Clinical profiles and treatment outcomes of outpatients with interstitial lung disease and mechanic's hands: A retrospective and observational cohort.

Idiopathic inflammatory myopathies, especially antisynthetase syndrome, often appear outside of the muscles as interstitial lung disease (ILD). Another typical finding is the presence of mechanic's hands. The aim of the present study was to describe the clinical, functional, tomographic, and serological data of patients with ILD and mechanic's hands and their response to treatment and survival rates. This is a retrospective study of ILD with concurrent myopathy. Among the 119 patients initially selected, 51 had mechanic's hands. All the patients were screened for anti-Jo-1 antibodies. An expanded panel of myopathy autoantibodies was also performed in 27 individuals. Of the 51 patients, 35 had 1 or more antibodies. The most common were anti-Jo-1, anti-PL-7, and anti-PL-12, while of the associated antibodies, anti-Ro52 was present in 70% of the 27 tested individuals. A significant response to treatment was characterized by an increase in predicted forced vital capacity (FVC) of at least 5% in the last evaluation done after 6 to 24 months of treatment. A decrease in predicted FVC of at least 5%, the need for oxygen therapy, or death were all considered treatment failures. All patients were treated with corticosteroids, and 71% with mycophenolate. After 24 months, 18 patients had an increase in FVC, 11 had a decrease, and 22 remained stable. After a median follow-up of 58 months, 48 patients remained alive and three died. Patients with honeycombing on high-resolution chest tomography (log-rank = 34.65; P < .001) and a decrease in FVC ≥5% (log-rank = 18.28, P < .001) had a poorer survival rate. Patients with ILD and mechanic's hands respond well to immunosuppressive treatment.

The impact of pain on daily activities in patients with idiopathic inflammatory myopathies: Report from the OMERACT myositis working group.

BACKGROUND: International focus groups with patients with idiopathic inflammatory myopathies (IIM) conducted by the OMERACT Myositis Working Group over the years demonstrated the pain as an important symptom experienced by these patients. In this study, we aimed to examine the frequency and degree of pain interference, the aspects of daily life impacted by pain, and the factors associated with pain interference in adults with IIM. METHODS: This was a prospective observational study with two visits. The patients who fulfilled the probable/definite IIM (ACR/EULAR Myositis Classification Criteria) were enrolled. Pain interference was assessed with PROMIS pain interference form (6a). Myositis core set measures and PROMIS fatigue (7a) and physical function (8b) were obtained at both visits. Logistic regression and linear mixed models were performed to assess the association between pain interference and other parameters. RESULTS: A total of 129 patients with IIM (60 % females) were recruited from U.S., South Korea, Netherlands, Sweden, and Australia. Approximately 71 % reported pain interference. The patients in the greater pain interference group were more likely to be female, had significantly worse patient/physician global disease activity, fatigue, and physical function than those in the lower pain interference group. The most commonly impacted life aspect was household chores. Manual muscle testing, patient/physician global disease activity, fatigue, and physical function were all significantly associated with pain interference score >60. CONCLUSION: The majority of the patients with IIM experience the impact of pain on their daily activities, particularly household chores. Myositis disease activity, duration, and subtype could be associated with greater pain interference.

Rituximab in the treatment of progressive interstitial lung disease associated with the antisynthetase syndrome.

