Anti-mitochondrial antibody-positive inflammatory myopathy with multiple arrhythmias resistant to high-dose glucocorticoids and intravenous cyclophosphamide: a case-based review

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of autoimmune diseases characterized primarily by muscle inflammation. Anti-mitochondrial antibodies (AMA) are typically associated with primary biliary cholangitis; however, they have also been linked to a rare subgroup of IIMs, namely "AMA-positive myositis," marked by a chronic disease course and muscle weakness, particularly affecting the paravertebral muscles, alongside muscle atrophy and cardiopulmonary complications. We report the case of a 40-year-old woman diagnosed with AMA-positive myositis, predominantly involving axial myopathy complicated by multiple arrhythmias and biopsy-proven focal segmental glomerulosclerosis with mitochondrial abnormalities on electron microscopy. The patient presented with progressive back pain and palpitations over a 3-month period. Although high-dose glucocorticoids and intravenous cyclophosphamide improved the axial myopathy and proteinuria, the cardiac condition remained unstable, necessitating permanent pacemaker implantation for persistent sinus dysfunction and radiofrequency catheter ablation for worsening atrial fibrillation (Af). Our literature review focusing on cardiac involvement in AMA-positive myositis revealed tachyarrhythmia was the most common (87.7%), particularly Af (55.4%), followed by cardiomyopathy (74.2%), myocarditis (43.2%), and bradyarrhythmia (40.0%). Arrhythmias and/or cardiac function deteriorated in 41.7% of patients treated with immunosuppressants and in 66.7% of patients treated without immunosuppressants, respectively. Furthermore, in the treated group, more patients with worsened cardiac lesions required additional electronic devices compared to those without (53.3% vs. 4.8%). Early detection and adequate management of cardiac complications in AMA-positive myositis are critical to prevent irreversible myocardial damage and fatal outcomes. In addition to cardiac complications, concomitant renal involvement associated with AMA-positive myositis may be also considered.

Idiopathic Inflammatory Myopathies: Recent Evidence Linking Pathogenesis and Clinical Features

Idiopathic inflammatory myopathies are rare and complex representatives of systemic connective tissue diseases. Described initially as only two entities, recent advances in molecular and imaging techniques now divide them into many subtypes, each with unique pathogenesis and clinical phenotypes. Dermatomyositis and its juvenile form are the most prevalent subtypes and are characterized by systemic vasculopathy and humoral autoimmunity. Genetic predisposition and environmental triggers initiate immune tolerance breakdown, leading to autoantibody production, complement activation, and tissue damage. Anti-synthetase syndrome primarily affects the lungs, where immune responses to aminoacyl-RNA synthetases drive vasculopathy, lung inflammation, and fibrosis. Immune-mediated necrotizing myopathies are muscle-specific, with autoantibodies inducing fiber necrosis and atrophy. Lastly, sporadic inclusion body myositis is a slowly progressive myopathy in which dysfunctional protein handling and autophagy are more important pathogenic elements than muscle inflammation itself. The expanding body of basic science evidence can be overwhelming, making it challenging to connect pathogenic mechanisms to clinical manifestations. This review aims to address this challenge by presenting recent insights into myositis pathogenesis from a practical perspective, reinforcing the links between basic science and clinical semiology.

A Serial Assessment of T1 and T2 Mapping Cardiac Magnetic Resonance Before and After Heart Failure Onset in a Case of Cardiomyopathy in Anti-mitochondrial Antibody-positive Myositis

A 69-year-old woman presented with heart failure and progressive muscle weakness and was diagnosed as anti-mitochondrial antibody (AMA) myositis with cardiac involvement. Immunosuppressive therapy with prednisolone and intravenous cyclophosphamide significantly improved the symptoms, hemodynamics, and cardiac function. Cardiac magnetic resonance (CMR) T1 and T2 mapping showed elevated native T1, T2, and extracellular volume fractions during heart failure exacerbation (day 37) compared to pre-hospitalization values (10 months before admission) and follow-up conducted 6 and 12 months after admission. This case underscores the importance of comprehensive evaluation, such as serial CMR imaging and immunosuppressive therapy, in managing myocardial involvement in AMA-positive myositis.

What is in the Myopathy Literature?

ABSTRACT

This update begins with the incidence and features of statin-associated muscle symptoms, which may often be misattributed. Articles on potential muscle mitochondria dysfunction from statins follow, along with recommendations for possibly avoiding statins in some patients with genetic myopathies. Next, autoimmune myopathies, including immune-mediated necrotizing myopathy, myositis with antimitochondrial antibodies, and overlap myositis with lupus, as well as the role of myxovirus protein A identification in muscle specimens, are addressed. The next section includes reports on the significance of elevated serum aldolase with normal creatine kinase and recommended approaches to evaluate a patient with rhabdomyolysis. A cluster of reports on muscle imaging, particularly using ultrasound and magnetic resonance imaging, are covered. They include studies of inherited and inflammatory myopathies and neck extensor myopathy on topics such as imaging features, patterns of involvement, diagnostic utility, and correlation with histopathology. Last, there are discussions on mexiletine versus lamotrigine for nondystrophic myotonias and the treatment of fatty acid oxidation disorders in adults.

Anti-mitochondrial M2 antibody-positive myositis may be an independent subtype of autoimmune myositis

It is still unknown whether anti-mitochondrial M2 antibody (AM2A)-positive myositis is an independent subtype of autoimmune myositis (AIM). As such, the aim of this study is to better characterize the clinicopathological features in a large cohort of patients. This study utilized the muscle biopsy samples from AM2A-positive patients, which were sent to the National Center of Neurology and Psychiatry for diagnostic purposes from January 2008 to December 2020. The clinicopathologic information of 201 patients were compared with those who were diagnosed with immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome, or dermatomyositis. AM2A-positive patients had the longest pre-biopsy disease duration (PBDD) at 48.7 ± 63.0 months and the highest frequency of arrhythmia of 51.1%. Necrotic and/or regenerating fibers were seen in 93.5% and membrane attack complex sarcolemmal deposits were noted in 43.3%, similar to IMNM. Furthermore, AM2A-positive patients with shorter PBDD showed more CD8-positive lymphocyte infiltrates. Clinically, shorter PBDD was associated with higher serum creatine kinase levels, whereas longer PBDD was associated with a higher frequency of arrhythmia. Principal component analysis separated disease groups with high weight of muscle pathology components on two-dimensional plotting, although AM2A-positive myositis and IMNM partly overlapped. On logistic regression model analysis, we obtained high sensitivity (0.846) and specificity (0.842) for distinguishing them using clinical and pathological variables. This largest cohort study suggests that AM2A-positive myositis may be an independent subtype of AIM characterized by a chronic myositis with IMNM-like pathology, along with a high prevalence of cardiac involvement and respiratory muscle weakness.

Clinical characteristics of primary biliary cirrhosis - idiopathic inflammatory myopathy overlap syndrome: A single center study

PURPOSE

Primary biliary cirrhosis-idiopathic inflammatory myopathy (PBC-IIM) overlap syndrome (OS) is a rare condition in which cardiac involvement is observed. We aimed to characterize the clinical features and associated factors of PBC-IIM OS patients with cardiac involvement.

