Myxovirus-like structures in a case of human chronic polymyositis

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.

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.

Autoimmune inflammatory myopathies

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

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.

Revisiting the Role of GSK3, A Modulator of Innate Immunity, in Idiopathic Inclusion Body Myositis

Idiopathic or sporadic inclusion body myositis (IBM) is the leading age-related (onset >50 years of age) autoimmune muscular pathology, resulting in significant debilitation in affected individuals. Once viewed as primarily a degenerative disorder, it is now evident that much like several other neuro-muscular degenerative disorders, IBM has a major autoinflammatory component resulting in chronic inflammation-induced muscle destruction. Thus, IBM is now considered primarily an inflammatory pathology. To date, there is no effective treatment for sporadic inclusion body myositis, and little is understood about the pathology at the molecular level, which would offer the best hopes of at least slowing down the degenerative process. Among the previously examined potential molecular players in IBM is glycogen synthase kinase (GSK)-3, whose role in promoting TAU phosphorylation and inclusion bodies in Alzheimer’s disease is well known. This review looks to re-examine the role of GSK3 in IBM, not strictly as a promoter of TAU and Abeta inclusions, but as a novel player in the innate immune system, discussing some of the recent roles discovered for this well-studied kinase in inflammatory-mediated pathology.

Historie der idiopathischen entzündlichen Myopathien

Die ersten Beschreibungen idiopathischer entzündlicher Myopathien (Myositiden), initial durchweg Dermatomyositiden, reichen über 150 Jahre zurück (E. L. Wagner, C E. Potain, H. Unverricht). G. Stertz vermutete 1916 erstmals einen Zusammenhang zwischen einem Malignom und einer Dermatomyositis. Die charakteristischen Hautveränderungen und histopathologischen Veränderungen bei den Dermatomyositiden sind schon früh beschrieben worden, wohingegen die typischen proximalen Extremitätenparesen in den ersten Jahrzehnten keineswegs regelmäßig in den Beschreibungen auftauchten. Die Behandlungsmöglichkeit mit Glukokortikoiden wurde erst vor 70 Jahren in den U.S.A. entdeckt, eine bis heute akzeptierte Klassifikation 1977 vom US-Amerikaner Bohan und Mitarbeitern beschrieben. Der Beitrag beschreibt die Erstbeschreibungen der nicht infektiösen entzündlichen Myopathien und deren Therapie.

What is New in Idiopathic Inflammatory Myopathies: Mechanisms and Therapies

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of disorders that cause muscle weakness and also have extramuscular manifestations involving various organ systems; namely the lung, skin, heart, and joints. Previously classified broadly as dermatomyositis (DM) and polymyositis now the spectrum of the disease has evolved into more clinical subtypes. There are now five clinicoserological subtypes recognized worldwide DM, antisynthetase syndrome (AS), overlap myositis (OM), immune mediated necrotizing myopathy (IMNM), and inclusion body myositis. Each of these subtypes has a unique phenotype and specific antibodies associated. With the evolving treatment options from the use of immunosuppressive medications to the use of targeted therapy with biologic agents, and further understanding of the pathogenesis of inflammatory myositis, we may have more effective treatment options. We discuss in this review, various myositis-associated antibodies associated with each clinicoserological subtype of IIM and their role. We also describe the evolving therapies and the evidence for the newer biologic therapies in the treatment of IIMs.

Paramyxovirus-like Structures in Lupus and Dermatomyositis

Paramyxovirus-like structures in so-called collagen disease have been reported in polymyositis and systemic lupus erythematosus. The identical structure was found in the present study in the skin lesions of discoid lupus erythematosus and dermatomyositis; these two are also called collagen diseases. This report deals with detailed ultrastructure and some aspects of the mode of formation of this structure as they are seen in the skin lesions of discoid lupus and dermatomyositis.

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.

Dysphagia in Patients with Sporadic Inclusion Body Myositis: Management Challenges

Dysphagia in inclusion body myositis (IBM) is common and associated with increased mortality and morbidity due to aspiration pneumonia, malnutrition and dehydration. There is currently no consensus on treatment of dysphagia in IBM and outcomes are variable depending on timing of intervention, patient preference and available expertise. There is a paucity of research exploring the pathophysiology of dysphagia in IBM and appropriate investigations. Increased knowledge of the aetiopathogenesis is likely to change the approach to treatment as well as improve the quality of life for patients. This review explores the epidemiology and pathophysiology of dysphagia in IBM and the currently available treatment strategies.

