Inclusion body myositis and myopathies

Treatment resistance in inclusion body myositis: the role of mast cells

Inclusion body myositis is the commonest acquired myopathy in those over 50 years of age. Although it is classified as an idiopathic inflammatory myopathy and the most frequent finding on muscle biopsy in inclusion body myositis is an endomysial inflammatory infiltrate, it is clinically distinct from other myositis, including a lack of response to immunosuppressive medication. Neurogenic changes are commonly reported in inclusion body myositis and inflammatory changes are observed in muscle following neurogenic injury. The objective of our study was to explore whether neurogenic inflammation plays a role in the pathogenesis of inclusion body myositis, possibly explaining its resistance to immunosuppression. The number of mast cells and presence of neuropeptides, substance P and calcitonin gene-related peptide, were assessed in 48 cases of inclusion body myositis, 11 cases of steroid responsive myositis, two cases of focal myositis associated with neurogenic injury, and ten normal controls. The number of mast cells in inclusion body myositis focal and myositis associated to neurogenic injury were significantly greater than that observed in steroid responsive myositis. Our findings suggest that neurogenic inflammation mediated through mast cells may play a role in the pathogenesis of inclusion body myositis, and focal myositis associated to neurogenic injury, and thus, explain in some part its lack of response to immunosuppressive treatments.

Bilateral Facial Palsy: A Rare Presenting Symptom for Inclusion Body Myositis

Inclusion body myositis is a common type of inflammatory myopathy among populations over the age of 50 years, classically presenting with weakness and atrophy of the forearms and quadriceps. While a third of patients may eventually present with mild facial weakness, findings of ptosis, facial palsy, or involvement of extraocular muscles are rarely, if ever, seen. The authors describe a unique case of inclusion body myositis in which a patient initially presented with bilateral severe facial palsy and exposure keratitis but minimal limb weakness. While midface weakness, unilateral lagophthalmos, and ptosis have been documented in one reported case, key presenting symptoms of bilateral facial palsy and symmetric paralytic lagophthalmos with corneal exposure have not been presented before. Therefore, this case serves as an important reminder to consider the inclusion body myositis in the differential diagnosis of bilateral facial palsy.

Effects of sporadic inclusion body myositis on skeletal muscle fibre type specific morphology and markers of regeneration and inflammation

Sporadic inclusion body myositis (sIBM) is a subgroup of idiopathic inflammatory myopathies characterised by progressive muscle weakness and skeletal muscle inflammation. Quantitative data on the myofibre morphology in sIBM remains scarce. Further, no previous study has examined fibre type association of satellite cells (SC), myonuclei number, macrophages, capillaries, and myonuclear domain (MD) in sIBM patients. Muscle biopsies from sIBM patients (n = 18) obtained previously (NCT02317094) were included in the analysis for fibre type-specific myofibre cross-sectional area (mCSA), SCs, myonuclei and macrophages, myonuclear domain, and capillarisation. mCSA (p < 0.001), peripheral myonuclei (p < 0.001) and MD (p = 0.005) were higher in association with type 1 (slow-twitch) than type 2 (fast-twitch) fibres. Conversely, quiescent SCs (p < 0.001), centrally placed myonuclei (p = 0.03), M1 macrophages (p < 0.002), M2 macrophages (p = 0.013) and capillaries (p < 0.001) were higher at type 2 fibres compared to type 1 fibres. In contrast, proliferating (Pax7+/Ki67+) SCs (p = 0.68) were similarly associated with each fibre type. Type 2 myofibres of late-phase sIBM patients showed marked signs of muscle atrophy (i.e. reduced mCSA) accompanied by higher numbers of associated quiescent SCs, centrally placed myonuclei, macrophages and capillaries compared to type 1 fibres. In contrast, type 1 fibres were suffering from pathological enlargement with larger MDs as well as fewer nuclei and capillaries per area when compared with type 2 fibres. More research is needed to examine to which extent different therapeutic interventions including targeted exercise might alleviate these fibre type-specific characteristics and countermeasure their consequences in impaired functional performance.

Atypical skin conditions of the neck and back as a dermal manifestation of anti-HMGCR antibody-positive myopathy

BACKGROUND

Immune-mediated necrotizing myopathy (IMNM) is an idiopathic inflammatory myopathy (IIM). Though patients with IMNM were not considered to show skin rash, several reports have showed atypical skin conditions in patients with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibody-positive IMNM (HMGCR-IMNM). The incidence and phenotype of skin conditions in patients with HMGCR-IMNM are not fully known.

RESULTS

Among the 100 IIM patients diagnosed from April 2015 through August 2022, 34 (34%) presented some form of skin condition, with 27 having typical skin rashes; this included 13 patients with dermatomyositis (DM), 8 with anti-synthetase syndrome (ASS), and 6 with IMNM. Meanwhile, 8 of 19 patients with HMGCR-IMNM (42%) presented atypical skin lesions, but no patients with other IIMs did (p < 0.001). Skin eruption with ash-like scales was observed in four HMGCR-IMNM patients, and non-scaly red patches and lumps in the other four patients; accordingly, their skin manifestations were considered as other dermal diseases except for IIM. However, skin and muscle biopsies revealed the atypical skin conditions of patients with HMGCR-IMNM to have the same pathological background, formed by Bcl-2-positive lymphocyte infiltrations.

CONCLUSIONS

HMGCR-IMNM patients frequently have atypical skin conditions of the neck and back. Skin biopsy specimens from these lesions showed the same Bcl-2-positive lymphocytic infiltrations as muscle biopsy specimens regardless of the different gross dermal findings. Thus, such atypical skin conditions may be suggestive for HMGCR-IMNM.

Compound muscle action potential of whole-forearm flexors: A clinical biomarker for inclusion body myositis

Objective

This study aimed to investigate the potential of whole-forearm flexor muscle (WFFM) compound muscle action potential (CMAP) as a quantitative biomarker for inclusion body myositis (IBM) pathology.

Methods

We prospectively enrolled 14 consecutive patients (10 men and 4 women) diagnosed with IBM based on muscle biopsies. We evaluated the baseline-to-peak amplitude of the WFFM CMAP and other quantitative parameters, including grip and pinch strength, Inclusion Body Myositis Functional Rating Scale (IBMFRS) score, and other routine muscle CMAP amplitudes.

Results

The WFFM CMAP was strongly correlated with disease duration and the IBMFRS score. The WFFM CMAP on the more affected side was lower than that on the less affected side. Furthermore, grip power was strongly correlated with the WFFM CMAP, whereas lateral pinch strength was strongly correlated with the WFFM and first dorsal interosseous CMAPs. The 3-point pinch strength was also correlated with the WFFM CMAP.

Conclusions

This study demonstrates that the WFFM CMAP may serve as a biomarker of severity in IBM.

Significance

Identification of this biomarker can support drug development, diagnosis, prognosis, and treatment options for patients with IBM.

Myositis-associated antibodies predict the severity of lung involvement in adult patients with inflammatory myositis - a cohort study of 70 adult patients with myositis in a single center

Introduction

Idiopathic inflammatory myopathies (IIMs) encompass a diverse group of diseases characterized by considerable variability in clinical manifestations, antibody profiles, and responsiveness to immunosuppressive therapies. This study aimed to investigate the association between organ involvement and distinct myositis autoantibodies in individuals with IIM in a single-center cohort.

Methods

Patients with ICD diagnoses M33.1, M33.2, M33.9, or M609 who (1) had been tested with Euroline blot assay for myositis autoantibodies and (2) met the classification criteria of definite/probable polymyositis (PM) or dermatomyositis (DM), anti-synthetase syndrome (ASS), or inclusion body myositis (IBM) were included. Medical journals were retrospectively examined with respect to clinical disease features.

Results

Seventy patients (median age 58 years; 66% females) were included and represented the following diagnosis: PM (n = 23), DM (n = 21), ASS (n = 23), and IBM (n = 3). Most of the patients (87%) presented a muscle biopsy indicative of myositis. The presence of autoantibodies was as follows: myositis-specific antibodies, MSA (n = 53), myositis-associated antibodies, MAA (n = 33), both MSA + MAA (n = 24), MSA only (n = 29), MAA only (n = 9), no MSA, or MAA (n = 8). Anti-Jo-1 was the most common MSA (19%), whereas the most common MAA was anti-Ro/SSA52 (31%). We observed a significant association between antibody patterns and lung disease. In our cohort, 47% of the patients in the whole study group, 86% of patients with anti-SSA52, and 100% with anti-Jo-1 had pulmonary involvement. Patients with both MSA and MAA had a higher incidence of lung disease and decreased CO-diffusion capacity. This was especially prominent in anti-Ro/SSA52-positive patients. Interestingly, none of the patients suffered from lung disease if only antibodies against Mi-2α, Mi-2β, NXP2, HMGCR, and TIF1γ were present or no MSA/MAA were detected.