OBJECTIVE: To assess the real-world, long-term effectiveness of rituximab (RTX) as a rescue therapy in patients with antisynthetase syndrome and progressive interstitial lung disease (ASS-ILD). METHODS: Multicentre observational retrospective longitudinal study of a cohort of patients with ASS-ILD that started treatment with RTX due to recurrent or ongoing progressive ILD despite therapy with glucocorticoids and immunosuppressants. RESULTS: Twenty-eight patients were analyzed. Examining the entire study population, before treatment with RTX the mean decline in %pFVC and %pDLCO from the ASS-ILD diagnosis to the initiation of RTX treatment (T0) was -6.44% and -14.85%, respectively. After six months of treatment, RTX reversed the decline in pulmonary function test (PFT) parameters: ∆%pFVC +6.29% (95% CI: -10.07 to 2.51; p=0.002 compared to T0) and ∆%pDLCO +6.15% (95% CI: -10.86 to -1.43; p=0.013). Twenty-four patients completed one year of therapy and 22 two years, maintaining the response in PFT: ∆%pFVC: +9.93% (95% CI: -15.61 to -4.25; p=0.002) and ∆%pDLCO: +7.66% (95% CI: -11.67 to -3.65; p<0.001). In addition, there was a significant reduction in the median dose of prednisone, and it could be suspended in 18% of cases. In 33% of patients who required oxygen therapy at the start of treatment, it could be discontinued. The frequency of adverse events reached 28.5% of cases. CONCLUSION: Based on our results, RTX appears to be effective as rescue therapy in most patients with recurrent or progressive ASS-ILD unresponsive to conventional treatment. The use of RTX was well tolerated in the majority of patients.

Review of Pulmonary Manifestations in Antisynthetase Syndrome.

Antisynthetase syndrome (ASyS) is now a widely recognized entity within the spectrum of idiopathic inflammatory myopathies. Initially described in patients with a triad of myositis, arthritis, and interstitial lung disease (ILD), its presentation can be diverse. Additional common symptoms experienced by patients with ASyS include Raynaud's phenomenon, mechanic's hand, and fever. Although there is a significant overlap with polymyositis and dermatomyositis, the key distinction lies in the presence of antisynthetase antibodies (ASAs). Up to 10 ASAs have been identified to correlate with a presentation of ASyS, each having manifestations that may slightly differ from others. Despite the proposal of three classification criteria to aid diagnosis, the heterogeneous nature of patient presentations poses challenges. ILD confers a significant burden in patients with ASyS, sometimes manifesting in isolation. Notably, ILD is also often the initial presentation of ASyS, requiring pulmonologists to remain vigilant for an accurate diagnosis. This article will comprehensively review the various aspects of ASyS, including disease presentation, diagnosis, management, and clinical course, with a primary focus on its pulmonary manifestations.

Novel Therapeutic Approaches in Connective Tissue Disease-Associated Interstitial Lung Disease.

Connective tissue diseases (CTD) comprise a group of autoimmune diseases that can affect multiple organs in the body including the lungs. The most common form of pulmonary involvement is interstitial lung disease (ILD). CTD-associated ILD (CTD-ILD) can take one of several courses including nonprogressive, chronically progressive, or rapidly progressive. Chronically and rapidly progressive patterns are associated with increased mortality. Limited randomized controlled trial data are available for treatment of CTD-ILD, with most data coming from systemic sclerosis-related ILD. The current first-line treatment for all CTD-ILD is immunosuppression with consideration of antifibrotics, stem cell transplant, and lung transplant in progressive disease. In this article, we review data for ILD treatment options in systemic sclerosis, rheumatoid arthritis, myositis, and primary Sjögren's syndrome-related ILDs.

Anasarca as the first presentation of anti-synthetase syndrome.

A woman in her 70s presented with anasarca and exertional dyspnoea. Investigation showed severe hypoalbuminaemia with no urinary or gastrointestinal protein losses. CT thorax reported lung consolidations, and transbronchial lung biopsy demonstrated organising pneumonia. Autoimmune myositis serology was positive for anti-Jo-1, anti-Ro-52, and anti-PM/Scl-100 antibodies. She was diagnosed with anti-synthetase syndrome with organising pneumonia. She was treated with oral prednisolone and oral mycophenolate mofetil with a good clinical response.

Thymic carcinoma presenting with overlap polyarthritis and myositis: A rare paraneoplastic syndrome in childhood.