Immune and myodegenerative pathomechanisms in inclusion body myositis

Inclusion Body Myositis (IBM) is a relatively common acquired inflammatory myopathy in patients above 50 years of age. Pathological hallmarks of IBM are intramyofiber protein inclusions and endomysial inflammation, indicating that both myodegenerative and inflammatory mechanisms contribute to its pathogenesis. Impaired protein degradation by the autophagic machinery, which regulates innate and adaptive immune responses, in skeletal muscle fibers has recently been identified as a potential key pathomechanism in IBM. Immunotherapies, which are successfully used for treating other inflammatory myopathies lack efficacy in IBM and so far no effective treatment is available. Thus, a better understanding of the mechanistic pathways underlying progressive muscle weakness and atrophy in IBM is crucial in identifying novel promising targets for therapeutic intervention. Here, we discuss recent insights into the pathomechanistic network of mutually dependent inflammatory and degenerative events during IBM.

Inclusion Body Myositis

PURPOSE OF REVIEW

Inclusion body myositis (IBM) is an enigmatic progressive disease of skeletal muscle. This review provides a summary of the clinical and pathophysiologic aspects of IBM.

RECENT FINDINGS

The development of diagnostic blood testing for IBM followed from the discovery of a B-cell pathway in IBM muscle and circulating autoantibodies against NT5C1A, further establishing IBM's status as an autoimmune disease. The key role of cytotoxic T cells in IBM is further supported by the identification of a link between IBM and T-cell large granular lymphocytic leukemia. The testing of research diagnostic criteria in patients is improving its accuracy. Increases in estimated prevalences may be due to a combination of true increases and improved recognition of disease.

SUMMARY

IBM has high unmet medical need. Advances in the mechanistic understanding of IBM as an autoimmune disease will drive effective therapeutic approaches. The identification of a B-cell pathway has resulted in the first identification of an IBM autoantigen and emphasized its status as an autoimmune disease. The recognition that large granular lymphocyte CD8+ T-cell expansions are present in both blood and muscle provides additional biomarkers for IBM and suggests a mechanistic relationship to the neoplastic disease T-cell large granular lymphocytic leukemia.

Clinicopathologic features of sporadic inclusion body myositis in China

This study is to investigate the clinical and pathologic features of sporadic inclusion body myositis (sIBM) in China. We retrospectively evaluated the clinical and pathological features of consecutive patients in our department between January 1986 to May 2012. Total 28 cases of sIBM (20 males, 8 females, mean age was 56.93±8.79) were obtained by review of all 4099 muscle biopsy reports. The proportion of sIBM was 0.68% (28/4099) in China. Muscle weakness of quadriceps appeared 100% in 28 cases, while conspicuous atrophy of quadriceps appeared only in five cases (17.86%). Creatase values of 28 patients with sIBM were normal or mildly elevated. Muscle biopsies showed that atrophic fibers resembled more frequent in small angular and irregular shape (82.14%), less common in small round shape (17.86%). Rimmed vacuoles resembled crack (67.86%) and round (32.14%) shape. Mononuclear cell invasion into necrotic muscle fibers (35.71%) was more frequent than non-necrotic muscle fibers (7.14%). sIBM was still a rare disease in China compared to other countries. There were some certain specific pathological characteristics existed in Chinese sIBM patients.

Formation of gelsolin amyloid fibrils in the rough endoplasmic reticulum of skeletal muscle in the gelsolin mouse model of inclusion body myositis: comparative analysis to human sporadic inclusion body myositis

Sporadic inclusion body myositis has a significant impact on the life of the elderly. Despite some similarities to other myopathies with established genetic defects, little is known about mechanisms of its development and no effective treatment is available. Therefore, there is a need for animal models that can faithfully reconstitute important aspects of this human disease. The authors recently expressed a mutant form of human gelsolin in mice under the control of a muscle-specific promoter. This induced myopathic changes reminiscent of human inclusion body myositis. In this study, immunogold labeling is used to further characterize this model. The study demonstrates a presence of gelsolin amyloid deposits within the rough endoplasmic reticulum. It further compares this mouse model to human sporadic inclusion body myositis.

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.

