Genetically predicted the causal relationship between gut microbiota and the risk of polymyositis/dermatomyositis: a Mendelian randomization analysis.

Introduction: Observational studies suggest associations between gut microbiota and polymyositis (PM) and dermatomyositis (DM), but causal relationships are unclear. We investigate the causal effects of gut microbiota on PM and DM, providing insights hoping to provide insights for future treatment and prevention. Methods: Summary statistics of gut microbiota were obtained from a multi-ethnic Genome Wide Association Studies (GWAS) meta-analysis, including 119 taxa from 18,340 Europeans. PM/DM statistics were extracted from GWAS analyses. Mendelian randomization (MR) with IVW, MR-Egger, and weighted median methods was performed. Sensitivity analyses addressed heterogeneity and pleiotropy. Of the 119 bacterial genera studied, six showed causal links. Results: Alloprevotella (OR: 3.075, 95% CI: 1.127-8.386, p = 0.028), Ruminococcaceae UCG003 (OR: 4.219, 95% CI: 1.227-14.511, p = 0.022), Dialister (OR: 0.273, 95% CI: 0.077-0.974, p = 0.045) were associated with PM. Anaerotruncus (OR: 0.314, 95% CI: 0.112-0.882, p = 0.028), Ruminococcaceae UCG002 (OR: 2.439, 95% CI: 1.173-5.071, p = 0.017), Sutterella (OR: 3.392, 95% CI: 1.302-8.839, p = 0.012) were related to DM. Sensitivity analyses validated these associations. Discussion: We establish causal relationships between Ruminococcaceae, Sutterella, Anaerotruncus with DM, Alloprevotella, Ruminococcaceae UCG003, and Dialister with PM. Common microbiota, like Ruminococcaceae, have significant clinical implications. These findings open up greater possibilities for the gut microbiota to contribute to the development of PM/DM and for future monitoring of the gut microbiota in patients with PM/DM.

Incidence and prevalence of idiopathic inflammatory myopathies in Thailand from the Ministry of Public Health data analysis.

The epidemiology of idiopathic inflammatory myopathies (IIMs) varies by country. Investigating the epidemiological profile among Thai IIMs could help to inform public health policy, potentially leading to cost-reducing strategies. We aimed to assess the prevalence and incidence of IIM in the Thai population between 2017 and 2020. A descriptive epidemiological study was conducted on patients 18 or older, using data from the Information and Communication Technology Center, Ministry of Public Health, with a primary diagnosis of dermatopolymyositis, as indicated by the ICD-10 codes M33. The prevalence and incidence of IIMs were analyzed with their 95% confidence intervals (CIs) and then categorized by sex and region. In 2017, the IIM cases numbered 9,074 among 65,204,797 Thais, resulting in a prevalence of 13.9 per 100,000 population (95% CI 13.6-14.2). IIMs were slightly more prevalent among women than men (16.8 vs 10.9 per 100,000). Between 2018 and 2020, the incidence of IIMs slightly declined from 5.09 (95% CI 4.92-5.27) in 2017 and 4.92 (95% CI 4.76-5.10) in 2019 to 4.43 (95% CI 4.27-4.60) per 100,000 person-years in 2020. The peak age group was 50-69 years. Between 2018 and 2020, the majority of cases occurred in southern Thailand, with incidence rates of 7.60, 8.34, and 8.74 per 100,000 person-years. IIMs are uncommon among Thais, with a peak incidence in individuals between 60 and 69, especially in southern Thailand. The incidence of IIMs decreased between 2019 and 2020, most likely due to the COVID-19 pandemic, which reduced reports and investigations.

Predictors of relapse of polymyositis/dermatomyositis associated interstitial lung disease.

