The ways in which COPD is different than ILD in terms of clinical phenotype, treatment response and outcomes and the fact that treprostinil has antifibrotic effects (likely though the activation of the prostaglandin E receptor 2) (39) could explain why the improvement of FVC was only seen in those with pulmonary hypertension due to ILD but not COPD. The gene discussed is PTGER2; the disease is pulmonary arterial hypertension.