Unraveling The Genetics of Shared Clinical and Serological Manifestations in Systemic Inflammatory Autoimmune Diseases.

OBJECTIVES: Systemic inflammatory autoimmune diseases (SIADs) such as systemic lupus erythematosus (SLE), primary Sjögren's syndrome (pSS) and idiopathic inflammatory myopathies (myositis) are complex conditions characterized by shared circulating autoantibodies and clinical manifestations, including skin rashes, among others. This study aimed at elucidating the genetics underlying these common features. METHODS: We performed targeted DNA sequencing of coding and regulatory regions from ~1,900 immune-related genes in a large SIAD cohort of 2,292 well-characterized Scandinavian patients with SLE, pSS and myositis, as well as 1,252 controls. A gene-based functionally-weighted genetic score for aggregate testing of all genetic variants, including rare variants, was complemented by in-silico functional analyses and in-vitro reporter experiments. RESULTS: Case-control association analysis detected known and potentially novel genetic loci in agreement with previous genetic and transcriptomics findings linked to the SIAD autoimmune background. Intriguingly, case-case comparisons between patient subgroups with and without specific autoantibodies revealed that the subgroups defined by ANA and anti-dsDNA antibodies have unique genetic profiles reflecting their heterogeneity. When focusing on clinical features, we overall showed that DUSP1 protective genetic variants lead to increased gene expression and potentially to anti-inflammatory effects on the SIAD-associated skin phenotype. This is consistent with recent genetic findings on eczema and with the previously reported downregulation of the MAPK signaling-related gene DUSP1 in other skin disorders. CONCLUSION: Together, this suggests common molecular mechanisms potentially underlying overlapping clinical manifestations shared among different disorders and informs clinical heterogeneity, which could be translated to improve disease diagnostic and treatment, also in more generalized disease frameworks.

Impact of cancer on the mortality of patients with idiopathic inflammatory myopathies by flexible parametric multistate modelling.

BACKGROUND: Patients with idiopathic inflammatory myopathies (IIM) have an increased risk of cancer, but their cancer-related disease burden remains unclear. OBJECTIVES: To explore how cancer might impact the mortality of patients with IIM and examine the associated prognostic factors for cancer and death. METHODS: We identified patients with IIM diagnosed between 1998 and 2020 and ascertained their cancer and death records via linkage to the Swedish healthcare and population registers. Transition hazards from IIM diagnosis to cancer and death were estimated in multistate models using flexible parametric methods. We then predicted the probability of having cancer or death, and the duration of staying alive at a given time from IIM and cancer diagnoses from a crude model. We also explored prognostic factors for progression to cancer and death in a multivariable model. RESULTS: Of 1826 IIM patients, 310 (17%) were diagnosed with cancer before and 306 (17%) after IIM diagnosis. In patients diagnosed with cancer after IIM, the 5-year probability of death from cancer and from other causes was 31% and 18%, respectively, compared to 7% and 15% in patients without cancer after IIM. We reported several factors associated with risk of progression to cancer and death. Specifically, patients with first cancer after IIM who were older at IIM diagnosis, had cancer history, dermatomyositis and a cancer diagnosis within 1 year following IIM faced a greater cancer-specific mortality. CONCLUSION: We observed a substantial increase in mortality from cancer, compared to before, rather than other causes after a cancer diagnosis following IIM, suggesting an unmet medical need for effective cancer management in IIM patients. This finding, along with the identified prognostic factors, provides useful insight into future research directions for improving cancer management in IIM patients.

Autoantibodies and damage in patients with idiopathic inflammatory myopathies: A longitudinal multicenter study from the MYONET international network.

