Anti-SRP immune-mediated necrotizing myopathy: A critical review of current concepts

Telitacicept add-on therapy in refractory idiopathic inflammatory myopathy: insights from a pilot study

OBJECTIVES

This study aimed to evaluate the therapeutic efficacy of telitacicept based on the conventional treatment in adults with idiopathic inflammatory myopathy (IIM), focusing on its impact on clinical manifestations.

METHODS

IIM patients who had been treated with telitacicept for at least 3 months based on the conventional treatment from January 2023 to January 2024 were included in this study. The clinical response to telitacicept was determined based on the ACR/EULAR criteria for minimal, moderate and major improvement in the Total Improvement Score. Disease activity was monitored using core set measures, while myositis damage was assessed with established assessment tools. The Manual Muscle Test for eight muscle groups (MMT-8) was used to assess the muscle performance.

RESULTS

A total of 11 patients administered with telitacicept (160 mg per week) were included in this study. Post-treatment assessments revealed improvements in all patients according to ACR/EULAR criteria. Notably, there was a significant reduction in the prednisone dosage from baseline to last visit [27.05 (12.47) to 12.05 (7.32) mg; P < 0.005]. An enhancement was observed in the MMT-8 score [which improved from 109.18 (14.18) to 137.64 (15.28); P < 0.005], and there was a reduction in creatine kinase level [from 2670.27 (2675.00) to 561.09 (754.09) U/l; P < 0.05].

CONCLUSION

Telitacicept demonstrated effectiveness in treating refractory inflammatory myopathy, contributing to a significant reduction in steroid dosage among the patients. These findings highlight the potential of telitacicept as a valuable therapeutic option in the management of IIM.

Effectiveness of proprotein convertase subtilisin/kexin type 9 inhibitors in managing hypercholesterolemia post-statin-associated immune-mediated necrotizing myopathy: report of five cases and literature review

Immune-mediated necrotizing myopathy (IMNM), a type of inflammatory myopathy, is associated with anti-SRP or anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (anti-HMGCR) antibodies, with statin use potentially inducing statin-associated IMNM (SAIMNM) due to HMGCR targeting. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors may offer a safer alternative for lipid-lowering in these patients. This study aims to describe the clinical characteristics of SAIMNM patients and evaluate the safety of PCSK9 inhibitors after myositis onset. We present the clinical characteristics of five SAIMNM patients and evaluate the safety of PCSK9 inhibitors in these cases. Additionally, we conducted a literature review using four different databases (Medline/PubMed, Scopus, Cochrane and DOAJ) to summarize the available data on IMNM. While numerous articles discussed statin-induced myositis, we selected only those studies that addressed the treatment of dyslipidemia after the management of IMNM. All five patients were women, with four having a history of statin use. One statin-naïve patient was positive for anti-SRP antibodies, while the others had anti-HMGCR antibodies. After a mean follow-up of 18.2 months, creatine phosphokinase (CPK) levels dropped from 1028.6 IU/L to 135 IU/L, and LDL cholesterol levels decreased from 206.2 mg/dL to 87.2 mg/dL. All patients were treated with steroids (with a gradual dosage reduction), and four of the five received second line immunosuppressive therapy, such as intravenous immunoglobulin, methotrexate, azathioprine, and mycophenolate mofetil. No disease recurrence occurred after starting PCSK9 inhibitors. A review of seven studies (15 patients) showed a mean CPK of 1531.9 IU/L. 40% received steroids and another immunosuppressant. Statin rechallenge caused relapse in two cases, but PCSK9 inhibitors were well tolerated, with only one patient needing additional immunosuppression. Additionally, ezetimibe and bempedoic acid were used successfully in some patients. Finally, lipid levels appeared to be lower after treatment with PCSK9 inhibitors. Administration of PCSK9 inhibitors appears to be an effective and safe option for the treatment of dyslipidaemia in patients with IMNM.