Thymic tumors are very rare neoplasms in children and account for less than 1% of mediastinal tumors in pediatric patients. One-third of the pediatric patients present with symptoms related to the compression of the tumor mass on the surrounding anatomic structures, and paraneoplastic syndromes such as myasthenia gravis, pure red cell aplasia, acquired hypogammaglobulinemia, and connective tissue disorders, which rarely occur in children with thymic tumors. Herein, we report a case of thymic carcinoma mimicking the symptoms of a connective tissue disease with symmetrical polyarthritis accompanying myositis, fever, weight loss, and malaise in a 15-year-old male patient. To our knowledge, this is the first case pediatric thymic carcinoma accompany with severe polyarthritis and myopathy, thus we have reviewed the current literature regarding the cases of thymic malignancies coexisting with paraneoplastic syndromes in children.

Myositis as a prominent manifestation of primary skeletal muscle peripheral T-cell lymphoma: a case report and literature review.

The patient presented to the clinic with painful muscle swelling in the right lower extremity, which improved with immunosuppressive therapy. Initially, the condition was diagnosed as polymyositis but recurred soon after. After imaging and biopsy, the final diagnosis was primary skeletal muscle peripheral T-cell lymphoma, not otherwise specified (PSM-PTCL, NOS). In this report, we discuss the challenges in diagnosing and treating this aggressive malignancy and review the literature on PSM-PTCL, NOS. Key Points • To date, there are few reports of PSM-PTCL, NOS, and our case is the tenth. • It is crucial to consider PSM-PTCL, NOS, when presenting with localized muscle edema and unexplained pain. • Histopathological examination is likely the most effective method for diagnosing this rare disease.

Cluster analysis of clinical phenotypes in idiopathic inflammatory myopathy patients complicated with cardiac involvement.

OBJECTIVE: This study aimed to classify idiopathic inflammatory myopathy (IIM) patients with cardiac involvement (IIM-CI) into different categories based on their clinical phenotypes via cluster analysis and to explore their differences in outcomes. METHODS: IIM-CI patients admitted to Peking Union Medical College Hospital from January 2015 to June 2021 were retrieved. The clinical data, laboratory examinations, and treatment were retrospectively reviewed, and the outcome was traced. A second-order clustering method was employed for categorization. RESULTS: A total of 88 IIM-CI patients were enrolled in this study and were classified into two categories through cluster analysis. Category I consisted of patients who exhibited distinct cardiac structural and functional changes, such as enlargement of atriums and/or ventricles, along with the remarkable heart insufficiency biomarkers, whereas patients of category II displayed more widely systemic injuries and intensive skeletal muscle weakness. In comparison, pulmonary hypertension (58.8% vs 16.7%, p < 0.01), arrhythmia (82.4% vs 27.8%, p < 0.01), and positive serum anti-mitochondrial-M2 antibody (52.9% vs 5.6%, p < 0.01) were more prevalent in category I than in category II, and serum N-terminal pro-B-type natriuretic peptide levels (1703.5 pg/L vs 364.0 pg/L, p = 0.02) were significantly elevated in category I, whereas skeletal muscle weakness (50.0% vs 74.1%, p = 0.02), interstitial lung disease (20.6% vs 63.0%, p < 0.01), skin rash (11.8% vs 48.1%, p < 0.01), arthralgia (2.9% vs 27.8%, p < 0.01), fever (2.9% vs 27.8%, p < 0.01), and dysphagia (2.9% vs 22.2%, p < 0.01) were more common in category II patients. Heart failure was the primary cause of death in category I, but severe pneumonia was predominantly responsible for deaths in category II. CONCLUSION: Two categories of IIM-CI were identified based on clinical features with distinctive characteristics. Two categories exhibited differences in clinical manifestations, autoantibody profiles, and the primary cause of death.

Association between anti-PL7 antibodies and increased fibrotic component in patients with antisynthetase syndrome and interstitial lung disease: a cross-sectional study.

