There have been tremendous progresses in research and improvement in therapeutic options for pulmonary arterial hypertension (PAH) and other types of pulmonary hypertension (PH) over the last 15 years. PAH and other PH have been shown to present similar histopathologic changes and therefore, do not indicate lung biopsies for a specific diagnosis. This may be due to shared physiopathologic mechanisms, involving initially endothelial alterations, leading to three main changes: vasoconstrictive phenomena, growth factor releases, leading to small vessel remodelling and to thrombotic phenomena. Genetic polymorphisms have been discovered in two genes of the transforming growth factor family (the bone morphogenetic protein receptor II and the activin receptor-like kinase) and one in the serotonin transporter gene. The genetic findings are not yet applicable for genetic counselling, but the physiopathologic discoveries have allowed major therapeutic progresses.