METHODS

Patients with PBC-IIM OS that visited our hospital from January 1983 to December 2021 were enrolled. Clinical presentations and laboratory and imaging data were recorded. The clinical data of patients with and without cardiac involvement were compared. According to the first instance of a disease flare, prognostic factors were also studied.

RESULTS

Thirty-four patients with PBC-IIM OS were enrolled. A total of 58.8% of patients presented with muscle weakness at disease onset, which primarily involved skeletal muscle (85.3%). Slight liver dysfunction was discovered in this OS cohort. In patients with cardiac involvement, palpitation (63.6%) and dyspnea (36.4%) were the most common onset symptoms. Arrhythmia was a vital manifestation in OS patients, in which half of OS patients had nonsustained ventricular tachycardia (50.0%, 11/22). Compared with noncardiac involvement, myalgia (4.5%, P = 0.004) and fever (0.0%, P = 0.011) were reported relatively rarely at disease onset in the group with cardiac involvement. The prognosis analysis showed that positivity for anti-Ro52 (HR=0.00, P = 0.034) negatively correlated with relapse in OS patients.

CONCLUSION

PBC-IIM OS has unique features. Typical clinical manifestations and early worsening cardiac indicators can be used to identify cardiac involvement and predict prognosis. Anti-Ro52 may have prognostic value for PBC-IIM OS.

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.

Prevalence and risk surveillance of anti-mitochondrial antibody-positive myositis: Outcomes of a nationwide survey

BACKGROUND

Anti-mitochondrial antibody (AMA)-positive myositis is a chronic disease characterized by skeletal muscle atrophy and is associated with cardiac complications and restrictive ventilatory impairment. This study aimed to determine the prevalence, rate of organ complications, and prognostic risk factors of AMA-positive myositis.

METHODS

We conducted a cross-sectional study using a nationwide questionnaire from 2011 to 2021, enrolling participants from neurology departments at 811 facilities certified by the Japanese Society of Neurology.

RESULTS

A total of 380 patients were identified, with a prevalence rate of 0.3 per 100,000 persons. The frequencies of cardiac complications and restrictive ventilatory impairment were 53 and 33 %, respectively; whereas, those of cardiac device and respirator introduction were 32 and 22 %, respectively. The frequencies of recurrence, subacute exacerbation, no muscle strength improvement, cardiac device introduction, respirator introduction, and death were 29, 25, 54, 32, 22, and 12 %, respectively. According to univariate analysis, abnormal echocardiograms (odds ratio [OR], 5.43), restrictive ventilatory impairment (OR, 3.70), and inflammatory changes revealed by muscle biopsy (OR, 0.34) were associated with subacute exacerbations, whereas abnormal echocardiograms (OR, 8.00) and durations from onset to admission and diagnosis (OR, 2.99) were associated with cardiac device introduction. Multivariable analysis showed that restrictive ventilatory impairment was associated with recurrence (adjusted OR, 3.01), adjusted for the duration from onset to admission and diagnosis, and with subacute exacerbations (adjusted OR, 3.86), adjusted for abnormal echocardiograms and inflammatory changes.

CONCLUSIONS

AMA-positive myositis is characterized by severe and urgent organ complications, and anticipatory management is critical for management of this disease.

Successful high-dose glucocorticoid therapy for anti-mitochondrial antibody-positive myocarditis arising during tocilizumab and low-dose glucocorticoid therapy for rheumatoid arthritis

Anti-mitochondrial antibody (AMA)-positive myopathy, a recently identified condition with significant cardiac involvement, poses a serious challenge in treatment consensus due to its extreme rarity. While several studies demonstrate the efficacy of high-dose prednisolone in managing this disease, the current literature lacks substantial evidence regarding the effectiveness of biologic therapy or low-dose prednisolone for remission induction. Here, we present a case of AMA-positive myocarditis that emerged during rheumatoid arthritis treatment with tocilizumab (TCZ) and low-dose prednisolone (PSL). Successfully, intensive immunosuppressive therapy with high-dose PSL proved effective in stabilizing this condition. Our case highlights the necessity of a robust immunosuppressive approach, favoring high-dose PSL over the combination of low-dose PSL and TCZ in this disease.

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

OBJECTIVE

This study aimed to classify idiopathic inflammatory myopathy (IIM) patients with cardiac involvement (IIM-CI) into different categories based on their clinical phenotypes via cluster analysis and to explore their differences in outcomes.

METHODS

IIM-CI patients admitted to Peking Union Medical College Hospital from January 2015 to June 2021 were retrieved. The clinical data, laboratory examinations, and treatment were retrospectively reviewed, and the outcome was traced. A second-order clustering method was employed for categorization.

RESULTS

A total of 88 IIM-CI patients were enrolled in this study and were classified into two categories through cluster analysis. Category I consisted of patients who exhibited distinct cardiac structural and functional changes, such as enlargement of atriums and/or ventricles, along with the remarkable heart insufficiency biomarkers, whereas patients of category II displayed more widely systemic injuries and intensive skeletal muscle weakness. In comparison, pulmonary hypertension (58.8% vs 16.7%, p < 0.01), arrhythmia (82.4% vs 27.8%, p < 0.01), and positive serum anti-mitochondrial-M2 antibody (52.9% vs 5.6%, p < 0.01) were more prevalent in category I than in category II, and serum N-terminal pro-B-type natriuretic peptide levels (1703.5 pg/L vs 364.0 pg/L, p = 0.02) were significantly elevated in category I, whereas skeletal muscle weakness (50.0% vs 74.1%, p = 0.02), interstitial lung disease (20.6% vs 63.0%, p < 0.01), skin rash (11.8% vs 48.1%, p < 0.01), arthralgia (2.9% vs 27.8%, p < 0.01), fever (2.9% vs 27.8%, p < 0.01), and dysphagia (2.9% vs 22.2%, p < 0.01) were more common in category II patients. Heart failure was the primary cause of death in category I, but severe pneumonia was predominantly responsible for deaths in category II.

CONCLUSION

Two categories of IIM-CI were identified based on clinical features with distinctive characteristics. Two categories exhibited differences in clinical manifestations, autoantibody profiles, and the primary cause of death.

Pulmonary manifestations and prognosis of a cohort of patients with interstitial lung disease and positive to anti-Th/To autoantibodies

INTRODUCTION

Th/To autoantibody may be relevant in evaluating patients with interstitial lung disease (ILD) because the clinical diagnosis of systemic sclerosis (SSc) may not be evident. The study's objective was to describe manifestations and evolution of pulmonary function in a cohort of ILD patients positive for Th/To autoantibodies.

METHODS

ILD patients positive for anti-Th/To autoantibody were enrolled in this protocol. Baseline clinical features were registered, and survival analysis was performed to identify risk factors associated with worse survival.