OBJECTIVE: To study the trajectories of changes in damage over time and explore associations with autoantibody defined subgroups using a large international cohort of patients with idiopathic inflammatory myopathies (IIM). METHODS: Data from the MYONET registry, including patients who were tested for autoantibodies and had at least one assessment of damage using the Myositis Damage Index (MDI), were analyzed. Patients were sub-grouped according to their autoantibody profiles (myositis-specific, myositis-associated, or seronegative). The index date was defined as the time point for the first registered MDI assessment. The longitudinal trajectories of damage with autoantibody status as the main predictor were analyzed using linear mixed models. RESULTS: A total of 757 adult patients were included in this study. Each year of disease duration since diagnosis had an estimated MDI score increase of 0.16 units for the seronegative group (reference). Compared with the seronegative group as reference, patients with dermatomyositis-specific autoantibodies developed less damage per year of follow-up since diagnosis (average 0.08 less score, P = 0.04), whereas patients with anti-PM/Scl autoantibodies developed more damage per year of follow-up since diagnosis (average 0.28 higher score, P = 0.03) independent of sex and age at diagnosis. The seronegative subgroup and the immune-mediated necrotizing myopathy autoantibody subgroup had the strongest correlation between severity of muscle damage and HAQ-DI scores at five years of follow-up, rho=0.84, P < 0.001 and rho=0.72, P < 0.001, respectively. CONCLUSION: Our study is the first to describe patterns and trajectories of change in damage over time in relation to autoantibody defined subgroups in a large international multicenter cohort of patients with IIM. Patients with anti-PM/Scl scored a greater extent of damage, whereas patients with dermatomyositis-specific antibodies had less damage than seronegative patients. Severity in muscle damage had moderate to strong correlation with functional disability among the IMNM and seronegative subgroups with lower correlations for the other subgroups. These findings suggest that autoantibodies may be useful predictors of long-term damage.

Current efforts and historical perspectives on classification of idiopathic inflammatory myopathies.

PURPOSE OF REVIEW: The classification of idiopathic inflammatory myopathies is challenging due to the large number of clinical, serological, histopathological and genetic findings, as well as the latest findings and developments in the field of myositis research. The latest official classification criteria are the 2017 European Alliance of Associations for Rheumatology (EULAR)/American College of Rheumatology (ACR) classification criteria for adult and juvenile idiopathic inflammatory myopathies, which have been extensively reviewed in recent years for their applicability, sensitivity and specificity. RECENT FINDINGS: The sensitivity and specificity of the 2017 ACR/EULAR criteria are sometimes performing better, but usually at the same level as the previous criteria. A large number of further suggestions for amendments to the criteria have been made. In particular there is a need to revise the criteria with regard to the addition of new myositis-specific autoantibodies, newly defined subgroups (especially antisynthetase syndrome, immune medicated necrotizing myopathy and overlap myositis) and possibly the addition of further diagnostic procedures (for instance, muscle MRI or PET CT) to improve the accuracy and timeliness of the criteria. SUMMARY: Efforts to optimize the myositis classification criteria have been extensive in recent years and a new global interdisciplinary collaboration of clinicians is currently taking place based on the previous results with the aim of revising the 2017 EULAR/ACR classification criteria.

The Dermatomyositis Disease Symptom Questionnaire (DM-DSQ): A Measure to Assess the Patient Experience of Dermatomyositis Symptoms.

OBJECTIVE: Dermatomyositis (DM) symptoms negatively affect the quality of life of individuals living with the disease. Disease-specific, patient-reported outcome (PRO) instruments are needed to assess symptoms important to individuals with DM. This study aimed to conceptualize patient DM experience and disease activity definition to refine the development of the Dermatomyositis Disease Symptom Questionnaire (DM-DSQ), a novel PRO instrument capturing patient-reported symptoms. METHODS: An observational, qualitative study was conducted with 30 individuals with DM (aged ≥ 18 yrs) in the US. A 1-hour semistructured interview, including concept elicitation and cognitive debriefing, was conducted with each participant. Inductive coding was used to identify concepts; a saturation analysis was conducted to confirm sample size. Concepts from transcripts were used to refine the preliminary conceptual model and DM-DSQ items. RESULTS: Concept elicitation analysis findings included disease symptoms (eg, muscle weakness) and functional impacts (eg, walking). The analysis achieved conceptual saturation; the first 5 interviews uncovered most of the concepts. During cognitive debriefing of the DM-DSQ, participants found the items relevant, comprehensive, and easily understood (except for "skin sensitivity in sunlight"). The revised DM-DSQ content appears preliminarily valid in the patient population surveyed, pending further additions and debriefing based on refinement of the preliminary conceptual disease model and items. CONCLUSION: The DM-DSQ is being used in a phase II clinical trial and could become a valuable tool for studies evaluating PROs in patients with DM. Preliminary results indicate its content validity; extensive psychometric analysis using clinical trial data will determine its ability to capture symptoms for patients with DM.

