review summarizes recent clinicoseropathological development in major subgroups of IIM. RECENT FINDINGS: Considering clinicoseropathological features, IIM are suggestively classified into four major subgroups: dermatomyositis, immune-mediated necrotizing myopathy (IMNM), antisynthetase syndrome (ASS), and inclusion body myositis (IBM). Many historically diagnosed polymyositis have been mainly reclassified as IBM, IMNM, and ASS. Different types of myositis-specific antibodies (MSA) suggest distinct clinicopathological subsets of IIM. Excluding IBM, at least one-third of the IIMs have no known associated MSA. SUMMARY: MSA are crucial for IIM classification but can be negative. Thus, IIM should be universally classified using stepwise or integrated information on clinical, serological, and pathological findings.

The performance of the European League Against Rheumatism/American College of Rheumatology idiopathic inflammatory myopathies classification criteria in an expert-defined 10 year incident cohort.

OBJECTIVES: To assess the performance of the EULAR/ACR idiopathic inflammatory myopathies (IIMs) classification criteria in a cohort of incident IIM cases and examine how criteria-assigned IIM subtype correlates with expert opinion. METHODS: Adults with newly diagnosed IIM attending Salford Royal NHS Foundation Trust were identified over a 10 year period. A retrospective review of all putative cases was performed and those fulfilling a consensus expert opinion diagnosis of IIM were included. Clinical, serological and histological data were collected and each case was assigned a single IIM subtype. The EULAR/ACR classification criteria were then applied and sensitivity, specificity and positive and negative predictive values were calculated, presented with 95% CIs. RESULTS: A total of 1637 cases were screened, with 255 consensus expert opinion IIM cases ultimately identified. Applying the EULAR/ACR classification criteria, the sensitivity to diagnose an IIM was 99.6% (95% CI 97.2, 100) and 80.9% (95% CI 76.0, 85.8) for the criteria cut-points of probable and definite diagnoses, respectively. In 94/255 cases the IIM subtype differed between consensus expert opinion and classification criteria, most strikingly in the group subtyped as PM by the EULAR/ACR criteria, where there was discrepancy in the majority (i.e. in 87/161). CONCLUSION: The EULAR/ACR criteria performed with high sensitivity in identifying IIM in this external cohort of incident IIM. However, substantial disagreements arose between consensus expert opinion and the criteria regarding IIM subtype assignments, resulting in a large proportion of criteria-assigned cases of PM having heterogeneous features. These results may have important implications for future use of these criteria in subsequent research.

Recent developments in classification criteria and diagnosis guidelines for idiopathic inflammatory myopathies.

PURPOSE OF REVIEW: The aim of this review was to summarize key developments in classification and diagnosis of the idiopathic inflammatory myopathies (IIMs). RECENT FINDINGS: The recently published European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for the IIMs provide a comprehensive, accurate and data-driven approach to identification of IIM cases appropriate for inclusion in research studies. Further, recent studies have advanced understanding of clinical manifestations of the IIMs and delineated the role of imaging, particularly magnetic resonance. SUMMARY: The recent publication of the EULAR/ACR classification criteria will potentially greatly improve IIM research through more accurate case identification and standardization across studies.Future inclusion of newly recognized clinical associations with the MSAs may further improve the criteria's accuracy and utility. Clear and comprehensive understanding of associations between clinical manifestations, prognosis and multisystem involvement can aid diagnostic assessment; recent advances include delineation of such associations and expansion of the role of imaging.

New Myositis Classification Criteria-What We Have Learned Since Bohan and Peter.

PURPOSE OF REVIEW: Idiopathic inflammatory myopathy (IIM) classification criteria have been a subject of debate for many decades. Despite several limitations, the Bohan and Peter criteria are still widely used. The aim of this review is to discuss the evolution of IIM classification criteria. RECENT FINDINGS: New IIM classification criteria are periodically proposed. The discovery of myositis-specific and myositis-associated autoantibodies led to the development of clinico-serological criteria, while in-depth description of IIM morphological features improved histopathology-based criteria. The long-awaited European League Against Rheumatism and American College of Rheumatology (EULAR/ACR) IIM classification criteria were recently published. The Bohan and Peter criteria are outdated and validated classification criteria are necessary to improve research in IIM. The new EULAR/ACR IIM classification criteria are thus a definite improvement and an important step forward in the field.