OBJECTIVE: To evaluate whether anti-PL7 and anti-PL12 autoantibodies are associated with a greater extent of the fibrotic component of ILD in ASSD patients. METHODS: Patients with ILD-ASSD who were positive for one of the following autoantibodies: anti-Jo1, anti-PL7, anti-PL12, and anti-EJ were included. Clinical manifestations, CPK levels, pulmonary function tests, and HCRT assessments were prospectively collected according to the Goh index. The fibrotic, inflammatory, and overall extension of the Goh index and DLCO were assessed by multiple linear analyses and compared between ASSD antibody subgroups. RESULTS: Sixty-six patients were included; 17 were positive for anti-Jo1 (26%), 17 for anti-PL7 (26%), 20 for anti-PL12 (30%), and 9 (14%) for anti-EJ. Patients with anti-PL7 and anti-PL12 had a more extensive fibrotic component than anti-Jo1. Anti-PL7 patients had a 7.9% increase in the fibrotic extension (cß = 7.9; 95% CI 1.863, 13.918), and the strength of the association was not modified after controlling for sex, age, and time of disease evolution (aß = 7.9; 95% CI 0.677, 15.076) and also was associated with an increase in ILD severity after adjusting for the same variables, denoted by a lower DLCO (aß = - 4.47; 95% CI - 8.919 to - 0.015). CONCLUSIONS: Anti-PL7-positive ASSD patients had more extensive fibrosis and severe ILD than the anti-Jo1 subgroup. This information is clinically useful and has significant implications for managing these patients, suggesting the need for early consideration of concurrent immunosuppressive and antifibrotic therapy.

A Review of Antisynthetase Syndrome-Associated Interstitial Lung Disease.

Our objective in this review article is to present a clinical case of a patient with antisynthetase syndrome (ASyS) and provide an overview of the pathogenesis, classification criteria, antibody profiles, clinical features, and current knowledge of treatment options, focusing on interstitial lung disease (ILD). ASyS is an uncommon autoimmune disease with a heterogenous clinical presentation characterized by the presence of autoantibodies against an aminoacyl-tRNA synthetase and manifested by myositis, fever, inflammatory arthritis, Raynaud's phenomenon, mechanics hands, and ILD. ASyS-associated ILD (ASyS-ILD) is the most serious complication of ASyS, which may evolve to rapidly progressive ILD; therefore, it often requires thorough clinical and radiologic evaluation including recognition of a specific clinical phenotype associated with the antisynthetase antibodies (ASAbs) to guide therapeutic interventions.

Dynamic change in red cell distribution width as a predictor for short-time mortality in dermatomyositis-associated rapid progressive interstitial lung disease.

AIM: We aimed to explore a new and readily available practical marker for rapidly progressive interstitial lung disease (RP-ILD) and poor short-term outcomes in patients with idiopathic inflammatory myopathies (IIM). METHODS: A total of 1822 consecutive patients with IIM between 2009 and 2021 were evaluated retrospectively. All proven cases of naïve ILD with complete medical records were included. Red cell distribution width (RDW) values at the initial stage, 3 months and last follow-up were collected. The clinical characteristics and outcomes of the patients were recorded. RESULTS: We identified 532 patients with IIM with an average follow-up of 4 years. ILD prevalence was higher in patients of elevated RDW (p<0.001). The patients with ILD and elevated RDW had lower levels of PaO2/FiO2, FVC% and DLco% and a higher prevalence of RP-ILD than those with normal RDW (p<0.001). Prognostic analysis revealed that RDW was an independent risk factor for prognosis in patients with IIM-ILD (HR=2.9, p=0.03). Patients with dermatomyositis (DM) with RP-ILD with a change in RDW within 3 months (∆RDW-3) greater than 0 were more likely to die within 3 months. Moreover, the prevalence of ∆RDW-3>0 was higher in patients with RP-ILD and positive for anti-melanoma differentiation-associated gene 5 antibody who died within 3 months (87.5%) compared with those alive at 3 months (24.6%) (p<0.001). CONCLUSION: These findings suggest that repeated RDW assays could assist physicians in identifying patients with DM-ILD who were at a high risk of RP-ILD and death.

