Relapse risk factors and clinical characteristics of idiopathic inflammatory myopathies in 105 patients.

OBJECTIVE: To identify the risk factors for relapse of idiopathic inflammatory myopathies (IIMs). METHODS: Patients who were newly diagnosed with IIMs and underwent muscle biopsy between 2000 and 2017 at Asan Medical Center were retrospectively reviewed. The relapse of IIMs was defined as the recurrence of muscle or cutaneous manifestations with a ≥50% increase in glucocorticoid dosage after reaching the low-dose glucocorticoid phase with clinically significant improvement. The factors associated with the relapse of IIMs were investigated by Cox proportional hazards analysis. RESULTS: Of 105 patients with IIMs, relapse was observed in 65 patients (62%). The titer of antinuclear antibody (ANA) was higher in the relapse group than in the non-relapse group (P = 0.033). Multivariable analysis showed that the relapse of IIMs was significantly associated with histopathologic features consistent with IIMs (hazard ratio [HR], 1.69; 95% confidence interval [CI], 1.01-2.83, P = 0.045) and the use of immunosuppressants before relapse (HR, 0.50; 95% CI, 0.29-0.86, P = 0.013). Doubling of ANA titer was also associated with relapse, albeit without statistical significance (HR, 1.13; 95% CI, 1.00-1.27, P = 0.052). CONCLUSION: In patients with IIMs, the use of immunosuppressants had a significant negative association with relapse. Administering immunosuppressants from the early period during the initial glucocorticoid tapering phase may be useful in reducing the risk of relapse in patients with IIMs. Key Points • Since idiopathic inflammatory myopathies (IIMs) have a low prevalence, it is poorly understood which factors are associated with the relapse of IIMs. • In this study, about two-thirds of 105 patients with IIMs experienced a relapse of IIMs. • The risk of relapse in patients with IIMs was negatively associated with the use of immunosuppressants during glucocorticoid tapering and low-dose glucocorticoid phase. • Even in less severe cases, the use of immunosuppressants might be a good option for the management of IIMs.

Prompt response to rituximab in a patient with resistant polymyositis with complications of dysphagia and dysphonia: a case report.

Introduction and importance: Polymyositis is an inflammatory process, primarily affecting proximal muscles, characterized by elevated muscle enzymes and distinctive electromyography patterns. Case presentation: The authors present a case of a 33-year-old male patient experiencing complications of polymyositis, including pharyngeal and laryngeal involvement leading to dysphagia and dysphonia. Steroids and intravenous immunoglobulin (IVIG) therapy proved ineffective. Subsequently, rituximab was administered, resulting in significant improvement in dysphagia, dysphonia, and proximal muscles within 3 days of the initial rituximab dose. Additionally, there was a remarkable decrease in creatine phosphokinase (CPK) levels. Clinical discussion: Immune-mediated myopathies (IMM) are rare diseases characterized by muscle inflammation and weakness. This case of probable polymyositis, diagnosed through clinical features and elevated CPK, was complicated by the patient's lack of response to glucocorticoids and IVIG therapy. Remarkably, rituximab treatment led to rapid improvement in muscle strength and symptoms, highlighting its potential effectiveness in refractory cases of polymyositis. Conclusions: Primary treatment for cases of polymyositis typically involves the use of glucocorticoids. However, approximately half of the patients do not respond adequately to corticosteroids alone. Alternatives, in such cases, encompass IVIG therapy and rituximab.

Precise identification and tracking of HMGCR-reactive CD4+ T cells in the target tissue of patients with anti-HMGCR immune-mediated necrotising myopathy.

