Sleep disordered breathing and subclinical impairment of respiratory function are common in sporadic inclusion body myositis

272nd ENMC international workshop: 10 Years of progress - revision of the ENMC 2013 diagnostic criteria for inclusion body myositis and clinical trial readiness. 16-18 June 2023, Hoofddorp, The Netherlands

Since the publication of the 2013 European Neuromuscular Center (ENMC) diagnostic criteria for Inclusion Body Myositis (IBM), several advances have been made regarding IBM epidemiology, pathogenesis, diagnostic tools, and clinical trial readiness. Novel diagnostic tools include muscle imaging techniques such as MRI and ultrasound, and serological testing for cytosolic 5'-nucleotidase-1A antibodies. The 272nd ENMC workshop aimed to develop new diagnostic criteria, discuss clinical outcome measures and clinical trial readiness. The workshop started with patient representatives highlighting several understudied symptoms and the urge for a timely diagnosis. This was followed by presentations from IBM experts highlighting the new developments in the field. This report is composed of two parts, the first part providing new diagnostic criteria on which consensus was achieved. The second part focuses on the use of outcome measures in clinical practice and clinical trials, highlighting current limitations and outlining the goals for future studies.

Does inspiratory muscle training improve lung function and quality of life in people with inclusion body myositis? A pilot study

Inclusion body myositis is the most common acquired myositis in adults, predominantly weakening forearm flexor and knee extensor muscles. Subclinical respiratory muscle weakness has recently been recognised in people with inclusion body myositis, increasing their risk of respiratory complications. Inspiratory muscle training, a technique which demonstrates efficacy and safety in improving respiratory function in people with neuromuscular disorders, has never been explored in those with inclusion body myositis. In this pilot study, six adults with inclusion body myositis (age range 53 to 81 years) completed eight weeks of inspiratory muscle training. Measures of respiratory function, quality of life, sleep quality and a two-minute walk test were performed pre and post-intervention. All participants improved their respiratory function, with maximal inspiratory pressure, sniff nasal inspiratory pressure and forced vital capacity increasing by an average of 50 % (p = .002), 43 % (p = .018) and 13 % (p = .003) respectively. No significant change was observed in quality of life, sleep quality or two-minute walk test performance. No complications occurred due to inspiratory muscle training This pilot study provides the first evidence that inspiratory muscle training may be safe and effective in people with Inclusion Body Myositis, potentially mitigating the complications of poor respiratory function.

Sleep Disturbances in Autoimmune Neurological Diseases

PURPOSE OF REVIEW

To summarize the current evidence on the associations between autoimmune neurological diseases (e.g., multiple sclerosis, myasthenia gravis) and sleep disturbances (e.g., insomnia, parasomnias), as well as to review the main characteristics of sleep disorders with an immune-related pathophysiology (e.g., narcolepsy, anti-IgLON5 disease).

RECENT FINDINGS

An immune-mediated damage of the areas in the central nervous system that control sleep and wake functions (e.g., hypothalamus, brainstem) can lead to sleep disorders and sleep symptoms. Sleep disturbances are the reason to seek for medical attention in certain neuroimmunological conditions (e.g., narcolepsy, anti-IgLON5 disease) where sleep-related alterations are the main clinical feature. The assessment of sleep-related symptomatology and disorders should be included in the routine evaluation of patients with autoimmune neurological diseases. Clinicians should be aware of the typical clinical presentation of certain neuroimmunological disorders mainly affecting sleep.

Characterizing Ventilatory Muscle Dysfunction in Inclusion Body Myositis

OBJECTIVE

Investigation of the frequency and progression of ventilatory muscle dysfunction in patients with inclusion body myositis, the most common myopathy after age of 50 yrs. Prior research is limited to case series and cross-section studies.

DESIGN

This is a retrospective review of pulmonary function tests, respiratory symptoms, and muscle strength testing.

RESULTS

Of the 54 patients reviewed (mean age: 65 ± 9 yrs and disease duration: 7 ± 7 yrs), the majority ( n = 32, 59%) had restrictive forced vital capacity deficits at initial visit. Patients with reduced forced vital capacity showed higher prevalence of respiratory symptoms; but age, body mass index, and limb strength were similar when compared with patients without restrictive forced vital capacity. Mean rate of forced vital capacity decline of 0.108 l/yr in inclusion body myositis patients. Lower baseline limb strength correlated with longer disease duration and future forced vital capacity decline (eg, weaker patients experienced faster decline).