Risk factors and predictive model for pulmonary arterial hypertension in adult idiopathic-inflammatory-myopathy patients: A cross-sectional study

OBJECTIVE

To identify clinical and laboratory risk factors for Pulmonary Arterial Hypertension (PAH) in Idiopathic-Inflammatory-Myopathy (IIM) patients as well as construct a predicting model for PAH.

METHODS

An IIM cohort in southeastern China was established, including 504 adult IIM patients who met the inclusion and exclusion criteria, and were hospitalized at four divisions of the First Affiliated Hospital, Zhejiang University School of Medicine (FAHZJU) from January 1st, 2018, to April 30st 2022. Serum cytokine profiles, myositis-specific antibodies as well as other factors of patients who met the inclusion and exclusion criteria were collected and analyzed.

RESULTS

Of the 504 adult IIM patients, 25 IIM patients developed PAH and 48.0 % of them deceased within six months. IIM patients complicated with PAH were found to suffer from worse outcome (p < 0.001). After multivariate logistic regression analysis, age (p < 0.001), bacterial infection (p = 0.005), MYOACT score (p = 0.009), Interleukin (IL)-17A (p = 0.017), anti-SRP antibody (p = 0.011) and steroid monotherapy (p = 0.001) were identified as factors significantly associated with PAH in IIM patients. A "BAIMS" model was constructed by including the above six items to predict PAH with a cut-off value of ≥ 3 and an Area Under the Curve (AUC) of 0.877.

CONCLUSION

PAH is a rare but potentially fatal complication in IIM patients. Aging, complication of bacterial infection, elevated disease activity, increased serum IL-17A level, positivity of anti-SRP antibody and steroid monotherapy were significantly correlated with development of PAH in IIM patients. In addition, the BAIMS model was found valuable in prediction and early-identification of PAH in IIM patients.

Identification of clinical subgroups in anti-SRP positive immune-mediated necrotizing myopathy patients using cluster analysis

Background

Anti-signal recognition particle immune-mediated necrotizing myopathy (anti-SRP IMNM) is a rare autoimmune disorder characterized by muscle weakness and necrosis. Identifying clinical subgroups within this patient population could facilitate the management of the disease.

Objectives

To identify distinct clinical subgroups of anti-SRP IMNM patients.

Design

A retrospective study was conducted on anti-SRP IMNM patients treated at West China Hospital of Sichuan University between January 2010 and October 2023.

Methods

Clinical data were collected. Unsupervised cluster analysis was conducted to classify patients into distinct subgroups based on their clinical features. Statistical analyses were performed to compare the clinical characteristics and outcomes among the identified clusters.

Results

A total of 116 patients were included in the study, and 3 distinct clinical subgroups were identified: Cluster 3 (acute), Cluster 2 (subacute), and Cluster 1 (poor prognosis). Patients in Cluster 3 exhibited a short disease course (median 3 months), severe muscle weakness (78.38% with Medical Research Council (MRC) score ⩽3), high muscle enzyme levels, and a good response to treatment. Cluster 2 patients were younger (mean age 45.83 years), had a longer disease course (median 6.5 months), milder muscle damage, and lower autoantibody titers. Cluster 1 patients were older (mean age 58.10 years), predominantly male (70.97%), and had higher incidences of interstitial lung disease (70.97%) and cardiac injury (45.16%). In Cluster 1, 16.13% of cases were refractory, and the relapse rate was 38.71%, which was significantly higher compared to the other two clusters.

Conclusion

This study highlights the clinical heterogeneity among anti-SRP IMNM patients and identifies three distinct clinical subgroups with unique characteristics. These findings provide insights for personalized management.

Refractory Severe Anti-SRP Myopathy that Improved with Long-term Rehabilitation Therapy: A Case Report

Background

Immune-mediated necrotizing myopathy (IMNM) is a type of autoimmune myositis. Anti-signal recognition particle (SRP) antibodies are highly specific to this disease.

