AB1315 MIOSITIS AUTOANTIBODIES PROFILE: DIAGNOSTIC RELEVANCE
Authors: Alicia García Dorta, Yvelise Barrios, Sonia Peña Montelongo, Hernández Díaz Marta, Andrea Monroy Calero, Beatriz Rodríguez Lozano, Andrés Franco, Sagrario Bustabad
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> The idiopathic inflammatory myopathies (IIM) are autoimmune systemic diseases that can affect several organs, but with special impact in the muscular-skeletal system. Autoimmunity is believed to have a role in its pathogenesis, with the presence of Autoantibodies (Abs) in more than 50% of the patients. Those Abs have been classified into Myositis-Specific Autoantibodies (MSA), with the Anti-Jo being the most frequent1-2; and Myositis-Associated autoantibodies (MAA), also found in other connective tissue diseases. The availability of a multiplex analysis (Myositis Profile) has opened up new possibilities for the specific investigations of these Abs in the day-to-day clinical practice 1-2. <h3>Objectives</h3> To describe the clinical spectrum and the Ab results obtained from the myositis profile in patients (hospital admissions and ambulatory) of a tertiary university hospital. <h3>Methods</h3> Retrospective descriptive study (January to June 2018) of the results obtained on the myositis profile. The clinical characteristics of the sample is described in the context of the Abs results. We considered that applications of this Myostis Ab Profile were justified if they had EPID and/or if they had 2 or more clinical and/or analytical characteristics associated with MII. Myositis Profiles consisted in a solid phase ELISA from EuroLINE MII 16 Antigens (Mi2-alfa, Mi2-beta, TIF1gamma, MDA5, NXP2, SAE1, Ku, Pm-Scl100, Pm-Scl75, Jo-1, SRP, PL7, PL12, EJ, OJ, RO-52). Statistical analysis SPSS 17.0. <h3>Results</h3> A total of 165 applications were studied, 47% requested by Reumatology, 30% by Neumology and 9% by Internal Medicine. Justifications were: ILD (n=49); osteomuscular (n=30), connective diseases (n=29), myositis (n=17), CK-NAC elevation (n=11), fibromyalgia (n=7) and others (n=22). 41% men and 59% women, Average Age 58 (+/- 15 years). We observe an increase of CKNAC, GOT, GPT y LDH in 21%, 12%, 19% y 24% respectively. They refer muscle weakness in 18%, Raynaud's phenomenon in 10%, arthritis in 15%, heliotrope eruption in 4%, Gottrons's papules in 1% and mechanics hand in 1%. Using the criteria specified in the method section, 52% of the applications were justified, being the 57% of them as ILD study. 32 (20%) of the 165 profiles were positive. 10 of the 49 patients with ILD had positive Abs (figure 1), 90% me. 8 of the 17 patients with myositis had positive Abs (figure 1), 63% women. 75% of them (6/8) were positive for MSA, the 65% were Anti-Jo1 (4/6). 1 patient with myositis associated with neoplasia (anti-OJ). 2 of 3 muscle biopsy were consistent with MII. 2 of 7 EMG were compatible. The 14 remaining patients had some positive Abs (figure 2): 7 connective tissue diseases studies, 4 osteomuscular pathology, 1 auto-inflammatory disease, 1 CK-NAC elevation and 1 with inflammatory bowel disease (IBD). <h3>Conclusion</h3> The use of this Ab profile as a protocol for patients with ILD without myositis clinical features, allowed us to classify a group of patients with autoimmune diseases. In this group, the distribution by sex, 9 males and 1 woman is highlighted. We achieved the diagnosis on the 47% of patient with myositis clinical suspicion. The usefulness of myositis profile allowed us to detect antibodies which are not in other immunologic assays. Distribution by sex, 3 men and 5 women. The implementation of this profile of auto-antibodies in patients without ILD and those without clinical and/or analytical characteristics associated with MII, did not provide any. <h3>References</h3> [1] McHugh, Z. B. (2016). Myositis-specific autoantibodies: an important tool to. Journal of Internal Medicine, 280; 8–23. [2] Protocolos de diagnóstico inmunológico en enfermedades autoinmune. (2014). Barcelona: Elsevier. <h3>Disclosure of Interests</h3> None declared