International Workshop on Inclusion Body Myositis held at the Institute of Myology, Paris, on 29 May 2009

Efficacy and safety of pharmacological treatments in inclusion body myositis: a systematic review

OBJECTIVE

To identify the best evidence on the efficacy of treatment interventions for inclusion body myositis (IBM) and to describe their safety.

METHODS

Systematic review of randomised controlled trials (RCTs) of pharmacological treatments of adults with IBM, conducted according to the Cochrane Handbook, updating a previous Cochrane review. The search strategy was run on Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE and EMBASE, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform. Assessment of risk of bias, data extraction and synthesis were performed independently by two reviewers. Data pooled in statistical meta-analyses, if possible.

RESULTS

From a total of 487 records, 48 were selected for full-text review, 14 fulfilled the inclusion criteria, but only 2 RCTs were included in meta-analyses due to clinical heterogeneity (different drug interventions or dosages). Treatments included various immunosuppressive and immunomodulatory agents, alongside interventions modulating muscle growth and protein homoeostasis. Efficacy was assessed across multiple outcomes, namely muscle strength, physical function, mobility and muscle trophicity. Trials of methotrexate (MTX), intravenous immunoglobulin, interferon beta-1a and MTX, MTX and anti-T-lymphocyte immunoglobulin, oxandrolone, MTX and azathioprine, bimagrumab, arimoclomol, and sirolimus provided low-quality to high-quality evidence of having no effect on the progression of IBM.

CONCLUSIONS

Drug interventions for IBM were not effective for most of the outcomes of interest. We observed inconsistency of outcome measures across trials. More RCTs are needed, of adequate size and duration, and using a standardised set of outcome measures.

Inclusion body myositis: Correcting impaired mitochondrial and lysosomal autophagy as a potential therapeutic strategy

Inclusion body myositis (IBM) is a late onset sporadic myopathy with a characteristic clinical presentation, but as yet unknown aetiology or effective treatment. Typical clinical features are early predominant asymmetric weakness of finger flexor and knee extensor muscles. Muscle biopsy shows endomysial inflammatory infiltrate, mitochondrial changes, and protein aggregation. Proteostasis (protein turnover) appears to be impaired, linked to potentially dysregulated chaperone-mediated autophagy and mitophagy (a type of mitochondrial quality control). In this review, we bring together the most recent clinical and biological data describing IBM. We then address the question of diagnosing this pathology and the relevance of the current biological markers that characterize IBM. In these descriptions, we put a particular emphasis on data related to the deregulation of autophagic processes and to the mitochondrial-lysosomal crosstalk. Finally, after a short description of current treatments, an overview is provided pointing towards novel therapeutic targets and emerging regulatory molecules that are being explored for treating IBM. Special attention is paid to autophagy inhibitors that may offer innovative breakthrough therapies for patients with IBM.

Epidemiology of the idiopathic inflammatory myopathies

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

Exploring challenges in the management and treatment of inclusion body myositis

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Late-onset myopathies: clinical features and diagnosis

Late-onset myopathies are not well-defined since there is no clear definition of 'late onset'. For practical reasons we decided to use the age of 40 years as a cut-off. There are diseases which only manifest as late onset myopathy (inclusion body myositis, oculopharyngeal muscular dystrophy and axial myopathy). In addition, there are diseases with a wide range of onset including 'late onset' muscle weakness. Well-known and rather frequently occurring examples are Becker muscular dystrophy, limb girdle muscular dystrophy, facioscapulohumeral dystrophy, Pompe disease, myotonic dystrophy type 2, and anoctamin-5-related distal myopathy. The above-mentioned diseases will be discussed in detail including clinical presentation - which can sometimes lead someone astray - and diagnostic tools based on real cases taken from the author's practice. Where appropriate a differential diagnosis is provided. Next generation sequencing (NGS) may speed up the diagnostic process in hereditary myopathies, but still there are diseases, e.g. with expansion repeats, deletions, etc, in which NGS is as yet not very helpful.

[Myositis: From classification to diagnosis]

Idiopathic inflammatory myopathies, or IIM, are a group of acquired diseases that affect the muscle to a certain extent, and may also affect other organs. They include dermatomyositis, which can affect the muscle eventualy, with a typical skin rash; inclusion body myositis, with a purely muscular expression resulting in a slow progressive deficit; and the former group of "polymyositis", a misnomer that actually includes other categories of IIM, such as immune-mediated necrotizing myopathies, with a severe muscle involvement often presents from the onset of the disease; antisynthetase syndrome, which combines muscle damage, joint involvement and a potentially life-threatening lung disease; and overlapping myositis, which combines muscle damage with other organs involvement connected to another autoimmune disease. The diagnosis of IIM is based on rigorous clinical examination and interrogation, electromyographic data and immunological testing for myositis specific antibodies. This antibody dosage must be extended or repeated if necessary to classify correctly the muscle disease under investigation, as the available tests may not perform well enough. Muscle biopsy, although very informative, is not anymore systematically recommended when the clinic and the antibodies are typical. However, some forms of IIM are sometimes difficult to classify; in these cases, muscle biopsy plays a crucial role in the precise etiological diagnosis.

