Integrated Diagnosis Project for Inflammatory Myopathies: An association between autoantibodies and muscle pathology

[Current update on dermatomyositis]

Dermatomyositis (DM) is a rare autoimmune disease with involvement of skin and muscle that is classified as an idiopathic inflammatory myopathy. In addition to cutaneous lesions as well as weakness and atrophy of muscles, the heart and lungs are the major affected organs. DM occurs in association with malignant tumors in 20% of affected adults. The pathogenesis of the disease is not completely understood. DM is a multifactorial disease influenced by genetic, environmental and immunological factors. The immune response is characterized by activation of innate and adaptive immune mechanisms and a strong activation of the type I interferon pathway. Myositis-specific antibodies are characteristic of DM and allow differential diagnosis. Therapies include corticosteroids, antimalarials, immunoglobulins, biologics such as rituximab or JAK inhibitors. Early diagnosis and treatment are essential for the prognosis.

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.

Overlap syndrome with antibodies against multiple transfer-RNA components presenting antisynthetase syndrome

Overlap syndrome is a clinical entity of myositis concomitant with one or more collagen diseases such as systemic lupus erythematosus, systemic sclerosis, and/or rheumatoid arthritis. It is not evident whether the myopathology of overlap syndrome is disease-specific or categorizes one of the four major subsets: inclusion body myositis, immune-mediated necrotizing myopathy, dermatomyositis, and antisynthetase syndrome. We report a patient with overlap syndrome who exhibited autoantibodies against multiple transfer-RNA components by RNA immunoprecipitation, suggesting antisynthetase syndrome. A 64-year-old woman developed systemic lupus erythematosus, systemic sclerosis, and myositis. Muscle biopsy showed perifascicular necrosis and perimysial alkaline phosphatase positivity, suggesting antisynthetase syndrome. Enzyme-linked immunosorbent assay was negative for autoantibodies to aminoacyl transfer-RNA synthetase, whereas RNA immunoprecipitation revealed a novel antibody to multiple transfer-RNA components. Although the myopathology of overlap syndrome may be diagnosed as any one of various subsets, this case suggests that the myopathological features of overlap syndrome may include antisynthetase syndrome.

Association of immune-mediated necrotizing myopathy with HLA polymorphisms

Immune-mediated necrotizing myopathy (IMNM) is a type of autoimmune myositis typically characterized clinically by proximal muscle weakness with elevated creatine kinase levels, pathologically by myofiber necrosis and regeneration with paucity of lymphocytic cell infiltration, and serologically by the presence of either of two myositis-specific autoantibodies, anti-SRP, and anti-HMGCR antibodies. However, the HLA loci and alleles associated with IMNM are still not fully understood at least partly because IMNM was a relatively recently established condition. In this study, we genotyped the six HLA loci (HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1) in 250 patients (237 patients over age 18 years and 13 juvenile patients) diagnosed with IMNM based on clinicopathological features and autoantibody information and performed a case control study with Japanese healthy subjects. In the adult patients, specific HLA alleles associated with IMNM were identified at all HLA loci, with DRB1*08:03 showing the strongest association (OR = 2.5; p = 0.00000017). Furthermore, subgroup analysis with various clinical information showed that C*03:04 (OR = 3.7; p = 0.00012) was a higher risk allele for collagen disease in adult patients, and B*13:01 (OR = 23.2; p = 0.021) and C*03:04 (OR = 5.8; p = 0.0074) were higher risk for juvenile patients with anti-HMGCR antibody-positive IMNM. These findings will help to better understand the HLA genetic background and features of IMNM in designing future studies.

Profile of specific and associated autoantibodies in patients with idiopathic inflammatory myopathies in a Colombian population

Objectives

Idiopathic inflammatory myopathies (IIMs) are chronic, autoimmune diseases with several forms of presentation. Diagnosis is mostly clinical in our region. Our aim was to evaluate the autoantibody profile of patients with IIMs.

Methods

This study is a cross-sectional study with a prospective recollection of data, conducted between 2019–2021, in a single center in Cali, Colombia. Patients with a clinical diagnosis or suspicion of IIM were included. The presence of myositis-specific/associated antibodies was evaluated by immunoblotting in serum samples. Phenotypic characterization was performed.