RESULTS

Fifty-two patients positive for anti-Th/To autoantibodies with ILD were included. Only 21% of the patients fulfilled the ACR/EULAR 2013 systemic sclerosis classification criteria, and 63.4% fulfilled the IPAF ATS/ERS 2015 criteria. Twenty-five percent of the patients died during follow-up. Respiratory failure was the principal cause of death. Twenty-nine patients (56%) were positive for other hallmark SSc autoantibodies. The most frequent HRCT pattern was nonspecific interstitial pneumonia (NISP). Survival was strongly associated to the systolic pulmonary arterial pressure (sPAP), male sex and the extent of fibrosis in HRCT; besides, patients positive for other hallmark SSc autoantibodies had worse survival compared to those positive only to anti-Th/To. Seventy-six percent of them behaved as fibrotic progressive pulmonary disease, with an absolute decline of the FVC of at least 5%.

CONCLUSIONS

Only a small proportion of ILD patients positive for Th/To meet the criteria to be classified as SSc; however, most met criteria for IPAF. A high proportion of patients behave as progressive fibrotic pulmonary disease. Survival is associated with sPAP, the extent of lung disease, and the presence of other hallmark SSc autoantibodies.

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

BACKGROUND

A few patients with inflammatory myopathy showed anti-mitochondrial antibody (AMA) positivity. This study aimed to report the clinical and pathological findings with vacuoles in 3 cases of such patients.

METHODS

Three cases with myositis from the Myositis Clinical Database of Peking University First Hospital were identified with AMA positivity. Their clinical records were retrospectively reviewed and the data was extracted. All the 3 cases underwent muscle biopsy.

RESULTS

Three middle-aged patients presented with chronic-onset weakness of proximal limbs, marked elevation of creatine kinase, and AMA-positivity. Two of the 3 cases meet the criteria of primary biliary cholangitis. All the 3 cases presented with cardiac involvement and proteinuria. Two cases developed type 2 respiratory failure. MRI of the thigh muscle showed multiple patches of edema bilaterally in both cases, mostly in the adductor magnus. Pathological findings include degeneration of muscle fibers, diffused MHC-I positivity, and complement deposits on cell membranes. Vacuoles without rims of different sizes were discovered under the membrane of the muscle fibers. A few RBFs were discovered in case 1, while a diffused proliferation of endomysium and perimysium was shown in case 2.

CONCLUSIONS

AMA-positive inflammatory myopathy is a disease that could affect multiple systems. Apart from inflammatory changes, the pathological findings of muscle can also present vacuoles.

Fatty infiltration in the posterior muscles of the lower extremities as an MRI feature in antimitochondrial antibody-associated myopathy

OBJECTIVE

Idiopathic inflammatory myopathy (IIM) with antimitochondrial M2 antibody (AMA-M2) has been associated with distinct clinical characteristics. In this study, we explore the magnetic resonance imaging (MRI) findings of the muscles of the lower extremities in AMA-M2-positive IIM to gain more insight.

METHODS

MRI of 22 lower extremity muscles was retrospectively evaluated in 14 patients with AMA-M2-positive IIM and 37 age- and sex-matched patients with AMA-M2-negative IIM. Muscles with inflammatory edema and fatty infiltration were assessed according to the Stramare and Mercuri criteria.

RESULTS

Patients with AMA-M2-positive IIM had significantly higher incidence of MRI involvement with fatty infiltration in five lower extremity muscles, namely the adductor magnus (AM) (13/14 VS 14/37, p < 0.001), semimembranosus (SM) (13/14 VS 17/37, p = 0.002), biceps femoris (BF) (12/14 VS 15/37, p = 0.004), soleus (13/14 VS 23/37, p = 0.041), and the medial head of the gastrocnemius (Gastroc M) (13/14 VS 17/37, p = 0.002) than patients with AMA-M2-negative IIM. Furthermore, the severity scores of fatty infiltrations of the above five muscles in AMA-M2-positive IIM were significantly higher than those in patients with AMA-M2-negative IIM (p < 0.001).

CONCLUSIONS

Severe fatty infiltrations of the AM, SM, BF, soleus, and Gastroc M in the posterior muscles of the lower extremities are dominant MRI features in our patients with AMA-M2-positive IIM. This unique muscle MRI character may be a helpful indicator in clinical practice for patients with AMA-M2-positive IIM. Key Points • Striking involvement and prominent fatty infiltrations of five lower extremity muscles (adductor magnus, semimembranosus, biceps femoris, soleus, and the medial head of the gastrocnemius) are interesting MRI performances. • Severe fatty infiltrations in the posterior muscles of the lower extremities are dominant MRI features in AMA-M2-positive IIM. • This unique muscle MRI character may be very helpful for the diagnosis of the AMA-M2-positive IIM.

Recovery of cardiac metabolic function after high-dose prednisolone in a patient with inflammatory myopathy associated with anti-mitochondrial antibody

Myocardial complications in the setting of inflammatory myopathy associated with anti-mitochondrial antibody (AMA) cause various cardiovascular complications. A 64-year-old Japanese man was diagnosed with inflammatory myopathy associated with AMA, and three years after diagnosis, the patient was referred to our hospital with leg edema and dyspnea on exertion. Right ventricular endomyocardial biopsy showed no disease-specific findings, with neither inflammatory cell infiltration nor non-caseating epithelioid cell granuloma, and only mild fibrosis; therefore, we finally diagnosed this patient with cardiac involvement in inflammatory myopathy associated with AMA. 123I-β-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) cardiac scintigraphy showed decreased uptake in wider areas discordant with late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR). One month after starting prednisolone (PSL), the symptoms of congestive heart failure and left ventricular (LV) systolic function had improved. Additionally, BMIPP uptake in the LV myocardium significantly improved compared to that before PSL administration, although decreased BMIPP uptake remained in areas concordant with LGE on CMR. Moreover, it is suggested that recovery of cardiac metabolic function after high-dose PSL administration, which was confirmed through improvement in BMIPP uptake in the LV myocardium, may have led to the improvement in both LV systolic function and heart failure.

Learning objective

Although the definitive diagnosis of cardiac involvement in inflammatory myopathy associated with anti-mitochondrial antibody is difficult because of the rarity of this condition and no disease-specific findings in imaging and histology, physicians should consider this in patients with cardiac dysfunction and muscle weakness. 123I-β-methyl-p-iodophenyl-pentadecanoic acid scintigraphy should be used to assess cardiac metabolic function and treatment efficacy and should be considered for patient management.

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.

Clinicopathological and circulating cell-free DNA profile in myositis associated with anti-mitochondrial antibody

OBJECTIVE

Anti-mitochondrial antibodies (AMAs) are associated with idiopathic inflammatory myopathies (IIMs). We aimed to summarize the clinicopathological characteristics, assess circulating cell-free mitochondrial DNA (ccf-mtDNA), and circulating cell-free nuclear DNA (ccf-nDNA) in AMA-associated IIMs.

