Session Type: Abstract Submissions (ACR)
Idiopathic inflammatory myopathies (IIM) are a group of autoimmune disorders characterized by muscle inflammation, progressive weakness with a combination of clinical, electromyography and laboratory findings, which includes the expression of autoantibodies. In the last few years there has been an increasing interest to study IIM in different geographic populations. The objective of the study was to identify ANA, the myositis specific antibodies (MSA) and the myositis associated antibodies (MAA) in a cohort of Mexican IIM patients.
Serum samples from 77 IIM patients were collected from five participating centers in Mexico. ANA were detected by indirect immunofluorescence (IIF) on HEp-2 cells (Antibodies Inc., Davis, CA., USA). MSA and MAA were tested by two different methods: Luminex ENA (FIDIS: Thera-Diag, Paris, France) kit (ALBIA), and EUROLine Autoimmune Inflammatory Myopathies 15 Analyte kit (Euroimmun, Luebeck, Germany, line immunoassay).
Of the 77 IIM patients, 55 (71%) had dermatomyositis (DM), 13 (17%) polymyositis (PM) and 9 (12%) juvenile dermatomyositis (JDM). The mean age was 40 years (6-69 years), 67 (87%) were female. The frequency of ANA by IIF was 81%, the most common IIF patterns were homogeneous and speckled representing close to 60%, the second most common pattern was cytoplasmic speckled 13% and then nucleolar 10%, 37% had the highest end point titer of 1:5,120.
By LIA the frequency of MSA was: Mi-2β (40.2%), Jo-1 (18.1%), SRP (5.2%), PL-12 and Mi-2α (3.9%), Anti-PL-7 (2.6%), Anti-EJ (1.3%) and Anti-OJ (0%). The most frequent MAA tested by LIA was PM/Scl-75 (12.9%), followed by Ku and TIF-1-gamma (9%), and MDA-5 (7.8%); with less than 4% attributed to PM/Scl-100, NXP-2 and SAE-1. Ro52/TRIM21 (16.9%) was detected by FIDIS ALBIA. Of the 16.9% of positive Ro52/TRIM21 patients, 30% were also positive for Jo-1 (LIA), and 54% for Mi-2β (LIA).
This is the first study of MSA and MAA in a cohort of Mexican IIM patients from 5 different centers. We observed a high prevalence of IIF ANA (81%) which is consistent with some previous reports. Homogeneous and speckled pattern represented approximately 60% of the ANA and the second most common pattern was cytoplasmic and nucleolar (13 and 10%, respectively). Regarding the analysis of the MSA and MAA we found an increased prevalence of anti-Mi2 antibodies (32.5%) an autoantibody typically associated with DM which was even higher frequency (~40%) when the two α and β isoforms of anti-Mi2 were analyzed. This is in contrast to many other geographic studies were anti-synthetase antibodies tend to be the most common IIM autoantibody. The most common MAA antibody was anti-Ro52/TRIM21, an autoantibody that has been associated with pulmonary fibrosis and polyautoimmunity. It is worth noting that up to 46% of the positive Ro52/TRIM21 patients did not share any MSA or MAA which may indicate that it is an independent marker in IIM sera.
M. A. Ortiz-Villalvazo,
J. E. Navarro-Zarza,
I. Garcia-De La Torre,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/study-of-autoantibodies-in-a-cohort-of-mexican-patients-with-idiopathic-inflammatory-myopathies/