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Novel cytoplasmic immunolocalization of RNA polymerase II in inclusion-body myositis muscle.

Sporadic inclusion-body myositis (IBM) is a progressive degenerative muscle disease of older persons. Abnormalities of gene-expression and RNA metabolism have recently been proposed to contribute to the IBM pathogenic cascade. We now demonstrate, using well characterized, epitope-specific antibodies, that the largest subunit of RNA polymerase II is abnormally accumulated in the cytoplasm of IBM muscle fibers, where it is co-localized with phosphorylated tau on IBM paired helical filaments. Since RNA polymerase II is a crucial nuclear factor involved in both transcription and mRNA processing, our results support the hypothesis that abnormality of either or both of those processes might be caused, in part, by pathological trafficking of RNA polymerase II, and that abnormal trafficking might be an important factor in the IBM pathogenic cascade.

Cytoplasm↗

Rimmed vacuoles and the added value of SMI-31 staining in diagnosing sporadic inclusion body myositis.

Problems in diagnosing sporadic inclusion body myositis may arise if all clinical features fit a diagnosis of polymyositis, but the muscle biopsy shows some rimmed vacuoles. Recently, immunohistochemistry with an antibody directed against phosphorylated neurofilament (SMI-31) has been advocated as a diagnostic test for sporadic inclusion body myositis. The aims of the present study were to define a quantitative criterion to differentiate sporadic inclusion body myositis from polymyositis based on the detection of rimmed vacuoles in the haematoxylin-eosin staining and to evaluate the additional diagnostic value of the SMI-31 staining. Based on clinical criteria and creatine kinase levels in patients with endomysial infiltrates, 18 patients complied with the diagnosis of sporadic inclusion body myositis, and 17 with the diagnosis of polymyositis. A blinded observer counted the abnormal fibres in haematoxylin-eosin-stained sections and in SMI-31-stained sections. The optimal cut-off in the haematoxylin-eosin test was 0.3% vacuolated fibres. Adding the SMI-31 staining significantly increased the positive predictive value from 87 to 100%, but increased the negative predictive value only to small extent. We conclude that (1) patients with clinical and laboratory features of polymyositis, including response to treatment, may show rimmed vacuoles in their muscle biopsy and that (2) adding the SMI-31 stain can be helpful in differentiating patients who respond to treatment from patients who do not.

Adult↗

Inclusion body myositis. An electrophysiologic study.

Inclusion body myositis is a rare and slowly progressive myositis associated with cytoplasmic inclusions and fibrillar nuclear material. These histopathologic findings are of unknown significance. The clinical presentation of IBM has marked similarities to that of chronic polymyositis with proximal greater than distal weakness and muscle wasting more pronounced in the lower than upper extremities. In contrast to polymyositis, however, relatively few individuals report neck flexor weakness or dysphagia. Corticosteroid treatment is usually ineffective. The clinical, histopathologic and electrophysiologic findings in a patient with IBM are presented. Of particular interest in this report is the detailed motor unit recruitment frequency data. A number of previous IBM reports fail to mention specific electrophysiologic data or present evidence suggestive of a possible combined neuropathic and myopathic disease. Recruitment intervals of 150 ms or greater in combination with decreased motor unit duration and amplitudes in the involved muscles imply a myopathic pathophysiology. These findings are discussed in relation to electrophysiologic data from previously reported cases.

Electromyography↗

The role of quantitative electromyography in inclusion body myositis.

OBJECTIVE AND METHODS: Inclusion body myositis is said to have both myopathic and neurogenic features on electrophysiological tests. Twenty one studies from 20 patients with biopsy defined inclusion body myosis, 13 of whom had quantitative electromyography (qEMG), were reviewed to determine if this technique added diagnostic specificity (one patient had both needle EMG and a later study with qEMG before muscle biopsy). RESULTS: Excessive numbers of polyphasic motor unit potentials (MUPs) (> 12% per muscle) were seen in 11 of the 13 patients. In 10 of 13 patients, mean MUP duration was abnormally reduced (26% to 48%). In three patients, mean MUP duration was abnormally reduced only after polyphasic MUPs were excluded. In all 13 patients, the simple MUP duration was reduced. Myopathy was unequivocally diagnosed in all 13 studies that included qEMG; of the remaining eight patients, the conclusions of the electrophysiological studies without qEMG was myopathy (one), neurogenic (four) or non-diagnostic (three). CONCLUSIONS: There is no evidence of a neurogenic component in inclusion body myosis if qEMG is used. Quantitative EMG is often necessary to make an electrophysiological diagnosis of a myogenic disorder in patients with inclusion body myosis.