Background: Polymyositis/dermatomyositis (PM/DM) patients often develop interstitial lung disease (ILD), which can lead to relapse despite anti-inflammatory treatments. This study aims to elucidate the clinical characteristics of relapses in PM/DM-associated ILD patients. Methods: We gathered clinical data, including laboratory results, pulmonary function tests, chest high-resolution computed tomography findings from patients treated at Okinawa Chubu Hospital between January 1, 2010 and December 31, 2018. Results: We identified a total of 74 patients, comprising 21 men and 53 women. Among them, 38 patients remained relapse-free with maintenance therapy, while 36 experienced relapses despite immunosuppressive management. We followed these patients until June 30, 2023, and 13 patients died. The median survival period was 51.4 months (range, 0.3-214 months). When comparing clinical variables, relapsed patients tended to be younger (49.9 vs. 64.1 years), reported myalgia and rash more frequently (63.9% vs. 28.9% and 61.15% vs. 21.1%, respectively). In terms of laboratory findings, lactate dehydrogenase (LDH) levels were higher in relapsed patients (613±464 vs. 381±203 U/L). Radiological findings showed that ground glass opacity (GGO) was more prevalent in relapsed patients (58.3% vs. 16.7%). A Cox-proportional hazards model for relapse demonstrated that serum LDH [hazard ratio (HR) 1.005, 95% confidence interval (CI): 1.000-1.009, P=0.02] and GGO (HR 1.863, 95% CI: 1.103-3.147, P=0.02) were valuable predictors of relapse. Receiver operating characteristic curve analysis of serum LDH indicated that a threshold of 450 correctly classified relapse in PM/DM-associated ILD patients. Conclusions: Serum LDH and GGO may serve as predictors of relapse in PM/DM-associated ILD patients.

Exploring the link between inflammatory myopathies and cancer: A comprehensive retrospective analysis in a Colombian cohort.

BACKGROUND: This study investigates the association between inflammatory myopathies (IM), and their correlation with cancer. There are several potential causes behind the association of cancer and inflammatory myopathies. The positivity of specific antibodies for myositis plays a significant role. Our objective is to describe cancer and inflammatory myopathies in Colombia, focusing on demographics, clinical characteristics, and laboratory data. METHODS: We retrospectively analyzed 112 IM patients diagnosed at Fundación Valle del Lili in Cali, Colombia, the cases met the EULAR/ACR criteria. Data included demographics, clinical signs, laboratory findings, and malignancy. Malignancy associations were explored using logistic regression. The survival analysis was assessed using Kaplan-Meier curves and the Log-Rank test. RESULTS: Dermatomyositis was the most common subtype (45.5%), with a female predominance (66.1%). Cancer diagnosis occurred in 11.6% of cases, predominantly thyroid cancer. The median time from myopathy onset to cancer diagnosis was 11 months, with 75% of cases within the first year. Bivariate analysis indicated associations between cancer and age, Gottron's papules, digital ulcers, and heliotrope rash. However, multivariate analysis identified age as the only significant malignancy risk factor. Survival analysis showed better rates in younger patients. CONCLUSION: This study provides into the link between IM and cancer in the Colombian population. Thyroid cancer predominated, with a slightly higher proportion of female cancer diagnoses. Age emerged as a significant risk factor for malignancy. Understanding this association is crucial for early detection and improving patient outcomes related to IM-associated malignancies.

A Case of COVID-19-Triggered Polymyositis Leading to Rhabdomyolysis.

