IL-17A production was significantly higher in SSc patients with ILD compared to patients without ILD (534.130±132.8 vs 396.9±112.5 pg/ml, p<0.0001) and in patients with DU compared to patients without DU (506.4±135 vs 387.7±111, p<0.003); conversely, in patients with PAH, IL-17A levels were found to be lower compared to patients without PAH (392.3±69.5 vs 476±144.3, p=0.026). This evidence concerns the gene IL17A and pulmonary arterial hypertension.