WHO group 1 PAH is the least common, but surprisingly, most research is on this group. In contrast, more research is necessary on groups like WHO groups 2, 3, 4, or 5. It yielded three drug classes such as PDE5 Is, prostacyclin analogs, and ERAs, and no treatment proved to be ideal except prostacyclin analog with mortality benefit [12]. The gene discussed is PDE5A; the disease is pulmonary arterial hypertension.