Pathological findings with vacuoles in anti-mitochondrial antibody-positive inflammatory myopathy.

BACKGROUND: A few patients with inflammatory myopathy showed anti-mitochondrial antibody (AMA) positivity. This study aimed to report the clinical and pathological findings with vacuoles in 3 cases of such patients. METHODS: Three cases with myositis from the Myositis Clinical Database of Peking University First Hospital were identified with AMA positivity. Their clinical records were retrospectively reviewed and the data was extracted. All the 3 cases underwent muscle biopsy. RESULTS: Three middle-aged patients presented with chronic-onset weakness of proximal limbs, marked elevation of creatine kinase, and AMA-positivity. Two of the 3 cases meet the criteria of primary biliary cholangitis. All the 3 cases presented with cardiac involvement and proteinuria. Two cases developed type 2 respiratory failure. MRI of the thigh muscle showed multiple patches of edema bilaterally in both cases, mostly in the adductor magnus. Pathological findings include degeneration of muscle fibers, diffused MHC-I positivity, and complement deposits on cell membranes. Vacuoles without rims of different sizes were discovered under the membrane of the muscle fibers. A few RBFs were discovered in case 1, while a diffused proliferation of endomysium and perimysium was shown in case 2. CONCLUSIONS: AMA-positive inflammatory myopathy is a disease that could affect multiple systems. Apart from inflammatory changes, the pathological findings of muscle can also present vacuoles.

Anti-synthase syndrome associated with SARS-Cov-2 infection.

BACKGROUND: Anti-synthetase syndrome (AS) is a rare autoimmune idiopathic inflammatory myopathy (IIM) with diverse manifestations, including arthritis, interstitial lung disease (ILD), Raynaud's phenomenon, unexplained persistent fever, and mechanic's hands. CASE PRESENTATION: We present the case of a 72-year-old woman, previously healthy, who was admitted to our hospital for treatment of cough and rapid breathing. The patient had elevated white blood cells and C-reactive protein, and tested negative for severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2). She was initially diagnosed with community-acquired pneumonia and received tamoxifen for anti-infection treatment, but her dystonia worsened. She eventually required non-invasive ventilator support, tested positive for SARS-Cov-2 again, and started antiviral therapy, corticosteroids to reduce alveolar effusion, anticoagulation, and other treatments. However, her condition continued to deteriorate, with the lowest oxygenation index reaching only 80mmHg. Ultimately, she underwent tracheal intubation and mechanical ventilation. Chest CT revealed rapid progressive interstitial changes in her lungs, and her hands showed noticeable fraternization changes. At this point, we suspected that the novel coronavirus infection might be associated with autoimmune diseases. The patient's autoimmune antibody spectrum showed positive results for anti-recombinant RO-52 antibody and myositis-specific antibody anti-alanyl tRNA synthetase (anti-PL-12). The patient was treated with dexamethasone sodium phosphate for anti-inflammatory and anti-fibrotic effects. After successful extubation, the patient was discharged with only oral prednisone tablets at a dose of 30 mg. CONCLUSIONS: This case presents an early diagnosis and successful treatment of anti-synthetase syndrome combined with SARS-Cov-2 infection, emphasizing the importance of comprehensive physical examination. Additionally, it highlights the rapid progression of interstitial lung disease under SARS-Cov-2 infection, which is often difficult to distinguish on imaging. In cases where treatment for SARS-Cov-2 infection is ineffective, early screening for autoimmune diseases is recommended. As there is currently no standardized method for treating AS-ILD, the successful treatment of this case provides a reference for clinical research on anti-synthetase syndrome in the later stage.