Case

A 76-year-old woman presented with a 4-month history of acute progressive limb muscle weakness and dysphagia. Blood examination revealed significantly elevated creatine kinase (CK) (3472 U/L) and SRP antibody positivity. The patient was near-bedridden and required alternative nutrition. She was treated with oral prednisolone and intravenous immunoglobulin. Rehabilitation therapy was initiated after confirming the decline in CK levels. She started with exercises on the bed and exercise load was gradually increased. Videofluoroscopic swallowing study showed severely weakened pharyngeal contractions and aspiration. Her symptoms improved slowly. She started transferring to a wheelchair after 2 months, gait training using parallel bars after 4 months, and was administered a paste diet once a day after 5 months. Rituximab was administered as additional treatment. Thereafter, the patient started gait training with a walker. The oral paste diet was increased to three times per day after 7 months, and a regular diet was adopted after 9 months. After 11 months, she was discharged home after achieving modified near independence in all activities of daily living.

Discussion

: Low-intensity rehabilitation therapies were initiated under the supervision of therapists with regular follow-up and progression of exercise intensity based on multidisciplinary team discussions. If CK levels indicate that the disease has stabilized, early intervention in rehabilitation is important to prevent declining physical function.

Successful treatment of anti-signal recognition particle antibody-positive myositis with intravenous cyclophosphamide: A case report

Myositis-specific autoantibodies play an important role on the disease phenotype of idiopathic inflammatory myopathies (IIMs). Anti-signal recognition particle (SRP) antibody-positive patients with IIMs may present with severe myopathy and highly elevated serum creatine kinase levels. These patients are often resistant to immunosuppressive therapy, but there is no established treatment strategy. A 51-year-old man referred to our department was diagnosed with IIM based on imaging and pathological findings. A high dose of corticosteroids followed by intravenous cyclophosphamide (IV-CY) treatment (750 mg three times) resulted in an improvement in clinical manifestations and functional outcomes, and recurrence did not occur. Our case suggests that IV-CY is an effective induction regimen for patients with anti-SRP antibody-positive IIMs.

An update on autoantibodies in the idiopathic inflammatory myopathies

Myositis-specific autoantibodies (MSAs) have become pivotal biomarkers for idiopathic inflammatory myopathies and have revolutionized understanding of the heterogeneous disease spectrum that affects both adults and children. The discovery and characterization of MSAs have substantially enhanced patient stratification based on clinical phenotype, thereby facilitating more precise diagnosis and ultimately improving management strategies. Advances in immunoassay technologies in the past 20 years have further propelled the field forward, enabling the detection of a growing repertoire of autoantibodies with high specificity and sensitivity; however, evolving research over the past decade has revealed that even within antibody-defined subsets, considerable clinical diversity exists, suggesting a broader spectrum of disease manifestations than previously acknowledged. Challenges persist, particularly among patients who are seronegative, where the failure to identify certain rare MSAs stems from the use of diverse detection methodologies and inadequate consensus-guided standardization and validation protocols. Bridging these diagnostic gaps is crucial for optimizing patient care and refining prognostic stratification in idiopathic inflammatory myopathies.

Autoantibody-Based Clinicoradiopathologic Phenotyping of Idiopathic Inflammatory Myopathies: An Indian Cohort

OBJECTIVES

We aim to characterize the clinical, pathological, laboratory and imaging features of various antibody defined IIM subgroups in Indian population.

METHODOLOGY

103 patients who satisfied 2017 ACR/ EULAR Classification criteria for IIM, and tested seropositive for myositis antibodies using Immunoblot technique were retrospectively identified. Patients were classified into following subgroups - Mi2B group, SRP group, Anti RNA Synthetase antibody group (Jo 1, PL 7, PL 12, OJ), multiple MSA, only MAA group (U1RNP, Ro 52, SS-A, SS-B, PM Scl 75, PM Scl 100). Clinical, laboratory, histopathology and imaging parameters were compared among different groups.