BACKGROUND: Anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR)-positive immune-mediated necrotising myopathy (IMNM) is characterised by the presence of IgG autoantibodies against HMGCR and a strong association with specific HLA-DR alleles. Although these findings implicate HMGCR-specific CD4+T-cells in the disease's pathogenesis, no such cells have been described. In this study, we aimed to identify and characterise HMGCR-reactive CD4+T-cells and assess their presence in affected muscle tissue from patients with anti-HMGCR+IMNM. METHODS: Peripheral blood mononuclear cells from patients with anti-HMGCR+IMNM (n=10) and dermatomyositis (DM; n=10) were stimulated with HMGCR protein and peptides identified using a natural antigen processing assay (NAPA; n=6). CD4+T-cell activation was assessed by CD154 upregulation via flow cytometry. T-cell receptor ß(TCR) sequencing was performed on paired HMGCR-reactive T-cells and muscle biopsy tissue (n=5). RESULTS: CD4+T-cell responses to HMGCR protein were higher in patients with anti-HMGCR+IMNM compared with DM (median 0.06 vs 0.00, p=0.0059). These responses were enriched in Th1-Th17 cells, and when present, they positively correlated with anti-HMGCR antibody levels (r2=0.89, p=0.0012). NAPA revealed convergent presentation of seven HMGCR core peptides, with substantial overlap in the peptide repertoires between patients. These HMGCR peptides elicited robust CD4+T-cell responses, with 9/10 anti-HMGCR+IMNM patients responding to at least one peptide, compared with 1/10 DM (p=0.0003). Analysis of HMGCR-reactive TCRs ß yielded antigen-reactive motifs that were enriched in muscle biopsies (projection score 0.03 vs 0.63, p=0.007). CONCLUSION: HMGCR-antigen-reactive CD4+T-cells are present in the circulation and target tissue of patients with anti-HMGCR+IMNM, suggesting an active role for these cells in the pathogenesis of anti-HMGCR+IMNM.

Comparison of Lineblot and Immunoprecipitation Methods in the Detection of Myositis-Specific and Myositis-Associated Antibodies in Patients with Idiopathic Inflammatory Myopathies: Consistency with Clinical Diagnoses.

Background: the reference method for detection of myositis-specific and myositis-associated antibodies (MSAs and MAAs) is considered immunoprecipitation (IP), but it is routinely replaced by semi-automated methods, like lineblot (LB). Few data are available on the consistency with clinical diagnoses; thus, we aim at analysing these aspects. Methods: sixty-nine patients with idiopathic inflammatory myopathies (IIM) were studied via LB (Myositis Antigens Profile 3 EUROLINE, Euroimmun) and IP (RNA and protein antigens). The degree of concordance between methods was calculated using Cohen's coefficient. Results: a substantial concordance was found for anti-Ku and anti-PM/Scl and a moderate concordance was found for anti-Jo1 and anti-Mi-2, while a fair concordance was found for anti-EJ, anti-SRP, and anti-Ro52 antibodies. The concordance could not be calculated for anti-OJ, anti-PL-7, anti-PL-12, anti-NXP2, anti-TIF1É£, and anti-MDA5, because they were only detected with one method. Multiple MSAs were found only with LB in 2/69 sera. Anti-MDA5, TIF1É£, NXP2 (detected via IP), and anti-Jo1 in anti-synthetase syndrome (both LB and IP) had the best concordance with clinical diagnosis. Conclusions: LB and IP show substantial concordance for PM/Scl and Ku, and moderate concordance for Jo1 and Mi-2, with a good concordance with clinical diagnoses. IP shows a high performance for DM-associated MSAs. LB seems to be more sensitive in detecting anti-Ro52 antibodies, but it identified multiple MSAs, unlike IP.

When a Child Refuses to Play: A Rare Myopathy.

Idiopathic inflammatory myopathies (IIM) are a rare group of systemic diseases characterized by progressive proximal muscle weakness and skeletal muscle inflammation. We describe a clinical report of a seven-year-old boy presenting with myalgia and proximal muscle weakness beginning three weeks earlier, with laboratory, MRI, and muscle biopsy findings consistent with IIM. The patient was treated with corticosteroids, methotrexate, immunoglobulin, and intensive motor rehabilitation, with favorable evolution. Diagnosis of Juvenile Polymyositis was confirmed. Three years later, we assisted a relapse of muscle weakness and muscle cytolysis with the onset of bilateral eyelid skin microulcers compatible with dermatomyositis. This report intends to highlight the importance of early diagnosis and treatment in IIM due to the significant burden associated with this group of diseases. In this case, the late onset of the skin lesion contributed to the challenge in this diagnosis.