Postpartum Necrotizing Myositis With Endometrial Prolapse.

BACKGROUND: Postpartum necrotizing myositis is a rare condition, typically presenting as a complication after uterine artery embolization or uterine compression suturing. Uterine ischemia can cause endometrial necrosis and even myometrial necrosis, which can lead to systemic infection. If a systemic infection is not promptly and actively treated, it may pose significant risk. CASE: A 35-year-old patient who had undergone bilateral uterine artery ligation, modified B-Lynch suture, and multiple compression sutures due to refractory postpartum hemorrhage frequently presented to clinic after postpartum discharge due to persistent fever and vaginal discharge. A bag-like prolapse from the vagina measuring 10×5 cm, accompanied by purulent discharge, was noted 78 days postsurgery. Subsequent pelvic magnetic resonance imaging revealed a uterine basal abscess and postpartum necrotizing myositis; an emergency laparoscopic supracervical hysterectomy was performed, with postoperative pathology confirming the diagnosis. After the patient's discharge, she was readmitted for inpatient treatment of a pelvic abscess. CONCLUSIONS: Although rare, postpartum necrotizing myositis should be considered in postpartum patients presenting with fever, abdominal pain, severe infection symptoms, and abnormal vaginal discharge. Culture and sensitivity testing are recommended to direct appropriate antibiotic therapy.

Clinical Characteristics of 118 Pediatric Patients With Acute Benign Myositis Associated With Influenza A Virus Infection.

OBJECTIVE: The objective of this study was to investigate the clinical and laboratory features of acute benign myositis associated with influenza A virus infection in children. METHODS: A retrospective analysis was performed on the clinical data of 118 children with acute benign myositis associated with influenza A virus infection who were admitted to the Children's Hospital of Chongqing Medical University during the epidemic period of influenza A from February 2023 to May 2023. RESULTS: (1) Most of the 118 children were preschool- or school-age. The most common symptom was sudden lower limb pain after fever, and bilateral calf myalgia was more common. The muscle enzyme spectrum ranged from 187.21 to 32191.00 µg/L (median: 3053 µg/L). Creatine kinase isoenzymes ranged from 5.15 to 749.7 µg/L (median 41.82 µg/L). Myoglobin ranged from 102.79 to 1200 µg/L (median 674.9 µg/L). (3) Examination: electromyography, muscle color Doppler ultrasound, radiograph and cardiac color Doppler ultrasound in Benign acute childhood myositis in children were rarely positive. (4) Treatment and prognosis: besides bed rest and a reduction of physical activity, oseltamivir treatment, drugs to improve energy metabolism, fluid replacement and alkalinization of symptomatic treatment. All children had a good prognosis without sequelae. CONCLUSIONS: This study summarized and analyzed the clinical characteristics of acute benign myositis associated with influenza A infection in children with the aim of allowing rapid and early diagnosis of the disease and reducing unnecessary diagnostic tests and treatments. Closely monitoring myalgia and the muscle enzyme spectrum is recommended to exclude other neuromuscular and metabolic diseases.

Paraneoplastic myopathies.

This chapter reviews the association between cancer and the idiopathic inflammatory myopathies (IIM), which includes dermatomyositis (DM), antisynthetase syndrome (ASyS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). Accumulating evidence shows that the risk of a coexisting malignancy is high in patients with DM, especially among those with anti-Tif1γ autoantibodies. Patients with IMNM and no defined autoantibodies also have an increased risk of malignancy. Recent evidence demonstrates that many IBM patients have increased numbers of circulating CD57+ CD8+ T cells, consistent with a diagnosis of large granular lymphocytic leukemia. In contrast, IMNM patients with anti-SRP or anti-HMGCR autoantibodies as well as patients with ASyS syndrome do not have a definitively increased risk of cancer. Patients who have a cancer treated with one of the immune checkpoint inhibitors can develop myositis (ICI-myositis), sometimes along with myasthenia gravis and/or myocarditis.

