What We Know About Infectious Agents and Myositis
What We Know About Infectious Agents and Myositis
Purpose of review Increasing evidence suggests that the idiopathic inflammatory myopathies (IIMs) result from certain environmental exposures in genetically susceptible individuals. Investigations have demonstrated that a variety of infections not only cause infectious myopathies but also could be possible triggers for IIM. This review summarizes published studies on the possible roles of infections in inflammatory muscle disease.
Recent findings Many infectious agents have been linked to the development of IIMs via case reports, epidemiologic investigations, and animal models. Additional agents possibly involved in triggering the development of IIMs have been recently described, including Torque teno virus (TTV) and Borrelia burgdorferi. Novel animal models of myositis have been recently developed using Leishmania infantum or Chikungunya virus (CHIKV). New technologies to assess infectious agents include high-throughput methods for pathogen identification and novel approaches to identify gene expression of pathogens in tissues.
Summary Understanding the causes of IIMs remains limited in part due to the rarity and heterogeneity of these disorders. Although no definitive studies have yet linked infectious agents with IIMs, additional evidence is accumulating and novel technologies may allow improved understanding of the roles of infections in IIMs and for possible future therapeutic and preventive measures.
Inflammatory myopathies, defined by chronic inflammation in muscles, are characterized clinically by a wide variety of symptoms including muscle tenderness, weakness, swelling, and pain, and include a large number of conditions such as infectious, toxic, endocrine, and other myopathies. Significant advances in defining the pathologic and molecular features of the inflammatory myopathies have been made recently, yet much remains unknown. When clinical, laboratory, and pathologic studies fail to identify the known causes of inflammation in a muscle, a diagnosis of idiopathic inflammatory myopathy (IIM) may be made. The most common IIM subtypes are dermatomyositis, polymyositis, and inclusion body myositis (IBM). The phenotypic heterogeneity observed in IIM may be related to heterogeneity in genetic and environmental risk factors, suggesting that the difficulty in understanding the role of infections in IIM may in part relate to the fact that different phenotypes have different infectious risk factors. In this review, we summarize recent findings on associations between infectious agents and onset of IIM and review previous reported pathogens related to infectious myopathies. Our review focuses on articles published in the last 10 years and we do not discuss infections occurring after the diagnosis and therapy of IIM, although these opportunistic infections are common and have been well documented.
Abstract and Introduction
Abstract
Purpose of review Increasing evidence suggests that the idiopathic inflammatory myopathies (IIMs) result from certain environmental exposures in genetically susceptible individuals. Investigations have demonstrated that a variety of infections not only cause infectious myopathies but also could be possible triggers for IIM. This review summarizes published studies on the possible roles of infections in inflammatory muscle disease.
Recent findings Many infectious agents have been linked to the development of IIMs via case reports, epidemiologic investigations, and animal models. Additional agents possibly involved in triggering the development of IIMs have been recently described, including Torque teno virus (TTV) and Borrelia burgdorferi. Novel animal models of myositis have been recently developed using Leishmania infantum or Chikungunya virus (CHIKV). New technologies to assess infectious agents include high-throughput methods for pathogen identification and novel approaches to identify gene expression of pathogens in tissues.
Summary Understanding the causes of IIMs remains limited in part due to the rarity and heterogeneity of these disorders. Although no definitive studies have yet linked infectious agents with IIMs, additional evidence is accumulating and novel technologies may allow improved understanding of the roles of infections in IIMs and for possible future therapeutic and preventive measures.
Introduction
Inflammatory myopathies, defined by chronic inflammation in muscles, are characterized clinically by a wide variety of symptoms including muscle tenderness, weakness, swelling, and pain, and include a large number of conditions such as infectious, toxic, endocrine, and other myopathies. Significant advances in defining the pathologic and molecular features of the inflammatory myopathies have been made recently, yet much remains unknown. When clinical, laboratory, and pathologic studies fail to identify the known causes of inflammation in a muscle, a diagnosis of idiopathic inflammatory myopathy (IIM) may be made. The most common IIM subtypes are dermatomyositis, polymyositis, and inclusion body myositis (IBM). The phenotypic heterogeneity observed in IIM may be related to heterogeneity in genetic and environmental risk factors, suggesting that the difficulty in understanding the role of infections in IIM may in part relate to the fact that different phenotypes have different infectious risk factors. In this review, we summarize recent findings on associations between infectious agents and onset of IIM and review previous reported pathogens related to infectious myopathies. Our review focuses on articles published in the last 10 years and we do not discuss infections occurring after the diagnosis and therapy of IIM, although these opportunistic infections are common and have been well documented.
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