METHODS

Medical records of 37 IIMs patients with AMAs were reviewed. Circulating cell-free mtDNA and ccf-nDNA levels in sera from IIMs patients with AMAs (n = 21), disease controls (n = 66) and healthy controls (HCs) (n = 23) were measured and compared. Twenty-eight immune-mediated necrotizing myopathy (IMNM) patients, 23 dermatomyositis (DM) patients, and 15 anti-synthetase syndrome (ASS) patients were enrolled as disease controls. Correlations between variables were analyzed.

RESULTS

Limb weakness was observed in 75.7% and neck weakness in 56.8% of patients. Cardiac involvement occurred in 51.4% of patients. Muscle pathology revealed 81.1% of IMNM, 5.4% polymyositis, and 13.5% nonspecific myositis. Microinfarction was observed in 8.1% of patients. Serum ccf-mtDNA levels in AMA-associated IIMs were significantly higher than those in HCs (p < 0.001), but no significant differences between AMA-associated IIMs and IMNM, DM, or ASS. Serum ccf-nDNA levels in AMA-associated IIMs were significantly higher than those in HCs (p = 0.02), and significantly lower than those in DM (p = 0.02). Serum ccf-nDNA levels correlated negatively with MMT8 total scores (rs = -0.458, p = 0.037) and positively with mRS scores (rs = 0.486, p = 0.025). Serum ccf-nDNA levels were significantly higher in the non-remission group (p < 0.01).

INTERPRETATION

AMA-associated IIMs exhibit distinct clinicopathological features. Serum ccf-nDNA may serve as a potential marker for disease severity and prognosis in AMA-associated IIMs.

Magnetic resonance imaging findings of the lower limb muscles in anti-mitochondrial M2 antibody-positive myositis

Anti-mitochondrial M2 antibody (AMA-M2)-positive myositis is an idiopathic inflammatory myopathy (IIM). Of all patients with myositis, 2.5-19.5% have AMA-M2 antibodies. However, the detailed distribution of muscles affected in AMA-positive myositis is unknown. Therefore, we examined lower muscle magnetic resonance imaging (MRI) findings of patients with AMA-positive myositis. Among the 63 patients with IIM at our institute, 5 (7.9%) were positive for AMA-M2 antibodies. However, one was also positive for anti-Jo1 antibodies; therefore, four patients were finally participated in this study. All patients had high-intensity MRI signals in the proximal muscles, including the gluteus maximus and iliopsoas muscles, and in the thigh muscles, including the vastus lateralis, vastus medialis, adductor magnus, and semimembranosus muscles. Lower leg muscles were relatively spared. Fascial edema was observed in all patients and was also present in the lower leg muscles. Subcutaneous edema was observed, particularly in the proximal portion of the lower limbs. In AMA-positive myositis, proximal muscles, including the gluteus maximus, vastus lateralis, adductor magnus, and the semimembranosus, were markedly affected, while the lower leg muscles were relatively preserved. Additionally, fascial edema was evident even in lower leg muscles. Therefore, muscle MRI can be a useful diagnostic aid for AMA-positive myositis.

Value of the HFA-PEFF diagnostic algorithms for heart failure with preserved ejection fraction to the inflammatory myopathy population

OBJECTIVES

The HFA-PEFF score has been validated to hold great diagnostic and prognostic utility for heart failure with preserved ejection fraction (HFpEF). Idiopathic inflammatory myopathy (IIM) is recognized as one of the potential etiologies underlying HFpEF. Here, we intended to investigate the real prevalence of HFpEF in IIM via the HFA-PEFF score and explore the prognostic value of this score.

METHODS

Two hundred twenty IIM patients were enrolled for assessment. The cohort was divided into low, intermediate and high tertiles of the HFA-PEFF score. Spearman's correlation analysis was used to explore the association between the score and disease activity. Chi-square test was applied to investigate the distribution discrepancy of HFA-PEFF tertiles among patients with different myositis-specific antibodies (MSAs) or myositis-associated antibodies (MAAs). Univariate and multivariate ordinal regression analyses were performed to screen risk factors for high HFA-PEFF scores. Survival curves were obtained using the Kaplan-Meier method and log-rank tests.

RESULTS

In total, 79 (35.9%), 107 (48.6%) and 34 (15.5%) patients were rated low, intermediate and high probability of HFpEF, respectively. The HFA-PEFF score correlated well with disease activity. Patients with positive AMA-M2 scored higher in the HFA-PEFF score (p = 0.011). During follow-up, patients with positive AMA-M2 or anti-SRP antibody developed an inclination towards concentric hypertrophy on echocardiography. Additionally, palpitation symptom, AMA-M2 positivity and elevated serum levels of LDH, cTnI were independent risk factors for high HFA-PEFF scores. Finally, a high-tertile HFA-PEFF score was related to lower overall survival rate (p < 0.001). Patients with positive AMA-M2 had poorer outcomes (p = 0.002).

CONCLUSION

HFpEF was prevailing in IIM patients according to the HFA-PEFF score. The HFA-PEFF score correlated well with disease activity and held significant prognostic value. Patients with AMA-M2 antibody were prone to have poor outcomes.

Cardiac involvement in polymyositis and dermatomyositis: diagnostic approaches

Polymyositis (PM) and dermatomyositis (DM) are rare idiopathic inflammatory myopathies (IIM). Myocardial involvement in patients with IIM is an unfavorable prognostic factor and one of the most common cause of mortality in this group of patients. The purpose of this review is to present current knowledge on cardiovascular manifestations observed in IIM. Data published in English until December 2021 were selected. Clinical symptoms suggesting cardiac involvement are non-specific and require a differential diagnosis in accordance with cardiological guidelines. Troponin I is specific to cardiac injury and should be preferred to other markers to evaluate the myocardium in IIM. Abnormalities in electrocardiography are common in IIM, especially non-specific changes of the ST-T segment. In standard echocardiography left ventricular diastolic dysfunction is reported frequently. New diagnostic technologies can reveal clinically silent myocardial abnormalities. However, the prognostic value of subclinical impairment of myocardial function require further studies.

Sick sinus syndrome concomitant with myopathy associated with anti-mitochondrial antibodies: a case report

Background

Anti-mitochondrial antibody (AMA)-associated myopathy is known to be concomitant with primary biliary cirrhosis and to cause both skeletal muscle disorders and arrhythmias, myocardium disorders, and respiratory muscle disorders. We report a case of AMA-associated myopathy in which the bradycardia-related symptoms preceded the skeletal muscle symptoms.

Case summary

A 59-year-old woman visited the emergency room in our hospital following a syncopal event. The patient was bradycardiac (45 b.p.m.) with a junctional rhythm resulting from sick sinus syndrome (SSS) and was suffering from heart failure. Blood tests revealed elevated creatine kinase (CK) and hepatic enzymes. She underwent permanent pacemaker implantation. However, it proved difficult to detect the electrical potential in the right atrium. Although successful atrial pacing was achieved at the lower right atrial septum, the atrial threshold was markedly high and she depended on ventricular pacing. One year later, neurological examination and muscle biopsy confirmed the diagnosis of AMA-associated myopathy. Following this diagnosis, steroid pulse therapy was initiated. Steroid administration relieved her symptoms and lowered the CK levels but the atrial standstill persisted. The patient takes low-dose prednisolone and has had an uneventful course for 3 years.