Inclusion body myositis: clinical features and pathogenesis

Inclusion body myositis (IBM) is often viewed as an enigmatic disease with uncertain pathogenic mechanisms and confusion around diagnosis, classification and prospects for treatment. Its clinical features (finger flexor and quadriceps weakness) and pathological features (invasion of myofibres by cytotoxic T cells) are unique among muscle diseases. Although IBM T cell autoimmunity has long been recognized, enormous attention has been focused for decades on several biomarkers of myofibre protein aggregates, which are present in <1% of myofibres in patients with IBM. This focus has given rise, together with the relative treatment refractoriness of IBM, to a competing view that IBM is not an autoimmune disease. Findings from the past decade that implicate autoimmunity in IBM include the identification of a circulating autoantibody (anti-cN1A); the absence of any statistically significant genetic risk factor other than the common autoimmune disease 8.1 MHC haplotype in whole-genome sequencing studies; the presence of a marked cytotoxic T cell signature in gene expression studies; and the identification in muscle and blood of large populations of clonal highly differentiated cytotoxic CD8⁺ T cells that are resistant to many immunotherapies. Mounting evidence that IBM is an autoimmune T cell-mediated disease provides hope that future therapies directed towards depleting these cells could be effective.

Routine monitoring of isometric knee extension strength in patients with muscle impairments using a new portable device: cross-validation against a standard isokinetic dynamometer

OBJECTIVE

Muscle strength is a critical clinical hallmark in both health and disease. The current study introduces a novel portable device prototype (MyoQuad) for assessing and monitoring maximal voluntary isometric knee extension torque (MVIT).

APPROACH

Fifty-six patients with inclusion body myositis were studied. Knee extension weakness is a key feature in this inflammatory muscle disease. Cross-validation with an isokinetic dynamometer (Biodex System 3 Pro) was performed. Between-day reproducibility and ability to monitor changes in muscle strength over time compared to the gold standard method as a reference, were also investigated.

MAIN RESULTS

The measurement was feasible even in the weakest patients. Agreement between methods was excellent (standard error of measurement (SEM) was 3.8 Nm and intra-class correlation coefficient (ICC) was 0.973). Least significant difference (LSD) was 4.9 and 5.3 Nm for the MyoQuad and the Biodex, respectively Measurements using the MyoQuad exhibited excellent between-day reproducibility (SEM was 2.4 Nm and ICC was 0.989 versus 2.6 Nm and 0.988 using the Biodex). Changes in MVIT at 6 and 12 months were similar between methods (timepoint  ×  method interaction was not significant; all p   >  0.19); strength changes classified according to LSD at 6 and 12 months were consistent between methods (>70% consistent classification)).

SIGNIFICANCE

The measurement of MVIT using the MyoQuad offers a cost-effective, portable and immediate alternative for the routine measurement of maximal voluntary isometric strength of the quadriceps. The MyoQuad offers a comfort and stability that cannot be provided by standard hand-held dynamometers. These results support quantitative muscle strength assessment using fixed yet flexible dynamometry within clinical routine and multicenter trials.

Muscle Shear Wave Elastography in Inclusion Body Myositis: Feasibility, Reliability and Relationships with Muscle Impairments

Degenerative muscle changes may be associated with changes in muscle mechanical properties. Shear wave elastography (SWE) allows direct quantification of muscle shear modulus (MSM). The aim of this study was to evaluate the feasibility and reliability of SWE in the severely disordered muscle as observed in inclusion body myositis. To explore the clinical relevance of SWE, potential relationships between MSM values and level muscle impairments (weakness and ultrasound-derived muscle thickness and echo intensity) were investigated. SWE was performed in the biceps brachii at 100°, 90°, 70° and 10° elbow flexion in 34 patients with inclusion body myositis. MSM was assessed before and after five passive stretch-shortening cycles at 4°/s from 70° to 10° elbow angle and after three maximal voluntary contractions to evaluate potential effects of muscle pre-conditioning. Intra-class correlation coefficients and standard errors of measurements were >0.83 and <1.74 kPa and >0.64 and <1.89 kPa for within- and between-day values, respectively. No significant effect of passive loading-unloading and maximal voluntary contractions was found (all p values  >0.18). MSM correlated to predicted muscle strength (all Spearman correlation coefficients (ρ) > 0.36; all p values < 0.05). A significant correlation was found between muscle echo intensity and muscle shear modulus at 70° only (ρ = 0.38, p <0.05). No correlation was found between muscle thickness and MSM (all ρ values > 0.23 and all p values > 0.25, respectively). Within- and between-day reliability of muscle SWE was satisfactory and moderate, respectively. SWE shows promise for assessing changes in mechanical properties of the severely disordered muscle. Further investigations are required to clarify these findings and to refine their clinical value.