RESULTS

Ro52 (n = 31; 22.46%) was the most common autoantibody seen in our cohort followed by Mi2B (n = 26; 18.84%) and SRP (n = 20; 14.49%). Skin manifestations (p = 0.053) and joint involvement (p = 0.023) were seen more frequently among Mi2B and MAA sub groups. Three out of 4 patients with persisting antibody positivity on serial measurements developed clinical relapse between 2 and 3 years after the initial episode. Remaining 2 patients showed declining titres of antibodies and developed no clinical relapses during follow up period of 5 and 6 years. Among histopathology features, perifascicular atrophy was found to be more prevalent among Mi2B (55.6%) and MAA subgroups (31.3%) (p value = 0.037). In thigh muscle MRI, Mi2B group showed a pattern of diffuse involvement of affected muscles without regional preference, with sparing of hamstring group. SRP group showed characteristic pattern of edema involving peripheral regions of Quadriceps femoris and central regions of Adductor group along with severe atrophy involving hamstring and adductor compartment muscles. ILD was seen in 27.5% of patients who underwent CT Chest. 3 patients were found to have underlying malignancy at the time of diagnosis of myositis (Mi2B = 2 and PM Scl = 1).

CONCLUSION

Classification of IIM patients based on myositis antibodies yields subgroups with certain differences in clinical, laboratory, histopathological and imaging features.

Case study of CD19 CAR T therapy in a subject with immune-mediate necrotizing myopathy treated in the RESET-Myositis phase I/II trial

Under compassionate use, chimeric antigen receptor (CAR) T cells have elicited durable remissions in patients with refractory idiopathic inflammatory myopathies (IIMs). Here, we report on the safety, efficacy, and correlative data of the first subject with the immune-mediated necrotizing myopathy (IMNM) subtype of IIM who received a fully human, 4-1BBz anti-CD19-CAR T cell therapy (CABA-201) in the RESET-Myositis phase I/II trial (NCT06154252). CABA-201 was well-tolerated following infusion. Notably, no evidence of cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome was observed. Creatine kinase levels decreased, and muscular strength improved post-infusion. Peripheral B cells were depleted rapidly following infusion, and the subject achieved peripheral B cell aplasia by day 15 post-infusion. Peripheral B cells returned at 2 months post-infusion and were almost entirely transitional. Autoantibodies to SRP-9, SRP-72, SRP-54, and Ro-52, decreased relative to baseline, whereas antibodies associated with pathogens and vaccinations remained stable. The infusion product consisted of predominantly CD4+ effector memory T cells and exhibited in vitro cytolytic activity. Post-infusion, CABA-201 expansion peaked at day 15 and was preceded by a serum IFN-γ peak on day 8 with peaks in serum IL-12p40 and IP-10 on day 15. These data detail the safety, efficacy, and pharmacodynamics of CABA-201 in the first IMNM subject.

The emerging roles of necroptosis in skeletal muscle health and disease

Necroptosis is a regulated form of cell death with implications in various physiological and pathological processes in multiple tissues. However, the relevant findings from post-mitotic tissues, such as skeletal muscle, are scarce. This review summarizes the potential contributions of necroptosis to skeletal muscle health and diseases. It first discusses the physiological roles of necroptosis in muscle regeneration and development. It then summarizes the contributions of necroptosis to the pathogenesis of multiple muscle diseases, including muscular dystrophies, inflammatory myopathies, cachexia, and neuromuscular disorders. Lastly, it unravels the gaps in our understanding and therapeutic challenges of inhibiting necroptosis as a potential intervention for muscle diseases. Specifically, the findings from the transgenic animal models and the use of pharmacological inhibitors of necroptosis are discussed with relevance to improving the structure and/or function of skeletal muscle in various diseases. Recent developments from experimental animal models and clinical data are presented to discuss the roles of necroptosis in skeletal muscle health and diseases.