Discussion

To the best of our knowledge, this is the first case of AMA-associated myopathy diagnosed by the first symptom related to bradycardia due to SSS. Patients with AMA-associated myopathy can experience a variety of cardiac symptoms, including arrhythmias, and initially complain of cardiac symptoms without symptoms of skeletal myopathy. This disease should be considered when diagnosing patients with arrhythmia and elevated CK.

Inflammatory Myopathy Associated with Anti-mitochondrial Antibody-negative Primary Biliary Cholangitis Diagnosed by a Liver Biopsy

Anti-mitochondrial antibody (AMA)-associated myopathies represent a homogeneous disease entity with severe arrhythmia and slowly progressive proximal muscle weakness with lordotic posture, irrespective of the presence of primary biliary cholangitis (PBC). We herein report a case of myositis associated with PBC without AMAs. A 48-year-old woman presented with clinical features very similar to AMA-associated myositis, despite negative AMAs. PBC, ascertained by a liver biopsy performed based on mildly elevated liver enzymes, and the efficacy of steroid therapy on muscle weakness confirmed the diagnosis of immune-mediated myositis. When AMAs are negative, a liver biopsy is indispensable for diagnosing treatable PBC-associated myositis.

Granulomatous myopathy: Sarcoidosis and beyond

Non-necrotizing granulomatous inflammation is a rare but easily recognized histopathological finding in skeletal muscle biopsy. A limited number of diseases are known to be associated with non-necrotizing granulomatous myopathy. Once identified, a careful evaluation for evidence of extramuscular granulomatosis and other signs suggestive of sarcoidosis is warranted as about half of the patients have sarcoid myopathy. In addition, the presence of granulomatous myopathy should trigger a search for clinical and pathological clues of inclusion body myositis (IBM), which accounts for most of the remaining patients and can coexist with sarcoidosis. Recognizing the features of IBM in patients with granulomatous myopathy can potentially spare the patients from unnecessary exposure to immunosuppressive therapies. In patients whose granulomatous myopathy remain unexplained, further investigations should aim at identifying myasthenia gravis and other autoimmune disorders, especially those known to cause granulomatous inflammation in other organs. Laboratory investigations should include acetylcholine receptor, antimitochondrial, antineutrophil cytoplasmic, thyroglobulin, and thyroid peroxidase autoantibodies. In the appropriate clinical context, exposure to immune checkpoint inhibitors and chronic graft-vs-host disease can be causes of granulomatous myopathy. In cases of unexplained granulomatous myopathy, natural killer/T-cell lymphoma should be considered and careful histopathological examination for atypical cells and appropriate immunostaining is crucial. Identifying the etiology of granulomatous myopathy in each patient can guide appropriate treatment.

Myositis Autoantibodies in Patients with Suspected Post-Treatment Lyme Disease Syndrome

Most patients suffering from Lyme disease are effectively treated with antibiotics. In some patients, however, problems persist for a long time despite appropriate therapy. The term post-treatment Lyme disease syndrome (PTLDS) is currently used for this condition in scientific literature. The pathogenesis is still not precisely known, but the involvement of immunopathological mechanisms is assumed. In our study, we analyzed the presence of autoantibodies including myositis-specific (MSA) and myositis-associated autoantibodies (MAA) in patients with laboratory proven history of Lyme disease and with clinical symptoms of PTLDS. A total of 59 patients meeting the criteria for PTLDS were enrolled in this study. The control group consisted of 40 patients undergoing differential diagnosis of neurological disorders without clinical and/or laboratory-proven history of Lyme disease. The presence of autoantibodies was determined by immunoblot methods and positive samples were further tested for serum creatine kinase (CK) and myoglobin levels. The presence of myositis autoantibodies was detected in 18 subjects with suspected PTLDS (30.5%), but only in 5% of control subjects exhibiting no evidence of Lyme disease history. The difference was statistically significant (p = 0.002). The subsequent biochemical analysis of muscle-damage markers in positive subjects found a mild elevation in six MSA/MAA-positive PTLDS patients. The study detected raised MSA/MAA autoantibodies formation in the group of PTLDS patients raising the question about their involvement in the pathogenesis of this syndrome.

Rare forms of inflammatory myopathies - part I, generalized forms

INTRODUCTION

The idiopathic inflammatory myopathies traditionally comprise dermatomyositis, polymyositis, immune-mediated necrotizing myopathy, anti-synthetase syndrome, and inclusion body myositis. In this review, we aimed to cover the less common forms of generalized myositis.

AREAS COVERED

We identified rare forms of widespread myositis on the basis of list provided by the homepage of the Neuromuscular disease center of Washington University, USA and on the basis of the authors' knowledge. We searched PubMed® and EMBASE® for relevant articles on these forms with the aim of providing as much as possible information on their clinical manifestations as well as guidance on their work-up and treatment.

EXPERT OPINION

There is substantial heterogeneity among the various rare forms of generalized myositis in terms of their frequency and characterization. Some forms are reasonably well defined, while others may not represent truly well-defined diseases, but rather variants of other myopathies. The landscape of rare forms appears to have evolved over time, with some forms now being better characterized, while others, such as SARS-Cov-2- and immune checkpoint inhibitor-related myositis have come to the fore only in recent years. Knowledge about rare forms of myositis can aid in their recognition and treatment.

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.

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.

The effect of immunosuppressive therapy on cardiac involvements in anti-mitochondrial antibody-positive myositis

AIMS

Anti-mitochondrial antibody (AMA)-positive myositis is frequently associated with various cardiac involvements, such as arrhythmia and left ventricular (LV) dysfunction. However, the efficacy of immunosuppressive therapy in these complications remains unknown. This study aimed to investigate the cardiac response to immunosuppressive therapy in patients with AMA-positive myositis.

METHODS AND RESULTS

The clinical data of 15 AMA-positive myositis patients with cardiac involvement were retrospectively collected at our centre. To evaluate the effects of immunosuppressive therapy, echocardiographic and laboratory data of patients who received glucocorticoid therapy with additional immunosuppressants (n = 6) and those who did not (n = 6) were compared. Also, the characteristics of patients with or without >5% LV ejection fraction (LVEF) decline during the follow-up period (n = 5 vs. n = 7) were compared. Thirteen patients (87%) had arrhythmias, and eight patients (53%) had LV wall motion abnormalities. Although arrhythmias decreased after treatment, reduced LVEF and LV wall motion abnormalities persisted. Further investigation revealed an increased LV end-systolic dimension and reduced LVEF in patients without additional immunosuppressive therapy, while those in patients with additional immunosuppressive therapy were maintained. Six of seven patients (86%) without LVEF decline received additional immunosuppressive therapy, whereas no patients with LVEF decline had additional immunosuppressive therapy.

CONCLUSIONS

Cardiac involvement in AMA-positive myositis may worsen even with glucocorticoid monotherapy, and there might be some associations between the change of LV function and additional immunosuppressive therapy.

