However, ET-1 expression is highest in the pulmonary vasculature and PAH patients have higher circulating plasma levels of ET-1 as well as increased ET-1 levels exiting the lung than entering the lung.[11,41] These observations suggest that the elevated plasma levels of ET-1 we observed in the HIV-associated PAH cohort likely reflects impaired pulmonary endothelium. The gene discussed is EDN1; the disease is pulmonary arterial hypertension.