Results

A total of 36 patients were included. The mean age was 50.6 (16.7) years, and 20 (55.6%) were female. Eighteen (50%) patients were seropositive, of which 11 (30.5%) presented one positive antibody, with anti-TIF1ɣbeing the most frequent (n = 4, 11.1%), followed by anti-Ro52 (n = 2, 5.6%). Seven patients (19.4%) showed >1 positive antibody. Dermatomyositis was the most frequent type of IIM in seropositive patients (n = 8, 44.4%), followed by anti-synthetase syndrome (n = 4, 22.2%). Weakness was symmetric and presented in the upper and lower extremities in 11 (61.1%) patients each. Both respiratory insufficiency and weight loss were seen in 7 (38.9%) patients, Gottron papules in six (33.3%) patients, and heliotrope rash, esophageal dysmotility, and myalgia in 5 (27.8%) patients. Pulmonary interstitial disease was seen in 4 (22.2%, with antibodies for anti-Ro52, anti-MDA5 + anti-Jo1 + anti-TIF1ɣ, anti-MDA5 + anti-SAE1 + anti-NXP2, and anti-cN1A + anti-Ro52) patients, and malignancy was seen in 2 (11.1%) patients (1 with anti-Mi2β and 1 with anti-TIF1ɣ + anti-Mi2α). In all, 7 (19.4%) patients required intensive care (2 seropositive, 1 with anti-PL7, 1 with anti-MDA5 + anti-Jo1 + anti-TIF1ɣ), and 1 (2.8%) (seronegative) patient died.

Conclusion

This study is the first study in the Southwest of Colombia that evaluates myositis-specific/associated antibodies in IIM. Half of the patients were seropositive. Anti-TIF1ɣwas the most frequent MSA and anti-Ro52 was the most frequent MAA. Several patients presented antibody combinations. Further studies are needed to fully associate phenotypes with antibodies.

Immune-mediated necrotizing myopathy (IMNM): A myopathological challenge

This review is focused on the myopathological spectrum of immune mediated necrotizing myopathies (IMNMs) and its differentiation with other, potentially mimicking, inflammatory and non-inflammatory myopathies. IMNMs are a subgroup of idiopathic inflammatory myopathies (IIMs) characterized by severe clinical presentation with rapidly progressive muscular weakness and creatine kinase elevation, often requiring early aggressive immunotherapy, associated to the presence of muscle specific autoantibodies (MSA) against signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR). Muscle biopsy usually shows unspecific features consisting in prominent necrosis and regeneration of muscle fibres with mild or absent inflammatory infiltrates, inconstant and faint expression of major histocompatibility complex (MHC) class I and variable deposition of C5b-9 on sarcolemma. Several conditions could present similar histopathological findings leading to possible misdiagnosis of IMNM with other IIMs or non-inflammatory myopathies (nIMs) and viceversa. This review analyses the muscle biopsy data in IMNMs through a systematic revision of the literature from the last five decades. Several histopathological variables have been considered in both SRP- and HMGCR-IMNM, and compared to other IIMs - as dermatomyositis (DM) and anti-synthethase syndrome (ASS) - or other nIMs -as toxic myopathies (TM), critical illness myopathy (CIM) and muscular dystrophy (MD) - to elucidate similarities and differences among these potentially mimicking conditions. The major histopathological findings of IMNMs were: very frequent necrosis and regeneration of muscle fibres (93%), mild inflammatory component mainly constituted by scattered isolated (65%) CD68-prevalent (68%) cells, without CD8 invading/surrounding non-necrotic fibres, variable expression of MHC-I in non-necrotic fibres (56%) and constant expression of sarcoplasmic p62, confirming those that are widely considered the major histological characteristics of IMNMs. Conversely, only 42% of biopsies showed a sarcolemmal deposition of C5b-9 component. Few differences between SRP and HMGCR IMNMs consisted in more severe necrosis and regeneration in SRP than in HMGCR (p = 0.01); more frequent inflammatory infiltrates (p = 0.007) with perivascular localization (p = 0.01) and clustered expression of MHC-I (p = 0.007) in HMGCR; very low expression of sarcolemmal C5b-9 in SRP (18%) compared to HMGCR (56%) (p = 0.0001). Milder necrosis and regeneration, detection of perifascicular pathology, presence of lymphocytic inflammatory infiltrates and myofibre expression of MxA help to distinguish DM or ASS from IMNM. nIMs can present signs of inflammation at muscle biopsy. Low fibre size variability with overexpression of both MHC-I and II, associated with C5b-9 deposition, could could be observed in CIM, while increased connective tissue should lead to consider MD, or TM in absence of C5b-9 deposition. Nevertheless, these features are not constantly detected and muscle biopsy could not be diriment. For this reason, muscle biopsy should always be critically considered in light of the clinical context before concluding for a definite diagnosis of IMNM, only based on histopathological findings. More rigorous collection and analysis of muscle biopsy is warranted to obtain a higher quality and more homogeneous histopathological data in inflammatory myopathies.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Recent research on myositis-specific autoantibodies in juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is an autoimmune disease manifesting as proximal muscle weakness and skin rash and can involve multiple systems and visceral organs. Myositis-specific autoantibodies (MSAs) are highly associated with various complications and prognosis in JDM. Patients with anti-Mi-2 antibodies tend to have good prognosis and typical clinical symptoms. Patients with anti-MDA5 antibodies often have diffuse interstitial lung disease and skin ulcer, with mild symptoms of myositis. Patients with anti-NXP2 antibodies often have calcinosis, and such antibodies are associated with gastrointestinal bleeding and perforation. Patients with anti-TIF1-γ antibodies have diffuse and refractory skin lesions. Anti-SAE antibodies are rarely detected in children, with few reports of such cases. This article reviews the features of clinical phenotypes in JDM children with these five types of MSAs, so as to provide a basis for the clinical treatment and follow-up management of children with JDM.