Adult↗

Multiple mitochondrial DNA deletions in sporadic inclusion body myositis: a study of 56 patients.

Inclusion body myositis, a chronic inflammatory disorder, is the most common cause of myopathy in adults over the age of 50. Diagnosis is based on clinical features and distinctive morphological findings by both light and electron microscopy. The causes of inclusion body myositis are still unknown. Ultrastructural mitochondrial changes and ragged-red fibers are common in patients with sporadic inclusion body myositis, and multiple [correction of mutiple] mitochondrial DNA (mtDNA) deletions have been reported in 3 such patients, suggesting that mtDNA mutations may have a pathogenetic role. We studied 56 patients with sporadic inclusion body myositis, using a combination of clinical, morphological, biochemical, and molecular genetic analyses to determine the frequency and the distribution of mtDNA deletions. Using the polymerase chain reaction, we found multiple mtDNA deletions in 73% of patients, compared to 40% of normal age-matched control subjects and 47% of disease control subjects. The presence of deletions correlated with morphological evidence of ragged-red, cytochrome c oxidase-negative fibers, and with defects of complexes I and IV of the electron transport chain. Although aging may account for a proportion of mtDNA deletions in patients with sporadic inclusion body myositis and control subjects, mtDNA alterations may be accelerated in sporadic inclusion body myositis.

Adult↗

Inclusion body myositis in twins.

Sporadic inclusion body myositis (s-IBM) is characterized by late onset of slowly progressive weakness that involves the quadriceps and volar forearm muscles early in the course of the disease. There are hereditary forms of inclusion body myopathy (h-IBM) that histologically resemble s-IBM. The lack of inflammation on biopsy and the different ages at onset and patterns of muscle weakness distinguish s-IBM from h-IBM. We report twin brothers with the typical clinical and histologic features of s-IBM. The occurrence of s-IBM in these twins suggests the possibility of a genetic susceptibility to developing s-IBM.

Age of Onset↗

Inclusion body myositis and myopathies.

Sporadic inclusion body myositis is a frequent, acquired, adult-onset vacuolar myopathy affecting proximal and distal muscles with a distinct, easily identifiable clinical pattern. Although its primary cause is still unknown, autoimmune, viral, and degenerative processes, alone or in combination, are being considered. A uniform and sustained therapeutic response using the currently available immunomodulatory agents has not yet been achieved. Hereditary, inherited noninflammatory rimmed vacuolar myopathies with similar histologic features, collectively called hereditary inclusion body myopathies, are being redefined with the use of molecular genetics. The implications of the recent advances in clinical and basic sciences are discussed in the present review.

Aged↗

The immunopathologic and inflammatory differences between dermatomyositis, polymyositis and sporadic inclusion body myositis.

In polymyositis and sporadic inclusion body myositis, clonal expansion of CD8+ cells which are primed to recognize previously unknown muscle antigens occurs. Compared with sporadic inclusion body myositis, however, in which the T-cell response may not be antigen driven, there is in polymyositis an overexpression of certain T-cell receptor gene families among the autoinvasive T-cells. Although studies on the endomysial expression of cytokines and cell adhesion molecules have provided additional support for the concept of an ongoing immune process, the site of sensitization and the mechanism by which the autoimmune process is triggered remains to be established. In dermatomyositis, a multiorgan disease, evidence exists that the complement-mediated microvascular injury by the putative antibody may not be limited to the endomysial vessels but may also involve the blood vessels in the dermis. The antigenic target on the endothelial cell in dermatomyositis patients and the pathogenic role of the recently studied anti-Mi-2 antibody directed against a helicase are still to be determined.

Dermatomyositis↗

[Inclusion body myositis. Report of 4 cases].

