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PubMed2000

Novel immunolocalization of alpha-synuclein in human muscle of inclusion-body myositis, regenerating and necrotic muscle fibers, and at neuromuscular junctions.

Alpha-synuclein (alpha-syn) is an important component of neuronal and glial inclusions in brains of patients with several neurodegenerative disorders. Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease of older patients. Its muscle phenotype shows several similarities with Alzheimer disease brain. A distinct feature of s-IBM pathology is specific vacuolar degeneration of muscle fibers characterized by intracellular amyloid inclusions formed by both amyloid-beta (Abeta) and paired-helical filaments composed of phosphorylated tau. We immunostained alpha-syn in muscle biopsies of s-IBM, disease-control, and normal patients. Approximately 60% of Abeta-positive vacuolated muscle fibers (VMF) contained well-defined inclusions immunoreactive with antibodies against alpha-syn. In those fibers. alpha-syn co-localized with Abeta, both by light microscopy, and ultrastructurally. Paired-helical filaments did not contain alpha-syn immunoreactivity. In all muscle biopsies, alpha-syn was strongly immunoreactive at the postsynaptic region of the neuromuscular junctions. alpha-syn immunoreactivity also occurred diffusely in regenerating and necrotic muscle fibers. In cultured human muscle fibers, alpha-syn and its mRNA were expressed by immunocytochemistry, immunoblots, and Northern blots. Our study provides the first demonstration that alpha-syn participates in normal and pathologic processes of human muscle. Therefore. its function is not exclusive to the brain and neurodegenerative diseases.

Cells, Cultured↗

PubMed1996

Sporadic inclusion body myositis: counts of different types of abnormal fibers.

Invasion of nonnecrotic muscle fibers by cytotoxic T cells, accumulation of congophilic amyloid inclusions in muscle fibers, and fiber necrosis are consistent histologic findings in sporadic inclusion body myositis (IBM). To evaluate the relative significance of these alterations, we quantitatively analyzed the frequency of these abnormalities in 31 electron microscopy proven cases of IBM (20 untreated and 11 immunosuppressed). Nonnecrotic muscle fibers invaded by T cells were severalfold more frequent than fibers displaying the other pathologic alterations. Comparison of muscle samples from treated and untreated patients revealed no significant differences in the respective frequencies of the three species of abnormal fibers. Moreover, there was no correlation of the frequency of any abnormality either with disease duration or length of treatment. The much higher frequency of the invaded than Congo red-positive fibers points to the importance of an immune-mediated mechanism in the disease; but the basic cause of the disease remains undefined.

Adult↗

PubMed1995

Common variable immunodeficiency and inclusion body myositis: a distinct myopathy mediated by natural killer cells.

Inclusion body myositis developed in two men, 36 and 48 years old with long-standing common variable immunodeficiency. Immunophenotypic analysis of the endomysial cells showed an increased number of natural killer (NK) cells (defined as CD57+, CD56+, CD3-, CD8-, CD68-) accounting for 8.5 to 9.5% of the total cells, compared with a mean of 1% in sporadic inclusion body myositis. The remaining cells were CD8+, macrophages, and CD4+ T cells. NK cells were positive for intercellular cell adhesion molecule-1 and invaded muscle fibers negative for major histocompatibility complex (MHC) class I. In contrast to ubiquitous endomysial expression of MHC class I antigen in sporadic inclusion body myositis, the MHC class I in common variable immunodeficiency and inclusion body myositis was absent or weakly expressed in only some of the muscle fibers surrounded by CD8+ cells. Enteroviral or retroviral RNA sequences were not amplified. Treatment with intravenous immunoglobulin improved strength in 1 patient whose repeated muscle biopsy specimen showed normal NK cells. We conclude that inclusion body myositis can develop in patients with common variable immunodeficiency. Common variable immunodeficiency with inclusion body myositis is an immune myopathy mediated by NK cells in a non-MHC class I-restricted cytotoxicity, and by CD8+ cells in an MHC class I-restricted process. This is the first description of an inflammatory myopathy in which NK cells participate in the myocytotoxic process.

Adult↗

PubMed1998

T-cell heterogeneity in muscle lesions of inclusion body myositis.

