Autoimmune Myopathies: Updates on Evaluation and Treatment

Abstract

The major forms of autoimmune myopathies include dermatomyositis (DM), polymyositis (PM), myositis associated with antisynthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). While each of these conditions has unique clinical and histopathological features, they all share an immune-mediated component. These conditions can occur in isolation or can be associated with systemic malignancies or connective tissue disorders (overlap syndromes). As more has been learned about these conditions, it has become clear that traditional classification schemes do not adequately group patients according to shared clinical features and prognosis. Newer classifications are now utilizing myositis-specific autoantibodies which correlate with clinical and histopathological phenotypes and risk of malignancy, and help in offering prognostic information with regard to treatment response. Based on observational data and expert opinion, corticosteroids are considered first-line therapy for DM, PM, ASS, and IMNM, although intravenous immunoglobulin (IVIG) is increasingly being used as initial therapy in IMNM related to statin use. Second-line agents are often required, but further prospective investigation is required regarding the optimal choice and timing of these agents.

Statin Autoimmune Necrotizing Myopathy Diagnosed After a Motor Vehicle Accident

“…2 Diagnosis of SINAM can be confirmed with serology for the HMGCoA ab, muscle biopsy (showing scattered necrotic muscle fibers undergoing myophagocytosis and scant inflammation) and EMG (showing increased spontaneous activity, myopathic motor unit action potentials (MUAPs) with low amplitude, short duration, polyphasia and early recruitment). 3 Typically, the first line treatment for SINAM is a combination of a steroid with a secondary immunosuppressive agent such as methotrexate, azathioprine, or mycophenolate. 4 Intravenous immunoglobulin (IVIG) is highly efficacious as a monotherapy and in cases of refractory SINAM.…”

TLR expression in peripheral monocyte subsets of patients with idiopathic inflammatory myopathies: association with clinical and immunological features

“…Monocytes are the circulating precursors of macrophages and dendritic cells and are characterized by their ability to phagocytize, produce cytokines, present antigens [5][6][7] and their expression of a wide range of toll-like receptors (TLRs), especially TLR2 and TLR4 [8,9]. In patients with dermatomyositis (DM), polymyositis (PM), immune mediated necrotizing myopathy (IMNM) and antisynthetase syndrome (AS) macrophages and dendritic cells are prominent in muscle biopsies [10], highlighting the relevance of monocytes in the immunopathology of IIM. Also, the relevance of TLRs in the pathogenesis of inflammatory myopathies has been demonstrated in animal models [11] and muscle biopsies of these patients [12].…”

A study on demographic pattern of idiopathic inflammatory myopathies in a tertiary care hospital

“…In 1975, Bohan and Peter proposed the diagnostic criteria for DM and PM using clinical, pathological and laboratory features which remain to be the gold standard in clinical practice. [2][3][4] Both adaptive and innate immune pathways are implicated in the development of IIM. Although there are many similarities, PM and DM demonstrate distinct immuno histopathological phenotypes, suggesting that the underlying pathogenesis may not be the same.…”