State of the art: 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 IMMs 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.