In the muscle lesions of inclusion body myositis (IBM), two populations of T cells can morphologically be distinguished, T cells that invade muscle fibers and T cells that remain in interstitial areas. Using combined immunohistochemistry and RT-PCR, we analysed the TCR expressed by these distinct T cell populations. In three of eight IBM muscle specimens, the autoinvasive T cells were stained with one of the available mAbs: anti-Vbeta5.3 in patient 1, anti-Vbeta5.2 in patient 2, and anti-Vbeta3 in patient 3. The corresponding TCR Vbeta mRNAs were amplified by RT-PCR and the PCR products were cloned and sequenced. In all three specimens, the TCRs expressed by the autoinvasive T cells were clonally restricted. Furthermore, in patient 1 two different mAbs labelled two distinct populations of T cells: an autoaggressive population of CD8 + Vbeta5.3 + cells that invaded muscle fibers and a noninvasive interstitial population of CD8 - Vbeta5.1 + cells. TCR sequence analysis revealed that the noninvasive Vbeta5.1 + T cells were clonally diverse, whereas the autoinvasive Vbeta5.3 + T cells were clonally restricted.

Antibodies, Monoclonal↗

PubMed2002

Understanding the immunopathogenesis of inclusion-body myositis: present and future prospects.

Sporadic Inclusion Body Myositis (s-IBM) is the most common acquired inflammatory myopathy. It has a stereotypic clinical presentation and a predictably progressive course that leads to severe muscle weakness and permanent disability. The combination of primary endomysial inflammation with autoimmune features identical to those seen in Polymyositis, and degenerative features with vacuolization of muscle fibers and deposits of tiny speckles of amyloid, are characteristic for the disease. In this review, the immunopathology of IBM is detailed. The inflammation which is prominent even late in the disease, is characterized by activated, CD8+ cytotoxic T cells that secrete perforin and invade MHC-I-expressing muscle fibers. The autoinvasive T cells are probably antigen driven because of specific rearrangement of their T Cell Receptor profile, restriction of the CDR3 region, upregulation of co-stimulatory molecules and their ligands on the muscle fibers, and activation of various cytokines, chemokines and adhesion molecules. The disease can be seen in association with HIV and HTLV-I infection, but viruses have not been amplified from the muscle fibers and the antigen or the factors that trigger inflammation are still unknown. The disease is mysteriously resistant to conventional immunotherapies in spite of the immunopathologic similarities with PM. The cause of the vacuolar formation in IBM is also unknown and the role, that the tiny amyloid deposits play in the disease remain unclear. The treatment approaches and the prospects for future immunotherapeutic interventions are discussed.

Electromyography↗

PubMed1983

Inclusion body myositis (IBM): myopathy or neuropathy?

Inclusion body myositis (IBM) is described in six elderly patients (three women) and in a young familial patient. They all showed the morphologically characteristic vacuoles containing osmiophilic membranous whorls and intracytoplasmic or intranuclear inclusions. There is a well-delineated bimodal age spectrum of IBM, with onset in the second and sixth decades, but otherwise the disorder seems to be a specific entity. Clinical, electrophysiologic, and morphologic features suggest a neurogenic origin in some cases.

Aged↗

PubMed1989

Inclusion body myositis. Observations in 40 patients.

Inclusion body myositis (IBM) was suspected on light microscopic grounds in 48 of 170 consecutive patients with inflammatory myopathies. One or more vacuoles containing membranous material, groups of atrophic fibres, and an autoaggressive endomysial inflammatory exudate occurred in 100, 96 and 92% of the muscle specimens. All three of these features were present in 88% of the specimens. Electron microscopy confirmed the presence of filamentous inclusions in 40 of 43 patients. The inclusions are typically near vacuoles and a minimum of three vacuolated fibres must be scrutinized to detect them with confidence. There is no electromyographic pattern that can reliably distinguish IBM from other inflammatory myopathies. The typical clinical features in the patients diagnosed by histological criteria as IBM were: insidious onset after age 50 yrs with painless, proximal lower extremity weakness; slow but relentless progression with selectively severe involvement of quadriceps, iliopsoas, tibialis anterior, biceps and triceps muscles; relatively early depression of the knee reflexes; and a normal or mildly elevated serum creatine kinase level. The male: female ratio was 3:1. Distal weakness occurred in about 50%, but only in 35% was it as great or greater than proximal weakness. Significant associated illnesses include other autoimmune disorders (15%), diabetes mellitus (20%), and diffuse peripheral neuropathy (18%). Prednisone treatment at dose levels frequently effective in polymyositis failed to prevent disease progression in those patients observed for 2 or more years. Our findings support the notion that IBM is a distinct entity in which a set of pathological features is associated with a constellation of clinical findings.

