Abstract
ObjectivesTo determine prevalence and co-existence of myositis specific autoantibodies (MSAs) and myositis associated autoantibodies (MAAs) and associated clinical characteristics in a large cohort of idiopathic inflammatory myopathy (IIM) patients. MethodsAdult patients with confirmed IIM recruited to the EuroMyositis registry (n = 1637) from four centres were investigated for the presence of MSAs/MAAs by radiolabelled-immunoprecipitation, with confirmation of anti-MDA5 and anti-NXP2 by ELISA. Clinical associations for each autoantibody were calculated for 1483 patients with a single or no known autoantibody by global linear regression modelling. ResultsMSAs/MAAs were found in 61.5% of patients, with 84.7% of autoantibody positive patients having a sole specificity, and only three cases (0.2%) having more than one MSA. The most frequently detected autoantibody was anti-Jo-1 (18.7%), with a further 21 specificities each found in 0.2–7.9% of patients. Autoantibodies to Mi-2, SAE, TIF1, NXP2, MDA5, PMScl and the non-Jo-1 tRNA-synthetases were strongly associated (p < 0.001) with cutaneous involvement. Anti-TIF1 and anti-Mi-2 positive patients had an increased risk of malignancy (OR 4.67 and 2.50 respectively), and anti-SRP patients had a greater likelihood of cardiac involvement (OR 4.15). Interstitial lung disease was strongly associated with the anti-tRNA synthetases, anti-MDA5, and anti-U1RNP/Sm. Overlap disease was strongly associated with anti-PMScl, anti-Ku, anti-U1RNP/Sm and anti-Ro60. Absence of MSA/MAA was negatively associated with extra-muscular manifestations. ConclusionsMyositis autoantibodies are present in the majority of patients with IIM and identify distinct clinical subsets. Furthermore, MSAs are nearly always mutually exclusive endorsing their credentials as valuable disease biomarkers.
Highlights
The idiopathic inflammatory myopathies (IIMs) polymyositis (PM) and dermatomyositis (DM) are heterogeneous conditions characterised by muscle inflammation and weakness, skin rashes and systemic complications including interstitial lung disease (ILD), cardiac involvement and malignancy
We have shown that autoantibodies specific or associated with myositis as identified by IPP are present in the majority (61.5%) of patients of IIM using four large combined cohorts of patients
myositis specific autoantibodies (MSAs) were found in 42.9% of the total cohort and in those where further clinical details were available were mostly associated with cutaneous features, apart from anti-Jo-1 and anti-SRP that were associated with arthritis and cardiac involvement respectively
Summary
The idiopathic inflammatory myopathies (IIMs) polymyositis (PM) and dermatomyositis (DM) are heterogeneous conditions characterised by muscle inflammation and weakness, skin rashes and systemic complications including interstitial lung disease (ILD), cardiac involvement and malignancy. Autoimmune mechanisms have a key role in pathogenesis, with the majority of patients developing autoantibodies. These autoantibodies target both nuclear and cytoplasmic components involved in gene transcription, protein translocation and anti-viral responses. Journal of Autoimmunity 101 (2019) 48–55 subsets with the MAAs typically found in myositis patients with overlap features of other connective tissue diseases, and the MSAs predominantly occurring in patients with PM/DM [1,2]. Studies have demonstrated MSA/MAA specificities associate with distinct clinical subsets of patients [3,4,5,6] with sero-clinical classifications potentially aiding in prompt diagnosis, as well as helping to predict disease course and response to treatments. We describe the prevalence, mutual exclusivity and clinical associations of myositis autoantibodies in a large European cohort of adult PM and DM patients
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