Clinical, Histological, and Immunohistochemical Findings in Inclusion Body Myositis

Sporadic inclusion body myositis (sIBM) is considered the most common acquired myopathy aged over 50 years. The disease is characterized by a particular process of muscle degeneration characterized by abnormal deposit of protein aggregates in association with inflammation. The aim of this study was to present clinical and muscle histopathological findings, including immunostaining for LC3B, p62, α-synuclein, and TDP-43, in 18 patients with sIBM. The disease predominated in males (61%) and European descendants, with onset of clinical manifestations around 59 years old. The most common symptoms were muscle weakness, falls, dysphagia, and weight loss. Hypertension was the main comorbidity. Most of the cases presented with paresis predominantly proximal in lower limbs and distal in upper limbs. Immunosuppressive treatment showed to be not effective. Muscle histological findings included dystrophic changes, endomysial inflammation, increased lysosomal activity, and presence of rimmed vacuoles and of beta-amyloid accumulation, in addition to high frequency of mitochondrial changes. There was increased expression of LC3B, p62, α-synuclein, and TDP-43 in muscle biopsies. The sIBM has characteristic clinical and histological findings, and the use of degeneration and autophagic markers can be useful for the diagnosis.

Development and evaluation of a standardized ELISA for the determination of autoantibodies against cN-1A (Mup44, NT5C1A) in sporadic inclusion body myositis

PURPOSE

Sporadic inclusion body myositis (sIBM) is an autoimmune degenerative disease of the muscle, with inflammatory infiltrates and inclusion vacuoles. Its pathogenesis is not fully understood and the diagnosis is hampered by its imprecise characteristics, at times indistinguishable from other idiopathic inflammatory myopathies such as polymyositis and dermatomyositis. The diagnosis may be assisted by the detection of autoantibodies targeting Mup44, a skeletal muscle antigen identified as cytosolic 5'-nucleotidase 1A (cN-1A, NT5C1A). A novel standardized anti-cN-1A IgG ELISA was developed and its diagnostic performance was evaluated by two reference laboratories.

METHODS

Recombinant human full-length cN-1A was expressed and purified, and subsequently utilized to set up a standardized ELISA. To evaluate the novel assay, laboratory A examined sera from North American patients with clinically and pathologically diagnosed definite sIBM (n = 17), suspected sIBM (n = 14), myositis controls (n = 110), non-myositis autoimmune controls (n = 93) and healthy subjects (n = 52). Laboratory B analyzed a Dutch cohort of definite sIBM patients (n = 51) and healthy controls (n = 202).

RESULTS

Anti-cN-1A reactivity was most frequent in definite sIBM (39.2-47.1%), but absent in biopsy-proven classic polymyositis or dermatomyositis. Overall diagnostic sensitivity and specificity amounted to 35.5 and 96.1% (laboratory A) and 39.2 and 96.5% (laboratory B).

CONCLUSIONS

Anti-cN-1A autoantibodies were detected by ELISA with moderate sensitivity, but high specificity for sIBM and may therefore help diagnose this infrequent and difficult-to-diagnose myopathy. The novel anti-cN-1A IgG ELISA can improve and accelerate the diagnosis of sIBM using sera where muscle biopsy is delayed or unfeasible.

Disease specificity of autoantibodies to cytosolic 5'-nucleotidase 1A in sporadic inclusion body myositis versus known autoimmune diseases

OBJECTIVES

The diagnosis of inclusion body myositis (IBM) can be challenging as it can be difficult to clinically distinguish from other forms of myositis, particularly polymyositis (PM). Recent studies have shown frequent presence of autoantibodies directed against cytosolic 5'-nucleotidase 1A (cN-1A) in patients with IBM. We therefore, examined the autoantigenicity and disease specificity of major epitopes of cN-1A in patients with sporadic IBM compared with healthy and disease controls.

METHODS

Serum samples obtained from patients with IBM (n=238), PM and dermatomyositis (DM) (n=185), other autoimmune diseases (n=246), other neuromuscular diseases (n=93) and healthy controls (n=35) were analysed for the presence of autoantibodies using immunodominant cN-1A peptide ELISAs.

RESULTS

Autoantibodies directed against major epitopes of cN-1A were frequent in patients with IBM (37%) but not in PM, DM or non-autoimmune neuromuscular diseases (<5%). Anti-cN-1A reactivity was also observed in some other autoimmune diseases, particularly Sjögren's syndrome (SjS; 36%) and systemic lupus erythematosus (SLE; 20%).

CONCLUSIONS

In summary, we found frequent anti-cN-1A autoantibodies in sera from patients with IBM. Heterogeneity in reactivity with the three immunodominant epitopes indicates that serological assays should not be limited to a distinct epitope region. The similar reactivities observed for SjS and SLE demonstrate the need to further investigate whether distinct IBM-specific epitopes exist.

Sporadic inclusion body myositis: A review of recent clinical advances and current approaches to diagnosis and treatment

Sporadic inclusion body myositis is the most frequent acquired myopathy of middle and later life and is distinguished from other inflammatory myopathies by its selective pattern of muscle involvement and slowly progressive course, and by the combination of inflammatory and degenerative muscle pathology and multi-protein deposits in muscle tissue. This review summarises the findings of recent studies that provide a more complete picture of the clinical phenotype and natural history of the disease and its global prevalence and genetic predisposition. Current diagnostic criteria, including the role of electrophysiological and muscle imaging studies and the recently identified anti-5'-nucleotidase (anti-cN1A) antibody in diagnosis are also discussed as well as current trends in the treatment of the disease.