Inclusion body myositis (IBM) is a primary inflammatory myopathy characterized by an older age at presentation. We describe four IBM cases fulfilling Mendell's diagnostic criteria. All patients were older than 60 years at diagnosis and the mean length of time from onset to diagnosis was 5.7 years. Two of them complained of leg weakness with unsteady gait and the other two, of upper limb weakness. Three patients had dysphagia, one of them had diaphragmatic paralysis and another had bilateral blepharoptosis. Histological sections of the muscle biopsy showed mononuclear cell invasion of nonnecrotic muscle fibers, rimmed vacuoles, intracellular amyloid deposits and 16-21 nm tubulofilaments by electron microscopy. Mitochondrial anomalies were found in two cases. Only one patient had transient response to steroid therapy. Our serie shows that clinical presentation of inclusion body myositis includes a broader spectrum than the classical description.

Aged↗

[Inclusion body myositis: clinical and myopathological features].

Inclusion body myositis has been recognized as a major form of idiopathic inflammatory myopathy. An old male patient with insidious onset and slowly progressive muscular weakness and artrophy has been reported in this article. The duration of symptom before biopsy was 23 years. The first symptom was dysphagia, and muscular weakness developed seven years later. Muscular atrophy was predominant symmetrically and proximally, particularly the quadriceps femoris muscles. Cervical and abdominal muscles were also affected. Myalgia was absent. Electromyogrophy showed myopathic alterations. Erythrocyte sedimentation rate, creatine kinase, immunoglobulins G increased slightly or moderately. Rheumatoid factor was positive, and he had been diagnosed as having rheumatoid arthritis for 23 years. Inclusion body myositis was ultimately diagnosed based on the muscle biopsy which showed mononuclear cell invasion of nonnecrotic muscle fibers, the characteristic rimmed vacuoles in cryostat sections and cytoplasmic inclusion bodies consisted of plenty of tubulofilaments by electron microscope.

Aged↗

Leukocytapheresis in inclusion body myositis.

A patient with inclusion body myositis was treated with a course of 22 leukocytaphereses combined with prednisone and azathioprine therapy. He improved clinically during an induction phase of frequent cytapheresis, which reduced the circulating levels of T lymphocytes and monocytes and decreased the ratio of the T4+ to T8+ lymphocyte subsets. During subsequent maintenance cytapheresis there was partial recovery of the T4+ population without recovery of T8+ lymphocytes, and the patient lost most of his clinical improvement. In contrast to T lymphocytes and monocytes, there was no persistent reduction in circulating B lymphocyte levels during the course of therapy. T8+ lymphocyte populations may regenerate more slowly than T4+ lymphocytes following depletion with leukocyatpheresis combined with prednisone and azathioprine therapy. A loss of T8+ suppressor relative to T4+ helper-cell function could lead to an intensification of autoimmune conditions.

Humans↗

[New insights in pathogenesis and therapy of sporadic inclusion body myositis (s-IBM)].

Sporadic inclusion body myositis (s-IBM) is a chronic progressive inflammatory myopathy which occurs preferentially in older patients. Histologic hallmarks are rimmed vacuoles and eosinophilic cytoplasmatic inclusions. The etiology is still unknown, but different pathogenetic mechanisms such as slow virus infection, autoimmunopathogenesis, myonuclear alterations, and mitochondrial defects have been implicated. A relation to neurodegenerative disorders and prion diseases has also been suggested. There is a poor response if any to immunosuppressive therapy. Stabilization of disease progression was shown only by intravenous immunoglobulin (IVIG) therapy. Future findings in the field of s-IBM pathogenesis may result in better therapeutic options.

Aged↗

Dysphagia in inclusion body myositis.

Four elderly patients with inclusion body myositis and dysphagia are described. Dysphagia was the presenting symptom in three, preceding generalised weakness by 1.5 to 7 years. Myotomy of the cricopharyngeal muscle improved the symptoms and signs in 3 of the 4 patients. It is suggested that inclusion body myositis is not an infrequent cause of dysphagia in elderly people, and is amenable to treatment.

Aged↗

Steroid-responsive inclusion body myositis associated with endometrial cancer.

