Primary Pulmonary Hypertension refers to an abnormally elevated blood pressure of the pulmonary artery for which the cause is unknown.

There is an increase in pulmonary vascular resistance, an increased pulmonary artery pressure, and certain changes in the pathology.

Pathological changes in Primary Pulmonary HTN:
-Hypertrophy and fibrosis of the vascular bed
-In situ thrombosis