Idiopathic inflammatory myopathies in adults: A comparative study of Bohan and Peter and European Neuromuscular Center 2004 criteria.

BACKGROUND: Bohan and Peter criteria are widely used for the diagnosis of idiopathic inflammatory myopathies (IIMs). Recently, European Neuromuscular Center (ENMC) formulated criteria to identify subgroups of IIMs. AIM: To compare the two diagnostic criteria in adult IIMs. MATERIALS AND METHODS: This was a retrospective review of case records of histologically confirmed IIMs in adults between January 2014 and May 2015. Both the Bohan and Peter, and ENMC 2004 criteria were applied in the same group of patients to subgroup the IIMs. Muscle biopsy was evaluated in all the four domains: muscle fiber, inflammatory, connective tissue, and vascular, with the basic panel of histological stains. Sporadic inclusion body myositis (s-IBM) was diagnosed using ENMC IBM diagnostic research criteria 2011. RESULTS: During the study period, 69 patients fulfilled the ENMC criteria for IIMs including 16 patients with s-IBM. The subgrouping as per the ENMC criteria (53) was: dermatomyositis (DM) in 30; polymyositis (PM) in 2; immune-mediated necrotizing myopathy (IMNM) in 9; and nonspecific myositis (NM) in 12 patients, whereas subgrouping by the Bohan and Peter criteria was DM in 9 and PM with and without connective tissue disease (CTD) in 26 patients only. There was underdiagnosis of DM, as perifascicular atrophy is not recognized as a diagnostic histological feature, and overdiagnosis of PM with and without CTD due to poor characterization of histological features in PM by the Bohan and Peter criteria. CONCLUSIONS: Systematic evaluation of muscle biopsy according to the ENMC criteria with basic panel of histochemical stains improved the diagnostic yield of IIM significantly when compared to the Bohan and Peter criteria.

[What's new in internal medicine?] / Quoi de neuf en médecine interne?

What's new in internal medicine will be dedicated to three topics: i) inflammatory myopathies constituting a heterogenous group of diseases whose clinical manifestations, immunological abnormalities, treatment response and outcomes vary widely; ii) alterations of gut microbiota contributing to the occurrence or development of a range of conditions, including autoimmune diseases for which further work is necessary to understand the correlation of dysbiosis with these diseases; iii) the reciprocal relationship between obesity, metabolic syndrome, atherosclerosis and autoimmune diseases. New data concerning systemic sclerosis, cutaneous vasculitis, adult Still's disease, autoantibodies anti DFS70, Epstein Barr virus and autoimmune diseases were also highlighted.

2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups.

OBJECTIVE: To develop and validate new classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIM) and their major subgroups. METHODS: Candidate variables were assembled from published criteria and expert opinion using consensus methodology. Data were collected from 47 rheumatology, dermatology, neurology and paediatric clinics worldwide. Several statistical methods were used to derive the classification criteria. RESULTS: Based on data from 976 IIM patients (74% adults; 26% children) and 624 non-IIM patients with mimicking conditions (82% adults; 18% children), new criteria were derived. Each item is assigned a weighted score. The total score corresponds to a probability of having IIM. Subclassification is performed using a classification tree. A probability cut-off of 55%, corresponding to a score of 5.5 (6.7 with muscle biopsy) 'probable IIM', had best sensitivity/specificity (87%/82% without biopsies, 93%/88% with biopsies) and is recommended as a minimum to classify a patient as having IIM. A probability of ≥90%, corresponding to a score of ≥7.5 (≥8.7 with muscle biopsy), corresponds to 'definite IIM'. A probability of <50%, corresponding to a score of <5.3 (<6.5 with muscle biopsy), rules out IIM, leaving a probability of ≥50 to <55% as 'possible IIM'. CONCLUSIONS: The European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for IIM have been endorsed by international rheumatology, dermatology, neurology and paediatric groups. They employ easily accessible and operationally defined elements, and have been partially validated. They allow classification of 'definite', 'probable' and 'possible' IIM, in addition to the major subgroups of IIM, including juvenile IIM. They generally perform better than existing criteria.

Integrated classification of inflammatory myopathies.

