Dermatomyositis: Muscle Pathology According to Antibody Subtypes

MRI patterns of thigh muscle involvement in immune-mediated necrotizing myopathy and dermatomyositis

BACKGROUND

Immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM) are characterized by weakness, hyperCKemia, associated autoantibodies, and varying extramuscular manifestations. Muscle MRI, currently subordinate to histopathology and serology in idiopathic inflammatory myopathy (IIM) classification, has an evolving role. Our study aims to define thigh muscle MRI involvement in IMNM and DM by direct comparison.

METHODS

This single-center, retrospective, cross-sectional study included 25 participants, who met IIM classification criteria (14 IMNM, 11 DM) and had available thigh MRI. Clinical and paraclinical data were available and reviewed. 11 muscles were graded for edema on MRI using a semi-quantitative scale (0: normal, 1: <30% of muscle involvement, 2: 31-75%, 3: > 75%). For 3 participants with no significant muscle edema, muscle fatty infiltration was scored according to the same scale. Using linear mixed-effects models, muscle scores were compared between the two groups and a secondary analysis was performed of only edema scores, excluding the 3 participants with fatty infiltration scores.

RESULTS

The most affected muscles in IMNM were the semimembranosus (3.0 [2.7-3.0] {median [IQR]}), biceps femoris-long head (BF-LH) (2.7 [2.0-3.0]), and adductors (2.5 [2.0-3.0]). In DM, the most affected muscles were the vastus lateralis (2.7 [2.3-3.0]), vastus intermedius (2.9 [2.2-3.0]), vastus medialis (2.3 [1.7-2.7]), semitendinosus (2.2 [1.0-2.7]), rectus femoris (RF) (2.0 [1.0-2.8]), biceps femoris-short head (BF-SH) (1.9 [1.0-2.7]), gracilis, and sartorius. Intergroup statistical difference of scores was significant (p < 0.01) for 10/11 thigh muscles excluding the RF (p = 0.19), supporting an inverse relationship of muscle involvement for DM and IMNM. The secondary comparative analysis of only muscle edema scores was significant (p < 0.05) for the same 10/11 muscles with a consistent direction for all comparisons.

CONCLUSION

DM and IMNM affect disparate thigh muscles on MRI. DM preferentially affects the anterior thigh, semitendinosus and BF-SH in the posterior thigh, and gracilis in the medial thigh, whereas IMNM preferentially affects the posterior thigh (semimembranosus and BF-LH) and adductors in the medial thigh.

Circulating cell-free DNA promotes inflammation in dermatomyositis patients with anti-NXP2 antibodies via the cGAS/STING pathway

OBJECTIVES

DM is a rare type I IFN (IFN-I)-driven autoimmune disease, and anti-nuclear matrix protein 2 (NXP2) antibody is related to severe muscle disease and poor prognosis. Circulating cell-free DNA (ccf-DNA), including ccf-mitochondrial DNA and ccf-nuclear DNA, activates the cGAS/STING pathway to induce IFN-I production in autoimmune diseases. We investigated whether serum-derived ccf-DNA had a pathogenic effect on skeletal muscle in anti-NXP2 antibody-positive DM.

METHODS

Serum ccf-DNA levels were measured, and correlations between ccf-DNA and clinicopathological indicators were performed. RNA sequencing, immunofluorescence, western blotting and reverse transcriptase quantitative polymerase chain reaction were performed on skeletal muscle samples. The serum-induced expression of p-STING in C2C12 cells was assessed in vitro.

RESULTS

We found that increased ccf-DNA levels were positively correlated with MYOACT scores in anti-NXP2 antibody-positive DM. RNA sequencing and immunofluorescence results revealed that the cytosolic DNA-sensing pathway was upregulated and that increased cytosolic dsDNA was colocalized with cGAS in skeletal muscle in anti-NXP2 antibody-positive DM. Western blot analysis revealed activation of the cGAS/STING pathway in patients with perifascicular atrophy (PFA) but not in patients without PFA. Reverse transcriptase quantitative polymerase chain reaction showed increased IFN-I scores in both patients with PFA and patients without PFA. Sera from patients with PFA increased p-STING expression in C2C12 cells, and DNase I treatment and STING inhibitor efficiently inhibited p-STING expression, respectively.

CONCLUSION

Increased ccf-DNA levels may be potential biomarkers for monitoring disease activity in anti-NXP2 antibody-positive DM. Activation of the cGAS/STING pathway is associated with PFA. Our findings identified a pathogenic effect of ccf-DNA on skeletal muscle via the cGAS/STING pathway.

The role of monocytes and macrophages in idiopathic inflammatory myopathies: insights into pathogenesis and potential targets

Idiopathic inflammatory myopathies (IIMs) are heterogeneous autoimmune disorders characterized by muscle inflammation, weakness, and extramuscular manifestations such as interstitial lung disease, skin rash, arthritis, dysphagia, myocarditis and other systemic organ involvement. Although T and B cells have historically been central to the understanding of IIM immunopathology, monocytes and their differentiated progenitor cells, macrophages, are increasingly being recognized as critical mediators of both tissue damage and repair. In subtypes such as dermatomyositis, immune-mediated necrotizing myopathy and antisynthetase syndrome, macrophages infiltrate skeletal muscle and other affected tissues, contributing to inflammation via production of pro-inflammatory cytokines, chemokines, and reactive oxygen species. Dysregulated interferon signaling, mitochondrial stress, and aberrant metabolic states in these cells further perpetuate tissue injury in IIMs. Conversely, certain macrophage subsets can support muscle fiber regeneration and dampen inflammation, underscoring the dual roles these cells can play. Future research into the heterogeneity of monocytes and macrophages, including single-cell transcriptomic and metabolomic approaches, will help clarify disease mechanisms, identify biomarkers of disease activity and prognosis, and guide novel therapeutic strategies targeting these innate immune cells in IIM.

Emerging mechanisms and therapeutics in inflammatory muscle diseases

Idiopathic inflammatory myopathies (IIMs), or myositis, are rare diseases marked by immune-driven muscle damage and complications like skin lesions and interstitial lung disease (ILD). Despite advances, challenges in diagnosis and treatment persist, particularly in inclusion body myositis (IBM), where no effective therapy exists. Recent breakthroughs, including transcriptomics and insights into antibody-mediated immunity and interferon (IFN) signaling, have clarified IIM pathophysiology and spurred the development of new therapies, such as chimeric antigen receptor (CAR) T cells and Janus kinase (JAK) inhibitors. We explore the latest findings on the mechanisms underlying adult-onset IIMs, emphasizing IBM pathobiology and its unique immune and degenerative pathways, such as a selective type 2 myofiber damage and severe cell stress. Finally, we highlight the recent advances in transcriptomics, single-cell analysis, and machine learning in transforming IIM research by improving diagnostic accuracy, uncovering therapeutic targets, and supporting the development of personalized treatment strategies.

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.

A case of vesiculobullous dermatomyositis with anti-NXP-2 antibody without malignancy

Vesiculobullous dermatomyositis (VD) is a rare manifestation of dermatomyositis (DM) and has been suggested to be associated with malignancy. Although the myositis-specific autoantibodies are associated with distinct clinical presentations of DM, those associated with VD remain unclear. Here, we present the case of a 54-year-old man with VD who tested positive for antinuclear matrix protein 2 (NXP-2) antibodies, one of the DM-specific autoantibodies. Serological and histopathological findings did not support autoimmune blistering disease. Physical and histological findings suggested that the severe oedema in combination with the interface dermatitis of DM contributed to blister formation. Although a systemic examination was performed, no evidence of malignancy was found. Following initiation of immunosuppressive therapy, the patient showed significant improvement in both skin lesions and myositis. This case represents the first report of anti-NXP-2-positive VD without malignancy or autoimmune blistering disease. Subcutaneous oedema, a characteristic feature of anti-NXP-2-positive DM, could be related to the formation of VD.