Marked Respiratory Failure in an Ambulant Patient with Immune-mediated Necrotizing Myopathy and Anti-Kv1.4 and Anti-titin Antibodies

We herein report a case of seronegative immune-mediated necrotizing myopathy (IMNM) concurrent with anti-Kv1.4 and anti-titin antibodies. A 72-year-old Japanese woman presented with a 29-year history of fluctuating high serum creatine kinase (CK) levels followed by intermittent ptosis and respiratory muscle weakness. This case highlights the fact that marked respiratory muscle weakness requiring intubation can be seen in an ambulant patient with IMNM. Marked respiratory muscle weakness, rhabdomyolysis-like acute elevation of CK levels, and anti-striational muscle antibodies may be a characteristic constellation of findings in a distinct subgroup of patients with inflammatory myopathy with myasthenia gravis or similar symptoms.

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.

Updates on the Immunopathology in Idiopathic Inflammatory Myopathies

PURPOSE OF REVIEW

To review recent advances in immunopathology for idiopathic inflammatory myopathies, focusing on widely available immunohistochemical analyses.

RECENT FINDINGS

Sarcoplasmic expression of myxovirus resistance protein A (MxA) is specifically observed in all types of dermatomyositis and informs that type I interferons are crucially involved in its pathogenesis. It is a more sensitive diagnostic marker than perifascicular atrophy. Diffuse tiny dots in the sarcoplasm highlighted by p62 immunostaining are characteristically seen in immune-mediated necrotizing myopathy. This feature is linked to a chaperone-assisted selective autophagy pathway. Myofiber invasion by highly differentiated T cells, a marker of which is KLRG1, is specific to inclusion body myositis and has a crucial role in its pathogenesis. The recent advances in immunopathology contribute to increased diagnostic accuracy and a better understanding of the underlying pathophysiology in different types of idiopathic inflammatory myopathies.

Antisynthetase syndrome: A distinct disease spectrum

The discovery of novel autoantibodies related to idiopathic inflammatory myopathies (collectively referred to as myositis) has not only advanced our understanding of the clinical, serological, and pathological correlation in the disease spectrum but also played a role in guiding management and prognosis. One group of the myositis-specific autoantibodies is anti-aminoacyl-tRNA synthetase (anti-ARS or anti-synthetase) which defines a syndrome with predominant interstitial lung disease, arthritis, and myositis. Autoantibodies to eight aminoacyl-tRNA synthetases have been identified with anti-Jo1 the most common in all of idiopathic inflammatory myopathies. Disease presentation and prognosis vary depending on which anti-aminoacyl-tRNA synthetase antibody is present. In this review, we will discuss the clinical characteristics, overlap features with other autoimmune diseases, prognostic factors, and management of the antisynthetase syndrome.

HLA-DRB1 allele and autoantibody profiles in Japanese patients with inclusion body myositis

Introduction

Inclusion body myositis (IBM) is an idiopathic inflammatory myopathy, characterized by unique clinical features including finger flexor and quadriceps muscle weakness and a lack of any reliable treatment. The human leukocyte antigen (HLA)-DRB1 allele and autoantibody profiles in Japanese IBM patients have not been fully elucidated.

Methods

We studied 83 Japanese IBM patients with a mean age of 69 years (49 males and 34 females) who participated in the ‘Integrated Diagnosis Project for Inflammatory Myopathies’ from January 2011 to September 2016. IBM was diagnosed by histological diagnosis. Various autoantibodies were screened by RNA immunoprecipitation and enzyme-linked immunosorbent assays. HLA-DRB1 genotyping was performed using polymerase chain reaction-sequence based typing. A total of 460 unrelated healthy Japanese controls were also studied.

Results

The allele frequencies of DRB1*01:01, DRB1*04:10, and DRB1*15:02 were significantly higher in the IBM group than in the healthy control group (Corrected P = 0.00078, 0.00038 and 0.0046). There was a weak association between the DRB1*01:01 allele and severe leg muscle weakness and muscle atrophy. While hepatitis type C virus infection and autoantibodies to cytosolic 5’-nucleotidase 1A were found in 18 and 28 patients, respectively, no significant association with HLA-DRB1 alleles was observed.

