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In anti-U1-ribonucleoprotein (anti-U1-RNP) antibody positive patients with systemic scleroderma (SSD), the clinical picture and course of the disease have specific features: there is a preponderance of its limited form; inflammatory damage to the joints and muscles comes to the fore; and cutaneous manifestations are mild. Moreover, a high frequency (68%) of interstitial lung disease is found. At the same time, the autoimmune profile in this group has been little studied.Objective:to investigate the level of major autoantibodies (autoAbs) in anti-U1RNP antibody positive patients with SSD and to compare the frequency of the autoAbs in this group and in the groups of patients with SSD phenotypes associated with anti-centromere antibodies (ACA) and anti-topoisomerase I (anti-Scl70) antibodies.Patients and methods. The investigation enrolled a total of 144 patients meeting the 2013 ACR/EULAR SSD classification criteria. Forty-four anti-U1RNP antibody positive patients were found to have autoAbs, rheumatoid factor (RF), anti-cyclic citrullinated peptide (ACCP), anti-Ro, anti-La, anti-double-stranded DNA (anti-dsDNA), anti-Smith (anti-Sm), anti-cardiolipin (aCL), anti-histidyl tRNA synthetase (anti-Jo1), anti-Scl70, and anti-RNA polymerase III (anti-RNAP-III) antibodies, and ACA in two points. The study group (anti-U1RNP antibody positive patients with SSD) and the comparison groups (anti-Scl70 and ACA positive patients) were comparatively analyzed.Results and discussion. Anti-U1RNP antibody positive patients with SSD were commonly observed to have overlaps (34%) with rheumatoid arthritis and systemic lupus erythematosus, as well as concurrence with Sjögren’s syndrome (SS) (32.5%). The study group was found to have frequently RF (27%), anti-Ro (41%), anti-dsDNA (50%) antibodies, rarely anti-Sm (9%), ACCP (9%), anti-La (7%), ACA (11%), anti-Scl70 (9%), and aCL (2%) antibodies. Anti-Jo1 and anti-RNAP-III antibodies were not detected in any patient. SSD patients who were highly positive for anti-U1RNP antibodies (more than 2 upper limits of the reference range) significantly more frequently exhibited RF, anti-Ro and anti-dsDNA antibodies (pConclusion. In addition to clinical features, patients with SSD and anti-U1RNP antibody overproduction differ from those with major SSD phenotypes by the more frequent presence of other autoAbs. Persons who are highly positive for anti-U1RNP show the steady-state elevated levels of RF, anti-Ro and anti-dsDNA antibodies and the rare detection of SSD-specific autoAbs (ACA, anti-Scl70 and anti-RNAP-III).

Various clinical and immunological phenotypes of systemic sclerosis (SS) differ in the frequency and severity of manifestations of the disease, the progression of damage to internal organs, and prognosis. The detection rate of anti-U1-ribonucleoprotein (RNP) (anti-U1RNP) antibodies in SSD ranges from 5 to 30%. They are found in various rheumatic diseases (SS, systemic lupus erythematosus, rheumatoid arthritis, polymyositis, and Sjo gren’s syndrome) and are associated with a more favorable course, a good response to treatment (in particular, that with glucocorticoids), and a good prognosis. In SS, the clinical and laboratory associations of anti-U1RNP have been insufficiently investigated. Objective: to compare clinical, laboratory, and instrumental findings in patients with SS positive for anti-U1RNP, anti-topoisomerase-I (anti-Scl70), and anticentromere antibodies (ACA). Subjects and methods. Sixty-five anti-U1RNP antibody-positive patients were selected for a study group (Group 1) from the general database of patients who met the 2013 ACR/EULAR criteria for SS and who were followed up at the V.A. Nasonova Research Institute of Rheumatology in 2012 to 2017. The comparison groups included 50 anti-Scl70 antibody-positive patients with SS (Group 2) and 50 ACA-positive ones (Group 3). Anti-U1RNP negativity was confirmed in patients of the comparison groups. Results and discussion . Most patients in Groups 1 and 3 had the limited type of SS (88 and 94%, respectively) and a chronic course of the disease (82 and 94%) while Group 2 patients showed an acute and subacute course (52%) and predominantly the diffuse type of SS (58%). All the patients with SS had a higher level of antinuclear factor. The feature of the anti-U1RNP positive group was a preponderance of the limited type of the disease with minimal skin damage concurrent with a more frequent involvement of the musculoskeletal system (damages to the joints (65%) and muscles (43%), as well as with the high rate of damage to internal organs (in particular, the lung, heart, and gastrointestinal tract). The patients of this group exhibited high inflammatory and immunological activities, hematological disorders (hypocomplementemia (15%) and leukopenia (14%)). Sjo gren’s syndrome was detected in one-third of these patients. Conclusion. Further study of anti-U1RNP-positive SS will be able to create a management algorithm and to more clearly define the risks and prognosis of the disease for this group of patients.