LAUSR

Background The mixed connective tissue disease (MCTD) is an autoimmune systemic disease characterised by clinical manifestations that are included in systemic lupus erythematous (SLE), scleroderma (SSc) or rheumatoid arthritis (RA). Moreover the MCTD exhibits anti-U1RNP high-titter antibodies. However, anti-U1RNP antibodies are not specific or exclusive from MCTD, because of can be detected in other systemic autoimmune diseases as SLE, SSc and RA. Objectives To verify the differentiation of MCTD patients from other systemic autoimmune diseases using anti-U1RNP titters. The secondary objective is to characterise anti-U1RNP titter in other systemic autoimmune diseases with clinical manifestation. Methods An observational retrospective study of patients with inflammatory autoimmune disease evaluated in the Rheumatology Department from 2012 since 2016 was performed. In all cases a blood-test with anti-U1RNP, anti-Sm, anti-Ro, and anti-La analysis was conducted. Clinical data was registered according to the patients’ medical history, with special emphasis being placed on renal affection, vascular affection, pulmonary hypertension, arthrtitis-synovitis, tendonitis-tenosynovitis, dry eye syndrome and Raynaud’s phenomenon. Biostatistical analysis was performed using R. Results We collected data from 355 patients with a mean age of 50.84 (15.49) years, 98.55% of them were female. 13.8% of patients showed anti-U1RNP high titters (up to 20 pg/mL), and a significant increase of anti-U1-RNP in MCTD patients in contrast to other connective pathologies (p Anti-Sm antibody also exhibit significantly higher values in MCTD patients than in RA (p=0.025) or scleroderma (p=0.003). No differences in anti-Ro and anti-La levels among all diagnosis were observed. Patients with the high anti-U1-RNP levels, regardless of the diagnosis, showed more Raynaud’s phenomenon and vascular affection, (p Specifically in SLE patients, those with the highest levels of anti-U1-RNP exhibit Raynaud’s phenomenon (p Conclusions In our patient series anti-U1RNP were significantly elevated in MCTD diagnosis, and in lesser extent anti-Sm antibodies. Anti-Ro and anti-La antibodies are increased in dry eye syndrome patients. In SLE patients, anti-La increased levels were associated to renal affection. Disclosure of Interest None declared