SARS-COVID-19 is known to manifest with a wide variety of symptoms, most of which are respiratory. Myalgias are a common symptom of COVID-19, but cases of severe virus-induced inflammatory muscle injury leading to rhabdomyolysis and polymyositis have also been reported. Here, we present and discuss a case of a 56-year-old woman who presented with an initial presentation of COVID-19 infection with inflammatory polymyositis leading to rhabdomyolysis. The patient was first treated for rhabdomyolysis with aggressive fluid resuscitation with intravenous normal saline without improvement in symptoms. She was then started on high-dose intravenous methylprednisolone for presumed immune-mediated polymyositis. An MRI of the bilateral lower extremities and a biopsy of the left thigh confirmed inflammatory myositis. After the initiation of steroids, liver function tests and creatinine kinase levels trended down, and symptoms improved. The patient was discharged with a prednisone taper and completely recovered at a follow-up six months later. Post-COVID severe musculoskeletal involvement, including polymyositis or rhabdomyolysis, is rare, with only a few other cases published so far. Viral myositis, supported by myopathological evidence, should be considered carefully in patients with a recent COVID-19 infection after ruling out more common causes of myositis. Some proposed mechanisms include direct infection of the muscle or an environmental event triggering autoimmunity. Treatment generally involves corticosteroids that are gradually tapered.

Anti-OJ antibody-positive anti-synthetase syndrome following SARS-CoV-2 infection: a case report and literature review.

BACKGROUND: COVID-19 can induce a systemic inflammatory response with variable clinical manifestations. Similar to various viruses, COVID-19 has been implicated in the pathogenesis of autoimmune diseases. This article highlights the potential for infections including the SARS-CoV-2 virus to induce exacerbations of pre-existing autoimmune diseases or even potentially unmask de novo autoimmune diseases in particular anti-synthetase syndrome (ASSD) in predisposed individuals. Although there are other case reports of ASSD following SARS-CoV-2 infection, here we present the first reported case of a gentleman with a newly diagnosed anti-OJ positive anti-synthetase syndrome following SARS-CoV-2 infection. CASE PRESENTATION: Described is a case of a 70-year-old man presenting to the emergency department with worsening dyspnea in the context of a recent COVID-19 infection. CT-chest revealed changes suggestive of fibrotic lung disease, consistent with usual interstitial pneumonitis (UIP) pattern. Despite recovery from his COVID-19 illness, the patient subsequently developed proximal myopathy with cervical flexion weakness on further assessment with persistently elevated creatinine kinase (CK). Myositis autoantibodies found a strongly positive anti-OJ autoantibody with MRI-STIR and muscle biopsy performed to further confirm the diagnosis. The patient received pulse methylprednisolone 1 g for 3 days with a long oral prednisolone wean and in view of multiple end-organ manifestations, loading immunoglobulin at 2 g/kg administered over two days was given. In addition, he was then commenced and escalated to a full dose of azathioprine given a normal purine metabolism where he remains in clinical remission to this date. At least 267 cases of rheumatic diseases has been associated with SARS-CoV-2 infection as well as COVID-19 vaccination. A literature search on PubMed was made to determine the amount of case reports describing myositis associated with SARS-CoV-2 infection. We found 3 case reports that fit into our inclusion criteria. Further literature searches on diagnostic approach and treatment of ASSD were done. CONCLUSION: Although SARS-CoV-2 infection itself can cause a directly mediated viral myositis, this case report highlights the possibility of developing virus-triggered inflammatory myositis through multiple aforementioned proposed mechanisms. Therefore, further studies are required to explore the relationship and pathophysiology of SARS-CoV-2 infection and the incidence of inflammatory myopathies.

Severe Post-Viral Polymyositis after COVID-19 in Childhood: A Case Report and Literature Review.

Polymyositis is a rarely reported complication of COVID-19 illness, especially in children. Molecular mimicry may be a cause of hyperactivated autoimmunity, leading to various clinical manifestations, including myopathies. Symptoms vary from mild muscle weakness to severe rhabdomyolysis. We review the literature on post-COVID myositis and report a case of severe polymyositis in a 7-year-old boy, following undefined viral infection 3 weeks before the onset of muscle pain. Patient's condition deteriorated from physical activity-associated pain in the lower limbs to severe muscle weakness leading to dysphagia and mechanical ventilation. As antibodies against SARS-CoV-2 were detected and other possible conditions causing myositis were excluded, the diagnosis of post-COVID polymyositis was considered as the most likely. The patient was treated with high doses of methylprednisolone and cyclophosphamide, resulting in improvement. Although COVID-19 is becoming a seasonal disease, the infection itself and post-viral disorders, such as polymyositis, are still of great interest and require better investigation to ensure appropriate management for each individual. Our experience suggests that aggressive immunosuppressive therapy might be a solution for severe post-COVID-related diseases. This literature review is provided in addition to the case report presented at the 29th European Paediatric Rheumatology Congress; the abstract is available online in the Proceedings of the 29th European Paediatric Rheumatology Congress.

