Idiopathic inflammatory myopathies and the anti-synthetase syndrome: A comprehensive review

Abstract

Autoantibodies are a hallmark in the diagnosis of many systemic autoimmune rheumatic diseases (SARD) including idiopathic inflammatory myopathies (IIM). Based on their specificity, autoantibodies in IIM are grouped into myositis specific (MSA) and myositis associated autoantibodies (MAA). Among the MSA, autoantibodies against aminoacyl-tRNA synthetases (ARS) represent the most common antibodies and can be detected in 25–35 % of patients. The presence of ARS and other autoantibodies have become a key feature for classification and diagnosis of IIM and are increasingly used to define clinically distinguishable IIM subsets. For example, anti-ARS autoantibodies are the key features of what has become known as anti-synthetase syndrome (aSS), characterized by multiple organ involvement, primarily interstitial lung disease, often accompanied by myositis, non-erosive arthritis, Raynaud’s phenomenon, fever, and “mechanic’s hands”. Autoantibodies directed to eight different ARS have been described: Jo-1 (histidyl), PL-7 (threonyl), PL-12 (alanyl), OJ (isoleucyl), EJ (glycyl), KS (asparaginyl), Zo (phenylalanyl) and Ha (tyrosyl). Each anti-ARS antibody seems to define a distinctive clinical phenotype. Although several research methods and commercial tests are available, routine testing for anti-ARS autoantibodies (other than anti-Jo-1/histidyl-tRNA synthetase) is not widely available, sometimes leading to delays in diagnosis and poor disease outcomes.

The Disappearance of a Hepatic Mass in Anti-Synthetase Syndrome

“…The use of electromyography and magnetic resonance imaging are controversial as they are costly and lack sensitivity and specificity. (1) Respiratory symptoms are by far the most commonly seen within the disease, where at least 60% of patients have such symptoms on presentation. Therefore, it is common that those patients presenting with unexplained ILD, should have ASyS in the differential diagnosis.…”

“…Therefore, it is common that those patients presenting with unexplained ILD, should have ASyS in the differential diagnosis. (1,10) Those not presenting with respiratory symptoms should have pulmonary function tests, and a thoracic highresolution CT. High-dose corticosteroids are the first-line treatment for ASyS. (11) Although corticosteroids are considered the mainstay of treatment, additional immunosuppressive agents, such as azathioprine and methotrexate, are often used, both as corticosteroid sparing agents and to achieve disease control.…”

“…(1)(2)(3) A number of autoantibodies, called myositis-specific autoantibodies (MSA), have been described in IIM. (4,5) The presence of MSA is a key feature for diagnosis of clinically distinguishable IIM subsets (polymyositis (PM), dermatomyositis (DM), inclusion body myositis, and myositis associated with malignancy and other connective tissue diseases).…”

Multiparametric autoimmune diagnostics: recent advances

“…17 Furthermore, for IIM, the sensitivity of ANA detection by IIF is limited, and due to the discovery of multiple other autoantigens (Tables 1 and 2), first-step application of IIM-specific multiparametric assays seems more appropriate. [18][19][20][21] As such, diagnostic testing for IIM should not be incorporated in the testing algorithm for SARD. 1 However, this requires early clinical recognition of IIM as a separate entity and, subsequently, close collaboration between the clinician and the laboratory specialist.…”

Diagnostic des myopathies inflammatoires au CHU de Bordeaux de 2012 à 2014

“…Cette classification a été remise en cause par la découverte de nouveaux AAC et le démembrement d'entités spécifiques, la PM « isolée » est devenue rare [3]. Il est désormais consensuel de classer les MI au sein des entités suivantes : dermatomyosites ; myosites de chevauchement [4] classées en trois entités : associées à une connectivite, associées à un AAC non spécifique, syndrome des AS [5] ; PM (définition histologique et absence d'AAC associé ou spécifique) et MNAI [6,7]. .…”