Adult↗

PubMed1985

Inclusion body myositis and systemic lupus erythematosus.

Inclusion body myositis (IBM) has been recognized as a distinct type of idiopathic inflammatory myopathy. Previous reports have emphasized the absence of immunologic abnormalities and lack of response to corticosteroid therapy in patients with IBM. We report a case of IBM associated with systemic lupus erythematosus and modest response of the myopathy to corticosteroid therapy. The clinical and immunologic features of IBM are more diverse than previously appreciated.

Cytoskeleton↗

PubMed2005

Preservation of in vitro muscle fiber function in dermatomyositis and inclusion body myositis: a single fiber study.

Five patients with untreated dermatomyositis, five with inclusion body myositis, and 16 healthy elderly volunteer subjects (controls) underwent open (dermatomyositis and inclusion body myositis) or percutaneous (controls) muscle biopsy. Biopsied muscles included deltoid, biceps and vastus lateralis. Chemically skinned single muscle fibers were activated with Ca(+2); the slack test was performed to determine maximal unloaded shortening velocity (Vo). Parameters measured include single fiber cross sectional area, maximal force, specific force and Vo. 429 Type I and 94 Type IIA fibers were studied. Cross sectional area and maximal force were greater in inclusion body myositis than dermatomyositis or control for Type I and IIA fibers. Specific force of Type I fibers was similar in inclusion body myositis and dermatomyositis but greater than in controls. Vo was greater in Type I, but not IIA, fibers in dermatomyositis compared with inclusion body myositis and controls. The force and velocity generating capacity of single muscle fibers is preserved in patients with dermatomyositis and inclusion body myositis suggesting that dysfunction of the contractile proteins does not contribute to clinical muscle weakness.

Adult↗

PubMed2001

Macrophagic myofasciitis associated with inclusion body myositis: a report of three cases.

We describe three patients with macrophagic myofasciitis and inclusion body myositis. All patients fulfilled diagnostic criteria for inclusion body myositis and myopathologic criteria for macrophagic myofasciitis. In the three cases macrophagic myofasciitis complicated the evolution of a known and painless inclusion body myositis and was diagnosed in a repeated deltoid biopsy because of the appearance of myalgia during the course of inclusion body myositis in all cases. The unexpected appearance of myalgia during the course of painless inclusion body myositis must arouse the suspicion of an association of another inflammatory muscle disease, macrophagic myofasciitis.

Adult↗

PubMed1998

Absence of characteristic features in two patients with inclusion body myositis.

According to recently published criteria a diagnosis of definite sporadic inclusion body myositis is made if the typical histopathological abnormalities (rimmed vacuoles and abnormal accumulations of proteins, in addition to mononuclear cell infiltrates) are present. The two women described here presented with myositis which was unresponsive to treatment. Patient 1 had features of non-progressive sporadic inclusion body myositis clinically, whereas patient 2 had a very slowly progressive limb girdle syndrome. The cryostat sections of the first biopsies did not show rimmed vacuoles, even in retrospect. Only a repeated biopsy, 12 years after presentation in one patient and 18 years after presentation in the other, disclosed the typical features of sporadic inclusion body myositis. The initial absence of abnormal fibres probably represents a real absence or scarcity rather then a sampling error due to a multifocal nature of the histological abnormalities. It is of importance for the clinician to realise that some patients with myositis unresponsive to treatment, even if both clinical and histological features do not suggest sporadic inclusion body myositis, may prove to have the disease on repeated histopathological examination.

Adult↗

PubMed1989

Childhood onset inclusion body myositis mimicking limb-girdle muscular dystrophy.

