In patients with IPAH, plasma Cu/Zn-SOD (148 U/ml; 95% CI, 114–213), Mn-SOD (40 U/ml; 95% CI, 34–115), and Ec-SOD (85 U/L, 95% CI, 79–119) activities were significantly lower compared to those in the 130 control subjects (212 U/ml, 95% CI: 153–266; 144 U/ml, 95% CI: 114–157; and 175 U/L, 95% CI: 143–193, respectively; p < 0.01 or p < 0.001). The gene discussed is SOD3; the disease is idiopathic pulmonary arterial hypertension.