Discussion

The simultaneous presence of both MAA and MSA indicates an increased risk of lung involvement in patients with inflammatory myopathies. The presence of any MAA, and especially anti-Ro/SSA52, is associated with more severe pulmonary disease. Our data suggest that MAA antibodies might be relevant markers for early detection and treatment of lung involvement in IIM.

Associations between anti-mitochondrial antibodies and cardiac involvement in idiopathic inflammatory myopathy patients : A systematic review and meta-analysis

OBJECTIVE

The objectives of this study are to analyze the association between anti-mitochondrial antibody (AMA) and cardiac involvement in idiopathic inflammatory myopathy (IIM) and to evaluate the diagnostic value of AMA for cardiac involvement in IIM patients.

METHODS

We conducted a comprehensive search in PubMed, Web of Science, EMBASE, and the Cochrane Library to identify English-language studies published before November 19, 2021. Stata 12.0 software (Stata Corp., College Station, TX, USA) was used for the statistical analyses. We used the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and summary receiver operating characteristic (SROC) curve to evaluate the diagnostic value of AMA for cardiac involvement in IIM patients. Statistical heterogeneity of studies was assessed using the I2 statistic with 95% confidence intervals (95% CIs).

RESULTS

Seven studies were included in the final analyses, with a total of 2308 IIM patients (including 171 AMA-positive and 2137 AMA-negative patients). The pooled sensitivity of AMA for cardiac involvement in IIM patients was 0.29 (95% CI: 0.19-0.43) and specificity was 0.92 (95% CI: 0.88-0.96). The pooled PLR was 3.9 (95% CI: 2.82-5.38), NLR was 0.76 (95% CI: 0.66-0.88), and the diagnostic odds ratio (DOR) was 5 (95% CI: 3-7). The area under the SROC curve was 0.76 (95% CI: 0.72-0.79).

CONCLUSION

The overall diagnostic value of AMA may not be very high for cardiac involvement in IIM patients.

Gender differences in patients with anti-MDA5-positive dermatomyositis: a cohort study of 251 cases

OBJECTIVE

To investigate the impact of sex differences on the clinical characteristics and prognosis of patients with anti-melanoma differentiation-associated gene 5-positive dermatomyositis (MDA5+ DM).

METHODS

We retrospectively analyzed a cohort of 251 patients with MDA5+ DM, including 71 in the male group and 180 in the female group. A multivariate logistic regression model was built to analyze independent risk factors for RPILD in each group. An ROC curve was drawn to evaluate the predictive value of independent risk factors. Kaplan‒Meier analysis was used to compare the cumulative survival rates, while the log-rank test was used to test for significant differences between the two groups.

RESULTS

Patients in the male group had a significantly higher prevalence of heliotrope rash, V sign, severe interstitial lung disease (ILD), and rapidly progressive interstitial lung disease (RPILD) than those in the female group. Anti-Ro52 positivity, high CRP level and short disease were identified as independent risk factors for RPILD in both male and female groups by multivariate logistic regression analysis. The mortality rates of males and females were 33.8% and 22.0%, respectively, and the survival time of patients in the male group was shorter than that in the female group.

CONCLUSION

Male patients with MDA5+ DM exhibit an increased risk of RPILD, elevated mortality rates and reduced overall survival time compared to their female counterparts, and anti-Ro52 positivity may be an unfavorable prognostic factor for these patients. Key Points • The prevalence of solar rash, V sign, severe interstitial lung disease (ILD) and rapidly progressive interstitial lung disease (RPILD) in anti-MDA5-positive female patients was significantly lower than that in male patients. • Positive Anti-Ro52, high CRP level, and short course of disease were independent risk factors for RPILD in both men and women. • Female patients exhibited a lower mortality rate than male patients (22.0% vs 33.8%) and demonstrated longer survival time.

Contribution of Complement, Microangiopathy and Inflammation in Idiopathic Inflammatory Myopathies

PURPOSE OF REVIEW

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group characterized by muscle weakness and skin symptoms and are categorized into six subtypes: dermatomyositis (DM), polymyositis (PM), anti-synthetase syndrome (ASS), immune-mediated myopathy (IMNM), inclusion body myopathy (IBM), and overlap myositis. Myositis-specific autoantibodies were detected for the diagnosis and classification of IIM. This review highlights the pathogenic contributions of the complement system, microangiopathy, and inflammation in IIM.

RECENT FINDINGS

Deposition of complement around capillaries and/or the sarcolemma was observed in muscle biopsy specimens from patients with DM, ASS, and IMNM, suggesting the pathomechanism of complement-dependent muscle and endothelial cell injury. A recent study using human muscle microvascular endothelial cells showed that Jo-1 antibodies from ASS induce complement-dependent cellular cytotoxicity in vitro. Based on both clinical and pathological observations, antibody- and complement-mediated microangiopathy may contribute to the development of DM and anti-Jo-1 ASS. Juvenile DM is characterized by the loss of capillaries, perivascular inflammation, and small-vessel angiopathies, which may be related to microinfarction and perifascicular atrophy. Several serum biomarkers that reflect the IFN1 signature and microangiopathy are elevated in patients with DM. The pathological observation of myxovirus resistance protein A (MxA), which suggests a type 1 interferon (IFN1) signature in DM, supports the diagnosis and further understanding of the pathomechanism of IIM. A recent report showed that an increase in triggering receptor expressed on myeloid cells (TREM-1) around perimysial blood vessels and muscles in patients with IIM plays a role in triggering inflammation and promoting the migration of inflammatory cells by secreting proinflammatory cytokines, such as tumor necrosis factor α.

SUMMARY

The deposition of complement in muscles and capillaries is a characteristic feature of DM, ASS, and IMNM. Microangiopathy plays a pathogenic role in DM, possibly resulting in perifascicular atrophy. Further understanding of the detailed pathomechanism regarding complement, microangiopathy, and inflammation may lead to novel therapeutic approaches for IIM.

From data to diagnosis: how machine learning is revolutionizing biomarker discovery in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of muscle disorders including adult and juvenile dermatomyositis, polymyositis, immune-mediated necrotising myopathy and sporadic inclusion body myositis, all of which present with variable symptoms and disease progression. The identification of effective biomarkers for IIMs has been challenging due to the heterogeneity between IIMs and within IIM subgroups, but recent advances in machine learning (ML) techniques have shown promises in identifying novel biomarkers. This paper reviews recent studies on potential biomarkers for IIM and evaluates their clinical utility. We also explore how data analytic tools and ML algorithms have been used to identify biomarkers, highlighting their potential to advance our understanding and diagnosis of IIM and improve patient outcomes. Overall, ML techniques have great potential to revolutionize biomarker discovery in IIMs and lead to more effective diagnosis and treatment.

Epidemiology of the idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic autoimmune diseases that affect the skeletal muscles and can also involve the skin, joints, lungs and heart. The epidemiology of IIM is obscured by changing classification criteria and the inherent shortcomings of case identification using healthcare record diagnostic coding. The incidence of IIM is estimated to range from 0.2 to 2 per 100,000 person-years, with prevalence from 2 to 25 per 100,000 people. Although the effects of age and gender on incidence are known, there is only sparse understanding of ethnic differences, particularly in indigenous populations. The incidence of IIM has reportedly increased in the twenty-first century, but whether this is a genuine increase is not yet known. Understanding of the genetic risk factors for different IIM subtypes has advanced considerably. Infections, medications, malignancy and geography are also commonly identified risk factors. Potentially, the COVID-19 pandemic has altered IIM incidence, although evidence of this occurrence is limited to case reports and small case series. Consideration of the current understanding of the epidemiology of IIM can highlight important areas of interest for future research into these rare diseases.

Inclusion body myositis with early onset: a population-based study

INTRODUCTION

Inclusion body myositis (IBM), an inflammatory myopathy with progressive weakness without efficient treatment, typically presents after 45 years of age and younger patients are sparsely studied.

METHODS

In a population-based study during a 33-year period, 142 patients with IBM were identified in western Sweden. Six patients fell outside the European Neuromuscular Centre 2011 criteria for IBM due to young age at symptom onset, verified by a muscle biopsy < 50 years of age. These were defined as early-onset IBM and included in this study. Medical records, muscle strength, comorbidities, muscle biopsies, and nuclear- and mitochondrial DNA were examined and compared with patients with IBM and age matched controls from the same population.

RESULTS

The median age at symptom onset was 36 (range 34-45) years and at diagnosis 43 (range 38-58) years. Four patients were deceased at a median age of 59 (range 50-75) years. The median survival from diagnosis was 14 (range 10-18) years. The prevalence December 31 2017 was 1.2 per million inhabitants and the mean incidence 0.12 patients per million inhabitants and year. The mean decline in quadriceps strength ± 1 standard deviation was 1.21 ± 0.2 Newton or 0.91 ± 0.2% per month and correlated to time from diagnosis (p < 0.001). Five patients had swallowing difficulties. All patients displayed mitochondrial changes in muscle including cytochrome c oxidase deficiency and the mitochondrial DNA mutation load was high.