Discovery of new myositis genetic associations through leveraging other immune-mediated diseases.

Genome-wide association studies (GWASs) have been successful at finding associations between genetic variants and human traits, including the immune-mediated diseases (IMDs). However, the requirement of large sample sizes for discovery poses a challenge for learning about less common diseases, where increasing volunteer numbers might not be feasible. An example of this is myositis (or idiopathic inflammatory myopathies [IIM]s), a group of rare, heterogeneous autoimmune diseases affecting skeletal muscle and other organs, severely impairing life quality. Here, we applied a feature engineering method to borrow information from larger IMD GWASs to find new genetic associations with IIM and its subgroups. Combining this approach with two clustering methods, we found 17 IMDs genetically close to IIM, including some common comorbid conditions, such as systemic sclerosis and Sjögren's syndrome, as well as hypo- and hyperthyroidism. All IIM subtypes were genetically similar within this framework. Next, we colocalized IIM signals that overlapped IMD signals, and found seven potentially novel myositis associations mapped to immune-related genes, including BLK, IRF5/TNPO3, and ITK/HAVCR2, implicating a role for both B and T cells in IIM. This work proposes a new paradigm of genetic discovery in rarer diseases by leveraging information from more common IMD, and can be expanded to other conditions and traits beyond IMD.

Anti-FHL1 autoantibodies in adult patients with myositis: a longitudinal follow-up analysis.

OBJECTIVES: To determine prevalence and clinical associations of anti-FHL1 autoantibodies in patients with idiopathic inflammatory myopathies (IIM), and to evaluate autoantibody levels over time. METHODS: Sera at the time of diagnosis from patients with IIM (n = 449), autoimmune disease controls (DC, n = 130), neuromuscular diseases (NMD, n = 16) and healthy controls (HC, n = 100) were analyzed for anti-FHL1 autoantibodies by Enzyme-Linked ImmunoSorbent Assay (ELISA). Patients with IIM FHL1+ and FHL1- were included in a longitudinal analysis. Serum levels were correlated to disease activity. RESULTS: Autoantibodies to FHL1 were more frequent in patients with IIM (122/449, 27%) compared with DC (Autoimmune DC and NMD, 13/146, 9%, p< 0.001) and HC (3/100,3%, p< 0.001). Anti-FHL1 levels were higher in IIM [median (IQR)=0.62 (0.15-1.04)] in comparison with DC [0.22 (0.08-0.58)], HC [0.35 (0.23-0.47)] and NMD [0.48 (0.36-0.80)] p< 0.001. Anti-FHL1+ patients with IIM were younger at time of diagnosis compared with the anti-FHL1- group (p= 0.05) and were seronegative for other autoantibodies in 25%.In the first follow-up anti-FHL1+ sample 20/33 (60%) positive at baseline had turned negative for anti-FHL1 autoantibodies. Anti-FHL1 autoantibodies rarely appeared after initiating treatment. Anti-FHL1 autoantibody levels correlated with CK (r = 0.62, p= 0.01), disease activity measure MYOACT (n = 14, p= 0.004) and inversely with manual muscle test-8 (r=-0.59, p= 0.02) at baseline. CONCLUSIONS: Anti-FHL1 autoantibodies were present in 27% of patients with IIM, of these 25% were negative for other autoantibodies. Other autoimmune diseases had lower frequencies and levels. Anti-FHL1 levels often decreased with immunosuppressive treatment, correlated with disease activity measures at diagnosis and rarely appeared after start of treatment.

The Role of Exercise to Improve Physiological, Physical and Psychological Health Outcome in Idiopathic Inflammatory Myopathies (IIM).