Atherosclerotic cardiovascular disease following a diagnosis of idiopathic inflammatory myopathy: analysis from a retrospective cohort in the TriNetX registry.

OBJECTIVE: Idiopathic inflammatory myopathies (IIM) confer an increased risk of morbidity from atherosclerotic cardiovascular disease (ASCVD). While ASCVD risk has been studied in other countries, these results may not be applicable to patients with dermatomyositis (DM) and polymyositis (PM) in the United States. This retrospective analysis of a cohort of patients identified by ICD code from TriNetX investigated the incidence of ASCVD after International Classification of Disease (ICD) codes of DM, PM, dermatopolymyositis (DPM) or juvenile dermatomyositis (JDM). METHOD: Patients were identified by entry of two ICD codes separated by at least 6 months, according to their first diagnosis code; ASCVD was defined as first ICD code for myocardial infarction, ischemic stroke, transient ischemic attack, or peripheral arterial disease. Cox proportional hazards regression modeled time from first IIM ICD code to ASCVD event. RESULTS: A total of 35,554 patients were identified with the mean age at first IIM code of 54 and 26.1% were male. The most common comorbidity for all groups except JDM was hyperlipidemia (39.9%) though 79.2% of patients were on no cholesterol lowering medication. ASCVD occurred in 30.4% of patients with PM, 24.3% of patients with DM and 0.9% of patients with JDM. Patients with PM had a median time to event of 9.7 years (95% Confidence interval (CI) 9.1, 10.7) and 14.3 years (95% CI 12.6, 14.8) for DM. This study demonstrates that ASCVD is a comorbidity occurring after a median of 12.5 years (95% CI 11.9, 13.6) in patients with IIM. CONCLUSIONS: ASCVD appears to be a long-term complication for IIM patients occurring in nearly a quarter of US patients without prior ASCVD with at least two ICD codes for IIM, with a median time to event of 12.5 years. There appears to be a practice gap in the recognition and treatment of hyperlipidemia in these patients. Key Points • Hyperlipidemia was a common comorbidity identified in patients with IIM though most patients were not on cholesterol lowering medication. • Development of ASCVD appears to be a long-term complication for patients with IIM in the United States.

Differences in the autoantibody phenotypes and long-term outcomes between juvenile- and adult-idiopathic inflammatory myopathies.