CONCLUSIONS

Based on forced vital capacity, there is a high frequency of ventilatory pump muscle weakness in inclusion body myositis, which is associated with a higher burden of respiratory symptoms. Baseline strength may indicate risk of respiratory decline and need for vigilant screening. Importantly, ventilatory and limb muscle decline may not progress in a corresponding manner, highlighting the importance of pulmonary function surveillance.

A cross-sectional study of memory and executive functions in patients with sporadic inclusion body myositis

INTRODUCTION/AIMS

Sporadic inclusion body myositis (IBM) is a degenerative and inflammatory acquired myopathy characterized by muscle deposition of various proteins typically associated with Alzheimer disease and other neurodegenerative diseases. Although cognitive impairment is not noted as a clinical feature of IBM, evidence is lacking. In this study we investigated whether cognitive performance of patients with IBM differs from population norms, focusing on cognitive domains affected in early Alzheimer disease (memory, executive function), and to test whether disease duration and the level of disability of IBM are associated with cognitive function.

METHODS

Twenty-four patients with IBM (mean [standard deviation]: age, 62.0 [7.2] years; disease duration, 9.6 [4.8] years) were assessed cross-sectionally on neuropsychological tests covering multiple cognitive domains, including the Preclinical Alzheimer Cognitive Composite (PACC). Performance was compared with published normative data adjusted for age, sex, and education (National Alzheimer's Coordinating Center; N = 3268). Associations were examined between PACC score, disease duration, and level of disability (assessed using the IBM Functional Rating Scale [IBMFRS]).

RESULTS

Across all cognitive tests, group performance was within ±1 standard deviation of the normative mean. There was no evidence of associations between PACC score and either disease duration (ρ = -0.04, P = .87) or IBMFRS total score (ρ = 0.14, P = .52).

DISCUSSION

Memory and executive function in patients with IBM did not differ from normative data, and we observed no evidence of associations between the cognitive composite and disease duration or level of disability. This addresses a question frequently asked by patients and will be of value for clinicians and patients alike.

Diaphragmatic dysfunction in neuromuscular disease, an MRI study

The aim of this exploratory study was to evaluate diaphragmatic function across various neuromuscular diseases using spirometry-controlled MRI. We measured motion of the diaphragm relative to that of the thoracic wall (cranial-caudal ratio vs. anterior posterior ratio; CC-AP ratio), and changes in the diaphragmatic curvature (diaphragm height and area ratio) during inspiration in 12 adults with a neuromuscular disease having signs of respiratory muscle weakness, 18 healthy controls, and 35 adult Pompe patients - a group with prominent diaphragmatic weakness. CC-AP ratio was lower in patients with myopathies (n=7, 1.25±0.30) and motor neuron diseases (n=5, 1.30±0.10) than in healthy controls (1.37±0.14; p=0.001 and p=0.008), but not as abnormal as in Pompe patients (1.12±0.18; p=0.011 and p=0.024). The mean diaphragm height ratio was 1.17±0.33 in patients with myopathies, pointing at an insufficient diaphragmatic contraction. This was also seen in patients with Pompe disease (1.28±0.36), but not in healthy controls (0.82±0.33) or patients with motor neuron disease (0.82±0.24). We conclude that spirometry-controlled MRI enables us to investigate respiratory dysfunction across neuromuscular diseases, suggesting that the diaphragm is affected in a different way in myopathies and motor neuron diseases. Whether MRI can also be used to evaluate progression of diaphragmatic dysfunction requires additional studies.

Assessment of thrombocytopenia, sleep apnea, and cardiac involvement in GNE myopathy patients

INTRODUCTION

We previously identified UDP-N-acetylglucosamine 2-epimerase (GNE) myopathy patients with sleep apnea and a past history of thrombocytopenia, but without disease-specific cardiac involvement. This study aimed to clarify the occurrence, severity, and serial changes of these complications.

METHODS

Thirty-three genetically confirmed GNE myopathy patients who participated in a 5-y longitudinal observational history study underwent platelet count and platelet-associated immunoglobulin G (PA-IgG) measurements, a sleep study, and electrocardiography (ECG), Holter ECG, and echocardiogram examinations.