Inclusion body myositis was initially recognized in patients with "steroid-resistant polymyositis" and subsequently in patients with other immune-mediated disorders. The finding of inclusion body myositis in a patient diagnosed for 30 years as having limb-girdle muscular dystrophy suggests yet another patient pool that may harbor this entity.

Adult↗

PubMed1993

Mitochondrial DNA deletions in inclusion body myositis.

Skeletal muscle specimens from three patients with inclusion body myositis, aged 39, 60 and 71 years, respectively, were investigated. Enzyme histochemical staining of cytochrome c oxidase (COX), succinate dehydrogenase and myofibrillar ATPase, and in situ hybridization of transcripts of mitochondrial DNA (mtDNA) were performed on consecutive sections. In all three cases a proportion of muscle fibres (2-5%) showed low or absent COX activity in spite of medium or high succinate dehydrogenase activity (COX deficient muscle fibres). Two probes detecting transcripts of different segments of mtDNA were used for the in situ hybridization. One of the probes (ND4 probe) detected transcripts of a segment of the NADH dehydrogenase subunit 4 gene, which is known to be affected in most cases of mitochondrial myopathy with large deletions of mtDNA. There was reduced hybridization of the ND4 probe in many COX deficient muscle fibres compared with adjacent normal fibres. The other probe (ND2 probe) detected transcripts of a segment of the NADH dehydrogenase subunit 2 gene, which usually is not included in mtDNA deletions. There was accumulation of transcripts corresponding to the ND2 probe in COX deficient fibres in all three cases. These findings demonstrate that deleted mtDNA had accumulated in COX deficient muscle fibres in patients with inclusion body myositis. Southern blot analysis of mtDNA in muscle revealed a 16.6 kb fragment corresponding to normal mtDNA in all three cases. In one case two additional less abundant fragments of smaller size, corresponding to deleted mtDNA, were detected. Ultrastructural investigation showed abnormal mitochondria in all three cases. Control muscle specimens were obtained from nine patients, aged 63-71 years, with muscle pain but without morphological evidence of muscle disease. Occasional COX deficient fibres (< 1%) were found in three of the control cases. The other six control cases showed no COX deficient fibres. Our results show that mtDNA deletions may be involved in the pathogenesis of inclusion body myositis and cause respiratory chain dysfunction in muscle fibre segments.

Adult↗

PubMed1998

Immune-mediated conditions and antibodies associated with sporadic inclusion body myositis.

We reviewed 99 patients with sporadic inclusion body myositis (IBM), searching for a coexisting autoimmune disease, other conditions with altered immune function, or the presence of autoantibodies. Thirteen patients had one or more of 11 diseases with altered immune function. Forty-three patients had elevated titers of one or more of nine different, albeit nondisease-specific, autoantibodies. Twenty-five patients had dysproteinemia or dysproteinuria. We conclude that IBM is frequently associated with systemic immune disorders or nonspecific autoantibodies. Although aging may explain some of these phenomena, an altered immune function need to be considered in the pathogenesis of IBM.

Autoantibodies↗

PubMed1999

Dermatomyositis with the features of inclusion body myositis associated with carcinoma of the bladder.

Inclusion body myositis (IBM) is a unique category of inflammatory myopathy. It is characterized histologically by the presence of muscle fibres with rimmed vacuoles and abnormal intracellular accumulations of proteins. We report here a 62-year-old patient with bladder carcinoma, where the signs of IBM overlapped with clinical features of dermatomyositis (DM). A combination of cutaneous changes typical for DM with histological and other features of IBM is exceedingly rare, and has not been previously addressed in dermatological literature. To the best of our knowledge this is also the first description of the association of DM/IBM with internal malignancy.

Carcinoma, Transitional Cell↗

PubMed2003

Proposed pathogenetic cascade of inclusion-body myositis: importance of amyloid-beta, misfolded proteins, predisposing genes, and aging.

