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Query: UMLS:C0027121 (myositis)
 4,538 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscle biopsies from patients with sporadic inclusion-body myositis (sIBM) consistently demonstrate that the inflammatory T cells almost invariably invade intact (not vacuolated) fibers, whereas the vacuolated fibers are rarely invaded by T cells. This indicates two concurrently ongoing processes, an autoimmune mediated by cytotoxic T cells and a degenerative manifested by the vacuolated muscle fibers and deposits of amyloid-related proteins. The autoimmune features of IBM are highlighted by the strong association of the disease with: a) HLA I, II antigens, in frequency identical to classic autoimmune diseases; b) other autoimmune disorders in up to 32% of the patients, autoantibodies, paraproteinemias, or immunodeficiency; c) HIV and HTLV-I infection with increasingly recognized frequency (up to 13 known cases); and d) antigen-specific, cytotoxic, and clonally expanded CD8+ autoinvasive T cells with rearranged T-cell receptor genes that persist over time, even in different muscles, and invade muscle fibers expressing MHC-I antigen and costimulatory molecules. In contrast to IBM, in various dystrophies the inflammatory cells are clonally diverse and the muscle fibers do not express MHC-I or costimulatory molecules in the pattern seen in IBM. Like other chronic autoimmune conditions with coexisting inflammatory and degenerative features (i.e., primary progressive MS), IBM is resistant to conventional immunotherapies. Recent data suggest that strong anti-T cell therapies can be promising and they are the focus of ongoing research.
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PMID:Inflammatory, immune, and viral aspects of inclusion-body myositis. 1643 43

Sporadic inclusion-body myositis (s-IBM), the most common muscle disease of older persons, is of unknown cause and there is no successful treatment. We summarize our most recent findings, which provide a better understanding of the steps in the pathogenetic cascade. We suggest that s-IBM is primarily a myodegenerative disease. Intriguing are the phenotypic similarities between s-IBM muscle fibers and the brains of Alzheimer disease, the most common neurodegenerative disease of older persons. In s-IBM, abnormal accumulation of the amyloid-beta (Abeta) precursor protein and its proteolytic fragment, Abeta, associated with the aging intracellular milieu of the muscle fiber, appear to be key upstream pathogenic events. We propose that the identified abnormal accumulation, misfolding, and aggregation of proteins, perhaps provoked by the aging milieu and aggravated by the oxidative stress, lead to the s-IBM-specific vacuolar degeneration and atrophy of muscle fibers.
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PMID:Inclusion-body myositis: a myodegenerative conformational disorder associated with Abeta, protein misfolding, and proteasome inhibition. 1643 44

Mitochondrial changes are frequently encountered in sporadic inclusion-body myositis (s-IBM). Cytochrome c oxidase (COX)-deficient muscle fibers and large-scale mitochondrial DNA (mtDNA) deletions are more frequent in s-IBM than in age-matched controls. COX deficient muscle fibers are due to clonal expansion of mtDNA deletions and point mutations in segments of muscle fibers. Such segments range from 75 microm to more than 1,000 microm in length. Clonal expansion of the 4977 bp "common deletion" is a frequent cause of COX deficient muscle fiber segments, but many other deletions also occur. The deletion breakpoints cluster in a few regions that are similar to what is found in human mtDNA deletions in general. Analysis in s-IBM patients of three nuclear genes associated with multiple mtDNA deletions, POLG1, ANT1 and C10orf2, failed to demonstrate any mutations. In s-IBM patients with high number of COX-deficient fibers, the impaired mitochondrial function probably contribute to muscle weakness and wasting. Treatment that has positive effects in mitochondrial myopathies may be tried also in s-IBM.
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PMID:Mitochondrial abnormalities in inclusion-body myositis. 1643 45

Neuronal oxidative stress occurs early in the progression of Alzheimer disease (AD), significantly before the development of the pathologic hallmarks, neurofibrillary tangles, and senile plaques. Study of Down syndrome, cases with autosomal dominant mutation, and sporadic AD all suggest amyloid-beta deposition and hyperphosphorylated tau function as compensatory responses and downstream adaptations to ensure that neuronal cells do not succumb to oxidative damage. Amyloid-beta and tau hyperphosphorylation also define vulnerable muscle cells in sporadic inclusion-body myositis (s-IBM). The role of the structural changes of s-IBM, as in AD, remains to be determined but may mark a critical response yielding a novel balance in oxidant homeostasis.
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PMID:Brain and brawn: parallels in oxidative strength. 1643 55