The Risk of Ventricular Tachyarrhythmias in Patients with Antimitochondrial Antibodies-Related Noncardiac Diseases

Antimitochondrial antibodies (AMA) are serum autoantibodies specific to primary biliary cholangitis and are linked to myopathy and myocardial damage; however, the presence of AMA as a risk factor for ventricular tachyarrhythmias (VTs) has remained unknown. This study aimed to elucidate whether the presence of AMA-related noncardiac diseases indicates VTs risk.This cohort study enrolled 1,613 patients (883 females) who underwent AMA testing to assess noncardiac diseases. The incidence of VTs and supraventricular tachyarrhythmias (SVTs) from a year before the AMA testing to the last visit of the follow-up were retrospectively investigated as primary and secondary objectives. Using propensity score matching, we extracted AMA-negative patients whose covariates were matched to those of 152 AMA-positive patients. In this propensity score-matched cohort, the incidence of VTs and SVTs in the AMA-positive patients were compared with that in AMA-negative patients.The AMA-positive patients had higher estimated cumulative incidence (log-rank, P = 0.013) and prevalence (5.9% versus 0.7%, P = 0.020) of VTs than the AMA-negative patients. The presence of AMA was an independent risk factor for VTs (hazard ratio, 4.02; 95% CI, 1.44-20.01; P = 0.005). Meanwhile, AMA were associated with atrial flutter and atrial tachycardia development. In AMA-positive patients, VTs were associated with male sex, underlying myopathy, high creatine kinase levels, presence of chronic heart failure or ischemic heart disease, left ventricular dysfunction, presence of SVTs, and the electrocardiographic parameters indicating atrial disorders.The presence of AMA-related noncardiac diseases is an independent risk factor for VTs.

Anti-mitochondrial antibodies in Indian patients with idiopathic inflammatory myopathies

AIMS

Anti-mitochondrial antibodies (AMAs) are associated with distinct clinical phenotypes including cardiac and hepatic manifestations in idiopathic inflammatory myopathies (IIMs). This article studies the prevalence, clinical characteristics and outcomes of AMA in Indian patients with IIM.

METHODS

Patients (97: 81 adult, 16 juvenile) clinically diagnosed with polymyositis or antibody-negative IIM were retrieved from the MyoCite bio-archive. They were tested for myositis-specific autoantibodies / myositis autoantibodies (MSAs/MAAs) using line immunoassay and antinuclear antibodies and AMAs using immunofluorescence assay (IFA). Patients were also screened for cardiac biomarkers (cardiac troponin I [c-TnI] and N terminal-pro brain natriuretic peptide [NT-pro-BNP] using immunometric immunoassay technique and enhanced chemiluminescence assay testing respectively) and hepatic manifestations using AMA testing. Results were formulated after carrying out analytical tests.

RESULTS

Of the cohort, 5 adults (6.2%) (M:F 0:1) with a median age and disease duration of 37 years and 2 months respectively, tested AMA+ while the children tested negative. Dermatomyositis was the commonest phenotype, with amyopathic forms being common, often with MSA positivity. Cancer-associated myositis and polymyositis were also seen. AMA positivity is associated with Gottron's sign and calcinosis. Comparable levels of C-TnI and NT-pro-BNP and AMA testing in patients help to rule out subclinical cardiac and hepatic involvement respectively.

CONCLUSION

Anti-mitochondrial antibodies are rare (6.2%) in different subtypes of IIM in the Indian population, and often coexist with MSAs. Their negative association with cardiac and hepatic involvement and probable association with Gottron's sign and calcinosis merit further investigation and long-term follow-up to understand the entire spectrum of the disease.

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-mitochondrial M2 antibody-positive myositis preceded by heart failure and cardiac conduction disturbance. A case report]

A 69-year-old man visited our hospital complaining of fatigue in the lower extremities while walking. The patient had a two-year history of congestive heart failure and received a permanent artificial pacemaker implantation for sick sinus syndrome. Physical examination revealed proximal muscle weakness and exaggerated lumbar lordosis. Serum creatine kinase level was 1,455 U/l. The atrophies of the paraspinal muscles at thoracic to lumbar spine levels, rectus abdominis and soleus muscles were detected on computed tomography. Muscle biopsy showed mild to moderate variability in muscle fiber size with regenerating and necrotic muscle fibers. Mononuclear cell infiltration was not found. HLA-ABC expression was minimum. After anti-mitochondrial M2 antibody was detected, administration of oral prednisolone resulted in improvements in muscle strength and serum creatine kinase level. Based on the clinical course, examination and clinical findings, the patient was diagnosed as anti-mitochondrial M2 antibody positive myositis. Anti-mitochondrial M2 positive myositis is not only difficult to diagnose by muscle biopsy, but can also be preceded or complicated by fatal cardiac complications.

Antimitochondrial Antibodies: from Bench to Bedside

Anti-mitochondrial antibodies (AMA) are directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes (PDC-E2) and are the typical biomarkers of primary biliary cholangitis (PBC), being present in 90-95% of patients, with increasing sensitivity at increasing titers. Albeit being highly specific for PBC diagnosis, AMA can be detected in less than 1% of healthy subjects, and thus the management subjects with no sign or symptom of liver disease is still a challenge and data concerning clinical risk of developing PBC in this subgroup of patients are controversial. Moreover, AMA can also be detected in patients affected by overlap syndrome, as well as hepatic diseases (i.e., NASH and viral hepatitis), while the association with autoimmune diseases, in particular Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus, is well established. Furthermore, new associations are being identified with inflammatory myositis and heart disease. AMA are directed towards the pyruvate dehydrogenase multi enzyme complex (PDC-E2) subunit, which represents an epithelial specific autoantigen for PBC. This review focuses on the main characteristics of AMA, their association with autoimmune diseases and liver diseases.

Inflammatory Myopathy Associated with Anti-mitochondrial Antibody Presenting Only with Respiratory Failure

A 56-year-old woman presenting with type II respiratory failure was transferred to our hospital. She did not exhibit muscle weakness or elevated serum myogenic enzymes, but needle electromyography revealed myogenic changes in the limb muscles, and her blood tests were positive for anti-mitochondrial antibodies (AMA). Muscle histopathological findings included immune-mediated necrotizing myopathy, so she was diagnosed with inflammatory myopathy associated with AMA. After treatment with corticosteroids and noninvasive positive pressure ventilation, her symptoms improved. If a diagnosis of type II respiratory failure is difficult, inflammatory myopathy associated with AMA should be considered as a differential diagnosis.

Life-threatening ventricular arrhythmia and left ventricular dysfunction associated with anti-mitochondrial antibody-positive myositis: a case report

BACKGROUND

Anti-mitochondrial antibody (AMA)-positive myositis is an atypical inflammatory myopathy characterized by chronic progression of muscle atrophy and cardiac involvement. Few detailed reports have shown the clinical course of the cardiac complications of AMA-positive myositis.