CONCLUSIONS

Early-onset IBM is a severe disease, causing progressive muscle weakness, high muscle mitochondrial DNA mutation load and a reduced cumulative survival in young and middle-aged individuals.

Exploring challenges in the management and treatment of inclusion body myositis

PURPOSE OF REVIEW

This review provides an overview of the management and treatment landscape of inclusion body myositis (IBM), while highlighting the current challenges and future directions.

RECENT FINDINGS

IBM is a slowly progressive myopathy that predominantly affects patients over the age of 40, leading to increased morbidity and mortality. Unfortunately, a definitive cure for IBM remains elusive. Various clinical trials targeting inflammatory and some of the noninflammatory pathways have failed. The search for effective disease-modifying treatments faces numerous hurdles including variability in presentation, diagnostic challenges, poor understanding of pathogenesis, scarcity of disease models, a lack of validated outcome measures, and challenges related to clinical trial design. Close monitoring of swallowing and respiratory function, adapting an exercise routine, and addressing mobility issues are the mainstay of management at this time.

SUMMARY

Addressing the obstacles encountered by patients with IBM and the medical community presents a multitude of challenges. Effectively surmounting these hurdles requires embracing cutting-edge research strategies aimed at enhancing the management and treatment of IBM, while elevating the quality of life for those affected.

Retrospective Study Shows That Serum Levels of Chemokine CXCL10 and Cytokine GDF15 Support a Diagnosis of Sporadic Inclusion Body Myositis and Immune-Mediated Necrotizing Myopathy

The implementation of novel blood-based biomarkers is desired to reduce the diagnostic delay and burden for myositis patients. In this retrospective study, the potential of C-X-C motif chemokine ligand 10 (CXCL10) and growth differentiation factor 15 (GDF15) was explored in an established patient cohort diagnosed with immune-mediated necrotizing myopathy (IMNM; n = 21), sporadic inclusion body myositis (IBM; n = 18), overlap myositis (OM; n = 3), dermatomyositis (DM; n = 2), and anti-synthetase syndrome (ASS; n = 1), comparing these results with healthy controls (n = 10) and patients with a hereditary neuromuscular disorder (n = 14). CXCL10 and GDF15 were quantified in sera with enzyme-linked immunosorbent assays and immunolocalized in skeletal muscle tissue. In myositis patients, serum CXCL10 levels were significantly increased 9.6-fold compared to healthy controls and 4.2-fold compared to disease controls. Mean levels of CXCL10 were 929 ± 658 pg/mL of serum in IBM and 425 ± 324 pg/mL of serum in IMNM. With the threshold set to 180 pg/mL of CXCL10, myositis patients could be differentiated from healthy and disease controls with a sensitivity of 0.80 and a specificity of 0.71. Incorporating a threshold of 300 pg/mL for GDF15 reduced false negatives to two IMNM patients only. Subsets of muscle-infiltrating immune cells expressed CXCL10, and serum levels correlated with muscle inflammation grade. We propose adding circulating CXCL10 and GDF15 to the blood-based diagnostic toolkit for myositis as a valuable patient-friendly approach.

The pattern of MHC class I expression in muscle biopsies from patients with myositis and other neuromuscular disorders

OBJECTIVE

Diagnostic muscle biopsies are routinely immunostained for major histocompatibility complex class I (MHC-I) protein. In this study we analysed the prevalence and patterns of MHC-I immunostaining in biopsies from patients with different types of myopathies and neurogenic disorders.

METHODS

All 357 diagnostic muscle biopsies processed at the Johns Hopkins Neuromuscular Pathology Laboratory from August 2013 to January 2017 were immunostained for MHC-I. The prevalence and patterns of MHC-I immunostaining were compared between patients with histologically normal muscle biopsies (n = 31), idiopathic inflammatory myopathies (IIMs; n = 170), non-inflammatory myopathies (n = 60) and neurogenic disorders (n = 96).

RESULTS

MHC-I immunostaining was abnormal in most patients with DM (98%), sporadic IBM (sIBM; 100%), immune-mediated necrotizing myopathy (IMNM; 100%) and polymyositis (77%). In contrast, MHC-I immunostaining was less frequently present in non-inflammatory myopathies (32%) or neurogenic disorders (30%). Overall, abnormal MHC-I immunostaining had a sensitivity of 0.95 and a specificity of 0.82 for diagnosing IIMs. A focal MHC-I staining pattern was associated with IMNM, whereas a global pattern was more prevalent in sIBM and a perifascicular pattern was significantly more common in dermatomyositis. Among 18 DM biopsies without perifascicular atrophy, 50% had a perifascicular MHC-I staining pattern. Sarcoplasmic upregulation staining was more common than sarcolemmal staining across all groups.

CONCLUSION

MHC-I immunostaining was useful to distinguish IIMs from non-inflammatory myopathies or neurogenic disorders. Of note, a perifascicular MHC-I staining pattern was present only in those with DM, including half of those without perifascicular atrophy; many of these biopsies may not otherwise have been diagnostic for DM.

Joint and muscle inflammatory disease: A scoping review of the published evidence

OBJECTIVES

Polyarthritis is commonly reported in idiopathic inflammatory myositis patients, but few studies have focused on the overlap of myositis with rheumatoid arthritis which is a difficult diagnosis in the absence of well-defined diagnostic criteria. The primary objective of this scoping review was to map the field of research to explore the potential diagnoses in patients presenting with both myositis and polyarthritis.

METHODS

Two electronic databases (MEDLINE/PubMed® and Web of Science®) were systematically searched using the terms (myositis OR 'inflammatory idiopathic myopathies') AND (polyarthritis OR 'rheumatoid arthritis') without any publication date limit.

RESULTS

Among individual records, 280 reports met inclusion criteria after full-text review. There was heterogeneity in the definition of overlap myositis as well as the characteristics of rheumatoid arthritis. In many studies, key data were lacking; rheumatoid factor status was reported in 56.8% (n=151), anti-citrullinated proteins antibodies status in 18.8% (n=50), and presence or absence of bone erosions in 45.1% (n=120) of the studies. Thirteen different diagnoses were found to associate myositis with polyarthritis: antisynthetase syndrome (29.6%, n=83), overlap myositis with rheumatoid arthritis (16.1%, n=45), drug-induced myositis (20.0%, n=56), rheumatoid myositis (7.5%, n=21), inclusion body myositis (1.8%, n=5), overlap with connective tissue disease (20.0%, n=56), and others (5.0%, n=14).

CONCLUSION

The spectrum of joint and muscle inflammatory diseases encompasses many diagnoses including primitive and secondary myositis associated with RA or arthritis mimicking RA. This review highlights the need for a consensual definition of OM with RA to better individualise this entity from the numerous differential diagnoses.

Myositis-related autoantibody profile and clinical characteristics stratified by anti-cytosolic 5'-nucleotidase 1A status in connective tissue diseases

INTRODUCTION/AIMS

Cytosolic 5'-nucleotidase 1A (cN-1A) autoantibodies have been recognized as myositis-related autoantibodies. However, their correlations with clinical characteristics and other myositis-specific and myositis-associated autoantibodies (MSAs/MAAs) are still unclear. We aimed to establish the prevalence and clinical and laboratory associations of cN-1A autoantibodies in a cohort of patients with connective tissue diseases.

METHODS

A total of 567 participants (182 idiopathic inflammatory myopathies [IIM], 164 systemic lupus erythematosus [SLE], 121 systemic sclerosis [SSc], and 100 blood donors [BD]) were tested for the presence of cN-1A autoantibodies and other myositis-specific and myositis-associated autoantibodies (MSAs/MAAs). Clinical and laboratory characteristics were compared between anti-cN-1A positive and negative patients with sporadic inclusion body myositis (sIBM) and between anti-cN-1A positive and negative patients with non-IBM IIM.

RESULTS

In the sIBM cohort, 30 patients (46.9%) were anti-cN-1A positive vs. 18 (15.2%) in the non-IBM IIM cohort, 17 (10%) were anti-cN-1A positive in the SLE cohort and none in the SSc or the BD cohorts. Anti-cN-1A positivity had an overall sensitivity of 46.9% and a specificity of 93.2% for sIBM. Dysphagia was more frequent in the anti-cN-1A positive vs. negative sIBM patients (p = .04). In the non-IBM IIM group, being anti-cN-1A antibody positive was associated with the diagnosis polymyositis (p = .04) and overlap-myositis (p = .04) and less disease damage evaluated by physician global damage score (p < .001).

DISCUSSION

cN-1A autoantibodies were predominantly found in IIM patients and was associated with dysphagia in sIBM patients. Notably, anti-cN-1A appears to identify a distinct phenotype of anti-cN-1A positive non-IBM IIM patients with a milder disease course.