Conclusion

Japanese IBM patients had the specific HLA-DRB1 allele and autoantibody profiles.

[Classification of idiopathic inflammatory myopathies based on clinical manifestations and myositis-specific antibodies]

OBJECTIVE

To investigate the classification of idiopathic inflammatory myopathies (IIM) based on clinical manifestations and myositis- specific antibodies using cluster analysis.

METHODS

We retrospectively analyzed the data of patients with IIM admitted in Nanfang Hospital in 2015-2019. The clinical data of the patients including serum creatine kinase (CK), interstitial lung disease (ILD), cancer, and myositis-specific antibodies were collected for two-step cluster analysis to identify the distinct clusters of patients, whose clinical characteristics were subsequently analysed.

RESULTS

A total of 71 patients with IIM were included in this study, including 30 (42.3%) with polymyositis (PM), 20 (28.2%) with classic dermatomyositis (DM), 16 (22.5%) with amyopathic dermatomyositis (CADM), and 5 (7.0%) with immune-mediated necrotizing myopathy (IMNM). Two-step cluster analysis identified 3 distinctive subgroups: Cluster 1 of 15 (51.7%) patients characterized by rash, positive anti-MDA5 antibody and hypoproteinemia (P < 0.05) with normal or slightly elevated CK level, mainly corresponding to CADM; Cluster 2 of 4 (57.1%) patients with significantly elevated CK and positive anti-SRP antibody (P < 0.001) corresponding to IMNM; and Cluster 3 of 17 (48.6%) patients consisting primarily of patients with PM, characterized by positivity for anti- aminoacyl transfer RNA synthetases antibodies (P=0.022) corresponding to antisynthetase syndrome (ASS).

CONCLUSIONS

Patients with IIM can be divided into 3 subgroups based on their clinical and serological characteristics (especially myositis-specific antibodies), and among them ASS may represent an independent IIM subgroup with unique clinical characteristics.

Assessment of diagnostic utility, clinical phenotypic associations, and prognostic significance of anti-NXP2 autoantibody in patients with idiopathic inflammatory myopathies: a systematic review and meta-analysis

The objectives of this study are to analyze the association between anti-nuclear matrix protein 2 (NXP2) autoantibody and idiopathic inflammatory myopathies (IIMs) and to assess the diagnostic and prognostic relevance of anti-NXP2 autoantibody in patients with IIMs. A systematic search was performed in PubMed, Web of Science, EMBASE, the Cochrane Library, and Scopus to identify studies published as of February 29, 2020. Data was analyzed using Stata 12.0 and Meta-DiSc 1.4. Twenty-eight studies (4764 patients with IIMs and 1981 controls) were included in the meta-analysis. Anti-NXP2 autoantibody showed a significant association with IIMs (odds ratio (OR) = 26.36, 95% confidence interval (CI): 12.05-57.67, P < 0.001), especially juvenile IIMs (OR = 62.48, 95% CI: 16.97-229.98, P < 0.001). The pooled sensitivity, specificity, and area under the curve were 0.19 (95% CI = 0.16-0.21), 1.00 (95% CI = 1.00-1.00), and 0.95 for patients with juvenile IIMs versus controls. Anti-NXP2 autoantibody was associated with an increased risk of developing five characteristics (edema, muscle weakness, myalgia/myodynia, dysphagia, and calcinosis) and reduced risk of interstitial lung disease (ILD) (P < 0.001). Anti-NXP2 autoantibody showed no association with increased risk of death in IIMs (P = 0.463). These findings suggest that anti-NXP2 autoantibody is specially related to IIMs and is related to edema, muscle weakness, myalgia/myodynia, dysphagia, calcinosis, and ILD in patients with IIMs. However, there is no evidence to suggest that the presence of anti-NXP2 autoantibody confers a poor prognosis with respect to overall survival. Key Points • This study summarized the diagnostic and prognostic accuracies of anti-NXP2 autoantibody for patients with IIMs. Anti-NXP2 autoantibody is related to edema, muscle weakness, myalgia/myodynia, dysphagia, calcinosis, and ILD in patients with IIMs.

Ultra-low dose rituximab as add-on therapy in anti-MDA5-positive patients with polymyositis /dermatomyositis associated ILD

OBJECTIVES

To evaluate the efficacy and safety of ultra-low dose (100 mg) rituximab (RTX) administration in anti-melanoma differentiation-associated gene 5 (MDA5) positive patients with polymyositis/dermatomyositis (PM/DM) associated interstitial lung disease.