Inclusion body myositis (IBM) is an uncommon chronic inflammatory myopathy. Although the association between other myopathies and cancer has been well established, the relationship between IBM and neoplasia is not completely understood. Unlike polymyositis (PM) or dermatomyositis (DM), IBM rarely responds to immunosuppressive treatment and the response is seldom long-lasting. We describe a case of IBM associated with endometrial carcinoma that also demonstrated a unique response to steroids alone which persisted despite cancer relapse. The factors that are associated with a response of IBM to steroids are discussed. An atypical, steroid-responsive form of the disease is delineated.

Adenocarcinoma↗

Familial inflammatory inclusion body myositis.

OBJECTIVE: To compare familial inflammatory inclusion body myositis (IBM) with hereditary inclusion body myopathies and sporadic IBM. PATIENTS AND METHODS: Clinical, biological, MRI, and histological data were analysed in two siblings with inflammatory IBM and compared with those of patients with sporadic and hereditary IBM. RESULTS: Both patients had a clinical phenotype of sporadic IBM, which differs from hereditary myopathies because of late age of onset--respectively 65 and 66 years, and different pattern of muscular involvement--asymmetric, mainly distal but also involving quadriceps. MRI showed selective fatty infiltration and oedema in the extensor compartment of thigh muscles. The diagnosis of IBM was confirmed by muscle biopsy, showing muscle fibres containing numerous rimmed vacuoles, a characteristic shared by all types of IBM. In contrast with hereditary IBM, histological analysis also showed inflammatory mononuclear infiltrate invading non-necrotic fibres, ragged red and oxidase c negative fibres, and positive Congo red staining. Moreover, HLA class II typing disclosed DR beta 1 0301 haplotype, which is significantly related to sporadic but not to hereditary IBM. With steroid treatment and monthly intravenous immunoglobulins, the disease was stabilised in both patients at protracted follow up. CONCLUSION: Sporadic and familial inflammatory IBM share the same clinical, biological, MRI, and histological features.

Aged↗

Apolipoprotein E epsilon 4 in inclusion body myositis.

The genetic predisposition to inclusion body myositis (IBM) is probably multifactorial. The deposition of the beta-amyloid protein is a characteristic histological feature of both IBM and Alzheimer's disease (AD). The epsilon 4 allele of apolipoprotein E (APO E) has been strongly associated with familial and late-onset AD. We therefore compared the APO E allele frequencies in a group of 14 patients with IBM with those in a group of patients with other inflammatory muscle diseases and in the general population. The frequency of the epsilon 4 allele in IBM was increased (0.29) compared with that in patients with other inflammatory muscle diseases (0.15) and the general population (0.13) (p < 0.05). These data suggest that APO E genotype may be one of the factors involved in determining the predisposition to the development of IBM.

Adult↗

Clinically unsuspected inclusion body myositis.

We describe a patient with inclusion body myositis presenting as chronic, therapy resistant polymyositis. Our report highlights the slow evolution of inclusion body myositis in some patients, and emphasizes the diagnostic importance of examining one or more muscle biopsy specimens by both frozen section and electron microscopy.

Biopsy↗

New advances in inclusion-body myositis.

The major new advances in seeking the pathogenic mechanisms of sporadic inclusion-body myositis and hereditary inclusion-body myopathy are discussed. Hypotheses are presented regarding the possible causes and significance of amyloid deposits in sporadic inclusion-body myositis and the roles of abnormally accumulated ubiquitin, beta-amyloid protein, beta-amyloid precursor protein, alpha 1-antichymotrypsin, hyperphosphorylated tau, and prion protein in the vacuolated muscle fibers in both sporadic inclusion-body myositis and hereditary inclusion-body myopathy. Because hereditary inclusion-body myopathy is virtually free of Congophilic amyloid deposits but, like sporadic inclusion-body myositis, contains large accumulations of beta-amyloid protein, it is possible that the lesions in hereditary inclusion-body myopathy may represent "early" changes. There are striking similarities between the pathology of inclusion-body myositis muscle and brains affected by Alzheimer's disease in regard to accumulation of ubiquitin, beta-amyloid protein and its precursor protein, alpha 1-antichymotrypsin, and hyperphosphorylated tau.

Amyloid↗