Applicability of a serodiagnostic line blot for idiopathic inflammatory myopathy: the muscle biopsy is not all

Introduction

Differential diagnosis of rare idiopathic inflammatory myopathies (IIM) is mainly based on clinical aspects, muscle biopsy analysis, and auxiliary assays that determine myositis-specific and associated autoantibodies (MSA and MAA). While MSAs are considered specific for their respective IIM subclass, MAAs can be present in more than one subclass and in other conditions. This study compares results of a multispecific line blot assay with the final diagnosis of IIM patients based on clinical features and muscle biopsy to draw conclusions for the test's applicability in the diagnostic workflow.

Methods

Samples from patients (n = 50) diagnosed with various forms of IIM, including patients (n = 5) with other myopathies, were analyzed using the EUROLINE Autoimmune Inflammatory Myopathies 16 Ag (IgG), an anti-HMGCR (IgG) line blot, and the Anti-cN-1A ELISA (IgG, all EUROIMMUN).

Results

MSA and MAA were detected in 74.0% (37/50) of sera and were concordant with the final diagnosis in 64.8% (24/37), discordant in 16.2% (6/37) and not evaluable in 18.9% (7/37) of cases. In 100% (5/5) of patients with other myopathies, no MSA was found. MSA/MAA-co-positivity was observed in 18.0% (9/50) of patients. In 30.0% (15/50) of cases, the muscle biopsy analysis was essential to establish the final diagnosis.

Conclusion

The agreement between serodiagnostic results and final diagnosis highlights the applicability of the EUROIMMUN myositis-related diagnostic test as first line diagnostic tool in the IIM diagnosis workflow and suggests morphological analysis in cases of inconclusive or negative serology. However, results of diagnostic assays shall always be interpreted in combination with clinical features.

Development of differential diagnostic models for distinguishing between limb-girdle muscular dystrophy and idiopathic inflammatory myopathy

OBJECTIVE

Limb-girdle muscular dystrophy (LGMD) is usually confused with idiopathic inflammatory myopathy (IIM) in clinical practice. Our study aimed to establish convenient and reliable diagnostic models for distinguishing between LGMD and IIM.

METHODS

A total of 71 IIM patients, 24 LGMDR2 patients and 22 LGMDR1 patients diagnosed at our neuromuscular center were enrolled. Differences in clinical, laboratory and histopathological characteristics were comprehensively compared. A nomogram and a decision tree were developed to distinguish between LGMD and IIM patients.

RESULTS

Compared to patients with LGMD, IIM patients exhibited a significantly older age of onset, a higher prevalence of cervical flexor weakness and a more commonly diffuse MHC-I expression on muscle pathology. The ratio of synchronous serum myoglobin (Mb, ng/ml) to creatine kinase (CK, U/L) before immunotherapy was significantly higher in IIM patients than in LGMD patients. Receiver operating characteristic analysis indicated a high differential diagnostic efficiency of synchronous Mb/CK with a cutoff value of 0.18. A nomogram prediction model and a decision tree were developed based on four independent indicators (age of onset, cervical flexor weakness, synchronous Mb/CK and diffuse MHC-I expression). Five-fold cross-validation and bootstrapping techniques substantiated the discriminate efficacy of the nomograph and decision tree.

CONCLUSION

We developed two practical differential diagnosis models for LGMD and IIM based on the analysis of four accessible indicators, including the age of onset, cervical flexor weakness, the ratio of synchronous Mb/CK values and diffuse MHC-I expression. Further studies with larger samples are needed to refine the predictive efficiency of the differential diagnostic models.

Validation of the 2018 (New) ENMC Classification Criteria for Dermatomyositis in Chinese Patients with Idiopathic Inflammatory Myopathies

OBJECTIVES

To validate the 2018 European Neuromuscular Centre classification (ENMC) criteria, compare its performance to the 1975 Bohan & Peter (B&P) and 2017 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) criteria for dermatomyositis (DM), and describe characteristics of different myositis-specific autoantibody (MSA)-positive patients defined by the ENMC-DM criteria.

METHODS

Medical records and data on MSAs and muscle biopsies were retrospectively obtained from 1370 Chinese patients with idiopathic inflammatory myopathy (IIM) between 2008 and 2020. Patients were diagnosed with DM by at least two rheumatologists and classified according to the ENMC-DM, EULAR/ACR, and B&P criteria.

RESULTS

Of the 1370 patients, 857, 671, 693, and 913 were diagnosed with DM using the specialists' gold standard, ENMC-DM, EULAR/ACR, and B&P criteria, respectively. Significant between-group differences were observed in the clinical symptoms, serum creatine kinase levels, and MSAs (P < 0.05). Based on muscle biopsy data, the B&P criteria had the highest sensitivity (94%) but lowest specificity (65%). Without muscle biopsy data, the ENMC-DM criteria had the highest specificity (92%) but lowest sensitivity (61%). The sensitivity and specificity of the EULAR/ACR criteria were intermediate (72% and 86%, respectively) regardless of muscle biopsy data availability. With MSA data, the sensitivity and specificity of the ENMC-DM criteria were 73% and 91% and increased to 76% and 97%, respectively, with both muscle biopsy and MSA data.

CONCLUSIONS

The ENMC-DM criteria had higher specificity than the other criteria, especially in the absence of muscle biopsy data. Sensitivity and specificity improved when both muscle biopsy and MSA data were available. Key Points • Idiopathic inflammatory myopathy presents diagnostic challenges due to its variable features and dermatomyositis has distinct subtypes based on myositis-specific autoantibodies (MSAs) with unique clinical phenotypes. • This study validates the ENMC-DM criteria in Chinese patients and provides a comprehensive comparison with the B&P and EULAR/ACR criteria. • It demonstrates that the new ENMC-DM criteria exhibit higher specificity, especially noteworthy in cases without muscle biopsy, and the study further highlights the improved sensitivity and specificity when combining muscle biopsy and MSAs, offering a refined approach for accurate DM classification.

Contribution of major histocompatibility complex class II immunostaining in distinguishing idiopathic inflammatory myopathy subgroups: A histopathological cohort study

Idiopathic inflammatory myopathies (IIM) are rare, acquired muscle diseases; their diagnosis of is based on clinical, serological, and histological criteria. MHC-I-positive immunostaining, although non-specific, is used as a marker for IIM diagnosis; however, the significance of major histocompatibility complex (MHC)-II immunostaining in IIM remains debated. We investigated patterns of MHC-II immunostaining in myofibers and capillaries in muscle biopsies from 103 patients with dermatomyositis ([DM], n = 31), inclusion body myositis ([IBM], n = 24), anti-synthetase syndrome ([ASyS], n = 10), immune-mediated necrotizing myopathy ([IMNM], n = 18), or overlap myositis ([OM], n = 20). MHC-II immunostaining of myofibers was abnormal in 63/103 of patients (61%) but the patterns differed according to the IIM subgroup. They were diffuse in IBM (96%), negative in IMNM (83%), perifascicular in ASyS (70%), negative (61%) or perifascicular (32%) in DM, and either clustered (40%), perifascicular (30%), or diffuse heterogeneous (15%) in OM. Capillary MHC-II immunostaining also identified quantitative (capillary dropout, n = 47/88, 53%) and qualitative abnormalities, that is, architectural abnormalities, including dilated and leaky capillaries, (n = 79/98, 81%) in all IIM subgroups. Thus, MHC-II myofiber expression patterns allow distinguishing among IIM subgroups. We suggest the addition of MHC-II immunostaining to routine histological panels for IIM diagnosis.

Myositis-specific and myositis-associated autoantibodies: their clinical characteristics and potential pathogenic roles

In recent years, various myositis-specific and myositis-associated autoantibodies have been identified in idiopathic inflammatory myopathies, including dermatomyositis (DM), anti-synthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). These autoantibodies exhibit unique characteristics in terms of organ involvement, severity, and treatment response, making their understanding crucial for accurate diagnosis and effective therapy. This review provides a comprehensive overview of the clinical features of recently discovered myositis-specific and associated autoantibodies, while exploring their potential roles in the pathogenesis and exacerbation of myositis. Key findings include the production of anti-TIF1γ antibodies in model mice, the upregulation of Mi2-related genes in anti-Mi2 antibody-positive dermatomyositis muscle tissue, and Jo-1 antigen-induced T cell activation, shedding light on whether disease mechanisms are driven by autoantibodies or autoantigens.