Anti-SRP Antibodies and Myocarditis in Systemic Sclerosis Overlap Syndrome with Immune-Mediated Necrotizing Myositis (IMNM)

Overlap syndrome of systemic sclerosis and idiopathic inflammatory myopathies is an increasingly frequent entity, but the association with immune-mediated necrotizing myositis has rarely been described. While myositis or myopathy may be features of scleroderma, it is imperative to correctly diagnose an overlap syndrome of these two, since it can be considered a different entity with specific management and a worse prognosis. Anti-signal recognition particle (anti-SRP) antibodies target the striated muscle fiber and inhibit myoblast regeneration, resulting in myofiber atrophy and necrosis. Anti-SRP antibodies are specific in immune-mediated necrotizing myopathy characterized by myonecrosis and minimal inflammatory reaction, with proximal muscle weakness and typical extra-muscular manifestation. There are controversial data on the association of cardiac manifestations and the presence of these antibodies, and recent studies cannot prove a significant correlation between the two. Myocarditis is a complication with an unpredictable, potentially severe outcome from heart failure and dilated cardiomyopathy to fatality. It can be difficult to diagnose, and a myocardial biopsy can be problematic in daily practice; thus, most practitioners rely on cardiac magnetic resonance with suggestive images for the correct diagnosis. This paper seeks to address the challenges associated with the diagnosis and treatment of collagen diseases by evaluating the role of anti-SRP antibodies in the pathogenesis of cardiac involvement.

Allogeneic CD19-targeted CAR-T therapy in patients with severe myositis and systemic sclerosis

Allogeneic chimeric antigen receptor (CAR)-T cells hold great promise for expanding the accessibility of CAR-T therapy, whereas the risks of allograft rejection have hampered its application. Here, we genetically engineered healthy-donor-derived, CD19-targeting CAR-T cells using CRISPR-Cas9 to address the issue of immune rejection and treated one patient with refractory immune-mediated necrotizing myopathy and two patients with diffuse cutaneous systemic sclerosis with these cells. This study was registered at ClinicalTrials.gov (NCT05859997). The infused cells persisted for over 3 months, achieving complete B cell depletion within 2 weeks of treatment. During the 6-month follow-up, we observed deep remission without cytokine release syndrome or other serious adverse events in all three patients, primarily shown by the significant improvement in the clinical response index scores for the two diseases, respectively, and supported by the observations of reversal of inflammation and fibrosis. Our results demonstrate the high safety and promising immune modulatory effect of the off-the-shelf CAR-T cells in treating severe refractory autoimmune diseases.

Mystical Myositis: A Case Series from Kalafong Provincial Tertiary Hospital, Pretoria, South Africa

Idiopathic inflammatory myositis (IIM) is an expanding field in rheumatology as more myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs) become available for testing. Clinical signs and specific clinical phenotypes are found in the MSA group, with as high as 70% of IIM patients having a positive myositis-specific antibody. Although IIM remains a heterogenous disease, assigning a phenotype to these patients will prove to be critical as we learn which cases require more aggressive therapy and what complications to search for as the disease progresses. The IIM patients for the last 5 years were reviewed and profiled using recently available myositis profile testing at our National Health Laboratory Services. Patients from our rheumatology clinic were categorized according to this antibody profile. Three cases diagnosed with dermatomyositis (DM) were selected for discussion in this article which include a patient with each of the following: anti-transcriptional intermediary factor 1-y (TIF1y) DM, anti-melanoma differentiation-associated protein 5 (MDA 5) DM, and anti-signal recognition particle (SRP) DM.

An externally validated clinical-laboratory nomogram for myocardial involvement in adult idiopathic-inflammatory-myopathy patients

OBJECTIVES

This study aimed at identifying clinical and laboratory risk factors for myocardial involvement (MI) in idiopathic inflammatory myopathies (IIMs) patients as well as constructing a risk-predicted nomogram for prediction and early identification of MI.

