Myositis-associated Antibodies Research Articles

E079 Preliminary analysis of autoantibody profiles of autoimmune inflammatory myopathies: study from a single North Indian tertiary care centre

Abstract Background/Aims Studies in autoimmune inflammatory myositis (AIM) have shown a strong role of autoantibodies in the diagnosis and prognosis of patients with myositis. This ongoing study shares the preliminary data of 139 patients with AIM from a North Indian tertiary care centre. This prospective, observational study was conducted at a 1250-bedded hospital to assess the prevalence of myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) in patients from the Indian subcontinent with AIM and the correlation of these antibodies with clinical features. Methods From November 2016 to September 2022, patients with AIM (satisfying the Bohan and Peter criteria of 1975) attending the Rheumatology and Clinical Immunology Department of Medanta Hospital were included after taking their informed consent, and divided into subgroups as dermatomyositis (DM), polymyositis (PM), CTD-associated myositis (CTD-M), cancer-associated myositis (CAM), and juvenile myositis (JM). The Institutional Ethics Committee approved the study. Clinical data and sera from patients were collected and analysed. Results The study included 139 individuals with a mean age of 45.4 years. Fifty-two had DM, 49 had PM, 25 had CTD-M, 6 had CAM, and 7 had JM. ANA positivity was found in 67.70%, MSA in 22.3%, MAA in 25.4%, and both in 12.3%. Antibodies against Mi-2 were identified in 13 (28.9%) patients, Jo-1 in 14 (32.50%), PL-7 in 3 (6.7%), PL-12 in 4 (8.9%), SRP in 9 (20%), and MDA-5 and NXP2 in 1 (2.2%) patient each. Antibodies against Ro were found in 28 (57.1%) of the patients, RNP in 8 (16.3%), and PM-Scl in 9 (18.4%). Mi-2 antibodies were mostly identified in DM patients and were significantly associated with skin rash. SRP positivity was mostly found mainly in PM. Raynaud's and ILD were linked to the presence of Jo-1 and Ro antibodies. Malignancy screening was negative in NXP2 and TIF1γ antibody-positive patients. Conclusion MSA was found in 22.3% of cases and MAA in 25.4%. Mi-2 antibodies were linked to rash, but none had ILD, whereas Jo-1 antibodies were linked to mechanic hands, arthritis, and ILD. We aim to gather more strong results in the future as additional patients are recruited in this continuing trial. Disclosure S. Dhuria: None. P. Khatri: None. N. Negalur: None. K. Telang: None. S. Ghosh: None. D. Yadavalli: None. V. Singal: None. R. Gupta: None.

Myositis specifikus antitest diagnosztika dermatomyositisben – mi a haszna a klinikai gyakorlatban?

The authors describe the myositis-specific and myositis-associated antibodies (MSA-s) in idiopathic inflammatory myopathies and dermatomyositis, with particular emphasis on aspects of clinical relevancy. The frequency and clinical significance of MSA-s in 50 dermatomyositis patients at our Clinic are presented. The most common MSA, anti-TIF-1 antibodies were found in 14% of our dermatomyositis patients and they were associated with cancers, in accordance with previous reports. For patients with a high tumor risk, a comprehensive tumor research using all imaging devices should be performed.

Myositis-Specific and Myositis-Associated Antibodies in Fibromyalgia Patients: A Prospective Study