Magnetic resonance imaging patterns revealing muscle pathology and clinical features in idiopathic inflammatory myopathies

OBJECTIVE

Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders significantly impacting skeletal muscles; however, the precise correlation between muscle magnetic resonance imaging (MRI) findings, muscle pathology, disease subtypes and clinical characteristics remains uncertain. Thus, we investigated the association of muscle MRI findings in IIMs with muscle pathology and clinical features.

METHODS

New-onset IIM patients underwent proximal upper and/or lower limb muscle MRI. Patterns of muscle oedema on MRI were categorised into fascial, honeycomb, peripheral, foggy, dense, or coarse dot patterns and compared with inflammatory cell infiltration sites in corresponding muscle biopsies. The incidence of MRI patterns was examined in patient subgroups using myositis-specific antibodies (MSAs) and 2017 EULAR/ACR classification criteria. Univariate and multivariate analyses were conducted to determine the odds ratios (ORs) of MRI findings for clinical characteristics.

RESULTS

Fifty-six of 85 patients underwent muscle biopsy. Foggy, honeycomb and fascial patterns at biopsy sites correlated with inflammatory cell infiltration in the endomysium (OR 11.9, P = 0.005), perimysium (OR 6.0, P = 0.014) and fascia (OR 16.9, P < 0.001), respectively. Honeycomb and foggy patterns were characteristic of patients with anti-TIF1γ or anti-Mi2 antibodies and MSA-negative dermatomyositis, and those with anti-SRP or anti-HMGCR antibodies and MSA-negative polymyositis (PM), respectively. The honeycomb pattern positively correlated with malignancy (OR 6.87, P < 0.001) and Gottron sign (OR 8.05, P = 0.002); the foggy pattern correlated with muscle weakness (OR 11.24, P = 0.005). The dense dot pattern was associated with dysphagia (OR 6.27, P = 0.006) and malignancy (OR 8.49, P = 0.002).

CONCLUSION

Muscle MRI holds promise in predicting muscle pathology, disease subtypes and clinical manifestations of IIMs.

Clinicopathological features and treatment outcome of juvenile idiopathic inflammatory myopathies with anti-melanoma differentiation associated gene 5 antibodies: A case series study

To characterize the clinicopathological features and treatment outcomes of juvenile idiopathic inflammatory myopathies (JIIM) with anti-melanoma differentiation associated gene 5 (MDA5) antibodies in a Chinese cohort. Anti-MDA5 antibody was detected by immunodot assay and indirect immunofluorescence assay on HEK293 cells in a series of Chinese JIIM cohort between 2005 and 2022. The clinical features, histological findings, and treatment outcomes of these anti-MDA5-antibody-positive patients were summarized. Of 59 JIIM patients, 3 (5.08%) were found to be anti-MDA5-antibody-positive. The frequency of anti-MDA5 antibody did not show significant difference between adult idiopathic inflammatory myopathies and JIIM cohorts (P = .720). The disease duration in patients with anti-MDA5 antibody was 2.83 ± 1.04 months. All 3 patients had typical skin lesions including Gottron sign and heliotrope rash, while interstitial lung disease and arthritis was only found in 1 patient. All 3 patients showed normal creatine kinase levels. On muscle biopsy, diffuse major histocompatibility complex class-I expression was seen in 3 patients and myxovirus-resistance protein A expression was found in 2 patients. All patients received long-term follow-up (6.42 ± 4.01 years). They were all drug-free and showed favorable treatment outcome with prednisone and additional immunosuppressant. Our study indicates that anti-MDA5 antibodies may not be common in Chinese JIIM. Anti-MDA5-positive JIIMs are characterized by typical skin lesions of dermatomyositis, normal CK levels, and increased major histocompatibility complex class-I expression. JIIMs with anti-MDA5 generally have good response to immunotherapies.

[Diagnosis of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis led by sarcoplasmic myxovirus resistance protein A expression on muscle pathology]

A 44-year-old woman with autism spectrum disorder developed bulbar symptoms and generalized muscle weakness 7 months before referral. Six months before, she was administered glucocorticoid for liver involvement. During the course, while she presented alopecia, skin ulcers, and poikiloderma, hyperCKemia was observed only twice. Due to complications including cardiac involvement and hearing loss as well, we suspected mitochondrial disease and performed a muscle biopsy. The muscle pathology showed sarcoplasmic myxovirus resistance A (MxA) expression with scattered pattern. Since anti-melanoma differentiation-associated gene 5 (MDA5) antibody was detected, we diagnosed the patient with anti-MDA5 antibody-positive dermatomyositis (DM). We reinforced immunosuppressive therapy, and her clinical symptoms and liver involvement were improved. When we diagnose a case of anti-MDA5 antibody-positive DM who is difficult to make clinical diagnosis, it may be valuable to evaluate sarcoplasmic MxA expression on muscle pathology.

Murine models of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are divided into polymyositis and dermatomyositis (DM) with specific cutaneous manifestation. Several myositis-specific autoantibodies (MSAs) have been identified in IIMs and were found to be associated with distinct clinical features, including anti-synthetase syndrome (ASyS) and immune-mediated necrotizing myopathy (IMNM). Moreover, MSA-related clinical features have been identified even within DM. Although MSAs are valuable for the diagnosis of IIMs, the pathogenic roles of these antibodies remain unknown. To investigate the pathogenesis of IIMs, classical murine models of autoimmune myositis, experimental autoimmune myositis, and C protein-induced myositis have been established by immunization with muscle-specific antigens, myosin, and myosin-binding skeletal C protein, respectively. To according to MSA-related autoimmunity, a murine model of ASyS was generated by immunization with a murine recombinant histidyl-transfer RNA (tRNA) synthetase, Jo-1, in which muscle and lung inflammation are induced depending on acquired immunity. Furthermore, it was found that the transfer of human Immunoglobulin G (IgGs) from patients with IMNM, comprising anti-signal recognition particles and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies, induced complement-mediated myositis in recipient mice. We found that CD8+ T cell-mediated myositis can be established depending on autoimmunity against transcriptional intermediary factor 1γ (TIF1γ), an autoantigen for MSAs induced by recombinant human TIF1γ immunization. These new murine models reflecting MSA-associated IIMs will reveal the immunological mechanisms underlying IIMs.

[Juvenile-onset anti-nuclear matrix protein 2 (NXP-2) antibody-positive dermatomyositis with joint contractures before manifestation of myositis: a case report]

A 23-year-old man was admitted to our hospital with a one-year history of muscle weakness and atrophy. He had noticed contractures of the fingers of both hands from the age of 18. Examination revealed a skin rash including heliotrope rash and Gottron's sign, joint contractures in the extremities, dysphagia, extensive muscle weakness and marked muscle atrophy. The serum creatine kinase level was 272 ‍IU/l and muscle biopsy showed typical perifascicular atrophy but little lymphocyte invasion. There was no interstitial pneumonia or malignancy, but muscle tendons showed elevated CT values suggesting calcification or fibrosis. Anti-nuclear matrix protein 2 (NXP-2) antibody-positive dermatomyositis was diagnosed on the basis of the serum antibody level. Methylprednisolone pulse therapy ameliorated the skin rash and bulbar palsy, but muscle weakness, atrophy and joint contractures were resistant to the treatment. There have been no previous reports of young adults with anti-NXP-2 antibody-positive dermatomyositis in whom joint contracture became evident as early as 4 years beforehand, which is a important feature for differential diagnosis of dermatomyositis.