METHODS

An IIMs cohort in southeastern China was constructed, including 504 adult IIMs patients who met the inclusion and exclusion criteria, and were hospitalized at four divisions of the First Affiliated Hospital, Zhejiang University School of Medicine from January 1st 2018 to April 30st 2022. After dividing patients into the training cohort and the validation cohort, risk factors for MI were identified through least absolute shrinkage and selection operator regression and multivariate logistic regression. A risk-predicted nomogram was established and validated internally and externally for discrimination, calibration and practicability.

RESULTS

In this cohort, 17.7% of patients developed MI and the survival was significantly inferior to that of IIMs patients without MI (P < 0.001). In the training cohort, age > 55 years old (P < 0.001), disease activity > 10 points (P < 0.001), interleukin-17A (IL-17A) > 7.5 pg/ml (P < 0.001), lactic dehydrogenase (LDH) > 425 U/L (P < 0.001), anti-mitochondrial antibodies (AMAs, P = 0.017), and anti-MDA5 antibody (P = 0.037) were significantly correlated with development of MI. A nomogram was established by including the above values to predict MI and was found efficient in discrimination, calibration, and practicability through internal and external validation.

CONCLUSION

This study developed and validated a nomogram model to predict the risk of MI in adult IIMs patients, which can benefit the prediction and early identification of MI as well as timely intervention in these patients.

Autoantibody evaluation in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), generally referred to as myositis is a heterogeneous group of diseases characterized by muscle inflammation and/or skin involvement, diverse extramuscular manifestations with variable risk for malignancy and response to treatment. Contemporary clinico-serologic categorization identifies 5 main clinical groups which can be further stratified based on age, specific clinical manifestations and/or risk for cancer. The serological biomarkers for this classification are generally known as myositis-specific (MSAs) and myositis-associated antibodies. Based on the use of these antibodies, IIM patients are classified into anti-synthetase syndrome, dermatomyositis, immune-mediated necrotizing myopathy, inclusion body myositis, and overlap myositis. The current classification criteria for IIM requires clinical findings, laboratory measurements, and histological findings of the muscles. However, the use MSAs and myositis-associated autoantibodies as an adjunct for disease evaluation is thought to provide a cost-effective personalized approach that may not only guide diagnosis but aid in stratification and/or prognosis of patients. This review provides a comprehensive overview of contemporary autoantibodies that are specific or associated myositis. In addition, it highlights possible pathways for the detection and interpretation of these antibodies with limitations for routine clinical use.

Current Biomarker Strategies in Autoimmune Neuromuscular Diseases

Inflammatory neuromuscular disorders encompass a diverse group of immune-mediated diseases with varying clinical manifestations and treatment responses. The identification of specific biomarkers has the potential to provide valuable insights into disease pathogenesis, aid in accurate diagnosis, predict disease course, and monitor treatment efficacy. However, the rarity and heterogeneity of these disorders pose significant challenges in the identification and implementation of reliable biomarkers. Here, we aim to provide a comprehensive review of biomarkers currently established in Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), myasthenia gravis (MG), and idiopathic inflammatory myopathy (IIM). It highlights the existing biomarkers in these disorders, including diagnostic, prognostic, predictive and monitoring biomarkers, while emphasizing the unmet need for additional specific biomarkers. The limitations and challenges associated with the current biomarkers are discussed, and the potential implications for disease management and personalized treatment strategies are explored. Collectively, biomarkers have the potential to improve the management of inflammatory neuromuscular disorders. However, novel strategies and further research are needed to establish clinically meaningful biomarkers.

Evidence of Cardiac Involvement in a Patient With Necrotizing Autoimmune Myopathy (NAM)

Necrotizing autoimmune myopathy (NAM) is a rare inflammatory myopathy primarily affecting skeletal muscles. Cardiac involvement has been reported in immune-mediated necrotizing myopathy (IMNM), but its extent remains poorly understood. We present a unique case of a 68-year-old male with anti-signal recognition particle (SRP) antibody-positive NAM initially presenting with elevated troponin levels. Our case demonstrates cardiac involvement as the presenting feature of NAM, which is a unique feature of inflammatory myopathy.