Fibromyalgia (FM) is a common rheumatologic disorder characterised by widespread muscular pain. Myalgia is also a common clinical feature in Connective Tissue Disease (CTD), and FM should be studied for the concomitant presence of a CTD. The aim of this study is to evaluate the prevalence of Myositis-Specific and Myositis-Associated Antibodies (MSA/MAA) in a cohort of FM patients. We enrolled 233 consecutive FM patients (defined according to the 2016 criteria) that did not report clinical signs of autoimmune disorders and followed them for at least one year. The patients were tested for MSA/MAA with immunoblotting. FM patients were seropositive for Antinuclear Antibodies (ANA) in 24% of cases, for MSA in 9%, and for MAA in 6%. A specific diagnosis of CTD was made in 12 patients (5.2%), namely, 5 cases of primary Sjögren's Syndrome and 7 of Idiopathic Inflammatory Myopathy. Seropositive patients showed clinical features similar to those who were seronegative at baseline. A CTD diagnosis was associated with ANA positivity (p = 0.03, X2 4.9), the presence of a speckled pattern (p = 0.02, X2 5.3), positivity for MAA (p = 0.004, X2 8.1), and MSA (p = 0.003, X2 9.2). In conclusion, a non-negligible proportion of FM patients may be seropositive for MSA/MAA, and that seropositivity might suggest a diagnosis of CTD.

The association between clinical, subclinical features and autoantibody profile in Vietnamese dermatomyositis patients.

There is still a lack of research in Vietnam on the autoantibody profile of dermatomyositis (DM) and its association with clinical and subclinical characteristics. Therefore, we conducted this study to investigate clinical and subclinical correlations with autoantibodies in DM patients. 72 DM patients at Vietnam National Hospital of Dermatology and Venereology (NHDV) from March 2019 to September 2021 were included in this cross-sectional study. Clinical manifestations and laboratory test results of the patients were obtained at the time of visit. Of these, 63 patients were tested for the presence of autoantibodies using an Immunoblot assay. Our findings show that the average age of patients was 41.7 years. The female-male ratio was 1.7:1. The most common skin and muscle manifestations were myalgia (79.2%), heliotrope rash (62.5%), shawl sign (61.1%), Gottron's sign (59.7%), muscle weakness (59.7%), Gottron's papule (52.8%), periungual telangiectasia (41.7%), V-sign (38.9%), poikiloderma (26.4%), periungual fissures (20.8%), Raynaud's phenomenon (15.3%). Among the 63 patients tested for autoantibodies, myositis-specific antibodies (MSAs) were found in 71.4% of the serum samples, and myositis-associated antibodies (MAAs) in 36.5%. Anti-TIF1γ antibody accounted for the highest percentage (28.6%), followed by anti-Ro52 (22.2%), anti-synthetase (17.5%), anti-Mi-2 and anti-MDA5 (both 14.3%). Anti-synthetase antibodies (ARS-Abs) showed a significant association with arthralgia, fever, and Raynaud's phenomenon, while anti-TIF1γ antibodies showed a strong association with V-sign and poikiloderma (p<0.05). Clinical features in dermatomyositis are heterogeneous. Our study results show some associations between clinical features and autoantibodies in patients with DM. The analysis of DM-related autoantibodies is clinically useful, will be essential for the approaches to diagnosis, and management of DM patients.

Comparison of Muscle Biopsy Features with Myositis Autoantibodies in Inflammatory Myopathies: A Pilot Experience

Abstract Background: Idiopathic inflammatory myopathies (IIM), also called autoimmune myositis, are heterogeneous. These include dermatomyositis (DM), inclusion body myositis, immune mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASS), and overlap polymyositis. Classification of IIM has evolved from clinical to clinico-pathologic to the recent clinico-sero-pathologic with the discovery of myositis-specific antibodies (MSA) and myositis-associated antibodies. The various antibodies have shown association with specific phenotypes. Objective: To analyze muscle biopsy features with respect to each MSA and MAA to understand the frequency of findings in each entity. Materials and Methods: Biopsy-proven cases of IIM where myositis profile was available were included in the study after obtaining Institutional Ethics Committee (IEC) approval. In addition to the stains and enzyme histochemistry, immunohistochemistry with MHC class I and II and MxA was performed. Features like perifascicular atrophy, perifascicular necrosis, scattered necrosis, inflammation, etc. were analyzed. Myositis profile was performed by line-blot technique using a 16-antigen panel. Cases were divided into different autoantibody subgroups. Various clinical, demographic, and muscle biopsy features were studied with respect to each MSA and MAA. Results: There were a total of 64 cases. Mi2 (N = 18) was the most common autoantibody. Some of the salient observations included PFA with perivascular inflammation in Mi2; pediatric cases and microinfarcts in NXP2; no PFA or inflammation in MDA5; perifascicular necrosis in JO1; extensive necrosis with sparse inflammation in SRP; more inflammation in overlap myositis; MxA positivity in DM; and absent in ASS. Conclusion: This is a pilot study documenting differences in biopsy phenotype with each MSA and MAA which is comparable to the literature. These findings can be used to characterize IIM in seronegative biopsies.