Treatment for inclusion body myositis

BACKGROUND

Inclusion body myositis (IBM) is a late-onset inflammatory muscle disease (myopathy) associated with progressive proximal and distal limb muscle atrophy and weakness. Treatment options have attempted to target inflammatory and atrophic features of this condition (for example with immunosuppressive and immunomodulating drugs, anabolic steroids, and antioxidant treatments), although as yet there is no known effective treatment for reversing or minimising the progression of inclusion body myositis. In this review we have considered the benefits, adverse effects, and costs of treatment in targeting cardinal effects of the condition, namely muscle atrophy, weakness, and functional impairment.

OBJECTIVES

To assess the effects of treatment for IBM.

SEARCH METHODS

On 7 October 2014 we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register for Controlled Trials (CENTRAL), MEDLINE, and EMBASE. Additionally in November 2014 we searched clinical trials registries for ongoing or completed but unpublished trials.

SELECTION CRITERIA

We considered randomised or quasi-randomised trials, including cross-over trials, of treatment for IBM in adults compared to placebo or any other treatment for inclusion in the review. We specifically excluded people with familial IBM and hereditary inclusion body myopathy, but we included people who had connective tissue and autoimmune diseases associated with IBM, which may or may not be identified in trials. We did not include studies of exercise therapy or dysphagia management, which are topics of other Cochrane systematic reviews.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

The review included 10 trials (249 participants) using different treatment regimens. Seven of the 10 trials assessed single agents, and 3 assessed combined agents. Many of the studies did not present adequate data for the reporting of the primary outcome of the review, which was the percentage change in muscle strength score at six months. Pooled data from two trials of interferon beta-1a (n = 58) identified no important difference in normalised manual muscle strength sum scores from baseline to six months (mean difference (MD) -0.06, 95% CI -0.15 to 0.03) between IFN beta-1a and placebo (moderate-quality evidence). A single trial of methotrexate (MTX) (n = 44) provided moderate-quality evidence that MTX did not arrest or slow disease progression, based on reported percentage change in manual muscle strength sum scores at 12 months. None of the fully published trials were adequately powered to detect a treatment effect. We assessed six of the nine fully published trials as providing very low-quality evidence in relation to the primary outcome measure. Three trials (n = 78) compared intravenous immunoglobulin (combined in one trial with prednisone) to a placebo, but we were unable to perform meta-analysis because of variations in study analysis and presentation of trial data, with no access to the primary data for re-analysis. Other comparisons were also reported in single trials. An open trial of anti-T lymphocyte immunoglobulin (ATG) combined with MTX versus MTX provided very low-quality evidence in favour of the combined therapy, based on percentage change in quantitative muscle strength sum scores at 12 months (MD 12.50%, 95% CI 2.43 to 22.57). Data from trials of oxandrolone versus placebo, azathioprine (AZA) combined with MTX versus MTX, and arimoclomol versus placebo did not allow us to report either normalised or percentage change in muscle strength sum scores. A complete analysis of the effects of arimoclomol is pending data publication. Studies of simvastatin and bimagrumab (BYM338) are ongoing. All analysed trials reported adverse events. Only 1 of the 10 trials interpreted these for statistical significance. None of the trials included prespecified criteria for significant adverse events.

AUTHORS' CONCLUSIONS

Trials of interferon beta-1a and MTX provided moderate-quality evidence of having no effect on the progression of IBM. Overall trial design limitations including risk of bias, low numbers of participants, and short duration make it difficult to say whether or not any of the drug treatments included in this review were effective. An open trial of ATG combined with MTX versus MTX provided very low-quality evidence in favour of the combined therapy based on the percentage change data given. We were unable to draw conclusions from trials of IVIg, oxandrolone, and AZA plus MTX versus MTX. We need more randomised controlled trials that are larger, of longer duration, and that use fully validated, standardised, and responsive outcome measures.

Amyloid deposits and inflammatory infiltrates in sporadic inclusion body myositis: the inflammatory egg comes before the degenerative chicken

Sporadic inclusion body myositis (sIBM) is the most frequently acquired myopathy in patients over 50 years of age. It is imperative that neurologists and rheumatologists recognize this disorder which may, through clinical and pathological similarities, mimic other myopathies, especially polymyositis. Whereas polymyositis responds to immunosuppressant drug therapy, sIBM responds poorly, if at all. Controversy reigns as to whether sIBM is primarily an inflammatory or a degenerative myopathy, the distinction being vitally important in terms of directing research for effective specific therapies. We review here the pros and the cons for the respective hypotheses. A possible scenario, which our experience leads us to favour, is that sIBM may start with inflammation within muscle. The rush of leukocytes attracted by chemokines and cytokines may induce fibre injury and HLA-I overexpression. If the protein degradation systems are overloaded (possibly due to genetic predisposition, particular HLA-I subtypes or ageing), amyloid and other protein deposits may appear within muscle fibres, reinforcing the myopathic process in a vicious circle.