Pathogenesis and therapy of inclusion body myositis

PURPOSE OF REVIEW

Inclusion body myositis (IBM) is a poorly understood progressive muscle disease of middle and later life. Its dual pathologies of autoimmunity and unexplained myofiber degeneration and loss have been enigmatic since its earliest descriptions over 40 years ago. No reliable effective therapy currently exists for IBM. This review provides an update of current issues in the pathogenesis and therapy of IBM.

RECENT FINDINGS

Recent studies have further defined the clinical features of IBM, including natural history, pattern of muscle involvement, and role of MRI imaging. Further potential immune mediators have been identified. An autoantibody directed against a muscle antigen appears to have high specificity for IBM among muscle diseases. Further evidence for myonuclear degeneration has been reported.

SUMMARY

IBM remains a poorly understood muscle disease, although understanding of the pathophysiological mechanisms continues to expand and is supporting new therapeutic approaches.

Polymyositis-dermatomyositis recognized during the follow-up of a patient with type 2 diabetes

Polymyositis-dermatomyositis is a rare systemic autoimmune disease which belongs to the class of idiopathic inflammatory myopathies. The disease exhibits high inter-individual variability, but chronic myositis is a common feature. As different manifestations often appear in atypical forms, establishing the precise diagnosis can be rather complicated. The prognosis and the patient’s life expectations highly depend on whether the clinician considers this possibility in the diagnostic process or not. The authors present the case of a 50-year-old woman who was referred to hospital with suspected myopathy by her general practitioner. The history of the patient, the overall clinical picture and some marked laboratory abnormalities raised the possibility of polymyositis-dermatomyositis, which was unequivocally confirmed by immunological tests. Drug therapy was started immediately with the administration of high dose corticosteroid (1–2 mg/kg/day methylprednisolone), which was found to be an effective strategy leading to fast and remarkable improvement in the patient’s condition. From the first hospital day, the patient also received insulin therapy in order to prevent any potential corticosteroid-induced imbalance in her carbohydrate metabolism. The long-term patient management was provided by an interdisciplinary team the members of which (both clinicians and other health care professionals) worked according to a co-ordinated, complex care plan, and managed not only the “physiological functions” but the different psychological and social problems as well, which are usually associated with the disease. The follow-up period of this polyphase disease process lasted for 4.5 years, during which only two relapses occurred, and muscle strength typically varied between 3 and 4 on a five grade scale with the exception of the relapse periods. Good outcome was attributed to the strict follow-up and individualized therapy/care. Orv. Hetil., 2012, 153, 467–474.

Inclusion body myositis

PURPOSE OF REVIEW

Sporadic inclusion body myositis (sIBM) is a poorly understood immune and degenerative disease of skeletal muscle. Here, current opinion of the nature of this disease is summarized.

RECENT FINDINGS

Recent findings for sIBM include further characterization of muscle involvement through magnetic resonance imaging, the role of muscle as a host for immune cells, progress in the role of extranuclear TDP-43 in causing cellular injury, and the discovery of a new sIBM autoantibody.

SUMMARY

sIBM understanding continues to advance, with progress regarding the mechanism of this disease.

Mice lacking TR4 nuclear receptor develop mitochondrial myopathy with deficiency in complex I

The estimated incidence of mitochondrial diseases in humans is approximately 1:5000 to 1:10,000, whereas the molecular mechanisms for more than 50% of human mitochondrial disease cases still remain unclear. Here we report that mice lacking testicular nuclear receptor 4 (TR4(-/-)) suffered mitochondrial myopathy, and histological examination of TR4(-/-) soleus muscle revealed abnormal mitochondrial accumulation. In addition, increased serum lactate levels, decreased mitochondrial ATP production, and decreased electron transport chain complex I activity were found in TR4(-/-) mice. Restoration of TR4 into TR4(-/-) myoblasts rescued mitochondrial ATP generation capacity and complex I activity. Further real-time PCR quantification and promoter studies found TR4 could modulate complex I activity via transcriptionally regulating the complex I assembly factor NDUFAF1, and restoration of NDUFAF1 level in TR4(-/-) myoblasts increased mitochondrial ATP generation capacity and complex I activity. Together, these results suggest that TR4 plays vital roles in mitochondrial function, which may help us to better understand the pathogenesis of mitochondrial myopathy, and targeting TR4 via its ligands/activators may allow us to develop better therapeutic approaches.