Idiopathic inflammatory myopathies (IIM) impact all aspects of health, physiological, physical, and psychological. Hallmark symptoms of IIM are muscle weakness, reduced muscle endurance and aerobic capacity. Recently, pain and fatigue as well as anxiety and depression have emerged as common and debilitating symptoms in patients with IIM. The aim of this scoping review is to, in a holistic way, describe how IIM impact patients' physiological, physical, and psychological health and how exercise has a role to treat as well as potentially counteract the effects of the disease. Inflammation induces non-immune response and organ damage. These changes with additional impact of physical inactivity lead to muscle impairment and reduced aerobic capacity. Pain, fatigue and low psychological well-being and overall quality of life are also common health aspects of IIM. Medical treatment can reduce inflammation but has in turn serious side effects such as muscle atrophy, type-II diabetes, and hypertension, which exercise has the potential to treat, and perhaps also counteract. In addition, exercise improves muscle function, aerobic capacity and might also reduce fatigue and pain. New evidence shows that reducing systemic inflammation may also improve patient-reported subjective health, quality of life and psychological well-being. Exercise in combination with medical treatment is becoming an important part of the treatment for patients with IIM as exercise has the potential to promote health aspects of various dimensions in patients with IIM.

Performance of the 2017 EULAR/ACR Classification Criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: a scoping review.

The 2017 EULAR/ACR classification criteria for adult/juvenile idiopathic inflammatory myopathies (IIM) were established using a data-driven approach by an international group of myositis experts to allow classification of IIM and its major subtypes. Since their publication, the performance of the criteria has been tested in multiple cohorts worldwide and significant limitations have been identified. Moreover, the understanding and classification of IIM have evolved since 2017. This scoping review was undertaken as part of a large international project to revise the EULAR/ACR criteria and aims to i) summarise the evidence from the current literature on the performance characteristics of the 2017 EULAR/ACR classification criteria in various cohorts and IIM subtypes, and ii) delineate the factors that need to be considered in the revision of the classification criteria. A systematic search of Medline (via PubMed), Cumulative Index to Nursing and Allied Health Literature, and conference abstract archives was conducted independently by three investigators for studies on the EULAR/ACR criteria published between October 2017 and January 2023. This scoping review of 19 articles and 13 abstracts revealed overall good performance characteristics of the EULAR/ACR criteria for IIM, yet deficiencies in lack of inclusion of certain IIM subtypes, such as immune mediated necrotising myopathy, amyopathic dermatomyositis, antisynthetase syndrome and overlap myositis. Published modifications that may improve the performance characteristics of the criteria for classification of IIM subtypes were also summarised. The results of this review suggest that a revision of the EULAR/ACR criteria is warranted.

Agreement between local and central anti-synthetase antibodies detection: results from the Classification Criteria of Anti-Synthetase Syndrome project biobank.

OBJECTIVES: The CLASS (Classification Criteria of Anti-Synthetase Syndrome) project is a large international multicentre study that aims to create the first data-driven anti-synthetase syndrome (ASSD) classification criteria. Identifying anti-aminoacyl tRNA synthetase antibodies (anti-ARS) is crucial for diagnosis, and several commercial immunoassays are now available for this purpose. However, using these assays risks yielding false-positive or false-negative results, potentially leading to misdiagnosis. The established reference standard for detecting anti-ARS is immunoprecipitation (IP), typically employed in research rather than routine autoantibody testing. We gathered samples from participating centers and results from local anti-ARS testing. As an "ad-interim" study within the CLASS project, we aimed to assess how local immunoassays perform in real-world settings compared to our central definition of anti-ARS positivity. METHODS: We collected 787 serum samples from participating centres for the CLASS project and their local anti-ARS test results. These samples underwent initial central testing using RNA-IP. Following this, the specificity of ARS was reconfirmed centrally through ELISA, line-blot assay (LIA), and, in cases of conflicting results, protein-IP. The sensitivity, specificity, positive likelihood ratio and positive and negative predictive values were evaluated. We also calculated the inter-rater agreement between central and local results using a weighted κ co-efficient. RESULTS: Our analysis demonstrates that local, real-world detection of anti-Jo1 is reliable with high sensitivity and specificity with a very good level of agreement with our central definition of anti-Jo1 antibody positivity. However, the agreement between local immunoassay and central determination of anti-non-Jo1 antibodies varied, especially among results obtained using local LIA, ELISA and "other" methods. CONCLUSIONS: Our study evaluates the performance of real-world identification of anti-synthetase antibodies in a large cohort of multi-national patients with ASSD and controls. Our analysis reinforces the reliability of real-world anti-Jo1 detection methods. In contrast, challenges persist for anti-non-Jo1 identification, particularly anti-PL7 and rarer antibodies such as anti-OJ/KS. Clinicians should exercise caution when interpreting anti-synthetase antibodies, especially when commercial immunoassays test positive for non-anti-Jo1 antibodies.

