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The ubiquitous RNA-processing molecule TDP-43 is involved in neuromuscular diseases such as inclusion body myositis, a late-onset acquired inflammatory myopathy. TDP-43 solubility and function are disrupted in certain viral infections. Certain viruses, high viremia, co-infections, reactivation of latent viruses, and post-acute expansion of cytotoxic T cells may all contribute to inclusion body myositis, mainly in an age-shaped immune landscape. The virally induced senescent, interferon gamma-producing cytotoxic CD8+ T cells with increased inflammatory, and cytotoxic features are involved in the occurrence of inclusion body myositis in most such cases, in a genetically predisposed host. We discuss the putative mechanisms linking inclusion body myositis, TDP-43, and viral infections untangling the links between viruses, interferon, and neuromuscular degeneration could shed a light on the pathogenesis of the inclusion body myositis and other TDP-43-related neuromuscular diseases, with possible therapeutic implications., (© 2024. The Author(s).)

Prevalence of muscle disease in human immunodeficiency virus (HIV) infection is less than 1% of patients with acquired immune deficiency syndrome. Sporadic inclusion body myositis (IBM) is observed in a few cases of patients infected by retroviruses such as HIV-1. A Caucasian man was diagnosed with HIV when he was 30 years old. The viral load was undetectable and CD4 cell count was 600/mm 3 when the diagnosis of inclusion body myositis was confirmed. Histological findings were typical of IBM. The treatment consisted of immunoglobulin therapy for three years without effect. Twenty-two patients were found in the English and French literature. They are younger than those who suffer from IBM without HIV (median age = 47, range: 30 to 59), and they are mostly men with considerable serum creatine kinase (CK) elevation (median CK level = 1322 IU/L, range: 465 to 10270), most of them were treated with Zidovudine., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To clarify whether there is any association between inclusion body myositis (IBM) and hepatitis C virus (HCV) infection., Methods: We assessed the prevalence of HCV infection in 114 patients with IBM whose muscle biopsies were analyzed pathologically for diagnostic purpose from 2002 to 2012 and in 44 age-matched patients with polymyositis diagnosed in the same period as a control by administering a questionnaire survey to the physicians in charge. We also compared clinicopathologic features including the duration from onset to development of representative symptoms of IBM and the extent of representative pathologic changes between patients with IBM with and without HCV infection., Results: A significantly higher number of patients with IBM (28%) had anti-HCV antibodies as compared with patients with polymyositis (4.5%; odds ratio 8.2, 95% confidence interval 1.9-36) and the general Japanese population in their 60s (3.4%). Furthermore, between patients with IBM with and without HCV infection, we did not find any significant difference in the clinicopathologic features, indicating that the 2 groups have essentially the same disease regardless of HCV infection., Conclusion: Our results provide the statistical evidence for an association between IBM and HCV infection, suggesting a possible pathomechanistic link between the 2 conditions., (© 2015 American Academy of Neurology.)

The objective of this study was to investigate the association of human T-lymphotropic virus-type I (HTLV-I) infection with sporadic inclusion body myositis in 11 patients from an endemic area in Japan. The clinical features were consistent with sporadic inclusion body myositis, and anti-HTLV-I antibodies were present in the sera of all patients. Their muscle biopsies showed the diagnostic features of inclusion body myositis, including endomysial T-cell infiltration, rimmed vacuoles, deposits of phosphorylated tau, and abnormal filaments in the nuclei and cytoplasm of the myofibers. The fibers expressed major histocompatibility complex class I antigens and were invaded by CD8 and CD4 cells. In a single human leukocyte antigen-A2-positive patient, in situ human leukocyte antigen-A*0201 / Tax11-19-pentamer staining showed pentamer-positive cells surrounding the muscle fibers. Double-immunogold silver staining and polymerase chain reaction in situ hybridization revealed that HTLV-I proviral DNA was localized on helper-inducer T cells, but not on muscle fibers. Human T-lymphotropic virus-type I proviral loads in peripheral blood mononuclear cells from each patient were similar to those in HTLV-I-associated myelopathy/tropical spastic paraparesis. This study suggests that HTLV-I infection may be one of the causes of sporadic inclusion body myositis, as has been reported in human immunodeficiency virus type-1 infection.