Clinical Significance of Myositis-Specific and Myositis-Associated Antibody Profiles in Dermatomyositis.

Myositis-specific autoantibodies (MSA) and myositis-associated autoantibodies (MAA) are clinically useful biomarkers that point to the diagnosis, clinical manifestations, and prognosis of dermatomyositis (DM). To estimate the prevalence of MSA as well as MAA and analyze possible clinical correlations of these autoantibodies in patients diagnosed with DM, we conducted a cross-sectional study of 30 patients who were diagnosed with DM. MSA were positive in 19 patients (63%) in which Mi 2 was positive in 8 (27%) patients, and this was the most frequently found MSA. A total of 11 (36.7%) patients showed positive MAA. AntiPM/Scl 75 and anti-Ro 52 were positive in 5 (16.7%) patients each and these were the most commonly found MAA. Anti-La was absent in all our patients. There were 8 (27%) patients in whom both MSA and MAA were positive. Either MSA and/or MAA were positive in 22 (73%) patients. On a bivariate analysis, the patients who were positive for anti-PM/Scl 75 showed a significant difference in manifesting cutaneous ulcers (P value 0.023). It was also found that anti-SAE-positive patients showed a significant difference with malignancy (P value 0.014). Anti-Ro 52-positive patients were less likely to have symmetrical proximal muscle weakness (P value 0.006). All patients who were anti-MDA 5 positive had myositis and none of the anti-MDA 5-positive patients had rapidly progressive interstitial lung disease (RPILD). More than one MSA in the same patient was noted in three patients.

Fever, Cutaneous Ulcers, and Arthritis Define the MDA5 Phenotype in Indian Patients with Idiopathic Inflammatory Myositis.

In idiopathic inflammatory myositis (IIM), anti-MDA5 (melanoma differentiation-associated gene 5) antibody-associated DM (MDA5 DM) is a distinct subset characterised by presentation with cutaneous involvement, association with ILD and delayed onset of muscle involvement which is believed to be not severe. To study the clinical profile and treatment outcomes of MDA5 DM patients. Records of patients fulfilling the ACR/EULAR classification criteria for IIM and testing positive for MDA5 antibody, were retrieved from the ongoingMyoIN registry database of our centre. Clinical, laboratory and treatment data were analysed. Follow-up details were noted. Parameters were compared between survivors and non-survivors using student's t-test or Mann-Whitney U tests for continuous variables and Chi square test and Fisher's exact for categorical variables. Eighteen patients (5 juvenile) were identified. Median age was 30(16-41) years and disease duration at time of diagnosis was 5.5 months with median follow up duration of 18 months (12-31). The prevalence of constitutional symptoms, cutaneous involvement, arthritis, and myositis were 94%, 100%, 78%, and 44% respectively. Ulcers were the most common cutaneous finding. Myositis when present was severe. Interstitial lung disease (ILD) was present in 6 patients which was rapidly progressive (RPILD) in 3. Anti-Ro-52 antibody (n=5) was the most common myositis associated antibody (MAA). There was no difference in the clinical profile of children and adults. Seven patients succumbed. RPILD was a predictor of mortality (p=0.04). Cutaneous relapses were common among survivors but responded well to further therapy. The MDA5 DM phenotype in this Indian cohort is characterised by fever, cutaneous ulcers and arthritis. RPILD was not uncommon and predicted mortality.

