What is the significance of primary hypertension?

No underlying cause. Primary hypertension, also called essential hypertension, means high blood pressure without a known underlying cause. It is diagnosed with two separate blood pressure readings above 140/90. Hypertension can cause damage to the heart, brain, kidneys, and eyes, so it should be treated appropriately by a physician.
Pulmonary htn. Largely depends on severity if the pulmonary artery systolic pressure is over 35 mmhg than a work is needed to find a cause . It can be seen as a result of lung disease . In some cases primary pulmonary hypertension is the cause which is a serious condition with a poor prognosis.