RESULTS

Among the 33 patients, three had low platelet counts and 17 out of 26 were PA-IgG positive. No patient exhibited bleeding tendencies, and 3 out of 28 had low platelet counts. Muscle weakness was more pronounced, and summed MMT and grip power significantly lower, in PA-IgG-positive patients than in PA-IgG-negative patients. Of 19 patients, 7, 4, and 3 who underwent a sleep study had mild, moderate, and severe sleep apnea, respectively, and three started continuous positive airway pressure (CPAP). The respiratory disturbance index was not significantly correlated with physical evaluation items or forced vital capacity. All patients underwent ECG, 32 underwent cardiac ultrasound, and 25 underwent Holter ECG. No disease-specific cardiac involvement was noted, no serial changes during the follow-up period were observed for ECG and echocardiography, and none of the patients required therapy for cardiac abnormalities.

DISCUSSION

PA-IgG is a potential disease biomarker in GNE myopathy patients, although its significance needs to be clarified. While none of the patients in this study experienced cardiomyopathy or arrythmia due to myopathy, sleep apnea was identified as a frequent complication.

Determinants and functional impacts of diaphragmatic involvement in patients with inclusion body myositis

BACKGROUND

We evaluated the functional consequences of diaphragm involvement in patients with inclusion body myositis (IBM).

METHODS

Ultrasound diaphragm thickening fraction (TFdi), lung function and dyspnea levels were compared between IBM patients and matched controls. Patients with IBM were grouped into "low" and "high" diaphragm activity based on TFdi values (with cutoff value being the lowest observed TFdi in the control group), and clinical characteristics were compared between groups.

RESULTS

20 IBM patients were included. TFdi was significantly lower in patients and correlated with time since symptom onset (rho = 0.74, P < .001). Patients had significantly lower forced vital capacity and higher dyspnea scores than controls. IBM patients with "low" diaphragm activity (n = 9) had lower 6-min walking distance, higher resting and exertional dyspnea and a larger positional decrease in vital capacity (all P ≤ .03) than patients with 'high' activity. Timed Up and Go time and St. George's Respiratory Questionnaire were not different between groups.

CONCLUSIONS

Diaphragm involvement in IBM is related to disease duration and has detrimental effects on lung function, dyspnea and exercise capacity. Further studies are required to investigate its potential as a therapeutic target.

Sirolimus for treatment of patients with inclusion body myositis: a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial

BACKGROUND

Inclusion body myositis is the most frequent myositis in patients older than 50 years. Classical immunosuppressants are ineffective in treating inclusion body myositis, and to date there are no recommendations for pharmacological approaches to treatment. When used after organ transplantation, sirolimus can block the proliferation of effector T cells, while preserving T regulatory cells, and induce autophagy, all of which are processes that are impaired in inclusion body myositis. In this pilot study, we aimed to test the efficacy of sirolimus in patients with inclusion body myositis.

METHODS

This randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial was done at a single hospital in Paris, France. The study included men and women (aged 45-80 years) who had a defined diagnosis of inclusion body myositis according to established criteria. Eligible participants were randomly assigned (1:1) to receive once-daily oral sirolimus 2 mg or placebo. Centralised balanced block randomisation (blocks of four) was computer generated without stratification. The study comprised a 15-day screening period (days -15 to 0) and a 52-week treatment period (day 0 to month 12). The primary endpoint was the relative percentage change from baseline to month 12 in maximal voluntary isometric knee extension strength. Secondary endpoints included the following assessments at months 6 and 12: 6-min walking distance, isometric muscle strength for hand grip (finger flexors), knee flexion and elbow flexion and extension, forced vital capacity, muscle replacement with fat measured by quantitative nuclear MRI, Inclusion Body Myositis Weakness Composite Index (IBMWCI), Inclusion Body Myositis Functional Rating Scale (IBMFRS), Health Assessment Questionnaire without Disability Index (HAQ-DI), and analyses of T-cell subpopulations by mass cytometry. The primary analysis was done on the intention-to-treat population. The trial is registered at ClinicalTrials.gov, NCT02481453.