METHODS

This retrospective study included anti-MDA5 antibody positive ILD subjects in the First Affiliated Hospital of Guangzhou Medical University from November 2017 to March 2019. Independent predictors for 180-day mortality were measured by Cox regression analysis. Patients were divided into 3 groups: Group 1 (non-cyclophosphamide (CTX)/RTX) (n = 10), Group 2 (CTX only) (n = 19) and Group 3 (RTX with/without CTX) (n = 11). The 180-day mortality was compared among 3 groups with Kaplan-Meier analysis. Post-RTX serological parameters as well as adverse events were evaluated.

RESULTS

Forty patients were included with the mean age of 51.3 years. Elevated IL-10 level and CD4⁺/8⁺ ratio were considered as risk factors of 180-day mortality. Kaplan-Meier analysis showed a trend toward decrease, albeit non-significant, in 180-day mortality in Group 3 (P = 0.26). The administration of 100 mg RTX brought down B cell within 7 days that lasted for 180 days. There were 7 and 6 infection events observed within 2 months of CTX/RTX treatment in Group 2 and 3, with 5 and 2 fatal cases respectively. Cytomegalovirus infection accounted for half infection events in Group 3.

CONCLUSION

We found a pronounced and prolonged B cell depletion following 100 mg RTX infusion and RTX add-on may be effective in anti-MDA5 positive ILD patients. However, infection, especially opportunistic infection, should be concerned during the treatment.

[Antisynthetase myopathy]

Inflammatory myopathies are a heterogeneous group of immune-mediated diseases that involve skeletal muscle as well as many other organs. The classification of inflammatory myopathies has been based on clinical diagnoses, pathological diagnoses, and autoantibodies, independently. Antisynthetase syndrome, characterized by myositis, interstitial lung disease, skin rash, arthropathy, and Raynaud phenomenon, is a clinical entity based on the presence of aminoacyl transfer RNA synthetase (ARS) antibodies in patients' serum. A cohort study of muscle biopsy entitled "Integrated Diagnosis Project for Inflammatory Myopathies" revealed that of 460 patients with idiopathic inflammatory myopathies, 51 (11%; female:male, 31:20) had antisynthetase myopathy. It is noted that anti-OJ antibodies, one of anti-ARS antibody subtypes, are clearly detected by RNA immunoprecipitation, but not conventional detection methods including line blot and enzyme-linked immunosorbent assays. The combined mean onset age of the patients was 60 years (range 13-85 years). There were no significant HLA-DRB1 alleles associated with anti-ARS antibodies. All patients with antisynthetase myopathy patients presented muscle limb weakness; 14 had severe weakness, 17 neck weakness, 15 dysphagia, and 15 muscle atrophy. Although patients with anti-OJ antibodies showed severe muscle weakness, the clinical presentations defined by anti-ARS antibodies were relatively homogeneous. In muscle pathology, perifascicular necrosis is a distinctive hallmark of antisynthetase myopathy. Patients with antisynthetase myopathy responded to the combination of immunosuppressive therapy, with favorable outcomes. However, interstitial lung disease, found in 41 patients, was more closely related to mortality than myositis. Antisynthetase myopathy has a distinct clinical and histological entity among idiopathic inflammatory myopathies.

Anti-signal Recognition Particle Antibody-positive Necrotizing Myopathy with Secondary Cardiomyopathy: The First Myocardial Biopsy- and Multimodal Imaging-proven Case

A 69-year-old Japanese woman was admitted to our hospital with progressive muscle weakness and dysphagia. She was taking pitavastatin for dyslipidemia. Her serum creatine kinase was 6,300 U/L. Pitavastatin was stopped, but her symptoms deteriorated, and cardiac congestion appeared. A muscle biopsy showed necrotizing myopathy (NM), and anti-signal recognition particle (SRP) antibody was positive. ¹⁸F-fluorodeoxyglucose-positron emission tomography showed an abnormal uptake, and magnetic resonance imaging showed abnormal gadolinium enhancement in the left ventricular wall. An endomyocardial biopsy revealed inflammatory cardiomyopathy. Steroid, tacrolimus, and intravenous immunoglobulins were effective against the symptoms. This is the first case of biopsy-proven secondary cardiomyopathy due to anti-SRP-positive NM.

Development of a New Classification System for Idiopathic Inflammatory Myopathies Based on Clinical Manifestations and Myositis-Specific Autoantibodies

Importance

Idiopathic inflammatory myopathies are heterogeneous in their pathophysiologic features and prognosis. The emergence of myositis-specific autoantibodies suggests that subgroups of patients exist.

Objective

To develop a new classification scheme for idiopathic inflammatory myopathies based on phenotypic, biological, and immunologic criteria.