Anti-NXP2 Antibody-positive Juvenile Dermatomyositis with Characteristic Fascial Thickening on Muscle Ultrasound and Improvement with Immunotherapy

We herein report a 12-year-old boy who presented with a fever, erythematous rash on the cheeks, back pain, and dysphagia. Blood tests revealed increased creatine kinase levels, and muscle ultrasonography (MUS) revealed characteristic fascial thickening in the lumbar paraspinal muscles, where myalgia was prominent. Sarcoplasmic expression of myxovirus-resistant protein A on a muscle biopsy and the presence of anti-nuclear matrix protein 2 (NXP2) antibodies confirmed the diagnosis of dermatomyositis. Prednisolone and intravenous immunoglobulin therapy improved the clinical and laboratory parameters as well as fascial thickening. MUS is useful for evaluating fasciitis associated with anti-NXP2 autoantibodies and monitoring therapeutic efficacy.

Elevated type I IFN signalling directly affects CD8+ T-cell distribution and autoantigen recognition of the skeletal muscles in active JDM patients

The link between type I IFN and adaptive immunity, especially T-cell immunity, in JDM still remained largely unclear. This study aimed to understand the effect of elevated type I IFN signaling on CD8+ T cell-associated muscle damage in juvenile dermatomyositis (JDM). This study used flow cytometry (FC) and RT‒PCR were used to examine the circulating cell ratio and type I IFN response. And scRNA-seq was used to examine peripheral immunity in 6 active JDM patients, 3 stable JDM patients, 3 juvenile IMNM patients and 3 age-matched healthy children. In vivo validation experiments were conducted using a mouse model induced by STING agonists and an experimental autoimmune myositis model (EAM). In vitro experiments were conducted using isolated CD8+ T-cells from JDM patients and mice. We found that active JDM patients showed an extensive type I IFN response and a decreased CD8+ T-cell ratio in the periphery (P < 0.05), which was correlated with muscle involvement (P < 0.05). Both new active JDM patients and all active JDM patients showed decreased CD8+ TCM cell ratios compared with age and gender matched stable JDM patients (P < 0.05). Compared with new pediatirc systemic lupus erythematosus (SLE) patients, new active JDM patients displayed decreased CD8+ T-cell and CD8+ TCM cell ratios (P < 0.05). Active JDM patient skeletal muscle biopsies displayed an elevated type I IFN response, upregulated MHC-I expression and CD8+ T-cell infiltration, which was validated in EAM mice. sc-RNAseq demonstrated that type I IFN signalling is the kinetic factor of abnormal differentiation and enhances the cytotoxicity of peripheral CD8+ T cells in active JDM patients, which was confirmed by in vivo and in vitro validation experiments. In summary, the elevated type I IFN signalling affected the differentiation and function of CD8+ T cells in active JDM patients. Skeletal muscle-infiltrating CD8+ T cells might migrate from the periphery under the drive of type I IFN and increased MHC I signals. Therapies targeting autoantigen-specific CD8+ T cells may represent a potential new treatment direction.

Baricitinib for anti-melanoma differentiation-associated protein 5 antibody-positive dermatomyositis-associated interstitial lung disease: a case series and literature review on Janus kinase inhibitors for the disease

Anti-melanoma differentiation-associated protein 5 antibody-positive dermatomyositis (anti-MDA5-DM) is frequently complicated by progressive interstitial lung disease (ILD), the prognosis of which is poor, and management is a major challenge. We treated three patients with anti-MDA5-DM-associated ILD (anti-MDA5-DM-ILD) using the Janus kinase (JAK) inhibitor, baricitinib, which improved lung opacities and saved two patients. We reviewed 6 patients with anti-MDA5-DM-ILD who had been treated with tofacitinib at our institution. Five of the patients survived, although discontinuation of tofacitinib due to complications was frequently observed. In addition, a literature search of patients with anti-MDA5-DM-ILD who were treated with JAK inhibitors yielded 21 articles involving 79 cases. All patients except one were treated with tofacitinib, and the survival rate was 75.9%. Although not statistically confirmed, the deceased patients tended to be older and had higher ferritin levels. A total of 92 complications were observed, 11 of which resulted in JAK inhibitor discontinuation. Cytomegalovirus reactivation comprised a substantial percentage of all complications and of those patients who required JAK inhibitor discontinuation. Five cases with fatal infective complications were also observed. While tofacitinib has been proposed to be a therapeutic option for anti-MDA5-DM-ILD, other JAK inhibitors, including baricitinib, are a treatment option. Further investigation is warranted to optimize treatment of anti-MDA5-DM-ILD.

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.

"Amyopathic" MDA5-positive dermatomyositis with severe lung involvement presenting with net myositic morphological features - insights from an autopsy study

Anti-MDA5-positive dermatomyositis (MDA5-DM) often presents with extramuscular, especially pulmonary and skin manifestations, and apparent clinical signs of frank myositis can be missing (so called amyopathic DM). We hereby present two male patients who died from respiratory failure during the course of MDA5-DM. While overt signs of myositis or any skin involvement were absent at admission to hospital we noticed conspicuous inflammatory alterations in various skeletal muscles morphologically, showing different degrees of affection. Furthermore, pathological changes of the lungs compatible with rapid progressive interstitial lung disease and characteristic cutaneous vasculoocclusive features were identified at autopsy. This observation shows that muscles and skin are subclinically affected in a widespread fashion, hence subtle signs of muscle involvement should be sought after in anti-MDA5-positive patients with predominant lung affection to ensure adequate treatment.

Clinical and immunological characteristics and prognosis of patients with autoantibody negative dermatomyositis: a case control study

OBJECTIVES

Myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs) are associated with distinctive dermatomyositis (DM) clinical phenotypes. The aim of this study is to explicate the clinical and immunological features of MSAs-negative DM patients.

METHODS

A total of 515 individuals diagnosed with DM was screened from 2013 to 2022 and 220 DM patients were enrolled in this retrospective cohort. Clinical and laboratory data of these patients were analyzed.

RESULTS

MSAs-negative DM patients were categorized into two groups: MAAs-negative (MSAs (-)/MAAs (-)) group and MAAs-positive (MSAs (-)/MAAs (+)) group. The percentage of Raynaud's phenomenon (P=0.026) was higher in the MSAs (-)/MAAs (+) DM patients than the MSAs-positive DM patients and MSAs (-)/MAAs (-) DM patients. The proportion of rapidly progressive interstitial lung disease (RP-ILD) in the MSAs-negative DM patients was lower than that in the MSAs-positive group. The MSAs (-)/MAAs (+) group had a higher proportion of organizing pneumonia and usual interstitial pneumonia (P=0.011), and elevated eosinophils in their bronchoalveolar lavage fluid (P=0.008). Counts of lymphocytes (P=0.001) and CD16+CD56+ natural killer (NK) cells (P=0.012) were higher in the MSAs-negative group. Additionally, the percentage of CD4+TNFα+ (P=0.040), CD4+IFNγ+ (P=0.037), and CD4+IL-2+ (P=0.018) cells among total CD4+ T cells were higher in the MSA-negative DM patients compared with the MSAs-positive DM patients. Besides, MSAs-negative patients demonstrated a more favorable prognosis than MSAs-positive patients. Multivariable regression analysis identified advanced onset age, higher level of carcinoembryonic antigen (CEA), and RP-ILD as risk factors for mortality in DM patients.

CONCLUSIONS

Compared with MSAs-positive group, MSAs-negative DM patients suffered less from organ involvement compared with MSAs-positive group and tend to have better prognosis. Key Points MSAs-negative DM patients exhibited distinct characteristics in comparison with MSAs-positive DM patients:   • The MSAs (-)/MAAs (+) DM patients demonstrated a higher prevalence of organizing pneumonia (OP) and usual interstitial pneumonia (UIP), and elevated eosinophil counts in bronchoalveolar lavage fluid.   • CEA levels were lower in MSAs-negative patients compared with MSAs-positive patients.   • Elevated counts of lymphocytes and CD16+CD56+ NK cells were identified in the MSAs-negative patients. Additionally, proportions of CD4+TNFα+, CD4+IFNγ+, and CD4+IL-2+ cells among total CD4+ T cells were higher in the MSAs-negative DM patients compared with DM MSAs-positive DM patients.   • MSAs-negative DM patients had a more favorable prognosis than MSAs-positive DM patients. A multivariable regression analysis revealed the advanced onset age, high CEA levels, and RP-ILD were risk factors for mortality in DM patients.