Theories of the pathogenesis of inclusion body myositis

Inclusion body myositis is a progressive disease of the skeletal muscle. Here, specific theories of its pathogenesis are reviewed and general considerations pertaining to modeling of this disease discussed. Understanding of inclusion body myositis disease mechanism remains extremely poor. Current published animal models do not represent the disease. Future studies need to consider the critical role of biomarkers and methodologic issues in their discovery.

Inclusion body myositis: current pathogenetic concepts and diagnostic and therapeutic approaches

Inclusion body myositis is the most common acquired muscle disease in older individuals, and its prevalence varies among countries and ethnic groups. The aetiology and pathogenesis of sporadic inclusion body myositis are still poorly understood; however genetic factors, ageing, and environmental triggers might all have a role. Unlike other inflammatory myopathies, sporadic inclusion body myositis causes slowly progressing muscular weakness and atrophy, it has a distinctive pattern of muscle involvement, and is unresponsive to conventional forms of immunotherapy. This review covers the clinical presentation, diagnosis, treatment, and the latest information on genetic susceptibility and pathogenesis of sporadic inclusion body myositis.

Inclusion body myositis with human immunodeficiency virus infection: four cases with clonal expansion of viral-specific T cells

OBJECTIVE

Sporadic inclusion body myositis (sIBM), a common adult-onset myositis, is characterized by an antigen-driven inflammatory response and vacuolar degeneration. The cause is unknown. We report the association of sIBM with human immunodeficiency virus (HIV) infection and explore the clonality and viral specificity of the autoinvasive T cells.

METHODS

Clinicopathological studies in four HIV-infected patients with IBM were performed. The clonal restriction of endomysial T cells, compared with peripheral blood, was examined by spectratyping. Immunohistochemical studies using human leukocyte antigen-A* 0201-gag tetramers and the most dominant Vb families were performed in serial muscle biopsy sections to examine whether clonally expanded autoinvasive T cells are viral specific and invade muscle fibers expressing the allele-specific monomorphic major histocompatibility complex class I antigen.

RESULTS

Prominent clonal restriction of certain Vb families was noted among the endomysial T cells with evidence of in situ expansion. Approximately 10% of the autoinvasive CD8(+) cells were human leukocyte antigen-A* 0201-HIV-gag specific and invaded muscle fibers expressing the specific human leukocyte antigen-A* 0201 allele. These cells belonged to restricted Vb families. The HIV gag antigen was present on several endomysial macrophages but not within the muscle fibers.

INTERPRETATION

sIBM develops in patients who harbor HIV. In HIV-IBM, a subset of CD8(+) T cells surrounding muscle fibers are viral specific and may play a role in the disease mechanism by cross-reacting with antigens on the surface of muscle fibers. This study provides a paradigm that a chronic viral infection in genetically susceptible individuals can trigger viral specific T cell clones that persist within the muscle and lead to development of sIBM.

Advances in diagnosis and management of inflammatory myopathies

Idiopathic inflammatory myopathies are rare causes of muscle weakness and may be difficult to diagnose and manage. The traditional classification of polymyositis (PM) and dermatomyositis (DM) has been expanded to include inclusion body myositis (IBM) and several other types as our knowledge of underlying immunopathologic mechanisms, specific antibodies, and clinical features has advanced. This has led to several modified and new classification systems and also to controversies over specific criteria required to make diagnoses of the several forms of inflammatory myopathies. The clinical response to treatment of PM and DM has been largely empiric, and IBM has proven to be refractory. There are efforts to formalize objective measures of treatment response to aid future randomized, controlled trials. This article reviews new information in the field of idiopathic inflammatory myopathies from the neurologic clinical perspective.

Tau aggregates are abnormally phosphorylated in inclusion body myositis and have an immunoelectrophoretic profile distinct from other tauopathies