Myositis with endomysial cell invasion indicates inclusion body myositis even if other criteria are not fulfilled

The objective of this study was to investigate if patients with endomysial mononuclear cell infiltrates invading non-necrotic fibers have a disease course consistent with inclusion body myositis (IBM), irrespective of other histopathological and clinical characteristics. All patients with a muscle biopsy showing endomysial inflammation with invasion of non-necrotic muscle fibers during the period 1979-2006 in two tertiary neuromuscular referral centers were classified into three groups: 1) patients whose biopsies also showed rimmed vacuoles; 2) patients whose biopsies showed no vacuoles but fulfilled clinical criteria for IBM, and 3) patients whose biopsies showed no vacuoles, and also did not fulfill clinical criteria for IBM (unclassified patients). These groups were compared with regard to age, gender, clinical features, and disease course including response to immunosuppressive treatment. Eighty-one individuals (41 men) were included. Rimmed vacuoles were found in 49 patients (60.5%). Fourteen patients (17.3%) fulfilled clinical criteria for IBM and 18 patients (22.2%) were unclassified at presentation. At follow up (mean duration 9 years) three women remained unclassified (4%). There were no differences in disease course or effect of treatment between the three groups. Men had more often rimmed vacuoles than women (73% vs 48%; p = 0.018), and women more often than men were unclassified. Women tended to show more often temporary improvement if treated (p = 0.07), but none had sustained improvement. In conclusion, patients with a muscle biopsy showing endomysial cell infiltration with invasion of non-necrotic muscle fibers most probably have IBM, regardless of clinical and other pathological features. Women lack typical features more often than men.

Inclusion body myositis - pathomechanism and lessons from genetics

Inclusion body myositis is a rare, late-onset myopathy. Both inflammatory and myodegenerative features play an important role in their pathogenesis. Overlapping clinicopathological entities are the familial inclusion body myopathies with or without dementia. These myopathies share several clinical and pathological features with the sporadic inflammatory disease. Therefore, better understanding of the genetic basis and pathomechanism of these rare familial cases may advance our knowledge and enable more effective treatment options in sporadic IBM, which is currently considered a relentlessly progressive incurable disease.

Vitamin D receptor gene polymorphisms and haplotypes in Hungarian patients with idiopathic inflammatory myopathy

Idiopathic inflammatory myopathies are autoimmune diseases characterized by symmetrical proximal muscle weakness. Our aim was to identify a correlation between VDR polymorphisms or haplotypes and myositis. We studied VDR-BsmI, VDR-ApaI, VDR-TaqI, and VDR-FokI polymorphisms and haplotypes in 89 Hungarian poly-/dermatomyositis patients (69 females) and 93 controls (52 females). We did not obtain any significant differences for VDR-FokI, BsmI, ApaI, and TaqI genotypes and allele frequencies between patients with myositis and healthy individuals. There was no association of VDR polymorphisms with clinical manifestations and laboratory profiles in myositis patients. Men with myositis had a significantly different distribution of BB, Bb, and bb genotypes than female patients, control male individuals, and the entire control group. Distribution of TT, Tt, and tt genotypes was significantly different in males than in females in patient group. According to four-marker haplotype prevalence, frequencies of sixteen possible haplotypes showed significant differences between patient and control groups. The three most frequent haplotypes in patients were the fbAt, FBaT, and fbAT. Our findings may reveal that there is a significant association: Bb and Tt genotypes can be associated with myositis in the Hungarian population we studied. We underline the importance of our result in the estimated prevalence of four-marker haplotypes.

Inclusion body myositis: a review of clinical and genetic aspects, diagnostic criteria and therapeutic approaches

Inclusion body myositis is the most common myopathy in patients over the age of 40 years encountered in neurological practice. Although it is usually sporadic, there is increasing awareness of the influence of genetic factors on disease susceptibility and clinical phenotype. The diagnosis is based on recognition of the distinctive pattern of muscle involvement and temporal profile of the disease, and the combination of inflammatory and myodegenerative changes and protein deposits in the muscle biopsy. The diagnostic importance of immunohistochemical staining for major histocompatibility complex I and II antigens, for the p62 protein, and of the recently identified anti-cN1A autoantibody in the serum, are discussed. The condition is generally poorly responsive to conventional immune therapies but there have been relatively few randomised controlled trials and most of these have been under-powered and of short duration. There is an urgent need for further well-designed multicentre trials of existing and novel therapies that may alter the natural history of the disease.

