Myositis Specific and Myositis Associated Autoantibodies in Idiopathic Inflammatory Myopathies : A Serologic study of 100 patients - 0308
Authors: I. Putova 1, K. Jarosova 2, M. Modra 1, J. Vencovsky 2. 1Laboratory of the Immunology, 2Dep. of the Clinical Rheumatology, Institute of the Rheumatology, Prague, Czech Republic
Background:
Patients with idiopathic inflammatory myopathies (IIM) often produce autoantibodies into their serum.
Objectives:
To determine the prevalence of myositis specific autoantibodies (MSA) and several myositis associated autoantibodies (MAA) in a group of patients with polymyositis (PM), dermatomyositis (DM), juvenile dermatomyositis (JDM), and cancer-associated dermatomyositis (CADM).
Methods:
A total of 100 patients - 52 with PM, 36 with DM, 6 with JDM, and 6 with CADM were serologically analyzed by immunoblot LIA ANA Update (Innogenetics, Belgium), LIA-myositis (Imtec, Germany), Western blot-myositis (Euroimmun, Germany), Western blot in house technique, and by counterimmunoelectrophoresis. Anti-nuclear antibodies (ANA) were detected by indirect immunofluorescence on Hep-2 cells. (Immunoconcepts, Germany).
Results:
MSA and/or MAA were found in sera of 63% patients with myositis, specifically in 71% of patients with PM, 66.7% of patients with DM, and 33.3% of patients with JDM. In the group with CADM, no specific antibody was detected apart from total ANA in 4 patients. The most frequently detected MSA was anti-Jo-1 in 28% of IIM patients, with higher frequency in PM (36.5%) than in DM (25%). A relatively high number of anti-Mi-2 positive sera were found, more often in DM (16.7%) than in PM. (9.6%). The most frequently detected MAA was anti-Ro52 in 36.5% of PM and 22% of DM sera. Anti-PM/Scl-100 and/or anti-PM/Scl-75 auto-antibodies were present in 15.4% and 19.4% of sera with PM and DM, respectively. Co-existence of MSA and MAA were observed in 23 samples, in most cases with simultaneous presence of anti-Jo-1 and anti-Ro (11samples). Simultaneous presence of anti-Jo-1 with anti-Ku72 and/or anti-Ku86 was seen in 6 sera, and of anti-Jo-1 with anti-Mi-2 autoantibodies in 2 samples. Single occurrence of anti-Ku antibodies was found only in 2 samples from PM and DM (1 each). In the group of patients with JDM, autoreactive antibodies were detected in two samples (anti-Mi-2 and anti-histone).
Conclusion:
Using mostly commercially available tools for detection of MSA/MAA, anti-Jo-1 was the most frequent antibody in the group of 100 IIM patients. This antibody was detected more frequently in PM than in DM patients. Relatively large number of samples contained more than one type of MSA/MAA. The strongest association was between anti-Ro52 and anti-Jo-1 reactivity, however other combinations exist. The association of anti-Ku with anti-Jo-1 is a predominant occurrence of this antibody and has not been previously reported. Searching for MSA in patients with myositis is recommended because of its diagnostic and prognostic value.
Comment:
This work demonstrated what others have previously found when examining their myositis cohorts for autoantibodies. However, their additional finding was that Ro-52 often keeps company with Jo-1, as does anti-Ku. The Jo-1/anti-Ku combination of autoantibodies has not been previously reported. It would be interesting to know if this subset differed phenotypically from the subset of myositis patients who had only Jo-1 autoantibodies present.