Clinical Subgroups and Factors Associated With Progression in Patients With Inclusion Body Myositis

BACKGROUND AND OBJECTIVES

Sporadic inclusion body myositis (IBM) is the most common acquired myopathy in individuals older than 50 years. The disorder is slowly progressive, and although many therapies have been investigated, response has generally been poor. Clinical heterogeneity may influence treatment responsiveness; however, data regarding heterogeneity in IBM are limited and often conflicting. We aim to identify clinically distinct subgroups within a large IBM cohort and prognostic factors for disease progression.

METHODS

Clinical, histologic, radiologic, and electrophysiologic data were analyzed for all patients with IBM and other forms of myositis enrolled in a longitudinal cohort from The Johns Hopkins Myositis Center from 2003 to 2018. Patients with IBM were included if they met at least one of the following criteria: Griggs possible, European Neuromuscular Centre 2011 probable, or Lloyd-Greenberg data-derived criteria for IBM. Univariate, multivariate, and graphical analyses were used to identify prognostic factors in patients with IBM. Thus, linear and logistic regressions were used to adjust for potential confounding variables. The evolution of creatine kinase and muscle strength was studied using multilevel linear regression models. Nonmodifiable risk factors (sex, race, disease duration, and age at the onset of first symptoms) were used as adjusting covariates for the regression analyses.

RESULTS

Among the 335 patients meeting the inclusion criteria for IBM, 64% were male with an average age of disease onset of 58.7 years and delay to diagnosis of 5.2 years. Initial misdiagnosis (52%) and immunosuppressant treatment (42%) were common. Less than half (43%) of muscle biopsies demonstrated all 3 pathologic hallmarks: endomysial inflammation, mononuclear cell invasion, and rimmed vacuoles. Black patients had significantly weaker arm abductors, hip flexors, and knee flexors compared with non-Black patients. Female patients had stronger finger flexors and knee extensors compared with their male counterparts. Younger age (<50 years) at onset was not associated with increased weakness.

DISCUSSION

Our study demonstrates that female and Black patients have distinct clinical phenotypes and trajectories within the overarching IBM clinical phenotype. These subgroups may have different responses to therapies, which may influence the design of future clinical trials in IBM.

Myositis with prominent B cell aggregates may meet classification criteria for sporadic inclusion body myositis

The objective of this study was to report the clinical, serological and pathological features of patients with autoimmune myositis other than dermatomyositis, who displayed both muscle weakness on physical examination and prominent B cell aggregates on muscle pathology, defined as ≥ 30 CD20+ cells/aggregate. Specifically, the presence of a brachio-cervical inflammatory myopathies or a sporadic inclusion body myositis (sIBM) phenotype was recorded. Over a three-year period, eight patients were identified from two university neuropathology referral centers. Seven of 8 (88%) patients had an associated connective tissue disease (CTD): rheumatoid arthritis (n=3), systemic sclerosis (n=2), Sjögren's syndrome (n=1) and systemic lupus erythematosus (n=1), while one patient died on initial presentation without a complete serological and cancer investigation. A brachio-cervical phenotype, i.e. neck weakness, proximal weakness more than distal and shoulder abduction weakness greater than hip flexors, was seen in two patients (25%), while one patient had both proximal and diaphragmatic weakness. In contrast, an IBM-like clinical phenotype was seen in the last five patients (63%), who either had finger flexor weakness and/or quadriceps weakness ≤ 4 on the manual muscle testing MRC-5 scale. Although these 5 patients met at least one set of classification criteria for sIBM, an integrated clinico-sero-pathological approach argued against a diagnosis of sIBM. In summary, in a weak patient with myositis plus an associated CTD and lymphoid aggregates at muscle pathology, B cell predominant aggregates may represent a morphological biomarker against a diagnosis of sIBM.

Low copy numbers of complement C4 and C4A deficiency are risk factors for myositis, its subgroups and autoantibodies

BACKGROUND

Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterised by myositis-related autoantibodies plus infiltration of leucocytes into muscles and/or the skin, leading to the destruction of blood vessels and muscle fibres, chronic weakness and fatigue. While complement-mediated destruction of capillary endothelia is implicated in paediatric and adult dermatomyositis, the complex diversity of complement C4 in IIM pathology was unknown.

METHODS

We elucidated the gene copy number (GCN) variations of total C4, C4A and C4B, long and short genes in 1644 Caucasian patients with IIM, plus 3526 matched healthy controls using real-time PCR or Southern blot analyses. Plasma complement levels were determined by single radial immunodiffusion.

RESULTS

The large study populations helped establish the distribution patterns of various C4 GCN groups. Low GCNs of C4T (C4T=2+3) and C4A deficiency (C4A=0+1) were strongly correlated with increased risk of IIM with OR equalled to 2.58 (2.28-2.91), p=5.0×10^-53 for C4T, and 2.82 (2.48-3.21), p=7.0×10^-57 for C4A deficiency. Contingency and regression analyses showed that among patients with C4A deficiency, the presence of HLA-DR3 became insignificant as a risk factor in IIM except for inclusion body myositis (IBM), by which 98.2% had HLA-DR3 with an OR of 11.02 (1.44-84.4). Intragroup analyses of patients with IIM for C4 protein levels and IIM-related autoantibodies showed that those with anti-Jo-1 or with anti-PM/Scl had significantly lower C4 plasma concentrations than those without these autoantibodies.

CONCLUSIONS

C4A deficiency is relevant in dermatomyositis, HLA-DRB1*03 is important in IBM and both C4A deficiency and HLA-DRB1*03 contribute interactively to risk of polymyositis.

Refractory ventricular tachycardia and heart failure due to anti-mitochondrial antibody-positive inflammatory myopathy

BACKGROUND

Anti-mitochondrial antibody (AMA)-positive inflammatory myopathy, a rare type of idiopathic inflammatory myopathy which was frequently difficult to diagnose, can affect muscles and the structure and electrical conduction of the heart. Early identification and treatment of this myopathy can prevent serious cardiovascular adverse events and improve cardiac function.

CASE PRESENTATION

We report a patient who experienced repeated syncope, ventricular tachycardia (VT) and heart failure accompanied by weakness and muscle atrophy. He was initially diagnosed with dilated cardiomyopathy and received implantable cardioverter-defibrillator therapy. He was subsequently misdiagnosed as muscular dystrophy due to progressive muscular atrophy. However, the patient developed repeated and refractory VT storms that were not alleviated by conventional therapy. Finally, he was diagnosed with AMA-positive inflammatory myopathy with cardiac injuries. The patient was markedly recovered by being treated with immunosuppressive and immunomodulatory therapy.

CONCLUSION

AMA could be screened when discovering myopathies accompanied by unexplained cardiac symptoms. Our findings provide insights into the diagnosis and therapy of this rare and severe disease.

Pediatric immune-mediated necrotizing myopathy

Immune-mediated necrotizing myopathy (IMNM) is a type of inflammatory myopathy. Most patients with IMNM produce anti-3-hydroxy-3-methylglutaryl coenzyme A reductase or anti-signal-recognition particle autoantibodies. IMNM is much rarer in children than in adults. We conducted this mini review focusing on pediatric IMNM to present current evidence regarding its epidemiology, clinical characteristics, diagnosis, and treatment. Our findings indicate that pediatric IMNM often causes severe muscle weakness and is refractory to corticosteroids alone. Furthermore, delayed diagnosis is common because of the clinicopathological similarity between IMNM and inherited myopathy. Raising awareness regarding pediatric IMNM may facilitate early diagnosis and effective treatment.

Diagnostic delay of myositis: an integrated systematic review

BACKGROUND

Idiopathic inflammatory myopathies (IIM) are a heterogenous group of rare muscular autoimmune diseases characterised by skeletal muscle inflammation with possible diagnostic delay. Our aim was to review the existing evidence to identify overall diagnostic delay for IIM, factors associated with diagnostic delay, and people's experiences of diagnostic delay.

METHODS

Three databases and grey literature sources were searched. Diagnostic delay was defined as the period between the onset of symptoms and the year of first diagnosis of IIM. We pooled the mean delay using random effects inverse variance meta-analysis and performed subgroup analyses.

RESULTS

328 titles were identified from which 27 studies were included. Overall mean diagnostic delay was 27.91 months (95% CI 15.03-40.79, I2 = 99%). Subgroup analyses revealed a difference in diagnostic delay between non-inclusion body myositis (IBM) and IBM types. There was no difference in diagnostic delay between studies in which myositis specific autoantibodies (MSA) were tested or not tested. In countries with gatekeeper health systems, where primary care clinicians authorize access to specialty care, people experienced longer periods of diagnostic delay than people with IIM in countries with non-gatekeeper systems. While studies discussed factors that may influence diagnostic delay, significant associations were not identified. No qualitative studies examining people's experiences of diagnostic delay were identified.

CONCLUSION

Diagnostic delay of IIM has extensive impacts on the quality of life of people living with this disease. Understanding the experiences of people with IIM, from symptom onset to diagnosis, and factors that influence diagnostic delay is critical to inform clinical practice and training activities aimed at increasing awareness of this rare disease and expediting diagnosis.