Inclusion body myositis (IBM) is a chronic progressive inflammatory myopathy in elders. Three patients with chronic hepatitis C developed IBM. Their muscle biopsies were examined by polymerase chain reaction (PCR) for two patients and immunohistochemistry for three patients. The hepatitis C virus (HCV)-RNA genome was detected in one of the two patients. The degenerated and atrophic muscle fibers were immunoreactive for an anti-HCV antibody in all three patients. Immunoreactivity for an anti-HCV antibody was not apparent in the muscle specimen from an IBM patient without HCV infection. Our findings suggest that HCV infection is related to the pathogenesis in some cases of IBM.

The inflammatory myopathies are a heterogeneous group of diseases due to autoimmunitary or infective causes. They are diagnosed by clinical electrophysiological features, and muscle biopsy. The autoimmunity group is subdivided in dermatomyositis, polimyositis and inclusion body myositis. The second group caused by viral genesis are called generally "myositis". The two groups have a different prognosis and therapy. The infective group denominated myositis have usually a viral etiology. We have evaluated 6 patients with viral myositis that are studied by physical examination, blood test (CK included), electromyographic pattern and muscle biopsy. The Authors emphasized the role of muscle biopsy for the diagnosis of this pathology and in particular for the myositis.

Sporadic inclusion body myositis (IBM) is the most common inflammatory myopathy affecting patients over the age of 50 years. Dysimmune and degenerative aetiologies have been postulated, but viral infections have not been associated with the disease. Two HIV-I (human immunodeficiency virus type 1) infected men and one woman infected with HTLV-1 (human T cell leukaemia virus type 1) developed progressive proximal muscle weakness unrelated to antiretroviral therapy. Their muscle biopsies were studied by light and electron microscopy, by immunocytochemistry to determine the expression of major histocompatibility complex (MHC) molecules and identify the type of infiltrating cells and T cell receptor (TCR) subunits, and by reverse transcription-polymerase chain reaction (RT-PCR) and single or double immunocytochemistry to search for retrovirally infected endomysial cells. The clinical features were consistent with sporadic IBM. The muscle biopsies showed primary endomysial inflammation, red-rimmed vacuoles, amyloid deposits, eosinophilic inclusions, and small round fibres in groups, all diagnostic of IBM. The muscle fibres expressed MHC class-1 antigens and were invaded primarily by CD8+ T-lymphocytes preferentially bearing TCR V beta 5.1 and V beta 13 chains. The HIV-1 or HTLV-1 antigens were detected only on endomysial macrophages on or around muscle fibres, but not within the muscle fibres. We conclude that IBM occurs in HIV-1 and HTLV-1 infected individuals and has a clinical, histological and immunological pattern identical to sporadic IBM in the non-retrovirally infected patients. Retroviruses do not directly infect the muscle, but persistent retroviral infections may provide superantigenic stimulation and trigger an endomysial inflammatory response identical to that occurring in sporadic IBM.

Inclusion body myositis (IBM) is a distinctive form of chronic inflammatory myopathy characterized pathologically by the finding of rimmed vacuoles and 15-18nm microtubular filamentous inclusions in muscle fiber nuclei and cytoplasm. The observation that these filaments resembled nucleocapsids of the paramyxovirus group and showed immunoreactivity with mumps virus (MV) antibodies has led to a long-standing postulate that IBM may be a "slow" mumps infection. We searched for the presence of MV RNA in 34 muscle biopsies (17 frozen and 17 paraffin-embedded) from 18 patients with IBM and 43 control biopsies (mainly from patients with other forms of inflammatory myopathy) using a polymerase chain reaction (PCR). The MV PCR was shown to be sensitive and specific for MV strains (including J-L) and the integrity of muscle RNA extracts was confirmed by PCR detection of constitutive Ableson tyrosine kinase mRNA. MV RNA was not found in any biopsy from the IBM group nor any of the control cases. Our results therefore do not support the mumps hypothesis for IBM.