Design, Setting, and Participants

An observational, retrospective cohort study was performed using a database of the French myositis network. Patients identified from referral centers for neuromuscular diseases were included from January 1, 2003, to February 1, 2016. Of 445 initial patients, 185 patients were excluded and 260 adult patients with myositis who had complete data and defined historical classifications for polymyositis, dermatomyositis, and inclusion body myositis were enrolled. All patients were tested for anti-histidyl-ARN-t- synthetase (Jo1), anti-threonine-ARN-t-synthetase (PL7), anti-alanine-ARN-t-synthetase (PL12), anti-complex nucleosome remodeling histone deacetylase (Mi2), anti-Ku, anti-polymyositis/systemic scleroderma (PMScl), anti-topoisomerase 1 (Scl70), and anti-signal recognition particle (SRP) antibodies. A total of 708 variables were collected per patient (eg, cancer, lung involvement, and myositis-specific antibodies).

Main Outcomes and Measures

Unsupervised multiple correspondence analysis and hierarchical clustering analysis to aggregate patients in subgroups.

Results

Among 260 participants (163 [62.7%] women; mean age, 59.7 years; median age [range], 61.5 years [48-71 years]), 4 clusters of patients emerged. Cluster 1 (n = 77) included patients who were male, white, and older than 60 years and had finger flexor and quadriceps weakness and findings of vacuolated fibers and mitochondrial abnormalities. Cluster 1 regrouped patients who had inclusion body myositis (72 of 77 patients [93.5%]; 95% CI, 85.5%-97.8%; P < .001). Cluster 2 (n = 91) regrouped patients who were women and had high creatine phosphokinase levels, necrosis without inflammation, and anti-SRP or anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies corresponding to immune-mediated necrotizing myopathy (53 of 91 [58.2%]; 95% CI, 47.4%-68.5%; P < .001). Cluster 3 (n = 52) regrouped patients who had dermatomyositis rash and anti-Mi2, anti-melanoma differentiation-associated protein 5 (MDA5), or anti-transcription intermediary factor-1γ (TIF1γ) antibodies, mainly corresponding with patients who had dermatomyositis (43 of 52 [82.7%]; 95% CI, 69.7%-91.8%; P < .001). Cluster 4 (n = 40) was defined by the presence of anti-Jo1 or anti-PL7 antibodies corresponding to antisynthetase syndrome (36 of 40 [90.0%]; 95% CI, 76.3%-97.2%; P < .001). The classification of an independent cohort (n = 50) confirmed the 4 clusters (Cohen κ light, 0.8; 95% CI, 0.6-0.9).

Conclusions and Relevance

These findings suggest a classification of idiopathic inflammatory myopathies with 4 subgroups: dermatomyositis, inclusion body myositis, immune-mediated necrotizing myopathy, and antisynthetase syndrome. This classification system suggests that a targeted clinical-serologic approach for identifying idiopathic inflammatory myopathies may be warranted.

Dermatomyositis: Diagnosis and treatment

The second article in this continuing medical education series reviews the initial evaluation of patients with suspected dermatomyositis (DM), the relevant work-up for malignancy and interstitial lung disease once a diagnosis of DM is made, and treatment recommendations for patients with DM based on disease severity, the presence of systemic symptoms, and myositis-specific antibody (MSA) profiles. This review emphasizes the emerging role of MSAs in the diagnosis of DM and highlights how MSAs can be used to guide the appropriate work-up for malignancy and interstitial lung disease. The treatment approach proposed by this continuing medical education series discusses both established and novel therapies for DM and highlights the importance of considering lesion type, degree of muscle involvement, presence of systemic symptoms, presence of MSAs, and patient age when determining the best treatment approach for a patient with DM.

A pattern-based approach to the interpretation of skeletal muscle biopsies

The interpretation of muscle biopsies is complex and provides the most useful information when integrated with the clinical presentation of the patient. These biopsies are performed for workup of a wide range of diseases including dystrophies, metabolic diseases, and inflammatory processes. Recent insights have led to changes in the classification of inflammatory myopathies and have changed the role that muscle biopsies have in the workup of inherited diseases. These changes will be reviewed. This review follows a morphology-driven approach by discussing diseases of skeletal muscle based on a few basic patterns that include cases with (1) active myopathic damage and inflammation, (2) active myopathic damage without associated inflammation, (3) chronic myopathic changes, (4) myopathies with distinctive inclusions or vacuoles, (5) biopsies mainly showing atrophic changes, and (6) biopsies that appear normal on routine preparations. Each of these categories goes along with certain diagnostic considerations and pitfalls. Individual biopsy features are only rarely pathognomonic. Establishing a firm diagnosis therefore typically requires integration of all of the biopsy findings and relevant clinical information. With this approach, a muscle biopsy can often provide helpful information in the diagnostic workup of patients presenting with neuromuscular problems.

