Significantly increased levels of ET-1 in EBC were found in all 12 patients with PAH associated with COPD (FEV1% 39.35 ± 11.45, FEV1/FVC% 46.95 ± 6.81, PaPs ≥ 35 mmHg) (group 1) compared to both COPD only (group 2) (22.36 ± 4 vs 7.25 ± 0.23 pg/ml; p < 0.0001) and to the control subjects (group 3) (5.24 ± 0.47 pg/ml; p < 0.0001) (Figure 1). The gene discussed is EDN1; the disease is chronic obstructive pulmonary disease.