Effect modification of cancer on the association between dysphagia and mortality in early idiopathic inflammatory myopathies.

OBJECTIVE: The interplay between dysphagia, cancer, and mortality in idiopathic inflammatory myopathies (IIM) has not been carefully studied. The aim of this study was to investigate possible effect modification of cancer on the association between dysphagia and mortality in early IIM. METHODS: A multi-center cohort of 230 adult IIM patients with dysphagia assessment within 6 months of disease onset was assembled. Crude mortality rates in IIM patients exposed or not to dysphagia were estimated for the 5-year period following cohort entry. To explore possible effect modification of cancer on the association between dysphagia and mortality, adjusted Cox models stratified on cancer status were performed as well as an interaction model. RESULTS: Mortality rates per 100 person-years for IIM patients exposed to dysphagia were 2.3 (95 %CI 1.0 to 4.5) in those without cancer compared to 33.3 (95 %CI 16.6 to 59.5) in those with cancer. In stratified Cox models, the main effect of dysphagia was HR 0.5 (95 %CI 0.2 to 1.5) in non-cancer and 3.1 (95 %CI 1.0 to 10.2) in cancer patients. In the interaction model, the combination of dysphagia and cancer yielded a HR of 6.4 (1.2 to 35.1). CONCLUSION: In this IIM cohort, dysphagia in non-cancer patients was not associated with increased mortality, while it was in presence of cancer, supporting effect modification of cancer on the association between dysphagia and mortality. This suggests that IIM patients with and without cancer differ and separate analyses for the two groups should be conducted when the outcome of interest is mortality.

Patient global assessment and inflammatory markers in patients with idiopathic inflammatory myopathies - A longitudinal study.

AIM: To explore if patient global assessment (PGA) is associated with inflammation over time and if associations are explained by other measures of disease activity and function in patients with idiopathic inflammatory myopathies (IIM). METHODS: PGA and systemic inflammatory markers prospectively collected over five years were retrieved from the International MyoNet registry for 1200 patients with IIM. Associations between PGA, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and creatine kinase (CK) were analyzed using mixed models. Mediation analysis was used to test if the association between PGA and inflammatory markers during the first year of observation could be explained by measures of disease activity and function. RESULTS: PGA improved, and inflammatory markers decreased during the first year of observation. In the mixed models, high levels of inflammatory markers were associated with worse PGA in both men and women across time points during five years of observation. In men, but not in women, the association between elevated ESR, CRP and poorer PGA was explained by measures of function and disease activity. With a few exceptions, the association between improved PGA and reduced inflammatory markers was partially mediated by improvements in all measures of function and disease activity. CONCLUSION: Increased levels of systemic inflammation are associated with poorer PGA in patients with IIM. In addition to known benefits of lowered inflammation, these findings emphasize the need to reduce systemic inflammation to improve subjective health in patients with IIM. Furthermore, the results demonstrate the importance of incorporating PGA as an outcome measure in clinical practice and clinical trials.

Current myositis clinical trials and tribulations.

With improved understanding of disease pathogenesis and availability of outcome measures, there has been a remarkable increase in the number of therapeutic clinical trials in idiopathic inflammatory myopathies (myositis) over the last three years reaching as many as five trials per site. These trials share similar design and inclusion/exclusion criteria resulting in a competitive clinical trial landscape in myositis. While these are exciting times for the myositis field, we have a number of concerns about the design and conduct of the myositis trials. These include competitive landscape, lengthy placebo arms, underrepresentation of minority groups among participants, use of patient reported outcome measures with limited/no data on validity in myositis, antiquated disease classification criteria, and unclear performance of the ACR/EULAR Myositis Response Criteria in skin-predominant patients despite inclusion of these patients in trials. In this viewpoint, we further discuss these concerns and offer potential solutions such as including patient perspectives in the trial design and adoption of innovative frameworks.