TRIAL REGISTRATION

PROSPERO Registration number: CRD42022307236 URL of the PROSPERO registration: https://www.crd.york.ac.uk/PROSPEROFILES/307236_PROTOCOL_20220127.pdf.

Clinical features of anti-mitochondrial M2 antibody-positive myositis: case series of 17 patients

OBJECTIVE

In 2012, a large number of myositis cases with anti-mitochondrial M2 (AMA-M2) antibody, which had well been known as the serological hallmark for primary biliary cholangitis (PBC), were reported in Japan. Recently, some case series from Japan, France, America, China and India have shown that approximately 2.5% to 19.5% of patients with myositis have AMA-M2 antibody. The objective of this study was to clarify the prevalence, clinical features, treatment outcome, and severity determinants of AMA-M2 positive myositis.

METHODS

This study was a multicenter observational study. We enrolled patients who were diagnosed with myositis during a ten-year period between 2012 and 2021.

RESULTS

Of the total of 185 patients with inflammatory myopathy, 17 patients were positive for AMA-M2 antibody. The typical symptoms were weakness mainly involving paravertebral muscles, weight loss, respiratory failure, and cardiac complications. Thirteen of the 17 patients had cardiac complications. A strong correlation was found between respiratory failure and modified Rankin Scale (mRS) score. A strong correlation was also found between respiratory failure and body weight, indicating that weight loss can be an indicator of potential progression of respiratory failure. Six of the 17 patients were complicated by malignancy.

CONCLUSIONS

This study showed significant correlations between % vital capacity (VC), body mass index (BMI), and mRS score in patients with AMA-M2-positive myositis. Immunotherapy often improved CK level and respiratory dysfunction. We therefore propose that %VC and BMI should be monitored as disease indicators in treatment of AMA-M2-positive myositis.

Inclusion body myositis: Update on the diagnostic and therapeutic landscape

Inclusion body myositis (IBM) is a progressive muscle disease affecting patients over the age of 40, with distinctive clinical and histopathological features. The typical clinical phenotype is characterized by prominent involvement of deep finger flexors and quadriceps muscles. Less common presentations include isolated dysphagia, asymptomatic hyper-CKemia, and axial or limb weakness beyond the typical pattern. IBM is associated with marked morbidity as majority of patients eventually become wheelchair dependent with limited use of their hands and marked dysphagia. Furthermore, IBM mildly affects longevity with aspiration pneumonia and respiratory complications being the most common cause of death. On muscle biopsy, IBM is characterized by a peculiar combination of endomysial inflammation, rimmed vacuoles, and protein aggregation. These histopathological features are reflective of the complexity of underlying disease mechanisms. No pharmacological treatment is yet available for IBM. Monitoring for swallowing and respiratory complications, exercise, and addressing mobility issues are the mainstay of management. Further research is needed to better understand disease pathogenesis and identify novel therapeutic targets.

The health-related quality of life, mental health and mental illnesses of patients with inclusion body myositis (IBM): results of a mixed methods systematic review

Background

Inclusion body myositis (IBM) is a rare neuromuscular disease (NMD) and effective therapies are not available. Thus, it is relevant to determine the health-related quality of life (HRQoL) in IBM patients including aspects of mental health and illnesses.

Objectives

To identify and summarize the assessment of HRQoL, mental health and illnesses in IBM, the major factors that determine and influence them as well as the respective influence of IBM in general and compared to other NMD as a systematic review.

Methods

We performed a mixed methods systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search was conducted within the databases PubMed, PsycINFO, LIVIVO and the Cochrane Database. Data were narratively summarized and categorized in the physical, psychological and social HRQoL dimensions.

Results

The systematic screening totalled 896 articles. Six studies were finally identified, comprising of 586 IBM patients. The applied patient reported outcome measures (PROMs) varied. Quantitatively, the main physical impairments (e.g. weakness, functioning, role perception) were assessed using the general population or other NMD as comparators. Results on social and psychological HRQoL were frequently inconsistent. Qualitatively, psychological and social limitations accompanied IBM related physical deteriorations.

Conclusions

A research gap exists regarding rigour determinants of HRQoL and mental illness in IBM. In-depth qualitative studies could help to prepare the ground for the assessment of long-term HRQoL data combined with appropriately focussed psychological PROMs advancing the understanding of the HRQoL in IBM throughout the course of the disease from a patient perspective.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02382-x.

Amyotrophic lateral sclerosis mimics

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disorder characterized by progressive degeneration of cortical, bulbar, and spinal motor neurons. When a patient presents with a progressive upper and/or lower motor syndrome, clinicians must pay particular attention to any atypical features in the history and/or clinical examination suggesting an alternate diagnosis, as up to 10% percent of patients initially diagnosed with ALS have a mimic of ALS. ALS is a clinical diagnosis and requires the exclusion of other disorders that may have similar presentations but a more favorable prognosis or an effective therapy. Because there is currently no specific diagnostic biomarker that is sensitive or specific for ALS, understanding the spectrum of clinical presentations of ALS and its mimics is paramount. While true mimics of ALS are rare, the clinician must correctly identify these disorders to avoid the misdiagnosis of ALS and to initiate effective treatment where available.

Epidemiology, survival and clinical characteristics of inclusion body myositis

OBJECTIVE

We performed a population-based study on inclusion body myositis with the primary aims to define the prevalence, survival rate and incidence and to investigate the symptom profiles associated with disease duration and sex over a 33-year period.

METHODS

Patients diagnosed between 1985 and 2017 in Region Västra Götaland, Sweden were identified according to the European Neuromuscular Centre diagnostic criteria from 2011.

RESULTS

We identified 128 patients, 89 men and 39 women with the strict clinico-pathologically definition of inclusion body myositis. The prevalence was 32 per million inhabitants, 19 per million women and 45 per million men December 31st 2017. Mean incidence was 2.5 per million inhabitants and year. Mean age at symptom onset was 64.4 years with quadriceps weakness being the most common presenting symptom followed by finger flexor weakness. Dysphagia was a common presenting symptom being more frequent in women (23%) than men (10%) and was during the disease course reported in 74% of men and 84% of women. Seventy-three patients were deceased, with mean survival of 14 years from symptom onset. Survival rate from both diagnosis date and symptom onset was decreased compared to the matched population. Twenty-one percent of the patients had an additional autoimmune disease. A cross-sectional analysis of autoantibodies in 50 patients and 28 matched controls showed autoantibodies to cytosolic 5'-nucleotidase 1A in 40% of the patients and 3.6% of controls.

INTERPRETATION

Inclusion body myositis is an autoimmune disease with decreased survival rate and with marked sex differences in both prevalence and clinical manifestations. This article is protected by copyright. All rights reserved.

Inflammatory myopathies: an update for neurologists

Idiopathic inflammatory myopathies (IIM) are a heterogenous group of treatable myopathies. Patients present mainly to the rheumatologist and neurologists, complaining of acute or subacute onset of proximal weakness. Extramuscular manifestations may occur, including involvement of the lungs, skin, and joints. Classically, the diagnosis used to be made based on the creatine kinase level increase, abnormalities in electroneuromyography and presence of inflammatory infiltrates in the muscle biopsy. Recently, the importance of autoantibodies has increased, and now they may be identified in more than half of IIM patients. The continuous clinicoseropathological improvement in IIM knowledge has changed the way we see these patients and how we classify them. In the past, only polymyositis, dermatomyositis and inclusion body myopathy were described. Currently, immune-mediated necrotizing myopathy, overlap myositis and antisynthetase syndrome have been considered the most common forms of IIM in clinical practice, increasing the spectrum of classification. Patients previously considered to have polymyositis, in fact have these other forms of seropositive IIM. In this article, we reviewed the new concepts of classification, a practical way to make the diagnosis and how to plan the treatment of patients suffering from IIM.

Cell environment shapes TDP-43 function with implications in neuronal and muscle disease

TDP-43 (TAR DNA-binding protein 43) aggregation and redistribution are recognised as a hallmark of amyotrophic lateral sclerosis and frontotemporal dementia. As TDP-43 inclusions have recently been described in the muscle of inclusion body myositis patients, this highlights the need to understand the role of TDP-43 beyond the central nervous system. Using RNA-seq, we directly compare TDP-43-mediated RNA processing in muscle (C2C12) and neuronal (NSC34) mouse cells. TDP-43 displays a cell-type-characteristic behaviour targeting unique transcripts in each cell-type, which is due to characteristic expression of RNA-binding proteins, that influence TDP-43's performance and define cell-type specific splicing. Among splicing events commonly dysregulated in both cell lines, we identify some that are TDP-43-dependent also in human cells. Inclusion levels of these alternative exons are altered in tissues of patients suffering from FTLD and IBM. We therefore propose that TDP-43 dysfunction contributes to disease development either in a common or a tissue-specific manner.