Panniculitis, an Uncommon Skin Manifestation in Adult Dermatomyositis

Objective: The skin manifestations of dermatomyositis (DM) are complex and diverse, with some rashes having diagnostic significance, while others have a certain suggestive effect on the patient’s condition, visceral damage, and prognosis. This case-cohort study was performed to investigate the skin manifestations of 205 adult inpatients with DM. We then analyzed the association between the clinical characteristics and panniculitis in adult patients with DM. Methods: This study was conducted at the First Medical Center of PLA General Hospital, Beijing, China from March 1, 2016 to December 30, 2020 with follow-up until December 31, 2021. This case-cohort study involved 205 eligible participants with DM who met the criteria for idiopathic inflammatory myopathy. Clinical data, cutaneous manifestations, and lesion locations were screened and analyzed. Serum samples were collected, and immunoblotting was used to detect 16 types of myositis-specific antibodies and myositis-associated antibodies. Results: The results showed that 16 (7.8%) of the 205 adult patients with DM had panniculitis. The panniculitis was mainly distributed in the subcutaneous fat of the abdomen, buttocks, and thighs. This condition was often accompanied by skin ulcers, atrophic scars, and calcinosis. Moreover, 9 (72.7%) of the 16 patients with panniculitis were positive for antibodies to nuclear matrix protein 2 (anti-NXP2 antibodies). Conclusion: The data showed that panniculitis is an uncommon skin manifestation in adult patients with DM, with a positivity rate of 7.8%. The appearance of panniculitis is likely associated with anti-NXP2 antibodies.

OA29 Blotting-based assays under-detected TIF1-gamma and NXP2 autoantibodies compared to immunoprecipitation in Juvenile Dermatomyositis cohorts

Introduction/BackgroundThe rare heterogenous autoimmune disease Juvenile Dermatomyositis (JDM) relies on prognostic tools including myositis specific antibodies (MSA) and myositis associated antibodies (MAA) to guide early treatment and reduce the risks of poor outcome. However, there is an emerging concern regarding the inter-assay validity due to the current lack of a standardised protocol for MSA/MAA screening across healthcare centres. Among available MSA/MAA screening assays, most laboratories prefer using immunoblot over immunoprecipitation, due to its practicality and lower cost. Notably, blotting-based assays were reported to have reduced specificity at detecting certain MSA/MAA subgroups.Description/MethodA total of 472 JDM patients recruited via UK Juvenile Dermatomyositis Cohort and Biomarker Study (JDCBS) were included in this study. For immunoprecipitation cohort, the sera of 383 JDM-diagnosed patients were determined at the University of Bath using radio-labelled protein immunoprecipitation, and 140kDa bands were confirmed with ELISA for NXP2 or MDA5. For immunoblot cohort (n = 89), MSA/MAA results were obtained from the patients’ records at the centre of care. The immunoprecipitation group and immunoblot group were investigated for the frequency of each autoantibody subgroup within each cohort. The objective was to determine the sensitivity of each assay in detecting myositis relevant antibodies (MSA/MAA) in the context of JDM.Discussion/ResultsOverall, the majority of patients were female, and self-identified as white. Specifically, in immunoprecipitation cohort, 70.9% of the patients were female, while 77.1% of the patients self-identified as white. In the immunoblot cohort, 72.7% of the patient were female, while 65.9% self-identified as white.Regarding MSA/MAA status in each cohort, 225 out of 383 (58%) immunoprecipitation samples were positive for at least 1 myositis relevant autoantibody (MSA/MAA). In the immunoblot cohort the proportion was 53% (47 out of 89 samples). Despite the similar gender and ethnicity distribution, the frequencies of autoantibody subgroups varied between two cohorts. In descending order, the 3 most common MSAs detected by immunoprecipitation group were anti-TIF1γ (18.1%), anti-NXP2 (15.8%) and anti-MDA5 (5.9%). On the contrary, anti-MDA5 (15.5%) was the most prevalent autoantibody detected by immunoblot, followed by anti-TIF1γ (11.3%) and anti-NXP2 (9.3%), respectively.The prevalence of more than one myositis relevant autoantibodies detected in a patient was rare in both cohorts. Specifically, when excluding anti-Ro52, a MAA that is not detected with immunoprecipitation, 2.2% of the total patients in immunoblot cohort had more than 1 MSA/MAA. This rate is lower in immunoprecipitation cohort, as only 0.5% of the patients in this cohort were determined to be positive for more than one autoantibody subgroup. When accounting for anti-Ro52 in immunoblot cohort, 7 out of 8 anti-Ro52 positive patients were also positive for anti-MDA5, making up 7.9% of immunoblot cohort.Key learning points/ConclusionThe variance between autoantibody frequencies detected by each method suggested that immunoprecipitation and immunoblot assays do not perform equally for all MSA and MAA. The lower detection of anti-TIF1γ in immunoblot is consistent with previous reports. Additionally, a potential reduction of sensitivity in anti-NXP2 detection using immunoblot is observed for the first time. Higher rate of anti-MDA5 in immunoblot cohort might reflect the earlier pre-treatment samples compared to the samples tested in immunoprecipitation cohort, as the titre of anti-MDA5 was reported to decrease with treatment. As MSA/MAA status are interpreted by clinicians to classify JDM patients into homogenous subgroups for more focused treatment plans, the reliability of autoantibody screening process is an issue of interest. Further investigations are necessary to characterise the sensitivity and specificity of each method.

