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

This paper reviews the knowledge we continue to gain in the areas of pathogenesis, evaluation of disease activity, and interventional strategies with regards to idiopathic inflammatory myositis. Potential new diagnostic criteria incorporate the use of magnetic resonance imaging and other imaging modalities along with the use of muscle biopsy pathologic features including that of immunologic markers. Specifically, this criterion reflects the upregulation of major histocompatibility complex molecules on muscle tissue during acute inflammation.
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PMID:Recent advances in juvenile dermatomyositis. 1576 May 87

Masticatory muscle myositis (MMM) is the most common inflammatory myopathy (IM) in dogs, associated with antibodies against myosin. To further elucidate the immunopathogenesis, we investigated muscles of 53 dogs with MMM, 32 dogs with polymyositis (PM), and 4 dogs suffering from both, with regard to the presence and location of CD4(+) and CD8(+)T cells, B cells, macrophages, major histocompatibility complex (MHC) class I and class II antigens, and autoantibodies. CD8(+)T cells were found in MMM (91%) and PM (75%), mostly paralleled (68% and 61%) by enhanced expression of MHC class I antigen on muscle fibers. CD8(+)T cells invading intact and neighboring necrotic muscle fibers were present in MMM (39%) and PM (42%). Dogs with MMM lacking intramuscular (26%) and circulating (36%) autoantibodies also had CD8(+) T-cell infiltrations and muscle-fiber lesions. Since MHC class I antigen and CD8(+) T cells were detected in the presence of CD4(+) T cells, regardless of antimuscular antibodies, we consider MMM and PM in the dog as a CD8(+) T-cell-mediated immunopathological disease that initiates muscle-fiber destruction and leads to production of myosin autoantibodies.
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PMID:Evidence for MHC I-restricted CD8+ T-cell-mediated immunopathology in canine masticatory muscle myositis and polymyositis. 1658 72

The idiopathic inflammatory myopathies (IIM) are systemic connective tissue diseases defined by chronic muscle inflammation and weakness associated with autoimmunity. We have performed low to high resolution molecular typing to assess the genetic variability of major histocompatibility complex loci (HLA-A, -B, -Cw, -DRB1, and -DQA1) in a large population of European American patients with IIM (n = 571) representing the major myositis autoantibody groups. We established that alleles of the 8.1 ancestral haplotype (8.1 AH) are important risk factors for the development of IIM in patients producing anti-synthetase/anti-Jo-1, -La, -PM/Scl, and -Ro autoantibodies. Moreover, a random forests classification analysis suggested that 8.1 AH-associated alleles B*0801 and DRB1*0301 are the principal HLA risk markers. In addition, we have identified several novel HLA susceptibility factors associated distinctively with particular myositis-specific (MSA) and myositis-associated autoantibody (MAA) groups of the IIM. IIM patients with anti-PL-7 (anti-threonyl-tRNA synthetase) autoantibodies have a unique HLA Class I risk allele, Cw*0304 (pcorr = 0.046), and lack the 8.1 AH markers associated with other anti-synthetase autoantibodies (for example, anti-Jo-1 and anti-PL-12). In addition, HLA-B*5001 and DQA1*0104 are novel potential risk factors among anti-signal recognition particle autoantibody-positive IIM patients (pcorr = 0.024 and p = 0.010, respectively). Among those patients with MAA, HLA DRB1*11 and DQA1*06 alleles were identified as risk factors for myositis patients with anti-Ku (pcorr = 0.041) and anti-La (pcorr = 0.023) autoantibodies, respectively. Amino acid sequence analysis of the HLA DRB1 third hypervariable region identified a consensus motif, 70D (hydrophilic)/71R (basic)/74A (hydrophobic), conferring protection among patients producing anti-synthetase/anti-Jo-1 and -PM/Scl autoantibodies. Together, these data demonstrate that HLA signatures, comprising both risk and protective alleles or motifs, distinguish IIM patients with different myositis autoantibodies and may have diagnostic and pathogenic implications. Variations in associated polymorphisms for these immune response genes may reflect divergent pathogenic mechanisms and/or responses to unique environmental triggers in different groups of subjects resulting in the heterogeneous syndromes of the IIM.
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PMID:Immunogenetic risk and protective factors for the idiopathic inflammatory myopathies: distinct HLA-A, -B, -Cw, -DRB1, and -DQA1 allelic profiles distinguish European American patients with different myositis autoantibodies. 1660 50