Inflammatory myopathy associated with PD-1 inhibitors

OBJECTIVE

To characterize the inflammatory myopathy associated with programmed cell death 1 inhibitors (PD-1 myopathy).

METHODS

We studied 19 Japanese patients with PD-1 myopathy (13 men and 6 women, mean age 70 years), who were referred to Keio University. As control groups, we used 68 patients with anti-signal recognition particle antibodies, 51 patients with anti-aminoacyl transfer RNA synthetase antibodies and 460 healthy subjects.

RESULTS

In regard to muscle-disease severity, 10 patients showed a mild form of disease and 9 patients showed a severe form. Non-small cell lung cancer was the most common underlying cancer. PD-1 inhibitor consisted of 11 nivolumab and 8 pembrolizumab. PD-1 myopathy occurred 29 days on average after the first administration of PD-1 inhibitor. The initial manifestation of muscle weakness was ptosis in 10 patients, 15 patients had ptosis, 13 diplopia, 8 facial muscle weakness, 10 bulbar symptoms, 13 limb weakness, 14 neck weakness, 4 cardiac involvement, 6 respiratory involvement and 16 myalgia. Ocular, facial, cardiac and respiratory involvement and myalgia were more frequently observed than controls. Serum creatine kinase was increased to 5247 IU/L on average. Autoantibodies related to inflammatory myopathy were negative, while anti-striational antibodies were found in 13 (68%) patients. HLA-C*12:02 alleles were more frequently detected than healthy controls. Muscle pathology was characterized by multifocal necrotic myofibers with endomysial inflammation and expression of MHC class I. Immunosuppressive therapy with corticosteroids was generally effective for muscle weakness.

CONCLUSIONS

Based on our clinical, histological and immunological findings, PD-1 myopathy is a discrete subset of inflammatory myopathy.

CD8+T-bet+ cells as a predominant biomarker for inclusion body myositis

BACKGROUND

Myositis is a heterogeneous group of muscular auto-immune diseases with clinical and pathological criteria that allow the classification of patients into different sub-groups. Inclusion body myositis is the most frequent myositis above fifty years of age. Diagnosing inclusion body myositis requires expertise and is challenging. Little is known concerning the pathogenic mechanisms of this disease in which conventional suppressive-immune therapies are inefficacious.

OBJECTIVES

Our aim was to deepen our understanding of the immune mechanisms involved in inclusion body myositis and identify specific biomarkers.

METHODS

Using a panel of thirty-six markers and mass cytometry, we performed deep immune profiling of peripheral blood cells from inclusion body myositis patients and healthy donors, divided into two cohorts: test and validation cohorts. Potential biomarkers were compared to myositis controls (anti-Jo1-, anti-3-hydroxyl-3-methylglutaryl CoA reductase-, and anti-signal recognition particle-positive patients).

RESULTS

Unsupervised analyses revealed substantial changes only within CD8+ cells. We observed an increase in the frequency of CD8+ cells that expressed high levels of T-bet, and containing mainly both effector and terminally differentiated memory cells. The senescent marker CD57 was overexpressed in CD8+_T-bet+ cells of inclusion body myositis patients. As expected, senescent CD8+_{T-bet+ CD57+} cells of both patients and healthy donors were CD28_nullCD27_nullCD127_null. Surprisingly, non-senescent CD8+_{T-bet+ CD57-} cells in inclusion body myositis patients expressed lower levels of CD28, CD27, and CD127, and expressed higher levels of CD38 and HLA-DR compared to healthy donors. Using classification and regression trees alongside receiver operating characteristics curves, we identified and validated a frequency of CD8+_T-bet+ cells >51.5% as a diagnostic biomarker specific to inclusion body myositis, compared to myositis control patients, with a sensitivity of 94.4%, a specificity of 88.5%, and an area under the curve of 0.97.

CONCLUSION

Using a panel of thirty-six markers by mass cytometry, we identify an activated cell population (CD8+_{T-bet+ CD57-} CD28_lowCD27_lowCD127_low CD38+ HLA-DR+) which could play a role in the physiopathology of inclusion body myositis, and identify CD8+_T-bet+ cells as a predominant biomarker of this disease.