OA17 An evolving case of Anti PM/Scl Anti body associated Aggressive Systemic Sclerosis

OA17 An evolving case of Anti PM/Scl Anti body associated Aggressive Systemic Sclerosis

Autoantibodies in the pathogenesis of idiopathic inflammatory myopathies: Does the endoplasmic reticulum stress response have a role?

Idiopathic inflammatory myopathies (IIMs) are a group of rare, acquired autoimmune diseases characterized by profound muscle weakness and immune cell invasion into non-necrotic muscle. They are related to the presence of antibodies known as myositis-specific antibodies and myositis-associated antibodies, which are associated with various IIM phenotypes and the clinical prognosis. The possibility of the participation of other pathological mechanisms involved in the inflammatory response in IIM has been proposed. Such mechanisms include the overexpression of major histocompatibility complex class I in myofibers, which correlates with the activation of stress responses of the endoplasmic reticulum (ER). Taking into account the importance of the ER for the maintenance of homeostasis of the musculoskeletal system in the regulation of proteins, there is probably a relationship between immunological and non-immunological processes and autoimmunity, and an example of this might be IIM. We propose that ER stress and its relief mechanisms could be related to inflammatory mechanisms triggering a humoral response in IIM, suggesting that ER stress might be related to the triggering of IIMs and their auto-antibodies’ production.

A New Method for the Assessment of Myalgia in Interstitial Lung Disease: Association with Positivity for Myositis-Specific and Myositis-Associated Antibodies.

In this study, it was found that myositis-specific and myositis-associated antibodies (MSAs and MAAs) improved the recognition of idiopathic inflammatory myopathies (IIMs) in interstitial lung disease (ILD) patients. The objective of this study is to propose a clinical method to evaluate myalgia in respiratory settings as a possible tool for the recognition of MSA/MAA positivity in ILD patients. We prospectively enrolled 167 ILD patients with suspected myositis, of which 63 had myalgia evoked at specific points (M+ILD+). We also enrolled in a 174 patients with only myalgia (M+ILD-) in a rheumatological setting. The patients were assessed jointly by rheumatologists and pulmonologists and were tested for autoantibodies. M+ILD+ patients were positive for at least one MAA/MSA in 68.3% of cases, as were M-ILD+ patients in 48.1% of cases and M+ILD- patients in 17.2% of cases (p = 0.01 and <0.0001, respectively). A diagnosis of IIM was made in 39.7% of M+ILD+ patients and in 23.1% of the M-ILD+ group (p = 0.02). Myalgia was significantly associated with positivity for MSA/MAAs in ILD patients (p = 0.01, X2: 6.47). In conclusion, myalgia in ILD patients with suspected myositis is associated with MSA/MAA positivity, and could support a diagnosis of IIM. A significant proportion of M+ILD- patients also had MSA/MAA positivity, a phenomenon warranting further study to evaluate its clinical meaning.

