Pulmonary arterial hypertension (PAH) is a group of diseases characterized by mean pulmonary artery pressure >20 mmHg and elevated pulmonary arterial resistance leading to right heart failure. PAH is progressive and potentially fatal. PAH may be idiopathic and/ or familial, have overt features of venous/capillary involvement (pulmonary veno-occlusive disease, PVOD/pulmonary capillary hemangiomatosis, PCH), induced by drug or toxin (drug-or toxin-induced PAH), or associated with other diseases like congenital heart disease, connective tissue disease, HIV, schistosomiasis, portal hypertension (PAH associated with other disease). The disease is pulmonary arterial hypertension (Monarch Disease Ontology entry MONDO_0015924). Also known as: PAH.