Botulinum toxin treatment improves dysphagia in patients with oculopharyngeal muscular dystrophy and sporadic inclusion body myositis

OBJECTIVE

Dysphagia can be troublesome in sporadic inclusion body myositis (sIBM) and oculopharyngeal muscular dystrophy (OPMD), but no established treatment exists. Cricopharyngeal muscle botulinum toxin injection has at case level been reported to be effective. We evaluated safety and efficacy of botulinum toxin injections in the cricopharyngeal muscle in patients with dysphagia due to sIBM or OPMD.

METHODS

Participants were included from our outpatient clinic. Cricopharyngeal constriction was confirmed by laryngoscopy. After EMG confirmation of needle placement in the cricopharyngeal muscle, botulinum toxin A was injected in awake patients. An individualized dose of 5-10 units of botulinum toxin A was applied initially and titrated up a maximum of 3 times. Outcome measures were change in dysphagia questionnaire, timed cold-water swallow test and subjective dysphagia status (worse, unchanged, improved). Due to the need for individualized dosing and a limited number of available patients, an uncontrolled, un-blinded design was used.

RESULTS

Thirteen patients, 3 with OPMD, received at least 1 injection. In the dysphagia questionnaire, all but 2 subjects, none with subjective worsening, improved (p < 0.001). Subjectively, seven felt an improvement, 4 no change and 2 a worsening. No overall change was seen the timed cold-water swallow test. No serious adverse events were observed.

CONCLUSION

Botulinum toxin injection of the cricopharyngeal muscle in patients with OPMD and sIBM had a beneficial effect on dysphagia in most of the treated patients. Two of 13 patients experienced a temporary worsening not reflected in dysphagia score. Limitations are the un-blinded and un-randomized design and subjective assessments methods.

PROSPECTIVE TRIAL REGISTRATION

EudraCT-number: 2014-002210-23.

Longitudinal assessment of reactivity and affinity profile of anti-Jo1 autoantibodies to distinct HisRS domains and a splice variant in a cohort of patients with myositis and anti-synthetase syndrome

Background

To address the reactivity and affinity against histidyl-transfer RNA synthetase (HisRS) autoantigen of anti-Jo1 autoantibodies from serum and bronchoalveolar lavage fluid (BALF) in patients with idiopathic inflammatory myopathies/anti-synthetase syndrome (IIM/ASSD). To investigate the associations between the reactivity profile and clinical data over time.

Methods

Samples and clinical data were obtained from (i) 25 anti-Jo1⁺ patients (19 sera with 16 longitudinal samples and 6 BALF/matching sera at diagnosis), (ii) 29 anti-Jo1⁻ patients (25 sera and 4 BALF/matching sera at diagnosis), and (iii) 27 age/gender-matched healthy controls (24 sera and 3 BALF/matching sera). Reactivity towards HisRS full-length (HisRS-FL), three HisRS domains (WHEP, antigen binding domain (ABD), and catalytic domain (CD)), and the HisRS splice variant (SV) was tested. Anti-Jo1 IgG reactivity was evaluated by ELISA and western blot using IgG purified from serum by affinity chromatography. In paired serum-BALF, anti-Jo1 IgG and IgA reactivity was analyzed by ELISA. Autoantibody affinity was measured by surface plasmon resonance using IgG purified from sera. Correlations between autoantibody reactivity and clinical data were evaluated at diagnosis and longitudinally.

Results

Anti-Jo1 IgG from serum and BALF bound HisRS-FL, WHEP, and SV with high reactivity at the time of diagnosis and recognized both conformation-dependent and conformation-independent HisRS epitopes. Anti-HisRS-FL IgG displayed high affinity early in the disease. At the time of IIM/ASSD diagnosis, the highest autoantibody levels against HisRS-FL were found in patients ever developing interstitial lung disease (ILD) and arthritis, but with less skin involvement. Moreover, the reactivity of anti-WHEP IgG in BALF correlated with poor pulmonary function.

Levels of autoantibodies against HisRS-FL, HisRS domains, and HisRS splice variant generally decreased over time. With some exceptions, longitudinal anti-HisRS-FL antibody levels changed in line with ILD activity.

Conclusion

High levels and high-affinity anti-Jo1 autoantibodies towards HisRS-FL were found early in disease in sera and BALF. In combination with the correlation of anti-HisRS-FL antibody levels with ILD and ILD activity in longitudinal samples as well as of anti-WHEP IgG in BALF with poor pulmonary function, this supports the previously raised hypothesis that the lung might have a role in the immune reaction in anti-Jo1-positive patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02745-6.

Subclinical involvement of the trunk muscles in idiopathic inflammatory myopathies

Background

Whole-body magnetic resonance imaging (WB-MRI) is a useful tool for revealing the disease-specific distribution of affected muscles and clinically asymptomatic muscle involvements in idiopathic inflammatory myopathies (IIMs).

Purpose

To examine inflammatory changes in the systemic skeletal muscles, including the thoracoabdominal trunk, in IIMs using WB-MRI.

Material and Methods

We prospectively obtained WB-MRI axial images from 10 patients with IIMs, including antisynthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), sporadic inclusion body myositis, and myopathy associated with antimitochondrial antibody. We evaluated 108 systemic skeletal muscles in short-tau inversion recovery (STIR) images and rated changes in signal intensity using a semiquantitative scale. Correlations between STIR sum score, peak creatine kinase (CK) and muscle strength were examined. We also investigated the correlation between STIR sum score within the thoracoabdominal trunk and forced vital capacity.

Results

High STIR signal changes were frequently identified in asymptomatic and routinely unexamined muscles. Thoracoabdominal trunk muscles were frequently involved in ASS and IMNM. Peak CK was positively correlated with the STIR sum score (R² = 0.62, p < .01). There was no significant correlation between the STIR sum score within the thoracoabdominal trunk and forced vital capacity.

Conclusion

WB-MRI can detect subclinical muscle inflammation in the systemic muscles including the trunk muscles. STIR sum score is positively correlated with serum peak CK level; therefore, it could be a biomarker of overall muscle inflammation.

Anti-Cortactin Autoantibodies Are Associated With Key Clinical Features in Adult Myositis But Are Rarely Present in Juvenile Myositis

OBJECTIVE

To define the prevalence and clinical phenotype of anti-cortactin autoantibodies in adult and juvenile myositis.

METHODS

In this longitudinal cohort study, anti-cortactin autoantibody titers were assessed by enzyme-linked immunosorbent assay in 670 adult myositis patients and 343 juvenile myositis patients as well as in 202 adult healthy controls and 90 juvenile healthy controls. The prevalence of anti-cortactin autoantibodies was compared among groups. Clinical features of patients with and those without anti-cortactin autoantibodies were also compared.

RESULTS

Anti-cortactin autoantibodies were more common in adult dermatomyositis (DM) patients (15%; P = 0.005), particularly those with coexisting anti-Mi-2 autoantibodies (24%; P = 0.03) or anti-NXP-2 autoantibodies (23%; P = 0.04). In adult myositis, anti-cortactin was associated with DM skin involvement (62% of patients with anti-cortactin versus 38% of patients without anti-cortactin; P = 0.03), dysphagia (36% versus 17%; P = 0.02) and coexisting anti-Ro 52 autoantibodies (47% versus 26%; P = 0.001) or anti-NT5c1a autoantibodies (59% versus 33%; P = 0.001). Moreover, the titers of anti-cortactin antibodies were higher in patients with interstitial lung disease (0.15 versus 0.12 arbitrary units; P = 0.03). The prevalence of anti-cortactin autoantibodies was not different in juvenile myositis patients (2%) or in any juvenile myositis subgroup compared to juvenile healthy controls (4%). Nonetheless, juvenile myositis patients with these autoantibodies had a higher prevalence of "mechanic's hands" (25% versus 7%; P = 0.03), a higher number of hospitalizations (2.9 versus 1.3; P = 0.04), and lower peak creatine kinase values (368 versus 818 IU/liter; P = 0.02) than those without anti-cortactin.

CONCLUSION

The prevalence of anti-cortactin autoantibodies is increased in adult DM patients with coexisting anti-Mi-2 or anti-NXP-2 autoantibodies. In adults, anti-cortactin autoantibodies are associated with dysphagia and interstitial lung disease.

Contribution of Rare Genetic Variation to Disease Susceptibility in a Large Scandinavian Myositis Cohort

OBJECTIVE

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of complex autoimmune conditions characterized by inflammation in skeletal muscle and extramuscular compartments, and interferon (IFN) system activation. We undertook this study to examine the contribution of genetic variation to disease susceptibility and to identify novel avenues for research in IIMs.

METHODS

Targeted DNA sequencing was used to mine coding and potentially regulatory single nucleotide variants from ~1,900 immune-related genes in a Scandinavian case-control cohort of 454 IIM patients and 1,024 healthy controls. Gene-based aggregate testing, together with rare variant- and gene-level enrichment analyses, was implemented to explore genotype-phenotype relations.

