During the past few decades, increased understanding of PAH pathophysiology has led to the development of several effective therapies, including prostacyclin (PGI2) analogues and derivatives, endothelin receptor antagonists, phosphodiesterase type 5 (PDE5) inhibitors, and a soluble guanylate cyclase (sGC) stimulator. The gene discussed is PDE5A; the disease is pulmonary arterial hypertension.