Sporadic inclusion body myositis (s-IBM) is the most frequent progressive acquired inflammatory myopathy in people older than 50 years. Abnormal aggregates of 'Alzheimer's proteins', including tau proteins, have been previously demonstrated in s-IBM. In the present study, we have investigated by immunohistochemistry and immunoblotting analysis the presence of tau proteins in muscle biopsy samples from patients with s-IBM and other myopathies with rimmed vacuoles, using newly developed antibodies raised against tau protein epitopes found in Alzheimer's disease brain. Tau immunoreactivity was shown in rimmed vacuoles or inclusions, preferentially with antibodies directed against phosphorylated carboxy-terminal epitopes of tau proteins. Cytoplasmic reactivity was also demonstrated in atrophic, nonvacuolated fibres, as well as in non-necrotic fibres invaded by inflammatory cells. Abnormally phosphorylated tau aggregates were also found in other compartments of the muscle fibre in s-IBM and other myopathies. Tau immunoblotting showed an electrophorectic profile of a doublet within the range of 60-62 kDa isovariants, which was different from tauopathies of the central nervous system. Finally, the unique pattern of immunoreactivity of s-IBM samples towards anti-tau antibodies is a new clue to a possible distinct subclass of peripheral tauopathy, different from the tauopathies of the central nervous system.

Inclusion body myositis--sensory dysfunction revealed with quantitative determination of somatosensory thresholds

In order to evaluate sensory function in inclusion body myositis (IBM), nine patients were subjected to sensibility screening and quantitative determination of somatosensory thresholds. Data were compared with results from electrophysiological examination and muscle biopsy. On sensibility screening all but one of the IBM patients had abnormal findings in hands and/or feet mostly affecting thermal sensibility. Vibratory thresholds were abnormal in five and thermal thresholds in four of the patients. Mean vibratory thresholds were significantly (P < 0.05) higher in the IBM patients when compared with the controls. Significantly increased heat pain thresholds were found in hands and feet when compared with the controls while thermal thresholds were normal. Nerve conduction velocities were decreased in three patients, EMG showed both myopathic and neuropathic abnormalities in six patients. Eight patients had neuropathic abnormalities on muscle biopsy. The sensory dysfunction found suggests an affection of peripheral nerves in IBM mainly affecting large diameter myelinated nerve fibres corroborating earlier findings of a peripheral neuropathy in IBM.

Genetic and environmental risk factors for idiopathic inflammatory myopathies

Although the studies discussed are beginning to reveal a number of genetic and possible environmental risk factors for myositis, further investigations are needed to fully understand and classify these syndromes. The difficulties in this process include small numbers of subjects with varying disease phenotypes available for study, polygenic risk factors for which it remains unclear which are primary and which are secondary or linked genes, and the lack of validated environmental exposure assessment tools. New technologies and international collaborative approaches, however, may overcome some of these difficulties and allow us to identify genetic and environmental risk factors, as well as the critical gene-environment interactions in the IIM and its subgroups. Nonetheless, our understanding of these diseases is still in the early stages. Although we have learned a great deal about these disorders through detailed investigations over the last several decades, we have even further to go to understand the environmental triggers and genetic susceptibilities for the myositis syndromes.

Sporadic inclusion body myositis and hereditary inclusion body myopathy

Sporadic inclusion body myositis (s-IBM) is a common but under-recognized myopathy in individuals over 50 years of age. An awareness of the clinical phenotype and of the electrodiagnostic and histopathologic features should lead to improved recognition, and should minimize confusion with polymyositis, motor neuron disease, and other neuromuscular disorders. Treatment efficacy has been difficult to judge because of the insidious progression of the disease over many years, but immunomodulating therapy is generally less effective than in polymyositis and dermatomyositis, and may not be effective at all in many patients. The hereditary inclusion body myopathies (h-IBM) are a heterogeneous group of recessively and dominantly inherited vacuolar myopathies that share some histologic features with s-IBM. Oxidative stress may play a role in the pathogenesis of both s-IBM and h-IBM.

Bcl-2, Bcl-x, and Bax expression by immunohistochemistry in inclusion body myositis: a study of 27 cases

CONTEXT

Bcl-2, Bcl-x, and Bax are among the variety of proteins that have been described as being involved in the regulation of apoptotic cell death. Bcl-2 and Bcl-x(L) inhibit apoptosis, and Bax is proapoptotic.

OBJECTIVE

To evaluate the expression of Bcl-2, Bcl-x, and Bax in inclusion body myositis (IBM).Design.-We examined muscle specimens from 27 patients (17 men, 10 women) with IBM to evaluate Bcl-2, Bcl-x, and Bax expression by immunohistochemistry.

