The NO/ET-1 ratio was significantly lower in patients with both SSc and PAH (32.6 ± 15.7; n = 16) than in patients with SSc but not PAH (87.8 ± 25.0; n = 26) and healthy control individuals (73.6 ± 35.7; n = 20), as shown in Figure 2c. Here, EDN1 is linked to systemic sclerosis.