[A case of antisynthetase syndrome with anti-EJ antibody complicated by pericarditis]

A 69-year-old man was admitted with neck muscle weakness, symmetric proximal muscle weakness, skin rash and elevated serum creatine kinase levels. Muscle biopsy showed perifascicular necrosis and perimysial alkaline phosphatase activity. Chest CT revealed interstitial lung disease and colorectal cancer was diagnosed on colonoscopy. He was serologically positive for anti-EJ antibody, leading to the diagnosis of antisynthetase syndrome (ASS). After laparoscopic low anterior resection of the rectum, he received intravenous methylprednisolone (1,000 mg/d for 3 days) followed by oral prednisolone (50 mg/d). Although his muscle weakness improved after corticosteroid therapy, he developed pericardial effusion with resultant asymptomatic hypotension and arrhythmia possibly due to pericarditis. Corticosteroid monotherapy was insufficient to control the disease, and, we decided to use oral cyclosporin concurrently. After this combined therapy started, pericardial effusion and arrhythmia were improved. We should keep in mind that pericarditis can occur in patients with anti-EJ antibody-positive ASS, and early combined therapy with corticosteroid and immunosuppressive drugs for ASS may improve the patient's prognosis.

Myositis-specific autoantibodies, a cornerstone in immune-mediated necrotizing myopathy

Over the past few years, myositis-specific autoantibodies played an increasing role in the inflammatory idiopathic myositis definition. They became the critical immunological marker for immune-mediated necrotizing myopathy diagnosis (IMNM) since the paradigm switch from histological to serological criteria. This review is focused on the key role of the anti-signal recognition particle (anti-SRP) and the anti-3-Hydroxy-3-MethylGlutaryl-Coenzyme A Reductase (anti-HMGCR) antibodies in immune-mediated necrotizing myopathy. Anti-SRP and anti-HMGCR antibodies are robust diagnostic tools in case of both the classical subacute form and the slowly progressive form of IMNM that may mimic muscular dystrophy. Anti-SRP and anti-HMGCR patients share clinical, biological and histological features with some antibody-associated specificity. Anti-SRP patients harbour more severe muscle weakness and atrophy with severe muscle damage on magnetic resonance imaging study. Approximately 10-20% of anti-SRP patients develop extramuscular symptoms, especially lung interstitial disease. Conversely, anti-HMGCR patients are often associated with statin exposure. In both cases, patients have a poor outcome with frequent relapse and the use of combined immunotherapy. Of note, various data suggest a direct pathogenic role of these antibodies reinforcing the interest in targeted therapeutic strategy.

[What's new in internal medicine?]

What's new in internal medicine will be dedicated to three topics: i) inflammatory myopathies constituting a heterogenous group of diseases whose clinical manifestations, immunological abnormalities, treatment response and outcomes vary widely; ii) alterations of gut microbiota contributing to the occurrence or development of a range of conditions, including autoimmune diseases for which further work is necessary to understand the correlation of dysbiosis with these diseases; iii) the reciprocal relationship between obesity, metabolic syndrome, atherosclerosis and autoimmune diseases. New data concerning systemic sclerosis, cutaneous vasculitis, adult Still's disease, autoantibodies anti DFS70, Epstein Barr virus and autoimmune diseases were also highlighted.

Idiopathic inflammatory myopathies overlapping with systemic diseases

A muscle biopsy is currently requested to assess the diagnosis of an idiopathic inflammatory myopathy overlapping with a systemic disease. During the past few years, the classification of inflammatory myopathy subtypes has been revisited progressively on the basis of correlations between clinical phenotypes, autoantibodies and histological data. Several syndromic entities are now more clearly defined, and the aim of the present review is to clarify the contribution of muscle biopsy in a setting of idiopathic inflammatory myopathies overlapping with systemic diseases.
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Potential Pathogenic Role of Anti-Signal Recognition Protein and Anti-3-hydroxy-3-methylglutaryl-CoA Reductase Antibodies in Immune-Mediated Necrotizing Myopathies

PURPOSE OF REVIEW

This review provides an overview of the potential pathogenic roles of anti-SRP and anti-HMGCR in IMNM over the past 5 years.

RECENT FINDINGS

Idiopathic inflammatory myopathies (IIM) are a group of acquired autoimmune disorders that mainly affect the skeletal muscle tissue. Classification criteria of IIM are comprised of polymyositis, dermatomyositis, inclusion body myositis and immune-mediated necrotizing myopathies. One important hallmark of autoimmune diseases is the detection of autoantibodies in patient sera. The anti-SRP (signal recognition particle) and anti-HMGCR (3-hydroxy-3-methylglutaryl coenzyme A reductase) antibodies are specifically associated with IMNM patients, and their detection has been described as related to disease severity. The muscles of IMNM patients are characterized by necrosis, atrophy and regenerating fibres with sparse inflammatory infiltrates. Although an important correlation between autoantibody titres, creatine kinase levels and disease progression/severity has been described in the last few years, the potential pathogenic roles of these autoantibodies have only recently been described.