Nailfold Capillaroscopy Changes in Patients with Idiopathic Inflammatory Myopathies.

Background/Objectives: Idiopathic inflammatory myopathies (IIMs) are rare autoimmune disorders characterized by progressive proximal muscle weakness and varying extra-muscular manifestations. The latest 2017 EULAR/ACR criteria classify them into subgroups. This study aims to evaluate the role of nailfold capillaroscopy (NFC) as a diagnostic and prognostic tool in IIMs by comparing capillaroscopic patterns across different IIM subtypes. Methods: We conducted an observational, cross-sectional study at the Institute of Rheumatology in Belgrade, analyzing 90 patients diagnosed with IIMs per the 2017 EULAR/ACR criteria. Patients were categorized into dermatomyositis (DM) (n = 37), polymyositis (PM) (n = 35), amyopathic dermatomyositis (ADM) (n = 13), and juvenile dermatomyositis (JDM) (n = 5). A control group of 35 patients with primary Raynaud's phenomenon was also included. NFC findings, clinical manifestations, and laboratory data were compared across the groups. Results: In DM, 81.9% exhibited a scleroderma capillaroscopic pattern, which was also present in 76.9% of ADM patients. In PM, the most common pattern was nonspecific changes (48.6%). JDM patients showed a high prevalence of scleroderma changes (n = 4 (80%)). Scleroderma patterns correlated with Gottron's papules, heliotrope rash, periungual erythema, Raynaud's phenomenon, and interstitial lung disease (ILD). No significant differences were found in laboratory parameters across capillaroscopic groups, except for a higher prevalence of anti-Jo1 antibodies in patients with nonspecific capillaroscopic changes. Conclusions: NFC is a valuable tool for differentiating IIM subtypes and correlating clinical manifestations with specific capillaroscopic patterns. The high prevalence of scleroderma changes in DM and ADM suggests their potential as a diagnostic and prognostic marker in IIMs. Further research with larger cohorts is warranted to validate these findings.

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.

Fulminant Myocarditis in Patients With Autoimmune Disease That Requires Extracorporeal Membrane Oxygenation Support.

Myocarditis is a potentially life-threatening inflammatory disease of the myocardium, often resulting from infectious and immune-mediated responses. Clinical presentation in severe cases often results in a devastating illness requiring extracorporeal membrane oxygenation support as a result of cardiogenic shock. Although endomyocardial biopsy is still considered the gold standard for diagnosis, it often reveals nonspecific lymphocytic infiltration. Because the precise cause is usually unknown, the initial treatment typically involves immunosuppression and frequent assessment of myocardial contractility. This report presents 3 rare cases of autoimmune diseases (polymyositis, immunoglobulin G4-related disease, and systemic lupus erythematosus) that require extracorporeal membrane oxygenation support as a result of fulminant myocarditis, including their follow-up periods.

Polymyositis and Severe Rhabdomyolysis in the Context of Influenza and COVID-19 Vaccination: A Case Report.

Rhabdomyolysis is characterized by muscle breakdown and the release of muscle enzymes into the bloodstream, which can lead to acute kidney injury (AKI) and electrolyte imbalances. This case report details a 52-year-old male who developed severe rhabdomyolysis and polymyositis following influenza and SARS-COV-2 vaccinations. Presenting with severe muscle pain and elevated creatine kinase (CK) levels, the patient's condition was managed with aggressive hydration and supportive care, resulting in significant recovery. While vaccine-related adverse effects such as myositis and rhabdomyolysis are rare, this case underscores the need for vigilance in monitoring post-vaccination complications and highlights the importance of recognizing and promptly treating vaccine-associated inflammatory myopathies to prevent severe complications. The findings contribute to the growing body of literature on vaccine-induced myopathies and emphasize the necessity of a multidisciplinary approach in managing such complex cases.