RESULTS

Gene-based aggregate tests of all variants, including rare variants, identified IFI35 as a potential genetic risk locus for IIMs, suggesting a genetic signature of type I IFN pathway activation. Functional annotation of the IFI35 locus highlighted a regulatory network linked to the skeletal muscle-specific gene PTGES3L, as a potential candidate for IIM pathogenesis. Aggregate genetic associations with AGER and PSMB8 in the major histocompatibility complex locus were detected in the antisynthetase syndrome subgroup, which also showed a less marked genetic signature of the type I IFN pathway. Enrichment analyses indicated a burden of synonymous and noncoding rare variants in IIM patients, suggesting increased disease predisposition associated with these classes of rare variants.

CONCLUSION

Our study suggests the contribution of rare genetic variation to disease susceptibility in IIM and specific patient subgroups, and pinpoints genetic associations consistent with previous findings by gene expression profiling. These features highlight genetic profiles that are potentially relevant to disease pathogenesis.

Myositis-Specific Autoantibodies and QTc Changes by ECG in Idiopathic Inflammatory Myopathies

OBJECTIVES

The aim of this study was to investigate cardiac involvement detected by electrocardiography (ECG) in patients with idiopathic inflammatory myopathies (IIM) and to evaluate possible associations between autoantibody profile and ECG changes in these patients.

METHODS

In a Scandinavian cross-sectional study, patients were included from two Danish centres and one Swedish centre. Resting 12-lead ECG was investigated in 261 patients with IIM compared with 102 patients with systemic sclerosis (SSc) and 48 healthy controls (HCs). ECG changes were correlated to clinical manifestations and myositis-specific (MSAs) and myositis-associated (MAAs) autoantibodies.

RESULTS

Patients with IIM had longer mean QTc duration and more frequently presented with prolonged QTc (≥ 450 ms; p= 0.038) compared with HCs. Longer QTc duration was recorded in SSc compared with IIM (433 ± 23 ms vs 426 ± 24 ms, p= 0.011), yet, no significant difference in the fraction with prolonged QTc (SSc: 22%, IIM: 16%; p= 0.19). In multivariable regression analyses, anti-Mi2 (p= 0.01, p= 0.035) and anti-Pl-7 (p= 0.045, p= 0.014) were associated with QTc duration and prolonged QTc in IIM. Elevated CRP was associated with prolonged QTc (p= 0.041).

CONCLUSION

Presence of QTc abnormalities was as common in patients with IIM as in patients with SSc, including prolonged QTc seen in almost one fifth of the patients. Anti-Mi2, anti-Pl-7, and elevated CRP may serve as biomarkers for cardiac disease in IIM, but needs to be confirmed in a larger prospective study.

Idiopathic inflammatory myopathies: CT characteristics of interstitial lung disease and their association(s) with myositis-specific autoantibodies

OBJECTIVES

Interstitial lung disease (ILD), one of the most common extramuscular manifestations of idiopathic inflammatory myopathies (IIMs), carries a poor prognosis. Myositis-specific autoantibody (MSA)-positivity is a key finding for IIM diagnosis. We aimed to identify IIM-associated lung patterns, evaluate potential CT-ILD finding-MSA relationships, and assess intra- and interobserver reproducibility in a large IIM population.

METHODS

All consecutive IIM patients (2003-2019) were included. Two chest radiologists retrospectively assessed all chest CT scans. Multiple correspondence and hierarchical cluster analyses of CT findings identified and characterized ILD-patient subgroups. Classification and regression-tree analyses highlighted CT-scan variables predicting three patterns. Three independent radiologists read CT scans twice to assign patients according to CT-ILD-pattern clusters.

RESULTS

Among 257 IIM patients, 94 (36.6%) had ILDs; 87 (93%) of them were MSA-positive. ILD-IIM distribution was 54 (57%) ASyS, 21 (22%) DM, 15 (16%) IMNM, and 4 (4%) IBM. Cluster analysis identified three ILD-patient subgroups. Consolidation characterized cluster 1, with significantly (p < 0.05) more frequent anti-MDA5-autoantibody-positivity. Significantly more cluster-2 patients had a reticular pattern, without cysts and with few consolidations. All cluster-3 patients had cysts and anti-PL12 autoantibodies. Clusters 2 and 3 included significantly more ASyS patients. Intraobserver concordances to classify patients into those three clusters were good-to-excellent (Cohen κ 0.64-0.81), with good interobserver reliability (Fleiss's κ 0.56).

CONCLUSION

Despite the observed IIM heterogeneity, CT-scan criteria enabled ILD assignment to the three clusters, which were associated with MSAs. Radiologist identification of those clusters could facilitate diagnostic screening and therapeutics. Interstitial lung disease in patients with idiopathic inflammatory myopathy could be classified into three clusters according to CT-scan criteria, and these clusters were significantly associated with myositis-specific autoantibodies.

KEY POINTS

• Cluster analysis discerned three homogeneous groups of interstitial lung disease (ILD) for which cysts, consolidations, and reticular pattern were discriminatory, and associated with myositis-specific autoantibodies. • Like muscle- and extramuscular-specific phenotypes, myositis-specific autoantibodies are also associated with specific ILD patterns in patients with idiopathic inflammatory myopathies.

Clinical features and diagnostic tools in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are rare autoimmune disorders affecting primarily muscles, but other organs can be involved. This review describes the clinical features, diagnosis and treatment for IIMs, namely polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (sIBM), immune-mediated necrotizing myopathy (IMNM), and myositis associated with antisynthetase syndrome (ASS). The diagnostic approach has been updated recently based on the discovery of circulating autoantibodies, which has enhanced the management of patients. Currently, validated classification criteria for IIMs allow clinical studies with well-defined sets of patients but diagnostic criteria to guide the care of individual patients in routine clinical practice are still missing. This review analyzes the clinical manifestations and laboratory findings of IIMs, discusses the efficiency of modern and standard methods employed in their workup, and delineates optimal practice for clinical care. Α multidisciplinary diagnostic approach that combines clinical, neurologic and rheumatologic examination, evaluation of electrophysiologic and morphologic muscle characteristics, and assessment of autoantibody immunoassays has been determined to be the preferred approach for effective management of patients with suspected IIMs.

Anti-HMGCR myopathy: clinical and histopathological features, and prognosis

PURPOSE OF REVIEW

This review aims to describe clinical and pathological features, prognosis and treatment in patients with anti-HMGCR antibody positive immune-mediated necrotizing myopathy (HMGCR-IMNM) based on recent findings.

RECENT FINDINGS

Using advances in diagnostic modalities that can confirm the presence of anti-HMGCR antibody, the clinical and pathological manifestations of HMGCR-IMNM were found to be broader than previously reported. Although only a small percentage of HMGCR-IMNM patients present with atypical manifestations, some of these patients show slow disease progression and clinical symptoms, which are similar to those of limb-girdle muscular dystrophies. Other atypical HMGCR-IMNM patients have skin conditions similar to dermatomyositis-like skin rush or dermatological presentations of Jessner-Kanoff disease or cutaneous lymphoma, whose pathological changes including CD8-positive and bcl-2-positive lymphocytic accumulations, similar to Jessner-Kanoff lymphocytic infiltration of skin or low-grade cutaneous lymphoma, which are observed in muscle and skin.

SUMMARY

Anti-HMGCR autoantibodies define unique populations of IMNM patients. Recent studies have revealed that clinicopathological manifestations of HMGCR-IMNM, especially extramuscular symptoms and pathological manifestations, are more common than previously recognized.

Physical activity in idiopathic inflammatory myopathies: two intervention proposals based on literature review

Idiopathic inflammatory myopathies (IIM) are rare diseases affecting skeletal muscles and leading to progressive muscle weakness and disability. Thanks to the better understanding of their pathogenesis, the management of IIM has been noteworthily implemented in recent years. Current therapeutic strategies include pharmacological and non-pharmacological interventions, among which physical exercise represents a useful option, able to ameliorate disease activity without worsening muscle inflammation. The aim of this narrative review is therefore to provide an updated overview of the benefits of physical exercise in patients with IIM and to suggest plausible training programs to be applied in patients with dermatomyositis, polymyositis, necrotizing myopathy, and inclusion body myositis. In this regard, a combined strategy mixing aerobic and resistance exercises could positively affect the pro-inflammatory and metabolic pathways occurring in skeletal muscles, while promoting muscle fiber regeneration and repair.