Ongoing developments in sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is an acquired muscle disorder associated with ageing, for which there is no effective treatment. Ongoing developments include: genetic studies that may provide insights regarding the pathogenesis of IBM, improved histopathological markers, the description of a new IBM autoantibody, scrutiny of the diagnostic utility of clinical features and biomarkers, the refinement of diagnostic criteria, the emerging use of MRI as a diagnostic and monitoring tool, and new pathogenic insights that have led to novel therapeutic approaches being trialled for IBM, including treatments with the objective of restoring protein homeostasis and myostatin blockers. The effect of exercise in IBM continues to be investigated. However, despite these ongoing developments, the aetiopathogenesis of IBM remains uncertain. A translational and multidisciplinary collaborative approach is critical to improve the diagnosis, treatment, and care of patients with IBM.

Evaluation and construction of diagnostic criteria for inclusion body myositis

OBJECTIVE

To use patient data to evaluate and construct diagnostic criteria for inclusion body myositis (IBM), a progressive disease of skeletal muscle.

METHODS

The literature was reviewed to identify all previously proposed IBM diagnostic criteria. These criteria were applied through medical records review to 200 patients diagnosed as having IBM and 171 patients diagnosed as having a muscle disease other than IBM by neuromuscular specialists at 2 institutions, and to a validating set of 66 additional patients with IBM from 2 other institutions. Machine learning techniques were used for unbiased construction of diagnostic criteria.

RESULTS

Twenty-four previously proposed IBM diagnostic categories were identified. Twelve categories all performed with high (≥97%) specificity but varied substantially in their sensitivities (11%-84%). The best performing category was European Neuromuscular Centre 2013 probable (sensitivity of 84%). Specialized pathologic features and newly introduced strength criteria (comparative knee extension/hip flexion strength) performed poorly. Unbiased data-directed analysis of 20 features in 371 patients resulted in construction of higher-performing data-derived diagnostic criteria (90% sensitivity and 96% specificity).

CONCLUSIONS

Published expert consensus-derived IBM diagnostic categories have uniformly high specificity but wide-ranging sensitivities. High-performing IBM diagnostic category criteria can be developed directly from principled unbiased analysis of patient data.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that published expert consensus-derived IBM diagnostic categories accurately distinguish IBM from other muscle disease with high specificity but wide-ranging sensitivities.

Sporadic inclusion body myositis: the genetic contributions to the pathogenesis

Sporadic inclusion body myositis (sIBM) is the commonest idiopathic inflammatory muscle disease in people over 50 years old. It is characterized by slowly progressive muscle weakness and atrophy, with typical pathological changes of inflammation, degeneration and mitochondrial abnormality in affected muscle fibres. The cause(s) of sIBM are still unknown, but are considered complex, with the contribution of multiple factors such as environmental triggers, ageing and genetic susceptibility. This review summarizes the current understanding of the genetic contributions to sIBM and provides some insights for future research in this mysterious disease with the advantage of the rapid development of advanced genetic technology. An international sIBM genetic study is ongoing and whole-exome sequencing will be applied in a large cohort of sIBM patients with the aim of unravelling important genetic risk factors for sIBM.

A retrospective cohort study identifying the principal pathological features useful in the diagnosis of inclusion body myositis

OBJECTIVE

The current pathological diagnostic criteria for sporadic inclusion body myositis (IBM) lack sensitivity. Using immunohistochemical techniques abnormal protein aggregates have been identified in IBM, including some associated with neurodegenerative disorders. Our objective was to investigate the diagnostic utility of a number of markers of protein aggregates together with mitochondrial and inflammatory changes in IBM.

DESIGN

Retrospective cohort study. The sensitivity of pathological features was evaluated in cases of Griggs definite IBM. The diagnostic potential of the most reliable features was then assessed in clinically typical IBM with rimmed vacuoles (n=15), clinically typical IBM without rimmed vacuoles (n=9) and IBM mimics-protein accumulation myopathies containing rimmed vacuoles (n=7) and steroid-responsive inflammatory myopathies (n=11).

SETTING

Specialist muscle services at the John Radcliffe Hospital, Oxford and the National Hospital for Neurology and Neurosurgery, London.

RESULTS

Individual pathological features, in isolation, lacked sensitivity and specificity. However, the morphology and distribution of p62 aggregates in IBM were characteristic and in a myopathy with rimmed vacuoles, the combination of characteristic p62 aggregates and increased sarcolemmal and internal major histocompatibility complex class I expression or endomysial T cells were diagnostic for IBM with a sensitivity of 93% and specificity of 100%. In an inflammatory myopathy lacking rimmed vacuoles, the presence of mitochondrial changes was 100% sensitive and 73% specific for IBM; characteristic p62 aggregates were specific (91%), but lacked sensitivity (44%).

CONCLUSIONS

We propose an easily applied diagnostic algorithm for the pathological diagnosis of IBM. Additionally our findings support the hypothesis that many of the pathological features considered typical of IBM develop later in the disease, explaining their poor sensitivity at disease presentation and emphasising the need for revised pathological criteria to supplement the clinical criteria in the diagnosis of IBM.

Update in inclusion body myositis

PURPOSE OF REVIEW

The purpose of this study is to review recent scientific advances relating to the natural history, cause, treatment and serum and imaging biomarkers of inclusion body myositis (IBM).

