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Open Access Highly Accessed Review

Idiopathic inflammatory myopathies: pathogenic mechanisms of muscle weakness

Sree Rayavarapu12, William Coley1, Travis B Kinder12 and Kanneboyina Nagaraju12*

Author Affiliations

1 Research Center for Genetic Medicine, Children’s National Medical Center, 111 Michigan Ave NW, Washington DC, USA

2 Institute of Biomedical Sciences, The George Washington University, 2300 Eye Street, N.W., Ross 605, Washington DC, USA

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Skeletal Muscle 2013, 3:13  doi:10.1186/2044-5040-3-13

Published: 7 June 2013

Abstract

Idiopathic inflammatory myopathies (IIMs) are a heterogenous group of complex muscle diseases of unknown etiology. These diseases are characterized by progressive muscle weakness and damage, together with involvement of other organ systems. It is generally believed that the autoimmune response (autoreactive lymphocytes and autoantibodies) to skeletal muscle-derived antigens is responsible for the muscle fiber damage and muscle weakness in this group of disorders. Therefore, most of the current therapeutic strategies are directed at either suppressing or modifying immune cell activity. Recent studies have indicated that the underlying mechanisms that mediate muscle damage and dysfunction are multiple and complex. Emerging evidence indicates that not only autoimmune responses but also innate immune and non-immune metabolic pathways contribute to disease pathogenesis. However, the relative contributions of each of these mechanisms to disease pathogenesis are currently unknown. Here we discuss some of these complex pathways, their inter-relationships and their relation to muscle damage in myositis. Understanding the relative contributions of each of these pathways to disease pathogenesis would help us to identify suitable drug targets to alleviate muscle damage and also improve muscle weakness and quality of life for patients suffering from these debilitating muscle diseases.

Keywords:
Adaptive immune; Autophagy; Cytokines; Endoplasmic reticulum stress; Innate immune; Myositis; Skeletal muscle; TLRs