FINDINGS

Between July 15, 2015, and May 13, 2016, we screened 285 patients, 44 of whom were randomly allocated to sirolimus (22 patients) or placebo (22 patients). We observed no difference in the primary outcome of relative percentage change from baseline to month 12 of the maximal voluntary isometric knee extension strength (median difference 3·78, 95% CI -10·61 to 17·31; p=0·85). For secondary outcomes, differences between the groups were not significant for changes in strength of other muscle groups (grip, elbow flexion and extension, or knee flexion), IBMWCI, IBMFRS, and lower limb muscle fat fraction. However, we observed significant differences in favour of sirolimus between the study groups for HAQ-DI, forced vital capacity, thigh fat fraction, and 6-min walking distance. Ten (45%) of 22 patients in the sirolimus group had a serious adverse event compared with six (27%) of 22 patients in the placebo group. Four (18%) patients in the sirolimus group stopped their treatment because of adverse events (severe mouth ulcers, aseptic pneumonia, renal insufficiency, and peripheral lower limb oedema), which resolved after treatment discontinuation. Canker sores were the most frequent side-effect and were mainly mild or moderate in ten patients.

INTERPRETATION

We found no evidence for efficacy of sirolimus for treating inclusion body myositis based on maximal voluntary isometric knee extension strength and other muscle strength measures, and the side-effects of treatment were substantial for some patients. However, we believe there was enough evidence of benefit in certain secondary outcomes to pursue a multicentre phase 3 trial to further assess the safety and efficacy of sirolimus.

FUNDING

Institut national de la santé et de la recherche médicale, Direction générale de l'offre de soins, and Association Française contre les Myopathies.

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.

Mortality and Causes of Death in Patients with Sporadic Inclusion Body Myositis: Survey Study Based on the Clinical Experience of Specialists in Australia, Europe and the USA

BACKGROUND

There is a paucity of data on mortality and causes of death (CoDs) in patients with sporadic inclusion body myositis (sIBM), a rare, progressive, degenerative, inflammatory myopathy that typically affects those aged over 50 years.

OBJECTIVE

Based on patient records and expertise of clinical specialists, this study used questionnaires to evaluate physicians' views on clinical characteristics of sIBM that may impact on premature mortality and CoDs in these patients.

METHODS

Thirteen physicians from seven countries completed two questionnaires online between December 20, 2012 and January 15, 2013. Responses to the first questionnaire were collated and presented in the second questionnaire to seek elaboration and identify consensus.

RESULTS

All 13 physicians completed both questionnaires, providing responses based on 585 living and 149 deceased patients under their care. Patients were reported to have experienced dysphagia (60.2%) and injurious falls (44.3%) during their disease. Over half of physicians reported that a subset of their patients with sIBM had a shortened lifespan (8/13), and agreed that bulbar dysfunction/dysphagia/oropharyngeal involvement (12/13), early-onset disease (8/13), severe symptoms (8/13), and falls (7/13) impacted lifespan. Factors related to sIBM were reported as CoDs in 40% of deceased patients. Oropharyngeal muscle dysfunction was ranked as the leading feature of sIBM that could contribute to death. The risk of premature mortality was higher than the age-matched comparison population.

CONCLUSIONS

In the absence of data from traditional sources, this study suggests that features of sIBM may contribute to premature mortality and may be used to inform future studies.

Pulmonary functions and sleep-related breathing disorders in lipid storage disease

PURPOSE

Pulmonary function abnormalities and sleep-related breathing disorders (SRBD) are frequent in subjects with several neuromuscular diseases but there is no data about lipid storage diseases (LSD). Therefore, we aimed to evaluate pulmonary functions and SRBD in adults with LSD.

METHODS

Pulmonary functions (forced expiratory volume (FEV₁), forced vital capacity (FVC), supine FVC, upright-supine FVC% change, maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), peak cough flow (PCF)), arterial blood gases, and polysomnographic data of all subjects were evaluated.