Current approach to diagnosis of inflammatory myopathies: Clinical features and myositis antibody profiles.

Diagnosis of inflammatory myositis has been made easier with the availability of commercial assays for myositis-specific and myositis-associated antibodies. Clinico-serological association studies have permitted a better definition of clinical subsets. Myositis-specific auto-antibodies are highly specific and non-overlapping, whereas myositis-associated antibodies are those seen also in other connective tissue disorders such as systemic lupus erythematosus, primary Sjogren's syndrome, and idiopathic pulmonary auto-immune fibrosis. Their value is pronounced when clinical features are subtle or non-specific or when the muscle is not the primary organ involved. Overall, the muscle-specific and myositis-associated antibodies have changed the landscape in terms of diagnostic utility, prognostication, and the approach to organ-specific evaluation and management of idiopathic inflammatory myopathies (IIMs).

Complement in autoimmune inflammatory myopathies, the role of myositis-associated antibodies, COVID-19 associations and muscle amyloid deposits

Introduction The inflammatory myopathies (IM) have now evolved into distinct subsets requiring clarification about their immunopathogenesis to guide applications of targeted therapies Areas covered Immunohistopathologic criteria of IM with focus on complement, anti-complement therapeutics and other biologic immunotherapies. The COVID19-triggered muscle autoimmunity along with the correct interpretation of muscle amyloid deposits are discussed. Expert opinion The IM, unjustifiably referred as idiopathic, comprise Dermatomyositis (DM), Necrotizing Autoimmune Myositis (NAM), Anti-synthetase syndrome-overlap myositis (Anti-SS-OM), and Inclusion-Body-Myositis (IBM). In DM, complement activation with MAC-mediated endomysial microvascular destruction and perifascicular atrophy is the fundamental process, while innate immunity activation factors, INF1 and MxA, sense and secondarily enhance inflammation. Complement participates in muscle fiber necrosis from any cause and may facilitate muscle-fiber necrosis in NAM but seems unlikely that myositis-associated antibodies participate in complement-fixing. Accordingly, anti-complement therapeutics should be prioritized for DM. SARS-CoV-2 can potentially trigger muscle autoimmunity but systematic studies are needed as the reported autopsy findings are not clinically relevant. In IBM, tiny amyloid deposits within muscle fibers are enhanced by inflammatory mediators contributing to myodegeneration; in contrast, spotty amyloid deposits in the endomysial connective tissue do not represent “amyloid myopathy” but only have diagnostic value for amyloidosis due to any cause.

Clinical and histopathological features of immune checkpoint inhibitor-related myositis in patients with advanced non-small cell lung cancer

Objective: To investigate the clinicopathologic features and outcome of myositis in patients with advanced non-small cell lung cancer treated with immune checkpoint inhibitors. Methods: The patients diagnosed with immune checkpoint inhibitor-related (ICI) myositis in the database of Respiratory Pathology Center of The First Affiliated Hospital, Guangzhou Medical University from June 2019 to December 2020 were retrospectively analyzed. We reported the muscle histology and main clinical manifestations of the patients in this study. Seven patients with advanced non-small cell lung cancer and ICI related myositis were examined; all of the patients were male, with a median age of 64 (range 42-79) years. Results: All seven patients developed myositis under therapy (three for pembrolizumab, three for sintilimab, and one for camrelizumab). Median delay between ICI initiation and myositis onset was 45 (range 15-176) days. Clinical manifestations were dominated by acute or subacute myalgia and limb weakness. Four patients had evidence of myocarditis. In all of the 7 patients, creatine kinase levels were elevated (median 2 354.4, range 468.6-19 709.2 U/L), while myositis-associated antibodies Ro-52 were positive in four patients. Muscle biopsy showed evident multifocal necrotic myofibers and infiltration of inflammation in two patients. Other patients only showed non-specific endomysial inflammation. Infiltration of inflammation mainly consisted of CD8+ T cells and CD68+ histocytes. After the identification of ICI related myositis, ICI treatment was withdrawn in all patients; 6 patients received corticosteroids therapy. All patients had shown marked clinical improvement. Conclusions: ICI myositis presents with remarkably homogeneous and unique clinicopathologic features, and half of the patients exhibit heightened risk for adverse cardiovascular events, which can be life-threatening if not treated in time. Timely identification of these patients, ICI withdrawal and rapid initiation of corticosteroids therapy can significantly improve patient outcome and/or save patients' lives.