CASE SUMMARY

A 47-year-old man presented with shortness of breath on exertion. Cardiac dilatation was visible on chest X-ray, and echocardiography demonstrated diffuse hypokinesis with a reduced left ventricular (LV) ejection fraction of 30%. He had mild muscle weakness in the bilateral iliopsoas muscles, and his creatine kinase (CK) and anti-mitochondrial M2 antibody levels were elevated. A liver biopsy showed no findings of primary biliary cholangitis. Coronary angiography revealed normal coronary arteries. An endomyocardial biopsy showed interstitial fibrosis and marked degeneration of the mitochondria. Fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography showed circumferential abnormal accumulation in the LV myocardium, and he was diagnosed with cardiomyopathy associated with AMA-positive myositis. Optimal drug therapy for heart failure was started, and a cardiac resynchronization therapy-defibrillator was implanted. However, his cardiac function did not improve, and he was hospitalized due to ventricular tachycardia storm 5 years after the diagnosis. Ventricular tachycardia was terminated by radiofrequency catheter ablation on the LV-anterior papillary muscle. Steroid therapy was initiated and resulted in a decreased uptake of FDG and a normalized CK level at 3 months after his second discharge; however, LV systolic dysfunction remained 1 year later.

DISCUSSION

Anti-mitochondrial antibody-positive myositis can affect the myocardium and cause severe LV dysfunction and life-threatening ventricular arrhythmia over time.

KEYWORDS

Anti-mitochondrial antibody-positive myositis • Endomyocardial biopsy • Ventricular tachycardia • Left ventricular dysfunction • Case report • Magnetic resonance imaging • Near-infrared spectroscopy-intravascular ultrasound.

Myositis with Anti-mitochondrial Antibody Type 2 with Diplopia and Ptosis

Anti-mitochondrial antibody type 2 is a diagnostic marker of primary biliary cirrhosis and complicates myositis. Myositis with anti-mitochondrial antibody type 2 is clinically characterized by slowly progressive limb, cardiac, and respiratory muscle weakness as well as serum creatinine kinase elevations. However, there has been few cases with eye symptoms. We herein report a 59-year-old woman with anti-mitochondrial antibody type 2 who presented with diplopia and ptosis. Magnetic resonance imaging revealed bilateral ocular muscle enlargement and abnormally high intensities in the lower limb muscles. Corticosteroid therapy improved these symptoms. Myositis with anti-mitochondrial antibody type 2 can present with eye symptoms.

[Anti-striational antibodies detected in a patient with late-onset myasthenia gravis suffering from severe bradycardia: a case report]

We report herein the case of a 79-year-old woman who experienced difficulties in swallowing, dysarthria, dropped head, and muscle weakness associated with diurnal and day-to-day variation. We made a diagnosis of generalized myasthenia gravis (MG) with anti-acetylcholine receptor antibodies. Contrast-enhanced computed tomography showed no sign of thymoma. As the MG worsened, the patient presented with severe bradycardia. Chest compressions were performed on days 6 and 7 after admission and she underwent implantation of a temporary pacemaker. The arrhythmia resolved after strong immunosuppressive treatment, and anti-striational antibodies, including anti-muscular voltage-gated potassium channel-complex (Kv1.4) antibody and anti-titin antibody, were subsequently detected. This case implies the possible involvement of anti-striational antibodies in bradycardia.

Pathology Features of Immune and Inflammatory Myopathies, Including a Polymyositis Pattern, Relate Strongly to Serum Autoantibodies

We asked whether myopathology features of immune or inflammatory myopathies (IIM), without reference to clinical or laboratory attributes, correlate with serum autoantibodies. Retrospective study included 148 muscle biopsies with: B-cell inflammatory foci (BIM), myovasculopathy, perimysial pathology (IMPP), myofiber necrosis without perimysial or vessel damage or inflammation (MNec), inflammation and myofiber vacuoles or mitochondrial pathology (IM-VAMP), granulomas, chronic graft-versus-host disease, or none of these criteria. 18 IIM-related serum autoantibodies were tested. Strong associations between myopathology and autoantibodies included: BIM with PM/Scl-100 (63%; odds ratio [OR] = 72); myovasculopathies with TIF1-γ or NXP2 (70%; OR = 72); IMPP with Jo-1 (33%; OR = 28); MNec with SRP54 (23%; OR = 37); IM-VAMP with NT5C1a (95%; OR = 83). Hydroxymethylglutaryl-CoA reductase (HMGCR) antibodies related to presence of myofiber necrosis across all groups (82%; OR = 9), but not to one IIM pathology group. Our results validate characterizations of IIM by myopathology features, showing strong associations with some serum autoantibodies, another objective IIM-related marker. BIM with PM/Scl-100 antibodies can be described pathologically as polymyositis. Tif1-γ and NXP2 antibodies are both common in myovasculopathies. HMGCR antibodies associate with myofiber necrosis, but not one IIM pathology subtype. Relative association strengths of IIM-related autoantibodies to IIM myopathology features versus clinical characteristics require further study.

Ventricular arrhythmia predicts poor outcome in polymyositis/dermatomyositis with myocardial involvement

OBJECTIVE

Myocardial involvement (MCI) is known to increase morbidity and mortality in polymyositis (PM) and dermatomyositis (DM). This study aims to investigate whether complicating with ventricular arrhythmia (VA) predicts poor outcomes in patients with PM/DM-related myocardial involvement (PM/DM-MCI).

METHODS

We reviewed all PM/DM-MCI patients admitted to Peking Union Medical College Hospital from October 1997 to April 2019. VA and the other possible risk factors for the composite endpoint, including death from any cause and rehospitalization for cardiac causes, were analyzed.

RESULTS

A total of 75 PM/DM-MCI patients (44 PM and 31 DM) were enrolled, of which 27 (36%) met the composite endpoint during a median follow-up of 24 months. Independent prognostic factors for the composite endpoint include VA [HR 4.215, 95% CI (1.737, 10.230)], NT-proBNP > 3415 pg/ml [HR 2.606, 95% CI (1.203, 5.646)], interstitial lung disease [HR 2.688, 95% CI (1.209, 5.978)], and anti-cardiac remodelling therapy [HR 0.302, 95% CI (0.115, 0.792)]. The 3-year event-free survival rate of patients without VA was significantly higher than that of patients with VA (63.3% vs 40.7%, P = 0.034). Skin lesions [OR 0.163, 95% CI (0.051, 0.523)] and positive antimitochondrial antibody [OR 3.484, 95% CI (1.192, 10.183)] were independent predictors of VA.

CONCLUSION

VA provides prognostic insights for PM/DM-MCI patients and predicts poor outcome. Polymyositis and positive antimitochondrial antibody are closely associated with the presence of VA in PM/DM-MCI.

Defining cardiac involvement in idiopathic inflammatory myopathies: a systematic review

OBJECTIVE

Recent advances in cardiac magnetic resonance imaging (CMR) and other diagnostic techniques have made it easier to identify subclinical cardiac inflammation and dysfunction in the idiopathic inflammatory myopathies (IIM). Herein, we systematically review the literature regarding cardiac involvement in IIM.