The signaling pathways involved in the immunobiology of polymyositis, dermatomyositis, and inclusion-body myositis are outlined in this Review, which is based on research performed during the past 10 years. In dermatomyositis, the complement cascade is activated and the expression of cytokines and chemokines is upregulated. In polymyositis and inclusion-body myositis, autoinvasive CD8+ T cells are clonally expanded. This T-cell subset possesses conserved amino-acid sequences in complementarity-determining region 3 of the T-cell receptor and, via the perforin pathway, exerts a myotoxic effect on muscle fibers that express major histocompatibility complex (MHC) class I molecules. In all inflammatory myopathies, molecules associated with T-cell transmigration and cytokine signaling, as well as chemokines and their receptors, are strongly expressed by endothelial and inflammatory cells. Early in the pathogenesis of polymyositis and inclusion-body myositis, expression of MHC class I molecules on muscle fibers is upregulated, even in the absence of autoinvasive CD8+ T cells. Emerging data indicate that such continuous upregulation of the expression of MHC class I molecules on muscle fibers leads to an endoplasmic reticulum stress response, intracellular accumulation of misfolded glycoproteins, and activation of nuclear factor kappaB pathways, which can further stimulate formation of MHC class I-CD8 complexes, resulting in a self-sustaining inflammatory response. Advances in our understanding of the signaling pathways involved in the pathogenesis of these inflammatory myopathies are expected to result in the identification of novel therapeutic targets for these diseases.
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PMID:Mechanisms of disease: signaling pathways and immunobiology of inflammatory myopathies. 1693 88

Sporadic inclusion-body myositis (sIBM) is the most common acquired muscle disease in Caucasians over the age of 50 years. Pathologically it is marked by inflammatory, degenerative, and mitochondrial changes that interact in a yet-unknown way to cause progressive muscle degeneration and weakness. The cause of the disease is unknown, but it is thought to involve a complex interplay between environmental factors, genetic susceptibility, and aging. The strongest evidence for genetic susceptibility comes from studies of the major histocompatibility complex (MHC), where different combinations of alleles have been associated with sIBM in different ethnic groups. The rare occurrence of familial cases of inclusion-body myositis (fIBM) adds additional evidence for genetic susceptibility. Other candidate genes such as those encoding some of the proteins accumulating in muscle fibers have been investigated, with negative results. The increased understanding of related disorders, the hereditary inclusion-body myopathies (hIBM), may also provide clues to the underlying pathogenesis of sIBM, but to date there is no indication that the genes responsible for these conditions are involved in sIBM. This review summarizes current understanding of the contribution of genetic susceptibility factors to the development of sIBM.
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PMID:Genetics of inclusion-body myositis. 1736 91

New classification of idiopathic inflammatory myopathy (IIM) defined three major entities, polymyositis (PM), dermatomyositis (DM) and sporadic inclusion body myositis (s-IBM). We report the clinical, electrophysiological and pathological characteristics of three patients with a rare form of IIM not fulfilling the diagnostic criteria for any of these three major entities. The three patients presented with a subacute, distal asymmetrical weakness in upper limbs. Muscle biopsy showed an active myositis, with necrosis and regeneration, T cell infiltrates with invasion of non-necrotic fibers, without rimmed vacuoles, and diffuse major histocompatibility complex-I (MHC-I) immunostaining in muscle fibers. All patients responded to immunosuppressive agents. Seven others cases were identified in the literature. It is important to recognize this atypical presentation as it seems to respond to immunosuppressive agents.
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PMID:Distal inflammatory myopathy: unusual presentation of polymyositis or new entity? 1853 49

The dominant clinical feature of polymyositis/dermatomyositis is weakness in proximal, rather than distal, musculature. Although rare, cases of focal/localized myositis in which polymyositis-like muscle inflammation is present in only one muscle or extremity have also been reported. The underlying mechanisms dictating involvement of specific muscle groups in polymyositis/dermatomyositis and focal/localized myositis have not been identified. Here, we describe a rare case of dropped-head syndrome due to localized idiopathic inflammatory myopathy (IIM) in the splenius capitis (neck extensor) muscle where major histocompatibility complex (MHC) class I expression was up-regulated in involved muscle fibers. Interestingly, the adjacent trapezius muscle was not affected, corresponding to muscle biopsy findings that did not show any sign of inflammation or MHC class I expression. Our case report therefore suggests that selection of affected muscle in IIM might be influenced by the MHC class I expression of the muscle.
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PMID:Selective expression of MHC class I in the affected muscle of a patient with idiopathic inflammatory myopathy. 1932 21