Hypothyroidism and dermato/polymyositis: a two-sample Mendelian randomization study.

Objective: Observational studies have revealed a higher probability of hypothyroidism in patients with dermatomyositis (DM) or polymyositis (PM), but there is no consensus on whether hypothyroidism causally influences DM or PM. In the present study, we assessed the causal association between hypothyroidism and the risk of dermatomyositis or polymyositis using two-sample Mendelian randomization (TSMR). Methods: The genome-wide association data of hypothyroidism and dermatomyositis/polymyositis were obtained from the IEU Open GWAS project. Then, TSMR was used to determine whether hypothyroidism is causally associated with DM or PM. Single-nucleotide polymorphisms (SNPs) significantly associated with hypothyroidism were identified and used as instrumental variables (IVs), and the causal relationship between hypothyroidism and DM/PM was examined using TSMR. MR pleiotropy and Cochran's Q test were used to confirm the heterogeneity and pleiotropy of identified IVs, then four different models, including the inverse variance weighted model (IVW), MR-Egger, weighted median and weighted model were applied in this MR analysis. Results: Sixty-eight SNPs for DM and 68 SNPs for PM were selected as the IVs (P<5×10-8; linkage disequilibrium R2 <0.001) to assess the causal association between hypothyroidism and DM/PM selected from GWASs on hypothyroidism. The results revealed a positive causal effect of hypothyroidism on both DM and PM (DM: OR 2.563, 95% CI [1.348, 4.874], P = 0.00156; PM: OR1.709, 95% CI [1.157, 2.525], P =0.007). Moreover, there was no heterogeneity or pleiotropy in the results. Conclusion: In conclusion, the MR analysis results provided strong evidence to indicate that hypothyroidism might be causally associated with DM and PM. These findings may have important implications for the pathogenesis and possible future therapies of DM/PM.

Pathogenic mechanisms of disease in idiopathic inflammatory myopathies: autoantibodies as clues.

Idiopathic inflammatory myopathies (IIMs) encompass a spectrum of autoimmune diseases characterized by muscle inflammation and systemic involvement. This review aimed to synthesize current evidence on the clinical significance and pathogenic mechanisms underlying autoantibodies associated with IIMs. Autoantibodies targeting aminoacyl-tRNA synthetases (ARS) play a pivotal role in antisynthetase syndrome (ASS), highlighting associations with interstitial lung disease (ILD) and distinctive clinical features. Anti-Mi-2 antibodies in dermatomyositis (DM) are hallmarked by characteristic cutaneous manifestations and favorable prognostic outcomes. Conversely, anti-TIF1 antibodies are correlated with DM and a higher risk of malignancies, implicating CD8+ T cells in its pathogenesis. Anti-MDA5 antibodies signify clinically amyopathic DM (CADM) with severe ILD, linked to dysregulated neutrophil extracellular trap (NET) formation. In immune-mediated necrotizing myopathies (IMNMs), anti-SRP and anti-HMGCR antibodies induce complement-mediated myopathy, typically following statin exposure. Additionally, anti-TRIM72 antibodies emerge as potential diagnostic markers in IIMs. Anti-cN1A autoantibodies are linked to inclusion body myositis (IBM) and play a decisive role in muscle protein degradation. Meanwhile, anti-FHL1 autoantibodies are associated with severe disease manifestations and muscle damage, as established in experimental models. Anti-eIF3 autoantibodies, recently identified in polymyositis (PM) patients, are rarely detected (<1%) and associated with a favorable prognosis. Elucidating these autoantibodies is anticipated to not only assist in early diagnosis and disease stratification but also inform targeted therapeutic interventions, emphasizing the intricate interplay between autoimmunity, cellular dysfunction, and clinical outcomes in IIMs.

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.

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.

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.

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.

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.