OBJECTIVE: To investigate differences in autoantibodies, clinical features, and long-term outcomes between juvenile-idiopathic inflammatory myopathy (IIM) and adult-IIM METHODS: Autoantibodies, clinical characteristics, and drug-free conditions for a maximum of 20 years were retrospectively analyzed in 320 Japanese IIM patients (juvenile-IIM, n = 34; adult-IIM, n = 286) using the Kyoto University Registry. RESULTS: Autoantibodies observed in juvenile-IIM were anti-TIF1-γ (15 %), anti-MDA-5 (15 %), anti-ARS (9 %), and anti-NXP-2 (6 %). Those observed in adult-IIM were anti-ARS (32 %), anti-MDA-5 (23 %), anti-TIF1-γ (8 %), anti-SRP (8 %), anti-Mi-2 (2 %), and anti-NXP-2 (1 %). The cumulative drug-free condition rate was higher in juvenile-IIM than in adult-IIM up to 20 years (juvenile-IIM vs. adult-IIM, 34 % vs. 18 %, p = 0.0016). Anti-TIF1-γ was associated with lesser muscle symptoms (60 % vs. 90 %), malignancy (0 % vs. 57 %), and glucocorticoid use (40 % vs. 86 %) in juvenile-IIM compared to adult-IIM, while juvenile-IIM more achieved drug-free conditions (60 % vs. 25 %). Both juvenile-IIM and adult-IIM with anti-MDA-5 demonstrated a high frequency of amyopathic dermatomyositis, interstitial lung disease (ILD), and multi-immunosuppressive therapy, with high drug-free conditions (50 % vs. 49 %). Both juvenile-IIM and adult-IIM with anti-ARS showed frequent skin rashes, muscle symptoms, and ILD, frequent need for multi-immunosuppressive therapy, and low drug-free condition rates (0 % vs. 3 %). Both juvenile-IIM and adult-IIM with anti-NXP-2 showed frequent skin rashes and muscle symptoms, low ILD frequency, and frequent use of methotrexate and glucocorticoids, which did not achieve drug-free conditions (0 % vs. 0 %). CONCLUSIONS: Drug-free condition was achieved more frequently in juvenile-IIM patients than adult-IIM patients. Specific autoantibodies were associated with different clinical characteristics and outcomes between juvenile-IIM and adult-IIM.

The usefulness of nailfold capillaroscopy in scleroderma-spectrum disorders: a single-centre observational study.

Introduction: Nail-fold capillaroscopy is a non-invasive method for assessment of the microcirculation in nail folds. This examination is particularly useful for diagnosis, assessment of activity, evaluation of the response to treatment, and assessment of the correlation of changes in microvessels with changes in organs in systemic sclerosis and in scleroderma-spectrum diseases, i.e. dermatomyositis, polymyositis, mixed connective tissue disease, and undifferentiated connective tissue disease. Aim: To perform capillaroscopic analyses of lesions in patients with scleroderma-spectrum diseases and determine the correlation of the capillaroscopic image with organ manifestations and the serological profile. Material and methods: The study involved 15 patients with scleroderma-spectrum disorders. Results: Mixed systemic connective tissue disease was diagnosed in 8 patients, and dermatomyositis was detected in 7 patients. The study assessed the frequency of clinical symptoms, e.g. interstitial lung disease or arthritis, and the presence of ANA antibodies. Scleroderma-like microangiopathy was diagnosed in 47% of patients with scleroderma-spectrum disorders. The early pattern was found in patients with mixed systemic connective tissue disease, whereas dermatomyositis was characterized by the late pattern. Non-specific changes were found in 27% of the patients, and a normal image was observed in 27% of the patients. Conclusions: The analysis also revealed that the reduced number of vessels correlated with the occurrence of interstitial lung disease, and the incidence of Raynaud's phenomenon and arthritis was statistically significantly higher in patients with systemic connective tissue disease than in those with dermatomyositis.

Upper Gastrointestinal (GI) Manifestations of Inflammatory Myositis: A Tale of Two Patients.

Myositis is a group of rare autoimmune disorders characterized by chronic inflammation of skeletal muscles that leads to a hallmark triad of muscle weakness, fatigue, and myalgia. Extra-muscular manifestations are sometimes seen and involve various organ systems, including the gastrointestinal (GI) tract. In this case series, two patients with polymyositis (PM) and dermatomyositis (DM), both of whom developed dysphagia as a complication of myositis, are discussed. Case 1 was a female with a known history of biopsy-proven dermatomyositis who presented with progressive peripheral edema and weakness affecting all extremities. Concurrently, she displayed symptoms of pneumonia and dysphagia associated with frequent spontaneous or self-induced vomiting to alleviate retrosternal discomfort. Esophagogastroduodenoscopy (EGD) revealed esophageal dilatation and an absence of a contractile response, consistent with myositis. Treatment comprised intravenous immunoglobulin (IVIG), mycophenolate, and lifestyle modifications, including dietary adjustments and maintaining an upright position postprandial. The second case was a female with muscle weakness and dysphagia. Video-fluoroscopic swallow assessment was significant for pharyngeal dysfunction without a sensory response to penetrated material, and the patient was at high risk of aspiration with any oral intake. The presence of pharyngeal dysfunction and dysphagia prompted treatment with IVIG, mycophenolate, and percutaneous endoscopic gastrostomy (PEG) tube placement. These cases have highlighted the upper GI complications observed in patients with myositis, accentuating the necessity for a personalized treatment approach. Timely intervention has shown promising results in symptomatic relief and improving patient outcomes. This emphasizes the importance of a multidisciplinary approach when addressing myositis-related upper GI manifestations.