Herp is a stress-response protein localized in the endoplasmic reticulum (ER) membrane. Herp was proposed to improve ER-folding, decrease ER protein load, and participate in ER-associated degradation (ERAD). Intra-muscle-fiber ubiquitinated multiprotein-aggregates containing, among other proteins, either amyloid-beta (Abeta) or phosphorylated tau are characteristic of sporadic inclusion-body myositis (s-IBM). ER stress and proteasome inhibition appear to play a role in s-IBM pathogenesis. We have now studied Herp in s-IBM muscle fibers and in ER-stress-induced or proteasome-inhibited cultured human muscle fibers. In s-IBM muscle fibers: (i) Herp was strongly immunoreactive in the form of aggregates, which co-localized with Abeta, GRP78, and beta2 proteasome subunit; (ii) Herp mRNA and protein were increased. In ER-stress-induced cultured human muscle fibers: (i) Herp immunoreactivity was diffusely increased; (ii) Herp mRNA and protein were increased. In proteasome-inhibited cultured human muscle fibers: (i) Herp immunoreactivity was in the form of aggregates; (ii) Herp protein was increased, but its mRNA was not. Accordingly, in s-IBM muscle fibers: (i) increase of Herp might be due to both ER-stress and proteasome inhibition; (ii) co-localization of Herp with Abeta, proteasome, and ER-chaperone GRP78 could reflect its possible role in processing and degradation of cytotoxic proteins in ER.
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PMID:Homocysteine-induced endoplasmic reticulum protein (Herp) is up-regulated in sporadic inclusion-body myositis and in endoplasmic reticulum stress-induced cultured human muscle fibers. 1644 12

The myositides are systemic autoimmune conditions of which the most important are polymyositis, dermatomyositis, and inclusion body myositis. In addition to the classic clinical diagnostic criteria, myositis-specific autoantibodies were identified about 15 years ago. Among the dozen or so myositis-specific autoantibodies reported to date, the most characteristic are directed against cytoplasmic antigens, such as tRNA synthetase (Jo-1 or PL-1, PL-7, PL-12, EJ, OJ, JS, and KS), signal-recognition particle (SRP), Mas, KJ, Fer (eEF1), and Wa. Antibodies to nuclear antigens include anti-Mi-2, anti-PMS (PMS1, and PMS2), and related antibodies (MLH1, DNA protein kinase catalytic subunit (DNA PKCS)...), and anti-56 kDa. Myositis-associated antibodies are not specific but may be found in patients with myositis. They are directed to nuclear or nucleolar antigens such as PM-Scl, Ku, RNP (U1-RNP and U2-RNP, U4/U6-RNP, and U5-RNP), Ro 52 kDa and, more rarely, Ro 60 kDa and La. Myositis-specific antibodies have proved useful on two fronts. They have improved the diagnosis of myositis by leading to the identification of characteristic clinical patterns, such as anti-synthetase syndrome. The place of autoantibodies alongside classic clinical and laboratory criteria remains to be determined, however. First, standardized assays will have to be developed to replace current detection methods, which use widely variable techniques and antigen preparations. Myositis-specific antibodies have also shed light on the pathogenesis of myositis. For instance, the development of antibodies to tRNA synthetases constitutes an original autoimmunity model that shows how muscle damage, probably of a nonspecific nature, can lead to the production of autoantibodies that perpetuate and aggravate the muscle lesions.
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PMID:Contribution of autoantibodies to the diagnosis and nosology of inflammatory muscle disease. 1711 Jan 50

Increased amyloid-beta precursor protein (A beta PP) and amyloid-beta (A beta) accumulation appear to be upstream steps in the pathogenesis of sporadic inclusion-body myositis (s-IBM). BACE1, participating in A beta production is also increased in s-IBM muscle fibers. Nogo-B and Nogo-A belong to a family of integral membrane reticulons, and Nogo-B binding to BACE1 blocks BACE1 access to A beta PP, decreasing A beta production. We studied Nogo-B and Nogo-A in s-IBM muscle and in our IBM muscle culture models, based on A beta PP-overexpression or ER-stress-induction in cultured human muscle fibers (CHMFs). We report that: (1) in biopsied s-IBM fibers, Nogo-B is increased, accumulates in aggregates, is immuno-co-localized with BACE1, and binds to BACE1; Nogo-A is undetectable. (2) In CHMFs, (a) A beta PP overexpression increases Nogo-B, Nogo-A, and BACE1, (b) ER stress increases BACE1 but decreases Nogo-B and Nogo-A, (c) Nogo-B and Nogo-A associate with BACE1. Accordingly, two novel mechanisms, A beta PP overexpression and ER stress, are involved in Nogo-B and Nogo-A expression in human muscle. We propose that in s-IBM muscle the Nogo-B increase may represent an attempt by muscle fiber to decrease A beta production. However, the increase of Nogo-B seems insufficient because A beta continues to accumulate and the disease progresses. We propose that manipulations, which increase Nogo-B in s-IBM muscle might offer a new therapeutic opportunity.
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PMID:NOGO is increased and binds to BACE1 in sporadic inclusion-body myositis and in A beta PP-overexpressing cultured human muscle fibers. 1776 14