Anti-synthetase syndrome is associated with a higher risk of hospitalization among patients with idiopathic inflammatory myopathy and COVID-19.

Background: Data with fine granularity about COVID-19-related outcomes and risk factors were still limited in the idiopathic inflammatory myopathies (IIMs) population. This study aimed to investigate clinical factors associated with hospitalized and severe COVID-19 in patients with IIMs, particularly those gauged by myositis-specific antibodies. Methods: This retrospective cohort study was conducted in the Renji IIM cohort in Shanghai, China, under an upsurge of SARS-CoV-2 omicron variant infections from December 2022 to January 2023. Clinical data were collected and analyzed by multivariable logistic regression to determine risk factors. High-dimensional flow cytometry analysis was performed to outline the immunological features. Results: Among 463 infected patients in the eligible cohort (n=613), 65 (14.0%) were hospitalized, 19 (4.1%) suffered severe COVID-19, and 10 (2.2%) died. Older age (OR=1.59/decade, 95% CI 1.18 to 2.16, p=0.003), requiring family oxygen supplement (2.62, 1.11 to 6.19, 0.028), patients with anti-synthetase syndrome (ASyS) (2.88, 1.12 to 7.34, 0.027, vs. other dermatomyositis), higher IIM disease activity, and prednisone intake >10mg/day (5.59, 2.70 to 11.57, <0.001) were associated with a higher risk of hospitalization. Conversely, 3-dose inactivated vaccination reduced the risk of hospitalization (0.10, 0.02 to 0.40, 0.001, vs. incomplete vaccination). Janus kinase inhibitor (JAKi) pre-exposure significantly reduced the risk of severe COVID-19 in hospitalized patients (0.16, 0.04 to 0.74, 0.019, vs. csDMARDs). ASyS patients with severe COVID-19 had significantly reduced peripheral CD4+ T cells, lower CD4/CD8 ratio, and fewer naive B cells but more class-switched memory B cells compared with controls. Conclusion: ASyS and family oxygen supplement were first identified as risk factors for COVID-19-related hospitalization in patients with IIMs. JAKi pre-exposure might protect IIM patients against severe COVID-19 complications.

Evaluating disease status in idiopathic inflammatory myopathies with quantitative muscle ultrasound.

INTRODUCTION/AIMS: Muscle strength, functional status, and muscle enzymes are conventionally used to evaluate disease status in idiopathic inflammatory myopathies (IIM). This study aims to investigate the role of quantitative muscle ultrasound in evaluating disease status in IIM patients. METHODS: Patients with IIM, excluding inclusion body myositis, were recruited along with age- and sex-matched healthy controls (HC). All participants underwent muscle ultrasound and clinical assessments. Six limb muscles were unilaterally scanned using a standardized protocol, measuring muscle thickness (MT) and echo intensity (EI). Results were compared with HC, and correlations were made with outcome measures. RESULTS: Twenty IIM patients and 24 HC were recruited. The subtypes of IIM were dermatomyositis (6), necrotizing myositis (6), polymyositis (3), antisynthetase syndrome (3), and nonspecific myositis (2). Mean disease duration was 8.7 ± 6.9 years. There were no significant differences in demographics and anthropometrics between patients and controls. MT of rectus femoris in IIM patients was significantly lower than HC. Muscle EI of biceps brachii and vastus medialis in IIM patients were higher than HC. There were moderate correlations between MT of rectus femoris and modified Rankin Scale, Physician Global Activity Assessment, and Health Assessment Questionnaire, as well as between EI of biceps brachii and Manual Muscle Testing-8. DISCUSSION: Muscle ultrasound can detect proximal muscle atrophy and hyperechogenicity in patients with IIM. The findings correlate with clinical outcome measures, making it a potential tool for evaluating disease activity of patients with IIM in the late phase of the disease.