Background Autoimmune myositis (AIM) is a syndrome characterized by involvement of the cellular and humoral immune systems in skeletal muscle pathology, response to immunotherapies and the presence of autoantibodies (Abs) in the serum of some patients. The prevalence of Abs vary between geographic regions because of differences in the genetic background and exposure to environmental factors among different populations.1 The discovery of myositis specific autoantibodies (MSAS) and myositis associated autoantibodies (MAAs) led to create a serologic classification because striking associations of some Abs with definite clinical features. Although it has been suggested that myositis Abs may identified distinct disease entities, in practice these Abs often segregate with overlap manifestations (arthritis, interstial lung disease, Raynaud’s phenomenon, vasculitis, sclerodactyly, calcinosis, discoid lupus, antiphospholipid syndrome).2 The relationships between Abs and clinical features are still unclear.
Objectives The objective of this study was to determine prevalence of MSAs and MAAs and to analyse relationships between clinical manifestations and serum autoantibodies in 70 patients with AIM in Bulgarian population.
Methods Sera were collected from 70 patients with AIM as diagnoses were determined using Bohan and Peter classification and Troyanov clinicoserologic classification. Sera were tested by indirect immunofluorescence using Hep-2 cells, Immunoblot test, enzyme linked immunosorbent assay. Associations between clinical manifestations and Abs were analyzed by Chi-square analysis, Fisher’s Exact test as P value didn’t exceed 0.05.
Results The most common autoantibodies were anti-Ro52 (in 43% of patients), anti-Ro60 (19%), anti-Jo-1 (16%) and anti-PM/Scl (14%). Other autoantibodies were detected in less patients with AIM respectively: anti-EJ (1,4%), anti-OJ (1,4%), anti-PL-7 (3%), anti-PL-12 (6%), anti-SRP (6%), anti-Mi-2 (9%), anti-Ku (1,4%), anti-La (6%).
We found statistically significant associations between some clinical manifestations and myositis Abs. It was identified relationship between anti-Jo-1 Abs and arthritis (p=0.002), interstial lung disease (p=0.015), vasculitis (p=0.048) in patients with AIM. PM/Scl Abs correlated with arthritis (p=0.015) and Raynaud’s phenomenon (p=0.015). Anti-Ro52 was associated with oropharyngeal dysphagia (p=0.042), interstial lung disease (p=0.024) and vasculitis (p=0.019). Mi-2 Abs didn’t correlate with typical skin features – heliotrope rash (p=0.19) and Gottron’s papule (d=0.13).
Conclusions The prevalence of most of Abs in patients with AIM corresponded with finding reported in other similar studies. The clinical features can be linked to the particular set of autoantibodies. In the study myositis Abs often associated with overlap manifestations. Therefore it has been suggested that much of AIM is composed of overlap myositis.
Nagaraju K, Plotz PH, Miller FW: Inflammatory muscle disease: etiology and pathogenesis. In Rheumatology edited by: Hochberg MC, Silman AJ, Smolen JS, Weinblatt ME, Weisman MH. ELSEVIER, Toronto, Canada; 2003:1523-1535.
Troyanov Y, Targoff IN, Tremblay J, Goulet J, Raymond Y, Senecal J. Novel classification of idiopathic inflammatory myopathies based on overlap syndrome features an autoantibodies. Medicine, 2005, 84: 231-249.
Disclosure of Interest None Declared