Inflammatory myopathies are a group of autoimmune diseases that affect muscles. In humans, the most common inflammatory myopathies are polymyositis, dermatomyositis, and inclusion body myositis. Autoantibodies may be found in humans with inflammatory myopathies, and these play an important role in diagnosis and disease classification. However, these Abs are typically not muscle specific. Spontaneously occurring canine inflammatory myopathies may be good parallel disorders and provide insights into human myositis. In dogs with inflammatory myopathy, muscle-specific autoantibodies have been found, especially in masticatory muscle myositis. We have identified the major Ag recognized by the autoantibodies in canine masticatory muscle myositis. This Ag is a novel member of the myosin binding protein-C family, which we call masticatory myosin binding protein-C (mMyBP-C). mMyBP-C is localized not only within the masticatory muscle fibers, but also at or near their cell surface, perhaps making it accessible as an immunogen. The gene for mMyBP-C also exists in humans, and mMyBP-C could potentially play a role in certain human inflammatory myopathies. Understanding the role of mMyBP-C in this canine inflammatory myopathy may advance our knowledge of mechanisms of autoimmune inflammatory muscle diseases, not only in dogs, but also in humans.
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PMID:Autoantibodies in canine masticatory muscle myositis recognize a novel myosin binding protein-C family member. 1787 94

Takotsubo syndrome may be associated with neuromuscular disorders, but has never been described in a patient with mitochondrial disorder. A 75-year-old woman developed muscle cramps, ptosis, fasciculations and slowly progressive weakness and wasting of all four limbs, starting 2.5 years earlier. After exclusion of various differential diagnoses, including non-specific granulomatous myositis, inclusion body myositis, and motor neuron disease, mitochondrial disorder was assumed. Muscle weakness progressed to respiratory insufficiency, requiring mechanical ventilation. Five days after intubation, she developed hypotension, torsades de pointes, ST-segment elevation, and negative T waves. Echocardiography revealed apical ballooning with akinesia of the left ventricular anteroseptal, apical, apicolateral and inferior segments. Coronary angiography was normal, and ventriculography confirmed apical hypokinesia and ballooning. Takotsubo syndrome was diagnosed, resolving completely within 7 weeks under bisoprolol. This case shows that Takotsubo syndrome occurs also in mitochondrial disorder and under mechanical ventilation, and may be triggered by stress from respiratory insufficiency, intubation, pain from tracheostomy, stress from mechanical ventilation, medication, or from the uncertain prognosis.
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PMID:Apical ballooning (Takotsubo syndrome) in mitochondrial disorder during mechanical ventilation. 1788 29

Electrodiagnostic methods play important roles for the diagnosis and evaluation of ALS. They are useful for 1) the early establishment of the diagnosis, 2) the differential diagnosis, and 3) the quantitative evaluation of the progression. Needle electromyography reveals active neurogenic changes over the wide territories of the body. Fibrillation potentials and positive sharp waves indicate presence of denervated fibers. However, they are not specific for ALS or even neurogenic process, and widespread occurrence of fibrillations are also characteristic for myositis and inclusion body myositis (IBM). Fasciculation potentials are spontaneous firing of the lower motor neuron and most of them are supposed to arise from the nerve endings. Fasciculation potentials are seen solely in neurogenic process and sufficiently specific for ALS. Its diagnostic role, especially in the early diagnosis, has been stressed by several researchers, including the present authors (Sonoo 1996), and fasciculation potentials will be given the same significance as fibrillation potentials in the coming Awaji criteria for the diagnosis of ALS. Motor unit potentials (MUPs) in ALS often show polyphasia and instability reflecting the presence of immature sprouts. Unstable MUPs (increased jiggle) are counterparts of instability in SFEMG. Giant MUPs are frequent, but low amplitude MUPs may be also observed in rapidly progressing cases. Observation of the recruitment pattern is crucial for the differential diagnosis from myopathies. Nerve conduction studies are important for the exclusion of other diagnoses, especially multifocal motor neuropathy (MMN). Some degree of slowing and disappearance of F-waves can occur simply due to loss of motor units. The utility of Neurophsiological Index remains to be confirmed. Repetitive nerve stimulation often reveals decremental responses, whose presence supports the diagnosis of ALS. Decremental responses in ALS usually occur in wasted muscles with low CMAP amplitude, and may predict the speed of further deterioration of the CMAP.
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PMID:[Electrodiagnosis of ALS]. 1796 43


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