RESULTS

Twenty-five subjects with LSD were evaluated [17 males, 8 females; age 34.9 ± 15 years; BMI 26.5 ± 3.4 kg/m²]. MIP was - 72.2 ± 32.7 cmH₂O (< - 80 cmH₂O in 13 subjects), MEP was 80.9 ± 39.1 cmH₂O (< 80 cmH₂O in 9 subjects, < 40 cmH₂O in 6 subjects), and PCF was 441.3 ± 190.9 L/min (< 360 L/min in 11 subjects). FVC was 87.8% ± 25.7 and 6 subjects had FVC < 80%. Seven subjects had diaphragm dysfunction (four upright-supine FVC% ≥ 15, three dyspnea in supine position with paradoxical abdominal respiration). Five subjects had hypoxemia (PaO₂ < 80 mmHg) and 8 subjects had hypercapnia (PaCO₂ > 45 mmHg). REM sleep had decreased in all subjects (10.2% ± 6.1). Obstructive sleep apnea (OSA) was found in 80% of the subjects (n = 20; 9 mild, 9 moderate, 2 severe). For subjects with OSA, apnea-hypopnea index (AHI) was 20.8 ± 15.9/h, oxygen desaturation index (ODI) was 11.9 ± 15.4/h, AHI_REM was 30.6 ± 19.7/h, AHI_NREM was 19.7 ± 16.6/h, ODI_REM was 27.2 ± 26.1/h, and ODI_NREM was 11.4 ± 15/h. Five subjects (20%) diagnosed as REM-related OSA. Nocturnal mean SpO₂ was 94.9% ± 1.7, lowest SpO₂ was 73.3% ± 13.9, and time spent with SpO₂ < 90% was 2.4% ± 7.2.

CONCLUSION

In subjects with LSD, pulmonary function impairment, daytime hypercapnia and hypoxemia, and OSA, especially REM-related OSA, are frequent. Therefore, pulmonary functions and polysomnography should be performed routinely.

Respiratory failure because of neuromuscular disease

PURPOSE OF REVIEW

Understanding the mechanisms and abnormalities of respiratory function in neuromuscular disease is critical to supporting the patient and maintaining ventilation in the face of acute or chronic progressive impairment.

RECENT FINDINGS

Retrospective clinical studies reviewing the care of patients with Guillain-Barré syndrome and myasthenia have shown a disturbingly high mortality following step-down from intensive care. This implies high dependency and rehabilitation management is failing despite evidence that delayed improvement can occur with long-term care. A variety of mechanisms of phrenic nerve impairment have been recognized with newer investigation techniques, including EMG and ultrasound. Specific treatment for progressive neuromuscular and muscle disease has been increasingly possible particularly for the treatment of myasthenia, metabolic myopathies, and Duchenne muscular dystrophy. For those conditions without specific treatment, it has been increasingly possible to support ventilation in the domiciliary setting with newer techniques of noninvasive ventilation and better airway clearance. There remained several areas of vigorous debates, including the role for tracheostomy care and the place of respiratory muscle training and phrenic nerve/diaphragm pacing.

SUMMARY

Recent studies and systematic reviews have defined criteria for anticipating, recognizing, and managing ventilatory failure because of acute neuromuscular disease. The care of patients requiring long-term noninvasive ventilatory support for chronic disorders has also evolved. This has resulted in significantly improved survival for patients requiring domiciliary ventilatory support.

Inclusion Body Myositis: A Case Presenting with Respiratory Failure and Autopsy Findings Leading to the Hypothesis of a Paraneoplastic Cause

BACKGROUND Sporadic inclusion body myositis (IBM) is the most common acquired myopathy seen in adults aged over 50 years, with a prevalence estimated at between 1 and 70 per million. Weakness of the diaphragm with loss of vital capacity is almost universal in IBM. This is almost always asymptomatic. When respiratory complications occur, they are most often due to aspiration. Respiratory failure due to diaphragmatic weakness is exceptionally rare, particularly as the presenting symptom of the disease. It is not currently considered to be a paraneoplastic syndrome. CASE REPORT Our patient presented with hypercarbic respiratory failure. This is the first such reported case without signs of weakness elsewhere of which we are aware. We suspected IBM based on her history of progressive weakness and findings on electromyography. There was a delay of 5 years in obtaining biopsy for confirmation, during which she presented with recurrent episodes of respiratory failure despite using non-invasive ventilation. An autopsy revealed the presence of papillary thyroid carcinoma with spread to local lymph nodes. On the basis that these co-morbidities are unlikely to have occurred by chance (we estimate 1×10-17), we hypothesize that IBM may be a paraneoplastic condition. We acknowledge that proof would require demonstrating a pathogenic antibody. CONCLUSIONS IBM should be considered in older patients (age >45) presenting with otherwise unexplained respiratory failure. A workup for possible malignancy in this setting appears reasonable.