A Review of Myositis-Associated Interstitial Lung Disease.

There is a well-established relationship between different subsets of idiopathic inflammatory myopathies (IIMs, myositis) and interstitial lung disease (ILD), with lung complications sometimes presenting prior to myopathic manifestations. The subtypes of myositis include those that are strongly associated with ILD, such as polymyositis (PM) and dermatomyositis (DM). Research has shown that in certain patients, these can then be further divided into subtypes using myositis-specific antibodies (MSAs), which are specific for myositis, and myositis-associated antibodies (MAAs), which can be found in myositis in overlap syndromes with other connective tissue diseases (CTDs). Notably, certain MSAs and MAAs are associated with ILD in patients with myositis. The clinical presentations of ILD in patients with myositis can vary widely and can be insidious in onset and difficult to diagnose. As ILD can progress rapidly in some cases, it is essential that clinicians are able to identify and diagnose ILD in patients with myositis. For this reason, the aim of this review is to highlight the clinical features, diagnostic criteria, important histopathologic, laboratory, and radiographic features, and treatment modalities for those patients with myositis-associated ILD.

[Idiopathic inflammatory myopathies : An interdisciplinary challenge]. / Idiopathische inflammatorische Myopathien : Eine interdisziplinäre Herausforderung.

Idiopathic inflammatory myopathies (IIM) are rare diseases (incidence 1:100,000) with a wide range of clinical symptoms and manifestations. Typical indicators of IIM are proximally emphasized muscle weakness and myalgias, which are usually accompanied by elevated creatine kinase levels and muscle atrophy. The autoantibody diagnostics separate IIM into different entities, which are each associated with a typical risk of organ manifestations and the occurrence of tumors. The IIM represents an interdisciplinary challenge and the diagnostics and treatment require the involvement of several disciplines including rheumatology, neurology, neuropathology, dermatology and pneumology. An accurate diagnosis and careful tumor screening are essential because of the association between certain subgroups of IIM and the occurrence of malignant tumors.

Identification and management of interstitial lung disease associated with systemic sclerosis (SSc-ILD), rheumatoid arthritis (RA-ILD), and polymyositis/dermatomyositis (PM/DM-ILD): development of expert consensus-based clinical algorithms.

BACKGROUND: Clinical guidance on the identification and management of connective tissue disease-associated interstitial lung disease (CTD-ILD) is needed for optimal clinical practice. We aimed to develop clinical algorithms for identifying and managing three common CTD-ILDs: those associated with systemic sclerosis (SSc-ILD), rheumatoid arthritis (RA-ILD), and polymyositis/dermatomyositis (PM/DM-ILD). RESEARCH DESIGN AND METHODS: Meetings were held October-November 2023 to create consensus-based algorithms for identifying and managing SSc-ILD, RA-ILD, and PM/DM-ILD in clinical practice, based on expert consensus statements for identification and management of CTD-ILD previously derived from a Delphi process. RESULTS: We developed clinical algorithms for SSc-ILD, RA-ILD, and PM/DM-ILD that highlight both commonalities and differences in the identification and management of these CTD-ILDs. Importantly, ILD should be suspected in patients with SSc, RA, or PM/DM who have respiratory symptoms. Chest high-resolution computed tomography has utility for screening, diagnosis and assessment of severity. Furthermore, regular follow-up and multidisciplinary management are important. Disease-specific considerations include unique risk factors such as anti-topoisomerase I antibodies in SSc-ILD, high-titer cyclic citrullinated peptide antibodies in RA, anti-aminoacyl tRNA synthetase antibodies in PM/DM, and anti-melanoma differentiation-associated gene 5 antibody in DM. CONCLUSIONS: These algorithms may help physicians to identify and manage patients with SSc-ILD, RA-ILD, or PM/DM-ILD.

