Currently, five classes of drugs, endothelin receptor antagonists, phosphodiesterase-5 (PDE5) inhibitors, soluble guanylate cyclase (sGC) activators, prostacyclin analogues, and prostacyclin receptors agonists are approved by the United States Food and Drug Administration (FDA) to treat PAH [4]. This evidence concerns the gene PDE5A and pulmonary arterial hypertension.