PURPOSE OF REVIEW: Sporadic inclusion-body myositis, the most common muscle disease of older persons, is of unknown cause, and there is no successful treatment. Interest in sporadic inclusion-body myositis has been enhanced by the recent identification within the sporadic inclusion-body myositis muscle fibers of several abnormally accumulated proteins, which provides novel and important clues to the pathogenesis of sporadic inclusion-body myositis. RECENT FINDINGS: This article summarizes the most recent findings leading to better understanding of the players in the pathogenetic cascade. It is suggested that lymphocytic inflammatory component is probably secondary, and it may contribute only slightly to muscle fiber damage in sporadic inclusion-body myositis. However, it is proposed that the identified abnormal accumulation, aggregation, and misfolding of proteins, combined with and perhaps provoked by an aging intracellular milieu, more essentially lead to the vacuolar degeneration and atrophy of the muscle fibers that are specific to sporadic inclusion-body myositis. Abnormal accumulations of the amyloid-beta precursor protein and of its proteolytic fragment, amyloid-beta, associated with the aging cellular muscle fiber environment, appear to be key pathogenic events. SUMMARY: In conceptualizing a treatment for sporadic inclusion-body myositis, the accumulations of amyloid-beta42 and other unfolded proteins are now phenomena to be reckoned with. One would like to stop intracellular increase of the unfolded/misfolded proteins by reducing their formation and/or increasing their disposal. In addition, the identification of factors that would decrease intra-muscle fiber expressions of beta- and gamma-secretases might lead to decreased production of putatively myotoxic oligomeric amyloid-beta42. Better understanding of the mechanisms and consequences of genes that predispose to sporadic inclusion-body myositis, and of human muscle fiber aging, could also provide new avenues toward the therapy of sporadic inclusion-body myositis. How to therapeutically capitalize on the new findings is now the challenge.

Age Factors↗

PubMed1999

Mapping of a candidate region for susceptibility to inclusion body myositis in the human major histocompatibility complex.

Inclusion body myositis (IBM) is a form of idiopathic inflammatory myopathy of unknown aetiology. A strong association with HLA class II (HLA-DR3) suggested a role for genes in the human major histocompatibility complex (MHC) in the predisposition to this disease. In this study, we have taken advantage of the ancestral haplotype (AH) concept and historical recombinations to map for a possible susceptibility gene(s) in the MHC. We performed detailed typing of three MHC-related HSP70 genes and defined allelic combinations in the context of MHC AH. We also modified existing methods to give a simple and accurate method for typing two TNF microsatellites. Using the HSP70 and TNF markers and HLA-DR, -B, and C4 typing of our patients with IBM, we defined a potential site for the MHC-associated susceptibility gene(s) in the region between HLA-DR and C4.

Alleles↗

PubMed2006

Sporadic inclusion body myositis--diagnosis, pathogenesis and therapeutic strategies.

Sporadic inclusion body myositis (sIBM) presents with a characteristic clinical phenotype of slow-onset weakness and atrophy, affecting proximal and distal limb muscles and facial and pharyngeal muscles. Histologically, sIBM is characterized by chronic myopathic features, lymphocytic infiltrates invading non-vacuolated fibers, vacuolar degeneration, and accumulation of amyloid-related proteins. The cause of sIBM is unclear, but two processes-one autoimmune and the other degenerative-appear to occur in parallel. In contrast to dystrophies, in sIBM the autoinvasive CD8(+) T cells are cytotoxic and antigen-driven, invading muscle fibers expressing major histocompatibility complex class I antigen and costimulatory molecules. The concurrent degenerative features include vacuolization, filamentous inclusions and intracellular accumulations of amyloid-beta-related molecules. Although viruses have not been amplified from the muscle fibers, at least 12 cases of sIBM have been seen in association with retroviral infections, indicating that a chronic persistent viral infection might be a potential triggering factor. Emerging data imply that continuous upregulation of cytokines and major histocompatibility complex class I on the muscle fibers causes an endoplasmic reticulum stress response, resulting in intracellular accumulation of misfolded glycoproteins and activation of the transcription factor NFkappaB, leading to further cytokine activation. In spite of the brisk, antigen-driven T-cell infiltrates, sIBM does not respond to immunotherapies. New therapies using monoclonal antibodies against lymphocyte signaling pathways might prove helpful in arresting disease progression.

Diagnosis, Differential↗