Clinicopathological features of graft versus host disease-associated myositis

BACKGROUND AND OBJECTIVE

Chronic graft versus host disease (GVHD)-associated myositis targeting skeletal muscle is a relatively rare but potentially debilitating complication following allogeneic hematopoietic stem cell transplantation (HSCT). We reviewed the clinicopathological features of GVHD-associated myositis among patients receiving allogeneic HSCT to elucidate the cellular pathogenesis.

METHODS

We retrospectively reviewed clinical data and muscle biopsy results from 17 consecutive patients diagnosed with GVHD-associated myositis at our institution between 1995 and 2019. Immunostaining findings of GVHD-associated myositis were compared to those of patients with anti-tRNA-synthetase antibody-associated myopathy (ASM) (n = 13) and dermatomyositis (DM) (n = 12).

RESULTS

The majority of patients with GVHD-associated myositis showed subacute or chronic progression of mild to moderate limb weakness together with elevated serum creatine kinase. These patients also exhibited mild C-reactive protein elevation but were negative for myositis-related autoantibodies. Programmed death-1 (PD-1)-positive cells were observed in muscle interstitium adjacent to myofibers expressing human leukocyte antigen (HLA)-DR. The interstitium was also HLA-DR-positive, similar to biopsy samples from ASM patients but not DM patients. The proportions of HLA-DR-positive muscle fibers and PD-1-positive interstitial cells were significantly higher in GVHD and ASM samples than DM samples. The PD-1-positive cells were mostly CD-8-positive lymphocytes.

DISCUSSION

GVHD-associated myositis is characterized by HLA-DR-positive myofibers and infiltration of PD-1-positive lymphocytes. These features distinguish GVHD-associated myositis from DM but not from ASM.

A case of anti-SAE1/2 antibody-positive dermatomyositis with extensive panniculitis: A possible cutaneous manifestation of treatment resistance

Dermatomyositis constitutes a heterogeneous group of autoimmune inflammatory conditions with a wide variety of clinical outcomes. The symptomatic heterogeneity carries skin, muscle, and joint manifestations; pulmonary and cardiac involvements; and concomitant malignancy. Any of these symptoms often appear at different combinations and time courses, thus posing difficulty in early diagnosis and appropriate treatment choice. Recent progress in laboratory investigations explored the identification of several myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies, allowing precise characterization for a clinical perspective of the disease. MSAs can be detectable in approximately 80% of patients with whole dermatomyositis, some of which closely reflect unique clinical features in the particular disease subset(s), including the distribution and severity of organ involvement, treatment response, and prognosis. However, only limited evidence has been available in dermatomyositis-associated panniculitis, mostly that in anti- melanoma differentiation-associated protein 5 antibody-positive disease. We present a rare case of a patients with dermatomyositis with extensive panniculitis on the trunk whose serum IgG autoantibodies reacted with both subunits of small ubiquitin-like modifier activating enzymes (SAEs), SAE1 and SAE2. The onset of panniculitis coincided with increased disease activity, including disease-related skin manifestations, fever, dysphagia, and muscle weakness in the extremities. These symptoms responded well to a high dose of systemic steroid, but even upon receiving a high-dose intravenous immunoglobulin, the panniculitic lesions and pruritic erythema flared with tapering of steroid dose, further requiring tacrolimus and mycophenolate mofetil to achieve disease remission. To our knowledge, this is the third reported case of anti-SAE autoantibody-positive dermatomyositis with panniculitis. We aim to extend the understanding of the current limitation and further perspective in the clinical management of the extremely rare skin manifestation associated with dermatomyositis.

Disease spectrum of myopathies with elevated aldolase and normal creatine kinase

BACKGROUND AND PURPOSE

Elevation of serum creatine kinase (CK) or hyperCKemia is considered a biological marker of myopathies. However, selective elevation of serum aldolase with normal CK has been reported in a few myopathies, including dermatomyositis, immune-mediated myopathy with perimysial pathology and fasciitis with associated myopathy. The aim was to investigate the disease spectrum of myopathies with isolated aldolase elevation.

METHODS

Medical records were reviewed to identify patients >18 years old seen between December 1994 and June 2020 who had pathologically proven myopathies with elevated aldolase and normal CK level. Patients with alternative causes of aldolase elevation were excluded.

RESULTS

Thirty-four patients with various types of myopathies were identified. Myopathies were treatable in 27 patients. The three most common etiologies were dermatomyositis (n = 8), overlap myositis (n = 4) and nonspecific myopathy (n = 4). Perimysial pathology comprising inflammation, fragmentation, vasculitis, calcified perimysial vessels or extracellular amyloid deposition was found in 17/34 patients (50%). Eight dermatomyositis patients with selective elevated aldolase were compared to 24 sex- and age-matched patients with dermatomyositis and hyperCKemia. Dermatomyositis patients with normal CK significantly (p < 0.05) had less frequent cutaneous involvement (50.0% vs. 100.0%) and fibrillation potentials (50.0% vs. 90.5%) but higher median erythrocyte sedimentation rate (33.5 vs. 13.5 mm/h) and more common perifascicular mitochondrial pathology (37.5% vs. 4.2%).

CONCLUSION

Isolated aldolase elevation can be found in a greater variety of myopathies than initially thought and most were treatable. Dermatomyositis is the most common myopathy with selective elevation of aldolase in our cohort, which features some unique characteristics compared to dermatomyositis with hyperCKemia.

Myofascial edema of gastrocnemius: A prominent MRI characteristic in dermatomyositis patients with anti-transcriptional intermediate factor 1-γ antibody

AIMS

This study was designed to evaluate the magnetic resonance imaging (MRI) patterns of the lower limb muscles in dermatomyositis (DM) with anti-transcriptional intermediate factor 1-γ (anti-TIF1-γ) antibody.

METHODS

This retrospective, observational, cross-sectional study enrolled 12 adult DM patients with anti-TIF1-γ antibody. Muscles were assessed for fascial edema, subcutaneous-tissue edema, muscle edema, and fatty replacement. These features were analyzed in relation to clinical characteristics.

RESULTS

All 12 patients underwent hip and thigh MRI, and 8 completed calf MRI. All patients showed myofascial edema, muscle edema, and fatty replacement, and 8 out of 12 further exhibited subcutaneous-tissue edema. Specifically, myofascial edema of the gastrocnemius was observed in all patients (8/8). The vastus intermedialis and vastus lateralis muscles showed the most severe muscle edema, whereas the caput breve of the biceps femoris, semitendinosus, and soleus muscles exhibited the most severe fatty replacement. Although only 1 patient exhibited asymmetric muscle weakness, 9 showed asymmetric muscle edema, and 10 showed asymmetric fatty replacement. Changes in muscle edema positively correlated with creatine kinase (CK) levels.

CONCLUSIONS

Myofascial edema of gastrocnemius was a prominent characteristic of anti-TIF1-γ-positive DM. Early detection of muscle edema, as well as CK levels, may be helpful for monitoring disease activity.

Complement and MHC patterns can provide the diagnostic framework for inflammatory neuromuscular diseases

Histopathological analysis stands as the gold standard for the identification and differentiation of inflammatory neuromuscular diseases. These disorders continue to constitute a diagnostic challenge due to their clinical heterogeneity, rarity and overlapping features. To establish standardized protocols for the diagnosis of inflammatory neuromuscular diseases, the development of cost-effective and widely applicable tools is crucial, especially in settings constrained by limited resources. The focus of this review is to emphasize the diagnostic value of major histocompatibility complex (MHC) and complement patterns in the immunohistochemical analysis of these diseases. We explore the immunological background of MHC and complement signatures that characterize inflammatory features, with a specific focus on idiopathic inflammatory myopathies. With this approach, we aim to provide a diagnostic algorithm that may improve and simplify the diagnostic workup based on a limited panel of stainings. Our approach acknowledges the current limitations in the field of inflammatory neuromuscular diseases, particularly the scarcity of large-scale, prospective studies that validate the diagnostic potential of these markers. Further efforts are needed to establish a consensus on the diagnostic protocol to effectively distinguish these diseases.

