Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by increased pulmonary artery pressure, leading to right heart failure and ultimately death if untreated. The classification of pulmonary hypertension (PH) has evolved over the years, with the fourth World Symposium on PH in 2008 revising previous classifications. PH is now divided into five subgroups: Group 1 includes idiopathic or familial PAH, Group 2 includes PAH due to left heart diseases, Group 3 includes PAH due to respiratory diseases, Group 4 includes chronic thromboembolic pulmonary hypertension, and Group 5 includes PAH with unclear or multifactorial mechanisms. The diagnosis of PAH is confirmed by right heart catheterization showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. Echocardiography is an important tool for screening and management. Treatment includes non-specific drugs such as oral anticoagulation and diuretics, as well as specific therapies like prostanoids, endothelin receptor antagonists, and phosphodiesterase type 5 inhibitors. The pathophysiology of PAH involves vascular obstruction, vasoconstriction, vascular remodeling, and thrombosis, leading to progressive increase in vascular resistance and right ventricular failure. Genetic mutations, particularly in the *BMPR2* gene, play a significant role in the development of PAH, but environmental factors also contribute. Understanding these mechanisms has led to the development of new treatments, but more research is needed to discover new pathways and strategies. Histopathological changes in PAH include medial hypertrophy, intimal fibrosis, and complex lesions such as plexiform lesions, which are focal intimal thickening with endothelial cell proliferation.Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by increased pulmonary artery pressure, leading to right heart failure and ultimately death if untreated. The classification of pulmonary hypertension (PH) has evolved over the years, with the fourth World Symposium on PH in 2008 revising previous classifications. PH is now divided into five subgroups: Group 1 includes idiopathic or familial PAH, Group 2 includes PAH due to left heart diseases, Group 3 includes PAH due to respiratory diseases, Group 4 includes chronic thromboembolic pulmonary hypertension, and Group 5 includes PAH with unclear or multifactorial mechanisms. The diagnosis of PAH is confirmed by right heart catheterization showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. Echocardiography is an important tool for screening and management. Treatment includes non-specific drugs such as oral anticoagulation and diuretics, as well as specific therapies like prostanoids, endothelin receptor antagonists, and phosphodiesterase type 5 inhibitors. The pathophysiology of PAH involves vascular obstruction, vasoconstriction, vascular remodeling, and thrombosis, leading to progressive increase in vascular resistance and right ventricular failure. Genetic mutations, particularly in the *BMPR2* gene, play a significant role in the development of PAH, but environmental factors also contribute. Understanding these mechanisms has led to the development of new treatments, but more research is needed to discover new pathways and strategies. Histopathological changes in PAH include medial hypertrophy, intimal fibrosis, and complex lesions such as plexiform lesions, which are focal intimal thickening with endothelial cell proliferation.