Anti-signal recognition particle positive necrotizing myopathy-sjogren’s syndrome overlap syndrome: a descriptive study on clinical and myopathology features

Background and objective

The aim of this study was to elucidate the clinical and myopathological characteristics of patients with anti-signal recognition particle (SRP) positive immune-mediated necrotizing myopathy (IMNM) overlap Sjogren’s syndrome (SS).

Materials and methods

We retrospectively analyzed the data of anti-SRP positive IMNM patients admitted in the Neurology Department of Tongji Hospital between January 2011 to December 2020. Patients were divided into two groups: anti-SRP IMNM overlap SS group and anti-SRP IMNM control group. The clinical features, laboratory results, histological features, treatment, and prognosis were compared between the two groups.

Results

A total of 30 patients with anti-SRP IMNM were included, including six anti-SRP IMNM overlap SS patients (two males, four females), with a median age of 39 years, and 24 anti-SRP IMNM patients (ten males, fourteen females), with a median age of 46 years. The anti-SRP IMNM overlap SS group had a lower prevalence of muscle atrophy (0 vs 50%, p = 0.019), and a higher prevalence of extramuscular manifestations, including cardiac abnormalities and ILD (Interstitial lung disease). CD4 + and CD68 + inflammatory infiltrations were significantly increased in anti-SRP IMNM overlap SS patients, with an increased presence of CD4 + cells in both necrotic(p = 0.023) and endomysial areas (p = 0.013), and more CD68 + cells (p = 0.016) infiltrated the endomysial area. Deposition of membrane attack complex (MAC) on sarcolemma (p = 0.013) was more commonly seen in the anti-SRP IMNM overlap SS group.

Conclusion

Our data revealed that anti-SRP IMNM-SS overlap patients may present with milder muscular manifestation, but worse extramuscular manifestations compared to anti-SRP IMNM patients without SS. CD4 + and CD68 + inflammatory infiltrations and MAC deposition were remarkably increased in anti-SRP IMNM-SS overlap patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-023-06354-5.

Predictors of cardiac involvement in idiopathic inflammatory myopathies

Objectives

Idiopathic inflammatory myopathies (IIM) are a group of rare disorders that can affect the heart. This work aimed to find predictors of cardiac involvement in IIM.

Methods

Multicenter, open cohort study, including patients registered in the IIM module of the Rheumatic Diseases Portuguese Register (Reuma.pt/Myositis) until January 2022. Patients without cardiac involvement information were excluded. Myo(peri)carditis, dilated cardiomyopathy, conduction abnormalities, and/or premature coronary artery disease were considered.

Results

230 patients were included, 163 (70.9%) of whom were females. Thirteen patients (5.7%) had cardiac involvement. Compared with IIM patients without cardiac involvement, these patients had a lower bilateral manual muscle testing score (MMT) at the peak of muscle weakness [108.0 ± 55.0 vs 147.5 ± 22.0, p=0.008] and more frequently had oesophageal [6/12 (50.0%) vs 33/207 (15.9%), p=0.009] and lung [10/13 (76.9%) vs 68/216 (31.5%), p=0.001] involvements. Anti-SRP antibodies were more commonly identified in patients with cardiac involvement [3/11 (27.3%) vs 9/174 (5.2%), p=0.026]. In the multivariate analysis, positivity for anti-SRP antibodies (OR 104.3, 95% CI: 2.5-4277.8, p=0.014) was a predictor of cardiac involvement, regardless of sex, ethnicity, age at diagnosis, and lung involvement. Sensitivity analysis confirmed these results.

Conclusion

Anti-SRP antibodies were predictors of cardiac involvement in our cohort of IIM patients, irrespective of demographical characteristics and lung involvement. We suggest considering frequent screening for heart involvement in anti-SRP-positive IIM patients.