Severe gastrointestinal involvements in patients with adult dermatomyositis with anti-NXP2 antibody

OBJECTIVE

Gastrointestinal (GI) involvements were scarcely reported in adult anti-nuclear matrix protein 2 (NXP2) dermatomyositis (NXP2+DM). In this study, we investigated the clinical, pathological and molecular features as well as treatment options of this rare yet life-threatening disease.

METHODS

We retrospectively collected the data of the cohort of NXP2+ DM from 2012 to 2022 in our hospital. RNA sequencing was performed in intestinal samples of perforated patients compared with healthy controls data set.

RESULTS

A total of 56 patients with adult NXP2+DM were collected including 10 cases with GI involvements. Abdominal pain and melena were the initial manifestations for GI involvements with a median 10-month time lag after the diagnosis of NXP2+DM when myositis largely subsided. Within weeks, GI perforation occurred in 8 of 10 patients, while five patients underwent eight surgical interventions subsequently. The short-term mortality was observed in four patients. NXP2+DM with GI involvements presented with more extramuscular systemic manifestations such as interstitial lung disease and subcutaneous calcinosis. The GI pathological features encompassed vasculitis/vasculopathy with high MxA expression, intestinal smooth muscle necrosis and serosal calcinosis. Gene expression profile validated the type-I interferon activation and revealed that epithelial mesenchymal transition and focal adhesion pathway may also contribute. Finally, vedolizumab, an anti-α4β7-integrin monoclonal antibody, exhibited promising therapeutic signals which should be further investigated.

CONCLUSIONS

GI involvement is a unique complication in patients with adult NXP2+DM. Timely recognition and targeted therapy may turn out to be lifesaving.

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.

[Two cases of anti-nuclear matrix protein 2 antibody-positive dermatomyositis sine dermatitis with severe diffuse subcutaneous edema and dysphagia]

Case 1 involved a 68-year-old woman who was admitted to our hospital because of muscle weakness, diffuse subcutaneous edema, dysphagia, and an elevated serum creatine kinase level that had worsened within the previous month. Case 2 involved a 78-year-old woman who was admitted to our hospital because of muscle weakness, bilateral shoulder pain, diffuse subcutaneous edema, and dysphagia that had gradually worsened during the past 5 months. Both patients showed severe diffuse subcutaneous edema and dysphagia and underwent enteral tube feeding. Although they had no skin lesions consistent with dermatomyositis, muscle biopsies showed myxovirus resistance protein A (MxA) expansion, and blood tests showed positivity for anti-nuclear matrix protein 2 (anti-NXP-2) antibody. Therefore, both presents were diagnosed with anti-NXP-2 antibody-positive dermatomyositis sine dermatitis (DMSD). Anti-NXP-2 antibody-positive dermatomyositis has been reported to be closely associated with DMSD, severe edema and dysphagia. Differential diagnosis for patients who develop myositis with severe subcutaneous edema and dysphagia should include anti-NXP-2 antibody-positive dermatomyositis, and it is important to consider measurement of anti-NXP-2 antibody.

Distinct HLA associations with autoantibody-defined subgroups in idiopathic inflammatory myopathies

BACKGROUND

In patients with idiopathic inflammatory myopathies (IIM), autoantibodies are associated with specific clinical phenotypes suggesting a pathogenic role of adaptive immunity. We explored if autoantibody profiles are associated with specific HLA genetic variants and clinical manifestations in IIM.

METHODS

We included 1348 IIM patients and determined the occurrence of 14 myositis-specific or -associated autoantibodies. We used unsupervised cluster analysis to identify autoantibody-defined subgroups and logistic regression to estimate associations with clinical manifestations, HLA-DRB1, HLA-DQA1, HLA-DQB1 alleles, and amino acids imputed from genetic information of HLA class II and I molecules.

FINDINGS

We identified eight subgroups with the following dominant autoantibodies: anti-Ro52, -U1RNP, -PM/Scl, -Mi2, -Jo1, -Jo1/Ro52, -TIF1γ or negative for all analysed autoantibodies. Associations with HLA-DRB1∗11, HLA-DRB1∗15, HLA-DQA1∗03, and HLA-DQB1∗03 were present in the anti-U1RNP-dominated subgroup. HLA-DRB1∗03, HLA-DQA1∗05, and HLA-DQB1∗02 alleles were overrepresented in the anti-PM/Scl and anti-Jo1/Ro52-dominated subgroups. HLA-DRB1∗16, HLA-DRB1∗07 alleles were most frequent in anti-Mi2 and HLA-DRB1∗01 and HLA-DRB1∗07 alleles in the anti-TIF1γ subgroup. The HLA-DRB1∗13, HLA-DQA1∗01 and HLA-DQB1∗06 alleles were overrepresented in the negative subgroup. Significant signals from variations in class I molecules were detected in the subgroups dominated by anti-Mi2, anti-Jo1/Ro52, anti-TIF1γ, and the negative subgroup.

INTERPRETATION

Distinct HLA class II and I associations were observed for almost all autoantibody-defined subgroups. The associations support autoantibody profiles use for classifying IIM which would likely reflect underlying pathogenic mechanisms better than classifications based on clinical symptoms and/or histopathological features.

FUNDING

See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript.

Intramuscular lesions in musculoskeletal MRI as a favourable prognostic sign in patients with anti-MDA5 antibody-positive dermatomyositis

OBJECTIVES

Anti-differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis, which has been described as clinically amyopathic dermatomyositis, complicates rapidly progressive interstitial lung disease (ILD). Owing to the absence of significant muscle symptoms, musculoskeletal MRI is often not performed. In this study, we aimed to devise a simple evaluation method using musculoskeletal MRI findings to elucidate the relationship between MRI findings and ILD prognosis and development.

METHODS

The medical records and MRI scans of the proximal muscles at the time of diagnosis were retrospectively reviewed for 28 patients with anti-MDA5 antibody-positive dermatomyositis who were admitted to The Jikei University Hospital and The Jikei University Kashiwa Hospital between January 2008 and March 2022. Three observers evaluated nine proximal muscles for high signals on either short-tau inversion recovery images and/or fat-saturated gadolinium-enhanced T1-weighted images in the fascia and/or in the margins of the muscles in contact with the fascia (fascial pattern), and/or high signals in the muscles away from the fascia (intramuscular pattern), and a consensus was reached.

RESULTS

Of the 28 patients, 15 presented with 'radiological myositis', where an intramuscular pattern was observed at any site. Patients with radiological myositis had significantly higher survival rates than those without radiological myositis, despite the lower rate of triple therapy with prednisolone, calcineurin inhibitors and cyclophosphamide. The spread of ILD on chest CT negatively and significantly correlated with the proportion of intramuscular lesions.

CONCLUSION

The detection of intramuscular lesions on musculoskeletal MRI using our novel evaluation method could be clinically useful as a favourable prognostic marker.

Symptomatic myopathies in sarcoidosis: disease spectrum and myxovirus resistance protein A expression

OBJECTIVES

Symptomatic myopathy in sarcoidosis patients is not always due to sarcoid myopathy (ScM). We investigated the clinical and pathological spectrum including myxovirus resistance protein A (MxA) expression among sarcoidosis patients.

METHODS

We reviewed the Mayo Clinic database (May 1980-December 2020) to identify sarcoidosis patients with myopathic symptoms and pathological evidence of myopathy.

RESULTS

Among 5885 sarcoidosis patients, 21 had symptomatic myopathy. Eight carried a diagnosis of sarcoidosis 5.5 years (median) prior to myopathy onset. Eleven patients had ScM. The remaining had non-sarcoid myopathies (five IBM, one immune-mediated necrotizing myopathy, one non-specific myositis, two non-specific myopathy and one steroid myopathy). Estimated frequency of IBM is 85 per 100 000 sarcoidosis patients. The following features were associated with non-sarcoid myopathies (P < 0.05): (i) predominant finger flexor and quadriceps weakness, (ii) modified Rankin scale (mRS) >2 at time of diagnosis, (iii) creatine kinase >500 U/l, and (iv) absence of intramuscular granulomas. Sarcoplasmic MxA expression was observed in scattered myofibres in three patients, two of whom were tested for DM-specific autoantibodies and were negative. Immunosuppressive therapy led to improvement in mRS ≥1 in 5/10 ScM, none of the five IBM, and 3/3 remaining patients with non-sarcoid myopathies.

