Specific phosphodiesterase (PDE)5 inhibitors, such as sildenafil, tadalafil, and vardenafil, are being used in clinical practice to treat erectile dysfunction (ED) as well as pulmonary arterial hypertension (PAH), but these agents have also been identified as one of the most successful cases of drug repurposing because they were initially developed for angina and then repositioned for further disorders [7,8]. This evidence concerns the gene PDE5A and pulmonary arterial hypertension.