RECENT FINDINGS

Several theories regarding the aetiopathogenesis of IBM are being explored and new therapeutic approaches are being investigated. New diagnostic criteria have been proposed, reflecting the knowledge that the diagnostic pathological findings may be absent in patients with clinically typical IBM. The role of MRI in IBM is expanding and knowledge about pathological biomarkers is increasing. The recent description of autoantibodies to cytosolic 5' nucleotidase 1A in patients with IBM is a potentially important advance that may aid early diagnosis and provides new evidence regarding the role of autoimmunity in IBM.

SUMMARY

IBM remains an enigmatic and often misdiagnosed disease. The pathogenesis of the disease is still not fully understood. To date, pharmacological treatment trials have failed to show clear efficacy. Future research should continue to focus on improving understanding of the pathophysiological mechanisms of the disease and on the identification of reliable and sensitive outcome measures for clinical trials. IBM is a rare disease and international multicentre collaboration for trials is important to translate research advances into improved patient outcomes.

Clinical assessment determines the diagnosis of inclusion body myositis independently of pathological features

BACKGROUND AND OBJECTIVE

Historically, the diagnosis of sporadic inclusion body myositis (IBM) has required the demonstration of the presence of a number of histopathological findings on muscle biopsy--namely, rimmed vacuoles, an inflammatory infiltrate with invasion of non-necrotic muscle fibres (partial invasion) and amyloid or 15-18 nm tubulofilamentous inclusions (Griggs criteria). However, biopsies of many patients with clinically typical IBM do not show all of these histopathological findings, at least at presentation. We compared the clinical features at presentation and during the course of disease in 67 patients with histopathologically diagnosed IBM and clinically diagnosed IBM seen within a single UK specialist muscle centre.

METHODS AND RESULTS

At presentation, using clinically focused diagnostic criteria (European Neuromuscular Centre (ENMC) 2011), a diagnosis of IBM was made in 88% of patients whereas 76% fulfilled the 1997 ENMC criteria and only 27% satisfied the histopathologically focused Griggs criteria. There were no differences in clinical features or outcomes between clinically and histopathologically diagnosed patients, but patients lacking the classical histopathological finding of rimmed vacuoles were younger, suggesting that rimmed vacuoles may be a later feature of the disease.

CONCLUSIONS

These findings have important implications for diagnosis and future studies or trials in IBM as adherence to histopathologically focused diagnostic criteria will exclude large numbers of patients with IBM. Importantly, those excluded may be at an earlier stage of the disease and more amenable to treatment.

[Inclusion-body myositis]

Sporadic inclusion-body myositis (sIBM) presents in average at the sixth decade of life and affects three men for one woman. It is a non-lethal, slowly progressive but disabling disease. Except the striated muscles, no other organs (such as the interstitial lung) are involved. The phenotype of this myopathy is particular since it involves the axial muscles (camptocormia, swallowing dysfunction) and limb girdle (notably the quadriceps) but also the distal muscles (in particular the fingers' and wrists' flexors) in a bilateral but non-symmetrical manner. The clinical presentation is then very suggestive of the diagnosis, which remains to be proven by a muscle biopsy. Histological features defining the diagnosis associate endomysial inflammatory infiltrates with frequent invaded fibres (the myositis) and amyloid deposits generally accompanying rimmed vacuoles (the inclusions). There is still today a debate to know if this disease is at its beginning a degenerative or an auto-immune condition. Nonetheless, usual immunosuppressive drugs (corticosteroids, azathioprine, methotrexate) or polyvalent immunoglobulines remain ineffective and even may worsen the handicap. Some controlled randomized trials will soon be launched for this condition, but for now, the best therapeutic approach to slow down the rapidity of progression of the disease is to maintain muscle exercise with the help of the physiotherapists.

Sporadic inclusion body myositis presenting with severe camptocormia

Sporadic inclusion body myositis (sIBM) is a slowly progressive idiopathic inflammatory myopathy. The characteristic early quadriceps and finger flexor muscle weakness often leads to the diagnosis of sIBM, especially when all canonical pathological features of sIBM are not present on muscle biopsy. Weakness of the paraspinal muscles, resulting in head drop and/or camptocormia, is a rare clinical finding along the course of sIBM, and even more rare as the presenting feature. We describe two patients with sIBM manifesting with camptocormia as the sole clinical manifestation for several years prior to the diagnosis by muscle biopsy. This observation emphasizes the role of sIBM in the etiology of camptocormia and the need to consider this common myopathy as a cause of weakness, despite the lack of classic quadriceps and finger flexor muscle weakness years after the onset of the paraspinal muscle weakness.

Acquired myopathy/dystrophies

Diseases of muscle may be congenital or acquired. They cause muscle weakness without sensory loss. The onset, distribution, and clinical course help to differentiate the type of muscle disorder. The diagnostic workup may include laboratory examination, electrodiagnostic studies, and muscle biopsy. A definitive diagnosis leads to better decision making with regard to treatment, genetic education, prognosis, functional expectations, and the impact of exercise on muscle function.