DISCUSSION

Symptomatic myopathy occurred in 0.36% of sarcoidosis. IBM was the second most common cause of myopathies after ScM. Frequency of IBM in sarcoidosis is higher than in the general population. Recognition of features suggestive of alternative aetiologies can guide proper treatment. Our findings of abnormal MxA expression warrant a larger study.

Incorporating circulating cytokines into the idiopathic inflammatory myopathy subclassification toolkit

Extensive diagnostic delays and deferred treatment impact the quality of life of patients suffering from an idiopathic inflammatory myopathy. In-depth subtyping of patients is a necessary effort to engage appropriate disease management and may require specialized and elaborate evaluation of the complex spectrum of clinical and pathological disease features. Blood samples are routinely taken for diagnostic purposes, with creatine kinase measurement and autoantibody typing representing standard diagnostic tools in the clinical setting. However, for many patients the diagnostic odyssey includes the invasive and time-consuming procedure of taking a muscle biopsy. It is proposed that further implementation of blood-based disease biomarkers represents a convenient alternative approach with the potential to reduce the need for diagnostic muscle biopsies substantially. Quantification of judicious combinations of circulating cytokines could be added to the diagnostic flowchart, and growth differentiation factor 15 and C-X-C motif chemokine ligand 10 come forward as particularly good candidates. These biomarkers can offer complementary information for diagnosis indicative of disease severity, therapeutic response and prognosis.

Muscle pathology of antisynthetase syndrome according to antibody subtypes

Identification of antisynthetase syndrome (ASS) could be challenging due to inaccessibility and technical difficulty of the serology test for the less common non-Jo-1 antibodies. This study aimed to describe ASS antibody-specific myopathology and evaluate the diagnostic utility of myofiber HLA-DR expression. We reviewed 212 ASS muscle biopsies and compared myopathologic features among subtypes. Additionally, we compared their HLA-DR staining pattern with 602 non-ASS myositis and 140 genetically confirmed myopathies known to have an inflammatory component. We used t-test and Fisher's exact for comparisons and used sensitivity, specificity, positive and negative predictive values to assess the utility of HLA-DR expression for ASS diagnosis. RNAseq performed from a subset of myositis cases and histologically normal muscle biopsies was used to evaluate interferon (IFN)-signaling pathway-related genes. Anti-OJ ASS showed prominent myopathology with higher scores in muscle fiber (4.6 ± 2.0 vs. 2.8 ± 1.8, p = 0.001) and inflammatory domains (6.8 ± 3.2 vs. 4.5 ± 2.9, p  = 0.006) than non-OJ ASS. HLA-DR expression and IFN-γ-related genes upregulation were prominent in ASS and inclusion body myositis (IBM). When dermatomyositis and IBM were excluded, HLA-DR expression was 95.4% specific and 61.2% sensitive for ASS with a positive predictive value of 85.9% and a negative predictive value of 84.2%; perifascicular HLA-DR pattern is common in anti-Jo-1 ASS than non-Jo-1 ASS (63.1% vs. 5.1%, p < 0.0001). In the appropriate clinicopathological context, myofiber HLA-DR expression help support ASS diagnosis. The presence of HLA-DR expression suggests involvement of IFN-γ in the pathogenesis of ASS, though the detailed mechanisms have yet to be elucidated.

Murine models of idiopathic inflammatory myopathy

Idiopathic inflammatory myopathies (IIMs) are characterized by inflammation of muscles and other organs. Several myositis-specific autoantibodies (MSAs) have been identified in IIMs and were found to be associated with distinct clinical features. Although MSAs are valuable for the diagnosis of IIMs, the pathogenic roles of these antibodies remain unknown. To investigate the pathogenesis of IIMs, several animal models of experimental myositis have been established. Classical murine models of autoimmune myositis, experimental autoimmune myositis, and C protein-induced myositis are established by immunization with muscle-specific antigens, myosin, and skeletal C protein, respectively. Furthermore, a murine model of experimental myositis was generated by immunization with a murine recombinant histidyl-tRNA synthetase, Jo-1, in which muscle and lung inflammation reflecting anti-synthetase syndrome are induced depending on acquired immunity. Recently, the transfer of human IgGs from patients with immune-mediated necrotizing myopathy, comprising anti-signal recognition particles and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies, was found to induce complement-mediated myositis in recipient mice. CD8⁺ T cell-mediated myositis can be established depending on autoimmunity against transcriptional intermediary factor 1γ (TIF1γ), an autoantigen for MSAs induced by recombinant human TIF1γ immunization. These new murine models reflecting MSA-related IIMs are useful tools for accurately understanding the pathological mechanisms underlying IIMs.

[Neuropathology I: muscular diseases]

Muscle diseases include hereditary and acquired diseases with clinical manifestation in both childhood and adulthood. The different muscle diseases may have ultrastructural alterations that help us further understand the pathology of the disease. Specific changes in sarcomere structure help to classify a congenital myopathy. The detection of cellular aggregates supports the classification of myositis. Pathologically altered mitochondria, on the other hand, can occur both in genetic mitochondriopathies but also secondarily in acquired muscle diseases like myositis. Ultrastructural analysis of the myocardium is also helpful in the diagnosis of hereditary cardiomyopathies in childhood. This review article highlights the ultrastructural features of different muscle diseases and pathognomonic findings in specific disease groups.

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.

Autoimmune inflammatory myopathies

The autoimmune inflammatory myopathies constitute a heterogeneous group of acquired myopathies that have in common the presence of endomysial inflammation and moderate to severe muscle weakness. Based on currently evolved distinct clinical, histologic, immunopathologic, and autoantibody features, these disorders can be best classified as dermatomyositis, necrotizing autoimmune myositis, antisynthetase syndrome-overlap myositis, and inclusion body myositis. Although polymyositis is no longer considered a distinct subset but rather an extinct entity, it is herein described because its clinicopathologic information has provided over many years fundamental information on T-cell-mediated myocytotoxicity, especially in reference to inclusion body myositis. Each inflammatory myopathy subset has distinct immunopathogenesis, prognosis, and response to immunotherapies, necessitating the need to correctly diagnose each subtype from the outset and avoid disease mimics. The paper describes the main clinical characteristics that aid in the diagnosis of each myositis subtype, highlights the distinct features on muscle morphology and immunopathology, elaborates on the potential role of autoantibodies in pathogenesis or diagnosis , and clarifies common uncertainties in reference to putative triggering factors such as statins and viruses including the 2019-coronavirus-2 pandemic. It extensively describes the main autoimmune markers related to autoinvasive myocytotoxic T-cells, activated B-cells, complement, cytokines, and the possible role of innate immunity. The concomitant myodegenerative features seen in inclusion body myositis along with their interrelationship between inflammation and degeneration are specifically emphasized. Finally, practical guidelines on the best therapeutic approaches are summarized based on up-to-date knowledge and controlled studies, highlighting the prospects of future immunotherapies and ongoing controversies.

Comparison of cytokine/chemokine profiles between dermatomyositis and anti-synthetase syndrome

Objectives

Dermatomyositis (DM) and anti-synthetase syndrome (ASS) are autoimmune diseases with multisystem involvement. Despite sharing some clinical and myopathological features, these are two diseases with different pathogeneses and prognoses. We aimed to clarify and compare cytokine/chemokine profiles in both disorders, which may help in the differential diagnosis.

Materials and methods

We collected clinical data and serum samples of consecutive patients with DM and ASS. Quantibody^® Human Inflammation Array 3 for cytokines/chemokines was performed in the serum of all participants. Receiver operating characteristic analysis with the area under the curve and Youden's index were performed.