K2P2.1 is a regulator of inflammatory cell responses in idiopathic inflammatory myopathies.

K2P2.1 (TREK1), a two-pore domain potassium channel, has emerged as regulator of leukocyte transmigration into the central nervous system. In the context of skeletal muscle, immune cell infiltration constitutes the pathogenic hallmark of idiopathic inflammatory myopathies (IIMs). However, the underlying mechanisms remain to be elucidated. In this study, we investigated the role of K2P2.1 in the autoimmune response of IIMs. We detected K2P2.1 expression in primary skeletal muscle and endothelial cells of murine and human origin. We observed an increased pro-inflammatory cell response, adhesion and transmigration by pharmacological blockade or genetic deletion of K2P2.1 in vitro and in in vivo myositis mouse models. Of note, our findings were not restricted to endothelial cells as skeletal muscle cells with impaired K2P2.1 function also demonstrated a strong pro-inflammatory response. Conversely, these features were abrogated by activation of K2P2.1 and improved the disease course of a myositis mouse model. In humans, K2P2.1 expression was diminished in IIM patients compared to non-diseased controls arguing for the translatability of our findings. In summary, K2P2.1 may regulate the inflammatory response of skeletal muscle. Further research is required to understand whether K2P2.1 could serve as novel therapeutic target.

Detection of Myositis Autoantibodies by Multi-Analytic Immunoassays in a Large Multicenter Cohort of Patients with Definite Idiopathic Inflammatory Myopathies.

BACKGROUND: The usefulness of myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs) for the assessment of idiopathic inflammatory myopathies (IIMs) is acknowledged, but laboratory standardization remains a challenge. We detected MSAs/MAAs by multi-analytic line immunoassay (LIA) and particle-based multi-analyte technology (PMAT) in a multicenter cohort of patients with IIMs. METHODS: We tested the sera from 411 patients affected with definite IIM, including 142 polymyositis (PM), 147 dermatomyositis (DM), 19 cancer-associated myositis, and 103 overlap myositis syndrome (OM), and from 269 controls. MSAs/MAAs were determined by 16Ags LIA in all sera, and anti-HMGCR by ELISA in 157/411 IIM sera and 91/269 control sera. The analytical specificity of LIA/HMGCR ELISA was compared with that of PMAT in 89 MSA+ IIM sera. RESULTS: MSAs/MAAs were positive in 307/411 (75%) IIM patients and 65/269 (24%) controls by LIA (Odds Ratio 9.26, 95% CI 6.43-13.13, p < 0.0001). The sensitivity/specificity of individual MSAs/MAAs were: 20%/100% (Jo-1), 3%/99.3% (PL-7), 4%/98.8% (PL-12), 1%/100% (EJ), 0.7%/100% (OJ), 9%/98% (SRP), 5.6%/99.6% (TIF1γ), 4.6%/99.6% (MDA5), 8%/96% (Mi-2), 1.5%/98% (NXP2), 1.7%/100% (SAE1), 4%/92% (Ku), 8.5%/99% (PM/Scl-100), 8%/96% (PM/Scl-75), and 25.5%/79% (Ro52). Anti-HMGCR was found in 8/157 (5%) IIM patients and 0/176 (0%) controls by ELISA (p = 0.007). Concordance between LIA/HMGCR ELISA and PMAT was found in 78/89 (88%) samples. Individual MSAs detected by LIA were associated with IIM subsets: Jo-1 with PM and OM, PL-12 with OM, Mi-2, TIF1γ, and MDA5 with DM, SRP with PM, and PM/Scl-75/100 with OM (p < 0.001 for all). CONCLUSIONS: Since MSAs are mostly mutually exclusive, multi-specific antibody profiling seems effective for a targeted clinical-serologic approach to the diagnosis of IIMs.

Distinct HLA associations with autoantibody-defined subgroups in idiopathic inflammatory myopathies.