RESULTS

Patient ages ranged from 29 to 80 years (mean 62.2 years). All biopsies were marked by endomysial chronic inflammation, muscle fiber necrosis, and regeneration. Rimmed (autophagic) vacuoles were present in all cases. Ragged red fibers were noted in 4 biopsies (15%), and cytochrome oxidase-deficient fibers were found in 10 biopsies (37%). Ultrastructural evidence of intranuclear or cytoplasmic tubulofilamentous inclusions, confirming the diagnosis of IBM, were noted in all cases. Paracrystalline mitochondrial inclusions were seen in 5 biopsies (18.5%). Inflammatory cells stained positively with Bcl-2 in all biopsies, Bax in 26 biopsies (96%), and Bcl-x in 8 biopsies (30%). Degenerating muscle fibers were highlighted with Bax in 24 biopsies (89%), Bcl-2 in 2 biopsies (7%), and Bcl-x in 3 biopsies (11%). Regenerative muscle fibers were noted to stain with Bax in 24 muscles (89%), Bcl-2 in 21 muscles (78%), and Bcl-x in 4 muscles (15%). Rimmed vacuoles were highlighted by Bax in 24 biopsies (89%) and only rarely by Bcl-2 (n = 2, 7%) and Bcl-x (n = 3, 11%). A subsarcolemmal staining pattern was observed in 21 biopsies (78%) with Bax, 6 biopsies (22%) with Bcl-2, and only 1 biopsy (4%) with Bcl-x.

CONCLUSIONS

(1) Bax (proapoptotic) immunostaining highlighted most autophagic vacuoles; (2) subsarcolemmal Bax and Bcl-2 immunoreactivity may be associated with mitochondrial defects that are commonly noted in IBM; (3) Bcl-2 and Bax immunoreactivity were not confined to degenerating muscle fibers and in fact appeared to be expressed more commonly in regenerating fibers, suggesting that their expression may be independent of apoptosis in the setting of IBM.

Rimmed vacuoles with beta-amyloid and ubiquitinated filamentous deposits in the muscles of patients with long-standing denervation (postpoliomyelitis muscular atrophy): similarities with inclusion body myositis

In the chronically denervated muscles of patients with prior paralytic poliomyelitis, there are secondary myopathic features, including endomysial inflammation and rare vacuolated fibers. To assess the frequency and characteristics of the vacuoles and their similarities with those seen in inclusion body myositis (IBM), we examined 58 muscle biopsy specimens from patients with prior paralytic poliomyelitis for (1) the presence of rimmed vacuoles; (2) acid-phosphatase reactivity; (3) Congo-red-positive amyloid deposits; (4) electron microscopy, searching for tubulofilaments; and (5) immunoelectron microscopy, using antibodies against beta-amyloid and ubiquitin. We found vacuolated muscle fibers in 18 of 58 (31%) biopsies, with a mean frequency of 2.06 +/- 0.42 fibers per specimen. The vacuoles contained acid phosphatase-positive material in 6 of the 18 (33.30%) specimens and stained positive for Congo red in five (27.80%). By immunoelectron microscopy, the vacuoles contained 5.17 +/- 0.13 nm fibrils and 14.9 +/- 0.31 nm filaments that immunoreacted with antibodies to beta-amyloid and ubiquitin in a pattern identical to the one seen in IBM. We conclude that vacuolated muscle fibers containing filamentous inclusions positive for amyloid and ubiquitin are not unique to IBM and the other vacuolar myopathies but can also occur in a chronic neurogenic condition, such as postpoliomyelitis. The chronicity of the underlying disease, rather than the cause, may lead to vacuolar formation, amyloid deposition, and accumulation of ubiquitinated filaments.

Autosomal dominant myopathy with congenital joint contractures, ophthalmoplegia, and rimmed vacuoles

We describe a new myopathy in a large family with 19 affected cases. Inheritance was autosomal dominant. Characteristic clinical features were congenital joint contractures, which normalized during early childhood, external ophthalmoplegia, and proximal muscle weakness. Muscle atrophy was most prominent in the pectoralis and quadriceps muscles. The clinical course was nonprogressive in childhood, but most adult cases experienced deterioration of muscle function, starting from 30 to 50 years of age. The major histopathological change of skeletal muscle in childhood was focal disorganization of myofilaments. In adults with progressive muscle weakness, the muscle biopsies showed dystrophic changes and rimmed vacuoles with cytoplasmic and intranuclear inclusions of 15- to 21-nm filaments. These findings suggests that this new disease should be classified as a variant of hereditary inclusion body myopathy.