Inclusion body myositis: therapeutic approaches

The idiopathic inflammatory myopathies are a heterogeneous group of diseases that include dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) and other less common myopathies. These are clinically and histopathologically distinct diseases with many shared clinical features. IBM, the most commonly acquired inflammatory muscle disease occurs in individuals aged over 50 years, and is characterized by slowly progressive muscle weakness and atrophy affecting proximal and distal muscle groups, often asymmetrically. Unlike DM and PM, IBM is typically refractory to immunotherapy. Although corticosteroids have not been tested in randomized controlled trials, the general consensus is that they are not efficacious. There is some suggestion that intravenous immunoglobulin slows disease progression, but its long-term effectiveness is unclear. The evidence for other immunosuppressive therapies has been derived mainly from case reports and open studies and the results are discouraging. Only a few clinical trials have been conducted on IBM, making it difficult to provide clear recommendations for treatment. Moreover, IBM is a slowly progressive disease so assessment of treatment efficacy is problematic due to the longer-duration trials needed to determine treatment effects. Newer therapies may be promising, but further investigation to document efficacy would be expensive given the aforementioned need for longer trials. In this review, various treatments that have been employed in IBM will be discussed even though none of the interventions has sufficient evidence to support its routine use.

Inclusion body myositis coexisting with hypertrophic cardiomyopathy: an autopsy study

Inclusion body myositis is an inflammatory myopathy characterized pathologically by rimmed vacuoles and the accumulation of amyloid-related proteins. Autopsy studies in these patients, including histochemical examinations of multiple skeletal muscles, have not yet been published. In this paper, we describe the autopsy findings of a patient with inclusion body myositis and hypertrophic cardiomyopathy. A 69-year-old man, who was a human T lymphotropic virus type 1 carrier, exhibited slowly progressive muscle weakness and atrophy, predominantly affecting the scapular, quadriceps femoris, and forearm flexor muscles. His disease course was more rapidly progressive than that typically observed; the patient died suddenly of arrhythmia 5 years after diagnosis. Autopsy findings revealed that multiple muscles, including the respiratory muscles, were involved. Longitudinal studies revealed an increased frequency of rimmed vacuoles and p62/sequestosome 1- and/or TAR DNA-binding protein 43-positive deposits in autopsied muscles, although the amount of inflammatory infiltrate appeared to be decreased. We speculated that muscle degeneration may be more closely involved in disease progression compared with autoimmunity. Genetic analysis revealed a myosin binding protein C3 mutation, which is reportedly responsible for familial hypertrophic cardiomyopathy. This mutation and human T lymphotropic virus type 1 infection may have affected the skeletal muscles of this patient.

Long-term observational study of sporadic inclusion body myositis

We describe a long-term observational study of a large cohort of patients with sporadic inclusion body myositis and propose a sporadic inclusion body myositis weakness composite index that is easy to perform during a clinic. Data collection from two groups of patients (Paris and Oxford) was completed either during a clinic visit (52%), or by extraction from previous medical records (48%). One hundred and thirty-six patients [57% males, 61 (interquartile range 55-69) years at onset] were included. At the last visit all patients had muscle weakness (proximal British Medical Research Council scale <3/5 in 48%, distal British Medical Research Council scale <3/5 in 40%, swallowing problems in 46%). During their follow-up, 75% of patients had significant walking difficulties and 37% used a wheelchair (after a median duration from onset of 14 years). The sporadic inclusion body myositis weakness composite index, which correlated with grip strength (correlation coefficient: 0.47; P < 0.001) and Rivermead Mobility Index (correlation coefficient: 0.85; P < 0.001), decreased significantly with disease duration (correlation coefficient: -0.47; P < 0.001). The risk of death was only influenced by older age at onset of first symptoms. Seventy-one (52%) patients received immunosuppressive treatments [prednisone in 91.5%, associated (in 64.8%) with other immunomodulatory drugs (intravenous immunoglobulins, methotrexate or azathioprine) for a median duration of 40.8 months]. At the last assessment, patients who had been treated were more severely affected on disability scales (Walton P = 0.007, Rivermead Mobility Index P = 0.004) and on the sporadic inclusion body myositis weakness composite index (P = 0.04). The first stage of disease progression towards handicap for walking was more rapid among patients receiving immunosuppressive treatments (hazard ratio = 2.0, P = 0.002). This study confirms that sporadic inclusion body myositis is slowly progressive but not lethal and that immunosuppressive treatments do not ameliorate its natural course, thus confirming findings from smaller studies. Furthermore, our findings suggest that immunosuppressant drug therapy could have modestly exacerbated progression of disability. The sporadic inclusion body myositis weakness composite index might be a valuable outcome measure for future clinical trials, but requires further assessment and validation.

Observations on the classification of the inflammatory myopathies

This brief review considers historical approaches to the classification of the inflammatory myopathies. The last 25 years have seen advances in our knowledge of the underlying immune mechanism but the initial trigger for the idiopathic inflammatory myopathies remains unknown. Existing classifications have their limitations, but with the absence of a "gold standard" a definitive classification is not yet possible. Despite these problems, a working classification is possible that is valuable for everyday clinical practice.