Pulmonary arterial hypertension (PAH) is characterized by abnormal remodeling and occlusion of pre-capillary arterioles in the lung with a subsequent increase in pulmonary vascular resistance. This can lead to right ventricular hypertrophy and ultimately right heart failure. Elastase is implicated in the pathobiology of PAH with evidence including: ultra-structural studies showing increased elastase activity in pulmonary arteries from children with congenital heart disease-associated PAH (1), increased elastase release from peripheral blood neutrophils isolated from patients with pulmonary hypertension compared with healthy controls (2) and elevated plasma concentrations of elastase in patients with idiopathic PAH (IPAH) (3).