Based on unique clinicopathological criteria, the most common immune inflammatory muscle disorders include Dermatomyositis (DM), Polymyositis (PM), Necrotizing Myositis (NM), and sporadic Inclusion Body Myositis (sIBM). DM is an undeniably a complement-mediated microangiopathy with destruction of capillaries, hypoperfusion, and inflammatory cell stress on the perifascicular regions. Necrotizing Myopathy is a poorly studied subacute myopathy triggered by toxic, viral, or autoimmune factors with macrophages as the final effector cells. In PM and IBM cytotoxic CD8-positive T-cells clonally expand in situ and invade MHC-I-expressing muscle fibers. In sIBM, in addition to autoimmune inflammation, there are degenerative features characterized by vacuolization and accumulation of stressor and amyloid-related molecules. Advances in the immunobiology of these disorders are discussed including the interaction between pro-inflammatory and beta-amyloid or stressor proteins. A critical review regarding tissue biomarkers and strategies for more effective treatments are presented.
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