Autoantibodies targeting nuclear and cytoplasmic autoantigens are used as markers in the diagnosis and classification of systemic autoimmune rheumatic diseases (SARD). The dense fine speckled (DFS) pattern is characterized by the fine-granular fluorescence of the nuclei in the interphase and the metaphase chromatin. DFS70 antibodies have been reported in healthy individuals, various autoimmune disorders, infection, cancer and inflammatory conditions. But there is still lack of information about its clinical significance. This study aimed to investigate the clinical significance of anti-DFS70 autoantibodies and the determination of accompanying pathologies. A total of 5710 serum samples routinely requested for ANA screening were tested between 2017 and 2019. Antinuclear antibody (ANA) and dsDNA were performed by indirect immunofluorescence method (IIF) (Euroimmun, Germany). Immunoblot (IB) method was used for the extractable nuclear antigen profile (ENA) (Euroimmun, Germany). Demographic and clinical data, were investigated from the medical records. Among 5710 samples tested for ANA, 23.7% were ANA positive by IIF. Mean age of the patients were 47.9 and 79.5% were female. Only 8.1% of the study group had SARD. The frequency of DFS pattern by ANA-IIF was 6.0% (342/5710), (mean age ± SD= 44.4 ± 16.7, 88% female). DFS70 pattern-positive patients were sub-grouped according to their diagnosis. SARD were detected 10.8% (mean age ± SD= 55.12 ± 14.10) in DFS70 pattern positive patient group (RA 6.1%, SS 2.6%, SLE 0.9%, SSc 0.6%, UCTD 0.6%). Autoantibodies accompanying anti-DFS70 antibody were determined as Ro-52, SS-A, nucleosome, histone, AMA-M2, dsDNA, respectively. Non-SARD diseases were determined in 89.2% of the patients with positive DFS70 pattern. Non-SARD diseases were detected as musculoskeletal complaints (47.4%), other rheumatic diseases like fibromyalgia (14.3%), dermatological diseases (9.4%), gastrointestinal system diseases (5.6%), hematological disorders (3.8%), thyroid /parathyroid diseases (3.5%), allergic diseases (2.3%), neurological diseases (2.3%) and neoplasia (breast cancer) (0.6%). The anti-DFS70 autoantibody is widely used to exclude the diagnosis of SARD in the absence of concomitant SARD-related autoantibodies. It has been observed that anti-DFS70 autoantibody may be associated with non-SARD rheumatic diseases and in many diseases (dermatological, gastrointestinal system, hematological, thyroid diseases) related to other systems. Therefore it is essential to evaluate these pathologies in patients positive for anti-DFS70 antibodies.

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