Folding and transport of proteins, such as major histocompatibility complex (MHC) class I, through the endoplasmic reticulum (ER) is tightly regulated in all cells, including muscle tissue, where the specialized ER sarcoplasmic reticulum is also critical to muscle fiber function. Overexpression of MHC class I protein is a common feature of many muscle pathologies including idiopathic myositis and can induce ER stress. However, there has been no comparison of the consequences of MHC overexpression in muscle at different ages. We have adapted a transgenic model of myositis induced by overexpression of MHC class I protein in skeletal muscle to investigate the effects of this protein overload on young muscle fibers, as compared with adult tissue. We find a markedly more severe disease phenotype in young mice, with rapid onset of muscle weakness and pathology. Gene expression profiling to compare the two models indicates rapid onset of ER stress in young muscle tissue but also that gene expression of key muscle structural proteins is affected more rapidly in young mice than adults after this insult. This novel model has important implications for our understanding of muscle pathology in dermatomyositis of both adults and children.
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PMID:Overexpression of MHC class I heavy chain protein in young skeletal muscle leads to severe myositis: implications for juvenile myositis. 1970 Jul 52

Association of statins with autoimmune disorders is rarely reported. We report a case of an apparently healthy 76-year-old woman who was on long-term statin therapy presenting with severe rhabdomyolysis, autoimmune hepatitis, and positive lupus antibodies. Patient presented with complaints of worsening fatigue, leg cramps, and progressive weakening of lower extremities over 3 weeks. The patient was on simvastatin daily for several years. Clinical examination on admission included muscle tenderness, lower extremity edema, and ascites. Her laboratory values on admission showed elevated creatine kinase and transaminases. Immunologic workup revealed positive ANA, anti-dsDNA and anti-SSA antibodies. F-actin antibody was also positive at high titer. Magnetic resonance imaging of the lower extremities showed findings consistent with myositis. Patient underwent biopsy of the thigh muscles, which showed inflammatory myositis. Liver biopsy was characteristic of autoimmune hepatitis. Patient responded well to immunosuppressive therapy with azathioprine and prednisone. Although statins are generally considered safe, recent data from long-term follow-up on patients who are on statins for long duration suggest that prolonged exposure to statins may trigger autoimmune reactions. The exact mechanism of statin-induced autoimmune reaction is unclear. Statins, as proapoptotic agents, release nuclear antigen into the circulation and may induce the production of pathogenic autoantibodies. The role of statins in inducing an endoplasmic reticular stress response with associated upregulation of major histocompatibility complex-1 expression and antigen presentation by muscle fibers has also been reported. Systemic immunosuppressive therapy has proven to be effective in many reported cases.
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PMID:Statins as a potential risk factor for autoimmune diseases: a case report and review. 2378 56

Myopathy with anti-signal recognition particle antibodies (SRP) is generally thought to be immune-mediated necrotic myopathy in previous studies. We report the clinical and histopathological features of myopathy with anti-SRP antibodies in Chinese patients. Muscle biopsy and immunoblots for myositis antibodies were carried out in 123 patients with idiopathic inflammatory myopathy. Among them, 16 (13.0%) patients had anti-SRP antibodies. Age of onset ranged from 24 to 77 years, and the disease began insidiously. Fourteen of 16 patients presented with chronic progression of proximal limb weakness, with 6 having myalgia. Serum creatine kinase levels ranged from 400 to 9082 IU/L. Muscle biopsies showed necrotic and/or regenerative muscle fibers in all 16, infiltrates of lymphocytes in 11 and morphological features of muscular dystrophy in 7. Eleven patients showed focal or diffuse major histocompatibility complex class 1 expression in sarcolemma or cytoplasm of muscle fibers, with 9 showing deposition of membrane attack complex in necrotic muscle fibers and 2 around capillaries. These findings indicate that anti-SRP antibodies are most likely to be related to IMNM. Myopathy with anti-SRP antibodies is not infrequent in Chinese patients with idiopathic inflammatory myopathy.
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PMID:Myopathy with anti-signal recognition particle antibodies: clinical and histopathological features in Chinese patients. 2449 86


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