Idiopathic Inflammatory Myopathies: A Review of the Classification and Impact of Pathogenesis

Abstract

Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune muscle diseases with significant morbidity and mortality. This review details and updates the pathogenesis and emerging importance of myositis-specific antibodies in the development of IIMs. An increase in the understanding of how these myositis-specific antibodies play a role in IIMs has led to the further categorization of IIMs from the traditional polymyositis versus dermatomyositis, to additional subcategories of IIMs such as necrotizing autoimmune myositis (NAM). The diagnosis of IIMs, including manual muscle testing, laboratory studies, and non-invasive imaging have become important in classifying IIM subtypes and for identifying disease severity. Treatment has evolved from an era where glucocorticoid therapy was the only option to a time now that includes traditional steroid-sparing agents along with immunoglobulin therapy and biologics, such as rituximab.

Skeletal muscles and Covid-19: a systematic review of rhabdomyolysis and myositis in SARS-CoV-2 infection

“…In health, the MDA-5 receptor has a role in innate immunity against viruses, including SARS-CoV-2 (129). Myositis specific autoantibodies are a frequent feature of IIM, though whether they are biomarkers or have a direct pathogenic role remains debatable (130). Anti-TIF-1-Gamma antibodies seen in a subset of dermatomyositis patients have immune epitopes of high sequence identity to those of SARS-CoV-2, leading the authors to speculate that coronaviridae exposure may contribute to the development of IIMs (131).…”

Interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) axis in idiopathic inflammatory myopathies and its association with laboratory and clinical parameters: a pilot study

“…Related congress abstracts 1. Partial results of the study, concerning clinical symptoms, results of 24 hour ECG Holter monitoring and results of biochemical tests in some of the patients from the study group have been presented at the students' conference: 57th Polish and 15th International…”

“…IIM is usually associated with muscle inflammation leading to progressive weakness; however, also the skin and internal organs may be affected [1,2]. The role of IL-33/ ST2 (interleukin-33/suppression of tumorigenicity 2) pathway has been studied recently in various diseases including infectious, autoimmune, metabolic and degenerative conditions [3].…”

Supervised Physical Therapy and Polymyositis/Dermatomyositis—A Systematic Review of the Literature

“…The terms polymyositis (PM) and dermatomyositis (DM) identify the two most common syndromes of the group of idiopathic inflammatory myopathies (IIM). Sporadic inclusion body myositis (sIBM) and immuno-mediated necrotising myopathy (IMNM) complete the group [ 1 , 2 , 3 , 4 ]. The common feature of IIM is the presence of inflammatory exudate and autoantibodies within the muscles.…”

“…The diagnostic criteria of IIM are still under discussion, and often these pathologies are misunderstood [ 3 , 6 ]. Only cases characterised by skin involvement (DM) can be identified according to the proposal of Bohan and Peter: (a) symmetrical weakness of the limb girdle muscles and anterior neck flexors, progressing over weeks to months, (b) elevation in serum of the skeletal muscle enzymes creatine kinase (CK), aldolase (ALD), glutamate oxaloacetate transaminase (GOT), glutamate pyruvic transaminase (GPT), lactate dehydrogenase (LDH), (c) electromyographic triad of small, short, polyphasic motor units, fibrillations, positive sharp waves (PSWs) and insertional irritability and bizarre, high-frequency repetitive discharges, (d) muscle biopsy evidence of necrosis of myofibers, phagocytosis, regeneration with basophils, large vesicular sarcolemmal nuclei and prominent nucleoli, atrophy in a perifascicular distribution, variation in fibre size and inflammatory exudates and (e) any one of the characteristic dermatologic features of the rash of DM [ 13 ].…”