Several studies reported elevated plasma ET-1 levels in SSc-PAH patients compared to those of healthy controls [34,35]; other authors found a correlation between the ET-1 levels and capillary size on nailfold videocapillaroscopy (NVC) [36], echocardiographic signs of impaired right ventricular function [32] and responses to the endothelin receptor antagonist bosentan in patients with SSc-PAH [37]. The gene discussed is EDN1; the disease is systemic sclerosis.