Systemic sclerosis is an autoimmune disease clinically characterized by vascular and immune dysfunction, leading to fibrosis
that can damage multiple organs. The presence of non-overlapping SSc-associated autoantibodies best presents the autoimmune
nature of systemic sclerosis. The primary purpose of this study was to investigate the autoantibody profile in Iranian patients
with systemic sclerosis. Sera from 481 patients with systemic sclerosis were collected from 2013 to 2016. Levels of anti-nuclear
antibodies (ANA) were quantitatively detected using the indirect immunofluorescence (IIF) method, and levels of specific
autoantibodies including anti-topoisomerase I antibody (ATA), anti-centromere antibody (ACA) and anti RNA polymerase III
antibody (anti-RNAP III) were determined qualitatively using the enzyme-linked immunosorbent assay (ELISA) technique.
Among all patients evaluated, a predominance of females (86.7%) was found, and 434 (90.2%) patients showed positive ANA
results by IIF. ANA was detected in 87.3% and 92.0% of limited cutaneous systemic sclerosis (lcSSc) and diffuse cutaneous
systemic sclerosis (dcSSc) patients, respectively, which was not significantly different. The frequency of anti-RNAP III, ACA,
and ATA was 5.19%, 6.09%, and 72.3%, respectively. Furthermore, anti-RNAP III, ATA, and ANA levels were correlated with
dcSSc, whereas ACA levels were correlated with lcSSc. It was confirmed that ATA expression is significantly higher in dcSSc
patients. This study had a lower frequency of ACA (6.09%) than most previous cohorts. The results demonstrated that the
clinical subtype of systemic sclerosis may correlate positively with the presence of specific autoantibodies.