Results

Eight newly diagnosed and treatment-naïve patients with DM, nine newly diagnosed and treatment-naïve patients with ASS, and 14 healthy controls were enrolled. Serum C-C motif chemokine ligand (CCL) 2, CCL4, C-X-C motif chemokine ligand (CXCL) 13, and tumor necrosis factor receptor 2 (TNFR2) were increased in patients with both DM and ASS. Serum interleukin (IL)-1 receptor type 1 (IL-1ra), IL-1b, CCL1, CXCL11, and CCL3 were modulated in patients with DM only, and IL-8, CXCL9, and tissue inhibitors of metalloproteinases-1 (TIMP-1) in patients with ASS only. Serum CCL2, CXCL13, and TNFR2 accurately distinguished patients with DM and ASS from healthy controls, as shown by the area under the curve >0.80. Moreover, receiver operating characteristic analysis showed that, as biomarkers for discrimination between DM and ASS, the combination of IL-1ra and TIMP-1, had an area under the curve of 0.944, a sensitivity of 87.5%, and a specificity of 88.9%.

Conclusion

Our study demonstrated that serum levels of cytokines/chemokines showed a different pattern in newly diagnosed patients with DM and ASS, in which serum IL-1ra and TIMP-1 could be used to distinguish between the two diseases.

Update on dermatomyositis

PURPOSE OF REVIEW

This review summarizes and comments on current knowledge in dermatomyositis.

RECENT FINDINGS

The 2018 European Neuromuscular Centre classification of dermatomyositis has been challenging by the discovery of clinicopathological features associated with dermatomyositis-specific antibody (DMSA) that were not incorporated in the original criteria. These features include but may not be limited to the presence of perifascicular necrosis in anti-Mi-2 dermatomyositis; presence of diffuse nonperifascicular sarcoplasmic myxovirus resistance protein A expression in anti-MDA5 dermatomyositis; and dermatomyositis sine dermatitis in anti-NXP-2 dermatomyositis. Variations and subclassifications within the same DMSA subtypes are observed: anti-MDA5 dermatomyositis is clinically subcategorized into good, intermediate, and poor prognostic subgroups; concurrent anti-CCAR1 and anti-TIF1-γ positivity identify anti-TIF1-γ-positive patient with a lower risk for cancer-associated myositis. Owing to distinct IFN1-signaling pathway activation in dermatomyositis, JAK-STAT inhibitor - the pathway-targeted therapy, have been studied with promising results in refractory dermatomyositis and some new-onset dermatomyositis. In addition, the potential serum biomarkers for IFN1 pathway activation are being investigated for their performance in monitoring the disease activity and the efficacy of the treatment.

SUMMARY

DMSA, evidence of prominent IFN1 pathway activation, and risk/severity-associated biomarkers would likely play major roles in future dermatomyositis classification, disease monitoring, and treatment decision.

What Is in the Myopathy Literature?

ABSTRACT

We cover intensive care unit-acquired neuromuscular disorders associated with coronavirus disease 2019. Outcomes may be worse than expected in these patients, and there is some evidence that coronavirus disease 2019 causes myopathy directly. Corticosteroid regimens in Duchenne muscular dystrophy are addressed including outcomes in pulmonary and cardiac function. A recent article notes a continued diagnostic delay in Duchenne muscular dystrophy. An interesting report of a Canary Islands cohort of patients with oculopharyngeal muscular dystrophy is discussed. Features and clinical pearls related to a series of patients with limb-girdle muscle dystrophy R12 (anoctaminopathy) and a misdiagnosis of idiopathic inflammatory myopathy are provided. The last section on autoimmune myopathy includes articles on clinical and pathologic features associated with myositis-specific antibodies and dermatomyositis, the epidemiology of immune-mediated necrotizing myopathies (IMNMs) in Olmsted County, Minnesota, and features of a German cohort of hydroxy-3-methylglutaryl coenzyme A reductase-associated IMNM. A recent article proposes the benefit of early intravenous immunoglobulin use for adults with IMNM. We also highlight a report of 2 unusual cases of antisignal recognition particle myopathy presenting with asymmetric distal weakness.

High prevalence of necrotizing myofibers in adult dermatomyositis muscle biopsies

INTRODUCTION/OBJECTIVES

This study aimed to analyze the presence, grade, and relevance of myofiber necrosis in the muscle tissues of patients with adult dermatomyositis. Second, these parameters were associated with the patients' demographic, clinical, and laboratory data.

METHOD

This was a retrospective study, from 2001 to 2021, which included 89 muscle biopsies of patients with definite dermatomyositis performed at the time of diagnostic investigation. Immunohistochemical analysis was performed on serially frozen muscle sections. The presence and degree of endomysial/perifascicular myofiber necrosis were also analyzed. The degree of necrosis was semi-quantitatively coded as absent/mild, moderate, or severe. The presence or absence of perifascicular atrophy and also perivascular lymphomononuclear infiltration was also evaluated.

RESULTS

Muscle biopsies from 89 patients, the majority of whom were Caucasian women, were evaluated. Both perifascicular atrophy and perivascular lymphomononuclear infiltrates were observed in 76 (85.4%) samples. Moderate or intense areas of myofiber necrosis in endomysial/perifascicular areas were found in 30/89 (33.7%) and 14/89 (15.7%) muscle biopsies, respectively, with a predominance of macrophagic infiltrate in relation to lymphomononuclear cells in these regions. The degree of muscle weakness in the limbs (upper and lower) was associated only with areas of intense myofiber necrosis.

CONCLUSIONS

A high prevalence of myofiber necrosis was observed, which patients resembled the initial clinical feature of patients with immune-mediated necrotizing myopathies. Key Point • A high prevalence of myofiber necrosis was observed in muscle biopsies of patients with dermatomyositis.

Pathophysiological Mechanisms and Treatment of Dermatomyositis and Immune Mediated Necrotizing Myopathies: A Focused Review

Idiopathic inflammatory myopathies (IIM), collectively known as myositis, are a composite group of rare autoimmune diseases affecting mostly skeletal muscle, although other organs or tissues may also be involved. The main clinical feature of myositis is subacute, progressive, symmetrical muscle weakness in the proximal arms and legs, whereas subtypes of myositis may also present with extramuscular features, such as skin involvement, arthritis or interstitial lung disease (ILD). Established subgroups of IIM include dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASyS), overlap myositis (OM) and inclusion body myositis (IBM). Although these subgroups have overlapping clinical features, the widespread variation in the clinical manifestations of IIM suggests different pathophysiological mechanisms. Various components of the immune system are known to be important immunopathogenic pathways in IIM, although the exact pathophysiological mechanisms causing the muscle damage remain unknown. Current treatment, which consists of glucocorticoids and other immunosuppressive or immunomodulating agents, often fails to achieve a sustained beneficial response and is associated with various adverse effects. New therapeutic targets have been identified that may improve outcomes in patients with IIM. A better understanding of the overlapping and diverging pathophysiological mechanisms of the major subgroups of myositis is needed to optimize treatment. The aim of this review is to report on recent advancements regarding DM and IMNM.

Rescue Treatment with Infliximab for a Bilateral, Severe, Sight Threatening Frosted Branch Angiitis Associated with Concomitant Acute Onset of Presumed Dermatomyositis

PURPOSE

To report a severe bilateral frosted branch angiitis associated with acute onset of systemic dermatomyositis.

METHOD

History and clinical examination, laboratory evaluation, fundus' and skin's color pictures, fluorescein angiography (FA), optical coherence tomography (OCT).

RESULTS

A 32-year-old female was referred for a bilateral frosted branch angiitis and vitreitis, with skin rash, muscle pain, weakness, severe headache, compatible with dermatomyositis. After an initial improvement following an aggressive treatment by systemic steroids and mycophenolate mofetil, she was switched to intravenous infliximab (RemicadeTM, Janssen Biotech, Inc. USA) due to lack of efficacy. Nine months later, her visual acuity was improved up to 20/20 in OU, with both retinal vasculitis and vitreitis being solved.

CONCLUSION

Dermatomyositis is a severe multiorgan disease which might severely involve eye structures. Anti-TNF-Alpha agents, particularly Infliximab, might offer a rapid control and long-term remission.