A Case of Overlapping Autoimmune Syndrome.

Overlapping autoimmune disorders are used to describe the coexistence of more than one autoimmune disease in the same patient. Mixed connective tissue disease (MCTD) and anti-synthetase syndrome (ASS) are autoimmune diseases that manifest with pulmonary involvement, presenting as persistent dyspnea. The coexistence of both conditions in the same patient is extremely rare. We herein report a case of a 44-year-old female who was diagnosed with MCTD with features of ASS (anti-Jo-1 antibody) in the setting of rheumatoid arthritis (anti-cyclic citrullinated peptide (anti-CCP) antibody), which shows temporary breathing improvement following treatment with corticosteroid and mycophenolate mofetil. However, after the completion of mycophenolate mofetil, she was found to be anti-Jo-1 antibody negative and anti-CCP antibody positive. Our case emphasizes the need to recognize overlapping autoimmune conditions in patients with complex clinical features and presentations with the immediate application of a comprehensive diagnostic approach and tailored treatment strategies. Early diagnosis and aggressive treatment are crucial for achieving remission and preventing organ damage.

Pathological autoantibody internalisation in myositis.

OBJECTIVES: Autoantibodies targeting intracellular proteins are common in various autoimmune diseases. In the context of myositis, the pathologic significance of these autoantibodies has been questioned due to the assumption that autoantibodies cannot enter living muscle cells. This study aims to investigate the validity of this assumption. METHODS: Confocal immunofluorescence microscopy was employed to localise antibodies and other proteins of interest in myositis muscle biopsies. Bulk RNA sequencing was used to examine the transcriptomic profiles of 669 samples, including those from patients with myositis, disease controls and healthy controls. Additionally, antibodies from myositis patients were introduced into cultured myoblasts through electroporation, and their transcriptomic profiles were analysed using RNA sequencing. RESULTS: In patients with myositis autoantibodies, antibodies accumulated inside myofibres in the same subcellular compartment as the autoantigen. Bulk RNA sequencing revealed that muscle biopsies from patients with autoantibodies targeting transcriptional regulators exhibited transcriptomic patterns consistent with dysfunction of the autoantigen. For instance, in muscle biopsies from patients with anti-PM/Scl autoantibodies recognising components of the nuclear RNA exosome complex, an accumulation of divergent transcripts and long non-coding RNAs was observed; these RNA forms are typically degraded by the nuclear RNA exosome complex. Introducing patient antibodies into cultured muscle cells recapitulated the transcriptomic effects observed in human disease. Further supporting evidence suggested that myositis autoantibodies recognising other autoantigens may also disrupt the function of their targets. CONCLUSIONS: This study demonstrates that, in myositis, autoantibodies are internalised into living cells, causing biological effects consistent with the disrupted function of their autoantigen.

A case of acute hypercapnic respiratory failure secondary to late onset nemaline rod myopathy: A multi-disciplinary approach.