Myositis Antibodies and Interstitial Lung Disease.

Interstitial lung disease (ILD) comprises a heterogeneous group of inflammatory and fibrotic conditions, often resulting in progressive lung function decline and increased mortality. Connective tissue disease (CTD) should be considered in all patients with ILD, as distinguishing between CTD-ILD and other forms of fibrotic lung disease has important therapeutic and prognostic implications. The idiopathic inflammatory myopathies (IIM) represent a CTD subtype of growing interest to ILD experts. The expansion and availability of myositis-specific and myositis-associated antibody testing has allowed for improved disease detection and characterization. In this review, we highlight the relationship between myositis antibodies and ILD. Select forms of IIM, such as the antisynthetase syndrome and clinically amyopathic dermatomyositis can present with rapidly progressive ILD, warranting timely disease diagnosis and management. Disease phenotypes, prevalence, laboratory testing, prognosis, and management strategies are described according to select myositis antibodies. Myositis antibodies provide valuable information for clinicians managing patients with ILD. This review aims to increase awareness of their role in disease detection, pathophysiology, and possibly therapeutics.

Positioning of myositis-specific and associated autoantibody (MSA/MAA) testing in disease criteria and routine diagnostic work-up

Nowadays, the importance of detection of myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) in diagnosis and in delineating disease subsets of idiopathic inflammatory myopathy (IIM) is highly acknowledged by IIM experts. Consequently, MSA/MAA are increasingly integrated in expert-based myositis (sub)classification criteria as well as in routine diagnostics. In contrast, MSA/MAA are under-represented in data-based (sub)classification criteria, mostly related to the lack of sufficient data on the wide spectrum of MSA/MAA in large multicenter cohorts. Unfortunately, the current commercially available assays to detect MSA/MAA show variable analytical and clinical performance characteristics. This challenges the design of prospective multicenter studies on MSA/MAA as well as the optimization of their routine clinical use. Additional validation studies and continuous harmonization initiatives on MSA/MAA detection from the pre-analytical to the post-analytical phase (e.g. from defining request criteria to guidelines for reporting), will be needed to overcome these hurdles. To speed up this process, we encourage close collaborations between IIM clinical experts, laboratory professionals and diagnostic companies.

Association of extended myositis panel results, clinical features, and diagnoses: a single-center retrospective observational study

Myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) are a feature of the idiopathic inflammatory myopathies (IIM), but are also seen in other rheumatic diseases, and in individuals with no clinical symptoms. The aim of this study was to assess the clinical utility of MSA and MAA and in particular the clinical relevance of weakly positive results. We included all patients at our institution who had at least one positive result on the Immunoblot EUROLINE myositis panel over a 6-year period (2015–2020). Associations with clinical features and final diagnosis were evaluated. Eighty-seven of 225 (39%) myositis panel tests met the inclusion criteria. There were 52 strong positives and 35 weak positives for one or more MSA/MAAs. Among the strong positive group, 15% (8/52) were diagnosed with IIM, 34.6% (18/52) with interstitial lung disease, 7.7% (4/52) with anti-synthetase syndrome, 25% (13/52) with connective tissue disease, and others accounted for 25% (13/52). In weak-positive cases, only 14% (5/35) had connective tissue disease and none had IIM. 60% (21/35) of weak-positive cases were not associated with a specific rheumatic disease. A significant number of positive myositis panel results, particularly weak positives, are not associated with IIM or CTD.

