EDNRA and systemic sclerosis: There are at least three ET-1 receptors: ETA, ETB, and ETC [8, 16, 17]; however, the function of ETC is poorly known; ETA and ETB are expressed on the majority of cells that actively contribute to SSc pathogenesis, such as fibroblasts, myofibroblasts, vascular smooth muscle cells, and platelets, while endothelial cells selectively express ETB [6–8, 16].