METHODS

We searched Medline and EMBASE from 1990-2020 using keywords related to IIM and cardiac disease. We included English language studies in adults with any immune-mediated, inflammatory muscle pathology.

RESULTS

We identified 10425 potentially relevant abstracts, of which 29 were included. Most frequently these included patients with polymyositis or dermatomyositis without symptomatic myocarditis. Five categories of cardiac investigation were used in these patients: cardiac enzyme testing, electrocardiography (ECG), transthoracic echocardiography (TTE), CMR and nuclear medicine testing. Patients with clinical myocarditis had universally abnormal cardiac troponin levels and ECG. Elevated cardiac troponin T was more common than troponin I (cTnI) and may correlate with disease activity, whereas cTnI was more specific for cardiac involvement. Non-specific ECG changes were common. The major finding on TTE was abnormal ejection fraction. Gross systolic dysfunction was unusual, but subclinical systolic dysfunction was reported in several studies. Abnormal diastolic function was common and may be associated with disease duration. Late gadolinium enhancement (reflecting regional necrosis or scar) and abnormal myocardial mapping parameters (reflecting myocardial inflammation, fibrosis and oedema) were frequently identified on CMR, suggesting significant subclinical myocardial pathology (despite typically normal ejection fraction).

CONCLUSION

Abnormal cardiac investigations are commonly found in asymptomatic IIM patients, which has potential prognostic and treatment implications.

Myocardial involvement in idiopathic inflammatory myopathies: a multi-center cross-sectional study in the CRDC-MYO Registry

OBJECTIVES

This study aimed to investigate the associated factors of myocardial involvements (MIs) in patients with idiopathic inflammatory myopathies (IIMs).

METHODS

In this multi-center cross-sectional study, 1946 patients with IIMs were enrolled from Chinese Rheumatism Data Center-Myositis Registry (CRDC-MYO). A total of 108 (5.5%) patients were identified with MIs, including congestive heart failure (n = 67, 62.0%), and severe arrhythmias (n = 61, 56.5%). The other 1838 IIM patients without IMs were set as the control group. Clinical features were collected including age, gender, comorbidities, clinical symptoms, clinical signs of both IIMs and MIs, lab findings including myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs), echocardiogram, and radiological exams. Multivariate logistic analysis was used to explore independent associated factors of MIs in patients with IIMs.

RESULTS

Several independent associated factors were identified in multi-variate logistic regression, including positivity for anti-mitochondrial antibody-subtype 2 (AMA-M2) (OR 5.194, 95% CI 2.509-10.753, P < 0.001), elevation of creatine kinase (CK) (OR 2.611, 95% CI 1.312-5.198, P = 0.006), elevation of C-reactive protein (CRP) (OR 2.150, 95% CI 1.211-3.818, P = 0.001), and pulmonary hypertension (OR 4.165, 95% CI 1.765-9.882, P = 0.009). AMA-M2 and pulmonary hypertension were the most consistent associated factors in the polymyositis subgroup and the dermatomyositis/clinically amyopathic dermatomyositis subgroup.

CONCLUSIONS

MIs are rare but serious complication of IIMs could lead to congestive heart failure and severe arrhythmias. IIM patients with AMA-M2 positivity, elevation of CK and CRP, and pulmonary hypertension are more likely to develop MI complications. Key Points • This study investigated the independent associated factors for clinically significant myocardial involvements among idiopathic inflammatory myopathies in a large-scale, nation-wide multi-center cross-sectional study.

Muscle pathological features and extra-muscle involvement in idiopathic inflammatory myopathies with anti-mitochondrial antibody

OBJECTIVE

Anti-mitochondrial antibodies (AMAs) can be detected in some idiopathic inflammatory myopathy (IIM) patients. We aimed to investigate the clinical features of IIM patients with AMAs.

METHODS

We retrospectively analysed 1,167 consecutive patients with IIM for AMA-associated myositis and compared them to age- and gender-matched AMA-negative IIM patients.

RESULTS

Twenty-nine patients (2.5%) were identified with AMA-positive myositis; eight of them had primary biliary cholangitis (PBC). There were no significant differences in skin rash, dysphagia, interstitial lung disease, and muscle strength between AMA-positive patients and AMA-negative patients. Of 23 cases, 12 (52.2%) showed immune-mediated necrotizing myopathy (IMNM)-like pathological features. amongst AMA-positive patients, 11 of 16 patients with isolated anti-AMAs were classified as IMNM which was significantly higher than that of patients with coexistent anti-AMAs and myositis-specific antibodies (p = 0.026). Moreover, subclinical cardiac involvement was significantly more common in AMA-positive patients than in AMA-negative patients (21/29 VS 33/116, p<0.001). In addition, patients without PBC had a significantly higher incidence of abnormal echocardiography findings than that of patients with PBC (p = 0.009). Patients without heart abnormalities took significantly less time to achieve disease remission and prednisone tapering to <10 mg than patients with heart abnormalities (p = 0.000 and p = 0.001, respectively).

CONCLUSIONS

IMNM was a major histopathological finding in IIM patients with isolated AMAs. AMAs were significantly associated with subclinical cardiac involvement in IIM. PBC seemed to be a protective factor for abnormal echocardiography findings in AMA-positive patients. Patients without heart involvement took less time to achieve disease remission and prednisone tapering off.

Antimitochondrial Antibody-associated Myopathy with Slowly Progressive Cardiac Dysfunction

A 45-year-old woman was referred to our hospital for the evaluation of proximal muscle weakness and serum creatine kinase elevation [corrected]. She had atrial fibrillation and left ventricular asynergy. She was diagnosed with myopathy, accompanied by cardiomyopathy of unknown etiology. She was treated with prednisolone. After long-term follow-up and a detailed examination, the patient was diagnosed with antimitochondrial antibody (AMA)-associated myopathy with cardiac involvement. Although the patient received medical treatment, including beta-blockers and prednisolone, her cardiac function deteriorated progressively. Physicians should consider AMA-associated myopathy when diagnosing myopathies of unknown etiology. The presence of cardiac involvement should be proactively investigated in AMA-associated myopathy.

Cardiac arrest in anti-mitochondrial antibody associated inflammatory myopathy

Insight into predictors of cardiac involvement in inflammatory myopathies is sparse. A negative prognostic role of anti-mitochondrial antibodies (AMA) has been noticed and is supported by the current case. We describe a male patient who at the age 40 suffered a cardiac arrest and over the following months experienced progressive heart failure, arrhythmias and proximal muscle weakness. Clinical, genetic and serologic testing and repeated imaging- and histopathological investigations resulted in a diagnosis of AMA-associated, necrotizing, inflammatory myositis with cardiac involvement. Besides a cardiac resynchronization therapy defibrillator, heart failure and antiarrhythmic drugs the patient received successive immunosuppressants, which improved skeletal muscle strength but not cardiac disease progression. At age 45 he died from end-stage heart failure. Clinicians must be aware of AMA-associated myositis as a cause of unclarified heart disease, even in patients with initially sparse extra-cardiac manifestations. Further knowledge of treatment strategies is highly needed for this disease entity.