MONDO_0001999 (idiopathic pulmonary arterial hypertension) is a sporadic form of pulmonary arterial hypertension (PAH) characterized by elevated pulmonary arterial resistance leading to right heart failure. IPAH is progressive and potentially fatal and not associated with an underlying condition or family history of PAH. The etiology is unknown. Also known as: IPAH, primary pulmonary arterial hypertension, primary pulmonary hypertension.