BACKGROUND: In patients with idiopathic inflammatory myopathies (IIM), autoantibodies are associated with specific clinical phenotypes suggesting a pathogenic role of adaptive immunity. We explored if autoantibody profiles are associated with specific HLA genetic variants and clinical manifestations in IIM. METHODS: We included 1348 IIM patients and determined the occurrence of 14 myositis-specific or -associated autoantibodies. We used unsupervised cluster analysis to identify autoantibody-defined subgroups and logistic regression to estimate associations with clinical manifestations, HLA-DRB1, HLA-DQA1, HLA-DQB1 alleles, and amino acids imputed from genetic information of HLA class II and I molecules. FINDINGS: We identified eight subgroups with the following dominant autoantibodies: anti-Ro52, -U1RNP, -PM/Scl, -Mi2, -Jo1, -Jo1/Ro52, -TIF1γ or negative for all analysed autoantibodies. Associations with HLA-DRB1∗11, HLA-DRB1∗15, HLA-DQA1∗03, and HLA-DQB1∗03 were present in the anti-U1RNP-dominated subgroup. HLA-DRB1∗03, HLA-DQA1∗05, and HLA-DQB1∗02 alleles were overrepresented in the anti-PM/Scl and anti-Jo1/Ro52-dominated subgroups. HLA-DRB1∗16, HLA-DRB1∗07 alleles were most frequent in anti-Mi2 and HLA-DRB1∗01 and HLA-DRB1∗07 alleles in the anti-TIF1γ subgroup. The HLA-DRB1∗13, HLA-DQA1∗01 and HLA-DQB1∗06 alleles were overrepresented in the negative subgroup. Significant signals from variations in class I molecules were detected in the subgroups dominated by anti-Mi2, anti-Jo1/Ro52, anti-TIF1γ, and the negative subgroup. INTERPRETATION: Distinct HLA class II and I associations were observed for almost all autoantibody-defined subgroups. The associations support autoantibody profiles use for classifying IIM which would likely reflect underlying pathogenic mechanisms better than classifications based on clinical symptoms and/or histopathological features. FUNDING: See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript.

Comparison of clinical features between patients with anti-synthetase syndrome and dermatomyositis: Results from the MYONET registry.

OBJECTIVES: To compare clinical characteristics, including the frequency of cutaneous, extramuscular manifestations, and malignancy, between adults with anti-synthetase syndrome (ASyS) and dermatomyositis (DM). METHODS: Using data regarding adults from the MYONET registry, a cohort of DM patients with anti-Mi2/-TIF1É£/-NXP2/-SAE/-MDA5 autoantibodies, and a cohort of ASyS patients with anti-tRNA synthetase autoantibodies (anti-Jo1/-PL7/-PL12/-OJ/-EJ/-Zo/-KS) were identified. Patients with DM sine dermatitis or with discordant dual autoantibody specificities were excluded. Sub-cohorts of patients with ASyS with or without skin involvement were defined based on presence of DM-type rashes (heliotrope rash, Gottron's papules/sign, violaceous rash, shawl sign, V sign, erythroderma, and/or periorbital rash). RESULTS: In total 1,054 patients were included (DM, n = 405; ASyS, n = 649). In ASyS cohort, 31% (n = 203) had DM-type skin involvement (ASyS-DMskin). A higher frequency of extramuscular manifestations, including Mechanic's hands, Raynaud's phenomenon, arthritis, interstitial lung disease, and cardiac involvement differentiated ASyS-DMskin from DM (all p< 0.001), whereas higher frequency of any of four DM-type rashes: heliotrope rash (n = 248, 61% vs n = 90, 44%), violaceous rash (n = 166, 41% vs n = 57, 9%), V sign (n = 124, 31% vs n = 28, 4%), and shawl sign (n = 133, 33% vs n = 18, 3%) differentiated DM from ASyS-DMskin (all p< 0.005). Cancer-associated myositis (CAM) was more frequent in DM (n = 67, 17%) compared with ASyS (n = 21, 3%) and ASyS-DMskin (n = 7, 3%) cohorts (both p< 0.001). CONCLUSION: DM-type rashes are frequent in patients with ASyS; however, distinct clinical manifestations differentiate these patients from classical DM. Skin involvement in ASyS does not necessitate increased malignancy surveillance. These findings will inform future ASyS classification criteria and patient management.