Diagnosis and Management of Immune-Mediated Myopathies

Immune-mediated myopathies (IMMs) are a heterogeneous group of acquired muscle disorders characterized by muscle weakness, elevated creatine kinase levels, and myopathic electromyographic findings. Most IMMs feature the presence of inflammatory infiltrates in muscle. However, the inflammatory exudate may be absent. Indeed, necrotizing autoimmune myopathy (NAM), also called immune-mediated necrotizing myopathy, is characterized by a necrotizing pathologic process with no or minimal inflammation in muscle. The recent discovery of antibodies associated with specific subtypes of autoimmune myopathies has played a major role in characterizing these diseases. Although diagnostic criteria and classification of IMMs currently are under revision, on the basis of the clinical and muscle histopathologic findings, IMMs can be differentiated as NAM, inclusion body myositis (IBM), dermatomyositis, polymyositis, and nonspecific myositis. Because of recent developments in the field of NAM and IBM and the controversies around polymyositis, this review will focus on NAM, IBM, and dermatomyositis.

Inclusion Body Myositis: What Most Impacts Patients' Lives

OBJECTIVE

Inclusion body myositis (IBM) is the most common form of idiopathic inflammatory myopathy in adults older than 50 years. Few studies have focused on the functional, physical, and social limitations of this disease. This study identifies pertinent symptoms that impact the health and daily function of patients with IBM.

METHODS

We used semistructured interviews with 10 biopsy-confirmed adults with IBM to identify the psychological, physical, and functional limitations that have the greatest impact on the lives of patients with IBM.

RESULTS

Participants with IBM provided 644 direct quotes identifying issues that have the greatest effect on their lives. Two hundred nine individual symptoms and 17 symptomatic themes were identified by patients as having a significant impact on their lives. The symptomatic themes mentioned most frequently involved mobility and ambulation, emotional distress, and activity impairment.

CONCLUSIONS

Identifying critical issues to patients with IBM is potentially useful for clinicians whose aim is to provide optimal care to patients with IBM.

Respiratory management of patients with neuromuscular disease: current perspectives

Neuromuscular ventilatory weakness can be difficult to recognize because the symptoms can be nocturnal, nonspecific, or attributed to other conditions. The presence of respiratory muscle weakness suggests a number of possible heterogeneous conditions, including neurodegenerative, autoimmune, and genetic neuromuscular diseases. In some conditions, disease-modifying management exists, but in the absence of such intervention, supportive respiratory therapy can improve quality of life and survival. In this review, we discuss the differential diagnosis and diagnostic approach to chronic neuromuscular respiratory weakness. We also review the clinical assessment and management of respiratory failure in these conditions.

Diagnostic criteria for inclusion body myositis

Inclusion body myositis (IBM) was first identified as a specific disorder about 40 years ago and is now recognized to be the most frequently presenting primary myopathy in middle age and beyond. Initial characterization was based on the observation of specific pathological features distinguishing it from polymyositis. It was soon appreciated that there were also distinguishing clinical features. The earliest diagnostic criteria were heavily biased towards pathological features, but over time revised criteria have given increasing importance to certain clinical features. Until the specific cause of IBM is determined, and the basic pathogenetic mechanisms are better understood, there can be no diagnostic gold-standard against which to compare the sensitivity and specificity of any proposed diagnostic criteria, but such criteria are essential to ensure that patients entering clinical, epidemiological, genetic, pathological or therapeutic studies represent a homogeneous population. It is likely that any currently accepted diagnostic criteria will, once a gold-standard is eventually established, be shown to have 'missed' patients with atypical features, but that has to be accepted to make certain that current studies are not contaminated by patients who do not have IBM. In other words, in everyday clinical practice there will be the occasional patient who an experienced myologist strongly suspects has IBM, but does not meet current criteria - the criteria lack sensitivity. But if the criteria are so broad as to include all such atypical cases, they would be likely to include patients who do not in fact have IBM - they would lack specificity. The sensitivity and specificity of existing criteria have been reviewed recently, in so far as it is possible to do so, and found to have high specificity but variable sensitivity.

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.

Emerging therapeutic options for sporadic inclusion body myositis

Sporadic inclusion body myositis is the most common inflammatory muscle disorder preferentially affecting males over the age of 40 years. Progressive muscle weakness of the finger flexors and quadriceps muscles results in loss of independence with activities of daily living and eventual wheelchair dependence. Initial signs of disease are often overlooked and can lead to mis- or delayed diagnosis. The underlying cause of disease is unknown, and disease progression appears refractory to available treatment options. This review discusses the clinical presentation of inclusion body myositis and the current efforts in diagnosis, and focuses on the current state of research for both nonpharmacological and pharmacological treatment options for this patient group.

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.