Ab1404 the Clinical Spectrum of Anti-U1rnp(+) Patients: Long Term Follow-Up From a Single Center Cohort

Background: Anti-U1-RNP autoantibody is known to define patients with mixed connective tissue disease (MCTD). These patients may present with overlapping clinical manifestations resembling systemic lupus erythematosus or scleroderma. However, the full clinical spectrum and long-term outcome of anti-U1RNP (+) patients has not been adequately investigated. Objectives: The aim of the current study was to describe the clinical spectrum and associations of anti-U1-RNP (+) patients. Methods: From the 25-year database of the immunology laboratory of the Department of Pathophysiology, those patients with ANA>1:320 and anti-U1RNP (+) were identified and their medical records were carefully reviewed. Demographic features, cumulative clinical, laboratory and immunological data, as well as given treatment were recorded and retrospectively analyzed. Anti-U1RNP (+) only patients were compared to those with at least another autoantibody while clinical associations were explored among serious complications including renal, CNS and hematologic manifestations. Results: Eighty five patients were identified and included in the study. The mean±SD age at disease onset was 35.3±17.3 years and the mean±SD disease duration from disease onset to last follow up was 15.2±10.3 years while 72 (84.7%) of patients were females. The most common presenting clinical manifestations were Raynaud's phenomenon (46.4%), rash (17.9%) and small hand arthritis (14.3%). During follow up, 40 (47%) patients eventually fulfilled the classification criteria for MCTD, 29 (34%) for SLE, 8 (9%) for Ssl, 4 (4.5%) SjD, 1 (1%) primary relapsing polychondritis and 1 (1%) retroperitoneal fibrosis. Anti-Ro antibodies were eventually detected in 22(25.%) patients, anti-Sm in 27 (31.8%), anti-La in 4 (4.5%), anti-phospholipid antibodies (aPLs) in 17 (20%) and anti-dsDNA in 24 (28%) patients. The presence of anti-Ro autoantibodies was statistically associated with renal involvement (p=0.045) while anti-Sm autoantibodies with the development of both serositis (p=0.008) and central nervous system involvement (p=0.007). Malar rash (p<0.001) and fever (p=0.039) were strongly associated with renal involvement. At the end of follow up, 3 patients had seizures (of whom 2 had aPLs) and 2 developed stroke (of whom 1 had aPLs). No patient developed end-stage renal disease while severe hematologic manifestations were very rare. Conclusion: Anti-URNP (+) patients display a mild clinical phenotype with a good long term outcome. The presence of additional autoantibodies may be associated with a less favorable prognosis. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.