Effects of blood-flow restricted resistance training on mechanical muscle function and thigh lean mass in sIBM patients

Sporadic inclusion body myositis (sIBM) is an idiopathic inflammatory muscle disease associated with skeletal muscle inflammation and a parallel progressive decline in muscle strength and physical function. Eventually, most sIBM patients require use of wheelchair after about 10 years of diagnosis and assistance to perform activities of daily living. This study presents data from a randomized controlled intervention trial (NCT02317094) that examined the effect of 12 weeks low-load blood-flow restricted (BFR) resistance training on maximal muscle strength, power, rate of force development (RFD), thigh lean mass (TLM), and voluntary muscle activation (VA) in sIBM patients. A time-by-group interaction in knee extensor strength was observed in the stronger leg (p ≤ 0.033) but not the weaker leg. Within-group changes were observed with BFR training (BFR) manifested by increased knee extensor strength in the strongest leg (+13.7%, p = 0.049), whereas non-exercising patients (CON) showed reduced knee extensor strength (-7.7%, p = 0.018). Maximal leg extensor power obtained for the stronger leg remained unchanged following BFR training (+9.5%, p = 0.37) while decreasing in CON (-11.1%, p = 0.05). No changes in TLM were observed. VA declined post-training (p = 0.037) in both BFR (-6.3% points) and CON (-7.5% points). The present data indicate that BFR resistance training can attenuate the rate of decline in mechanical muscle function typically experienced by sIBM patients. The preservation of muscle mass and mechanical muscle function with BFR resistance training may be considered of high clinical importance in sIBM patients to countermeasure the disease-related decline in physical function.

Cardiopulmonary exercise performance and factors associated with aerobic capacity in neuromuscular diseases

INTRODUCTION/AIMS

Aerobic deconditioning, due to lower levels of physical activity, could impact independence for people with neuromuscular conditions. We report the maximal cardiopulmonary response in a cohort of people with Charcot Marie Tooth disease type 1A (CMT 1A) and inclusion body myositis (IBM). We also explored potential predictors of aerobic capacity with measures of physical impairment and functional performance.

METHODS

Participants underwent maximal cardiopulmonary exercise testing (CPET) using a semi-recumbent cycle ergometer. Data were analyzed to determine the peak O₂ consumption (VO₂ peak), anaerobic threshold (AT), maximum heart rate (MHR), ventilatory equivalent for CO₂ slope (V_E /VCO₂ ), and respiratory exchange ratio (RER). Impairment, functional and patient reported measures were also recorded. Predicted CPET variables were calculated based on published normative data for age, gender, and weight.

RESULTS

Twenty-two people with CMT and 17 people with IBM were recruited. Both groups showed significantly lower VO₂ peak, MHR, AT, and V_E /VCO₂ . The CMT group overall performed better than the IBM group, with significantly higher VO₂ peak, MHR, and AT, but lower V_E /VCO_2. Linear regression analysis demonstrated that VO₂ peak was related to body fat percentage and 6-min walk distance for both groups, and steps per day for the IBM group.

DISCUSSION

Lower than predicted CPET variables were observed that were not explained by cardiopulmonary limitations or reduced effort, implicating peripheral factors in limiting the cycling task. Regression analysis implied prediction of VO2 peak by body fat percentage and 6-min walk distance. Six-minute walk distance could be a potential proxy measure of cardiopulmonary fitness.

Re-evaluation of the prognostic significance of oropharyngeal dysphagia in idiopathic inflammatory myopathies

OBJECTIVE

To investigate the prognostic significance of videofluorographic swallowing study (VFSS)-confirmed oropharyngeal dysphagia in idiopathic inflammatory myopathies (IIMs).

METHOD

We reviewed the medical records of patients who were diagnosed with IIM between 2009 and 2020 at Seoul St Mary's Hospital. All oropharyngeal dysphagia cases were limited to VFSS-confirmed dysphagia found during the initial diagnostic work-up for IIM. We described the findings on VFSS and the course of the dysphagic symptoms. Logistic regression and survival analyses were performed to evaluate the risk of pneumonia and mortality, respectively.

RESULTS

We found 88 patients with IIM who met the criteria. Among them, 17 patients (19%) had oropharyngeal dysphagia. Except for two cases lost to follow-up and one deceased case, all of the patients with dysphagia (14 of 14) had swallowing function restored within 6 months. The risk of pneumonia within 3 months from the diagnosis of IIM was significant [odds ratio = 4.49, 95% confidence interval (CI) 1.07-18.88]. The median follow-up duration was 34 and 27 months for the groups without and with dysphagia, respectively. The survival analysis failed to demonstrate that the presence of oropharyngeal dysphagia increased the risk of death (hazard ratio = 0.77, 95% CI: 0.085-7.00).

CONCLUSIONS

Oropharyngeal dysphagia found at the initial diagnosis of IIM improved within 3-6 months in nearly all cases. Furthermore, IIM patients who had oropharyngeal dysphagia at the initial diagnosis of IIM were not likely to have shorter survival, even if the risk of pneumonia was increased in the short term.

Small intestinal biopsy findings consistent with celiac disease in patients with idiopathic inflammatory myopathy: Review of existing literature

BACKGROUND

Case reports have described patients with idiopathic inflammatory myopathies (IIM) and a concurrent diagnosis of celiac disease (CeD) for whom the muscle inflammation (myositis) component of IIM improves after the patients start standard treatment with gluten-free diet (GFD). A connection between IIM and CeD is not commonly recognized.

AIM

In this first systematic review of the topic, we aimed to explore all peer-reviewed publications of IIM cases and concomitant small intestinal biopsy findings consistent with CeD, published after 1975.

METHODS

Systematic literature searches were performed in MEDLINE, PubMed, and EMBASE, supplemented by screening of references and non-systematic searches via Google and Google Scholar.

RESULTS

Altogether 30 cases published between 1976 and 2017 were uncovered. Information about gastrointestinal symptoms prior to CeD diagnosis was available for 19 patients, with 6/19 (32%) reporting no GI symptoms. CeD-related serological data were available in 23/30 patients. Endomysial antibodies were present in 10/18 (56%), while only 2/9 (22%) had antibodies against tissue transglutaminase. Serum antibodies to native gliadin were present in 16/18 (89%). Clinical effects of a GFD on the IIM were reported for 24 patients, with signs of improvement in 14/24 (58%), including three patients with otherwise therapy-resistant inclusion body myositis. Longitudinal follow-up data available from the published studies indicated that 7/24 (29%) remained in clinical IIM remission with GFD as the sole therapeutic intervention.

CONCLUSION

In the IIM cases presented here, duodenal biopsy findings consistent with celiac disease was sometimes present without classical CeD symptoms or positive traditional CeD serology, and in the majority of cases, the IIM improved after introduction of a gluten-free diet. While extra vigilance towards CeD in IIM patients seems warranted, there is need for more research to clarify if GFD has effects on organ systems other than the small intestine in patients with IIM and small intestinal biopsy findings consistent with CeD.

Idiopathische inflammatorische Myopathien: Aktuelles zu Diagnose und Klassifikation

Auf dem Sektor der Kollagenosen ist der wissenschaftliche Fortschritt bei der Myositis in den letzten 15–20 Jahren bemerkenswert. Durch kontinuierliche Forschung und intensive Vernetzung der Myositis-Experten ist es gelungen, neue Untergruppen zu identifizieren und somit für die Prognose wichtige Organmanifestationen rechtzeitig zu erkennen. Vor dem Hintergrund dieser Neuerungen verfolgt diese Übersichtsarbeit sowohl das Ziel, möglichst alle Facetten der Erkrankung zu präsentieren, als auch die moderne Einteilung der idiopathischen inflammatorischen Myopathien zu erläutern. Außerdem werden die neuen Klassifikationskriterien vorgestellt, die die Kriterien von Bohan und Peter aus dem Jahr 1975 abgelöst haben. Im Artikel werden ihre Stärken und Schwächen sowie ihr Optimierungspotenzial diskutiert.

Sporadic Inclusion Body Myositis: A Clinicopathological Study

Background

Sporadic inclusion body myositis (s-IBM) is rare in India.

Aim

The aim of this study was to diagnose s-IBM according to the European Neuromuscular Center (ENMC) IBM research diagnostic criteria 2011.

Materials and Methods

A retrospective review of patient records diagnosed as s-IBM according to the above criteria during the period from January 2010 to May 2015 was done with an emphasis on pattern of muscle weakness.Serumcreatine kinase (CK) andelectromyography (EMG) were noted. Muscle biopsy was evaluated with basic panel of histochemical stains including Congo red stain. Immunohistochemistry (IHC) with ubiquitin was done in 10 biopsies. IHC for major histocompatibility complex-1 and electron microscopy studies were not performed.

Results

The diagnosis of s-IBM constituted 5 clinicopathologically defined, 12 clinically defined, and 10 probable IBM in the study period. There was male predominance with median age at 51 and duration of disease varying from 1-5 years. All the patients presented with insidious onset of muscle weakness of quadriceps and/or forearm flexors. CK varied from 57-2939 IU/L. EMG was myopathic in 22, mixed in 2, and neuropathic in 3. Endomysial inflammation was seen in 23 (85.19%) and rimmed vacuoles in 24 (88.89%). Amyloid was demonstrated in only 5 (18.52%) and ubiquitin in 2 biopsies. Mitochondrial abnormalities were seen in 92.59% biopsies.

Conclusions

Application of the ENMC IBM research diagnostic criteria allowed diagnosis of clinically-defined and probable IBM in the absence of all pathology criteria. Rimmed vacuoles in 88.89% of biopsies indicate presentation at a late stage. Use of ancillary techniques can improve diagnostic yield.