Inflammatory myopathies comprise a multitude of diverse diseases, most often occurring in complex clinical settings. To ensure accurate diagnosis, multidisciplinary expertise is required. Here, we propose a comprehensive myositis classification that incorporates clinical, morphological and molecular data as well as autoantibody profile. This review focuses on recent advances in myositis research, in particular, the correlation between autoantibodies and morphological or clinical phenotypes that can be used as the basis for an 'integrated' classification system.

Diagnosis and classification of idiopathic inflammatory myopathies.

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of diseases, collectively termed myositis, sharing symptoms of muscle weakness, fatigue and inflammation. Other organs are frequently involved, supporting the notion that these are systemic inflammatory diseases. The IIMs can be subgrouped into dermatomyositis, polymyositis and inclusion body myositis. The myositis-specific autoantibodies (MSAs) identify other and often more distinct clinical phenotypes, such as the antisynthetase syndrome with antisynthetase autoantibodies and frequent interstitial lung disease and anti-SRP and anti-HMGCR autoantibodies that identify necrotizing myopathy. The MSAs are important both to support myositis diagnosis and to identify subgroups with different patterns of extramuscular organ involvement such as interstitial lung disease. Another cornerstone in the diagnostic procedure is muscle biopsy to identify inflammation and to exclude noninflammatory myopathies. Treatment effect and prognosis vary by subgroup. To develop new and better therapies, validated classification criteria that identify distinct subgroups of myositis are critical. The lack of such criteria was the main rationale for the development of new classification criteria for IIMs, which are summarized in this review; the historical background regarding previous diagnostic and classification criteria is also reviewed. As the IIMs are rare diseases with a prevalence of 10 in 100 000 individuals, an international collaboration was essential, as was the interdisciplinary effort including experts in adult and paediatric rheumatology, neurology, dermatology and epidemiology. The new criteria have been developed based on data from more than 1500 patients from 47 centres worldwide and are based on clinically easily available variables.

The juvenile idiopathic inflammatory myopathies: pathogenesis, clinical and autoantibody phenotypes, and outcomes.

The aim of this review was to summarize recent advances in the understanding of the clinical and autoantibody phenotypes, their associated outcomes and the pathogenesis of the juvenile idiopathic inflammatory myopathies (JIIMs). The major clinical and autoantibody phenotypes in children have many features similar to those in adults, and each has distinct demographic and clinical features and associated outcomes. The most common myositis autoantibodies in JIIM patients are anti-p155/140, anti-MJ and anti-MDA5. Higher mortality has been associated with overlap myositis as well as with the presence of anti-synthetase and anti-MDA5 autoantibodies; a chronic illness course and lipodystrophy have been associated with anti-p155/140 autoantibodies; and calcinosis has been associated with anti-MJ autoantibodies. Histologic abnormalities of JIIMs detectable on muscle biopsy have also been correlated with myositis-specific autoantibodies; for example, patients with anti-MDA5 show low levels of inflammatory infiltrate and muscle damage on biopsy. The first genome-wide association study of adult and juvenile dermatomyositis revealed three novel genetic associations, BLK, PLCL1 and CCL21 and confirmed that the human leucocyte antigen region is the primary risk region for juvenile dermatomyositis. Here, we review the well-established pathogenic processes in JIIMs, including the type 1 interferon and endoplasmic reticulum stress pathways. Several novel JIIM-associated inflammatory mediators, such as the innate immune system proteins, myeloid-related peptide 8/14, galectin 9 and eotaxin, have emerged as promising biomarkers of disease. Advances in our understanding of the phenotypes and pathophysiology of the JIIMs are leading to better tools to help clinicians stratify and treat these heterogeneous disorders.

[Acquired inflammatory myopathies: interest of specific autoantibodies for their classification]. / MYOPATHIES INFLAMMATOIRES.

The former classification of myositis based on the clinical phenotype and muscle histology is now changing. We started from the concept of "dermatopolymyositis" to the recognition of inclusion body myositis and more recently of immune mediated necrotizing myopathies. Furthermore, during the last 10 years, the routine access to myositis associated or specific auto-antibodies permitted to fine tune homogenous subgroups of myositis patients with common phenotype, immunopathology and prognosis. Using this approach, the polymyositis group has completely disappeared, the former patients now being reclassified as having and inclusion body myositis or an overlap syndrome such as the anti-synthetase syndrome. The different subgroups of myositis associated with their specific auto-antibodies are described here.