Autoantibodies in Patients With Immune-Related Adverse Events From Checkpoint Inhibitors: A Systematic Literature Review.

Immune-related adverse events (irAEs) from immune checkpoint inhibitors (ICIs) are sometimes associated with autoantibodies, but we do not know how frequently or whether these autoantibodies are present before ICI initiation. Our aim was to determine the positivity rate of autoantibodies in patients with organ-specific ICI-associated irAEs and determine their value as pretreatment biomarkers. We searched for all English, peer-reviewed publications from MEDLINE, Embase, and Cochrane Library through February 20, 2020, and included any publication describing patients with irAEs and reporting results of any autoantibody investigation. Three reviewers independently extracted data, and 1 reviewer verified all data for accuracy and quality of reporting. We identified 515 publications. Most reports described endocrine, rheumatic, gastrointestinal/hepatic, and myositis/myasthenia/myocarditis irAEs. Autoantibodies were present in close to 50% of patients with ICI-associated endocrinopathies. Anti-BP180 was found in more than 50% of patients with skin irAEs. Antibodies were also common in patients with the triad of myositis/myasthenia/myocarditis including striational antibodies (49%), acetylcholine receptor antibodies (40%), and myositis-associated antibodies (27%). Only 11% of patients with arthritis had either rheumatoid factor or cyclic citrullinated peptide antibodies, and only 30% of patients with sicca had Sjögren antibodies. Autoantibodies were also relatively uncommon in patients with hepatitis (antinuclear antibody, 18%) and colitis (perinuclear antineutrophil cytoplasmic antibody, 19%). Some cohort studies analyzing pre-ICI seropositivity suggest there may be a role for autoantibodies as biomarkers of irAEs. Reported autoantibody positivity is high in irAEs involving the endocrine organs, skin, and muscle, but lower in irAEs affecting other organ systems. Autoantibody investigations in pre-ICI treatment patients have yielded mixed results regarding their utility as a biomarker of irAEs.

Myocardial involvement in idiopathic inflammatory myopathies: a multi-center cross-sectional study in the CRDC-MYO Registry.

This study aimed to investigate the associated factors of myocardial involvements (MIs) in patients with idiopathic inflammatory myopathies (IIMs). In this multi-center cross-sectional study, 1946 patients with IIMs were enrolled from Chinese Rheumatism Data Center-Myositis Registry (CRDC-MYO). A total of 108 (5.5%) patients were identified with MIs, including congestive heart failure (n = 67, 62.0%), and severe arrhythmias (n = 61, 56.5%). The other 1838 IIM patients without IMs were set as the control group. Clinical features were collected including age, gender, comorbidities, clinical symptoms, clinical signs of both IIMs and MIs, lab findings including myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs), echocardiogram, and radiological exams. Multivariate logistic analysis was used to explore independent associated factors of MIs in patients with IIMs. Several independent associated factors were identified in multi-variate logistic regression, including positivity for anti-mitochondrial antibody-subtype 2 (AMA-M2) (OR 5.194, 95% CI 2.509-10.753, P < 0.001), elevation of creatine kinase (CK) (OR 2.611, 95% CI 1.312-5.198, P = 0.006), elevation of C-reactive protein (CRP) (OR 2.150, 95% CI 1.211-3.818, P = 0.001), and pulmonary hypertension (OR 4.165, 95% CI 1.765-9.882, P = 0.009). AMA-M2 and pulmonary hypertension were the most consistent associated factors in the polymyositis subgroup and the dermatomyositis/clinically amyopathic dermatomyositis subgroup. MIs are rare but serious complication of IIMs could lead to congestive heart failure and severe arrhythmias. IIM patients with AMA-M2 positivity, elevation of CK and CRP, and pulmonary hypertension are more likely to develop MI complications. Key Points • This study investigated the independent associated factors for clinically significant myocardial involvements among idiopathic inflammatory myopathies in a large-scale, nation-wide multi-center cross-sectional study.