BackgroundSystemic sclerosis (SSc), an autoimmune disease, has endothelial dysfunction and tissue fibrosis. The lack of its specific activity markers urges the research. Endocan is an immunomodulatory protein associated with endothelial dysfunction. We aimed to measure of the endocan level in systemic sclerosis (SSc) patients’ sera to test its relation to disease activity and treatment responses. Also, to evaluate its specificity by comparing these data with Behçet’s disease (BD) and rheumatoid arthritis (RA) patients’ data.ResultsSSc and RA patients were in activity but in the BD group; eight were active and seven were inactive. The endocan level was higher in the three groups in comparison to the controls without statistically significant differences (p value RA 0.697, SSc 0.063, and BD 0.196). A statistically significant difference in endocan levels between SSc patients with and without vascular manifestations (pulmonary hypertension and finger pitting ulcers, p < 0.0001, p = 0.0097, respectively). There were no significant correlations between endocan level and the erythrocyte sedimentation rate and C-reactive protein (positive rheumatoid factor for RA) in the three groups (p > 0.05). There were no significant correlations between endocan level and activity scores in the three groups (p > 0.05). The cut-off value of endocan was 1.3 ng/ml.ConclusionEndocan is a non-specific marker for the vascular pathogenesis in systemic sclerosis but not a good predictor for its activity.