Background: Nemaline rod myopathy (NRM) is a rare muscle disorder defined by muscle weakness, respiratory insufficiency, and dysphagia. Respiratory muscle involvement can lead to acute hypercapnic respiratory failure, posing significant challenges in management. Case presentation: Our patient is a 73-year-old male with a history of polymyositis, who presented with acute hypercapnic respiratory failure secondary to a suspected polymyositis flare. Despite initial management, the patient experienced complications, including dysphagia, thrombocytopenia, and altered mental status. Neurological consultations revealed conflicting opinions regarding the primary diagnosis, suggesting inclusion body myositis. The patient's condition continued to deteriorate, prompting discussions about prognosis and palliative care options. This case highlights the challenges in managing respiratory failure in patients with late-onset nemaline myopathy and the importance of multidisciplinary care in addressing complex medical needs. Conclusion: This case emphasises the complexity of managing respiratory failure in patients with late-onset nemaline myopathy and the significance of adopting a multidisciplinary approach. Timely interventions, including respiratory support, dysphagia management, and palliative care discussions, are vital in optimizing patient care and quality of life. Further research is warranted to elucidate optimal management strategies and improve outcomes in this patient population.

Whole-body muscle magnetic resonance imaging in inflammatory myopathy with mitochondrial pathology.

Introduction: Inflammatory myopathy with mitochondrial pathology (IM-Mito) is a rare condition described in a few case series, and it is not clear whether it is a specific disease or a variant of Inclusion Body Myositis (IBM). Radiological data of IM-Mito patients has only been evaluated in one study. Aim: To analyze whole-body muscle magnetic resonance imaging (MRI) features in patients with IM-Mito compared with individuals with IBM. Methods: Fourteen IM-Mito and ten IBM patients were included. IM-Mito was defined by endomysial inflammatory infiltrate, presence of at least 1% of Cytochrome C Oxidase negative fibers, and absence of rimmed vacuoles in muscle biopsy; and IBM was defined by the presence of dystrophic muscular abnormalities, endomysial inflammatory infiltrate, and rimmed vacuoles. Patients underwent clinical evaluation and whole-body muscle MRI to determine the presence of edema, and fatty infiltration in various muscles. Results: Muscle imaging abnormalities were asymmetric in most patients with IM-Mito and IBM. Muscles with the highest average degree of fatty infiltration in both conditions were the quadriceps and medial gastrocnemius. Most patients with IM-Mito and IBM showed imaging patterns of rectus femoris relatively spared compared to other quadriceps muscles. The flexor digitorum profundus was the most affected muscle of the upper limbs in both IBM and IM-Mito. Discussion: Although the results suggest some similarities in muscle imaging features between IM-Mito and IBM, there remains uncertainty whether these two conditions are part of the same clinical spectrum.

Microarray analysis of microrna expression in peripheral blood mononuclear cells of patients with polymyositis and dermatomyositis.

Background and Objectives: MicroRNAs (miRNAs) represent a new class of biomarkers in the context of connective tissue disorders. The miRNA expression profiles in peripheral blood mononuclear cells (PBMCs) of patients with polymyositis (PM) and dermatomyositis (DM) have not been fully elucidated. The objective is to investigate miRNAs expression profile in PBMCs of patients with PM/DM. Methods: Microarray technology was used to identify differentially expressed miRNAs in PBMCs obtained from 6 untreated PM/DM patients and 3 healthy controls (HCs). TaqMan-based stem-loop real-time PCR detection was used for validation in a cohort of 34 PM/DM patients and 20 HCs. Results: Microarray analysis revealed 38 differentially expressed miRNAs (24 up-regulated and 14 down-regulated) in PM/DM patients compared to HCs. Four miRNAs (miR-320a, miR-335-3p, miR-34a-5p and miR-454-3p) were chosen for real-time PCR validation. The expression of miR-34a-5p was significantly upregulated in PM/DM group (P < 0.05). In subgroup analysis, miR-34a-5p was significantly upregulated in interstitial lung disease (ILD) group and DM group (P < 0.001). The level of SIRT1, a validated target of miR-34a, was significantly lower in PBMCs of PM/DM patients compared with HCs. Conclusions: MiR-34a-5p may potentially participate in the pathogenesis of PM/DM through SIRT1, and may serve as a potential new biomarker for PM/DM-ILD.