Pulmonary hypertension (PH) can be caused by anything that raises the blood pressure in the pulmonary arteries. Pulmonary arterial hypertension (PAH), a subtype of PH, is caused specifically by the narrowing of the pulmonary arteries. PH can be caused by genetic variants, congenital (present at birth) defects, heart disease, lung disease, connective tissue diseases, blood cell disorders, blood clots, or the use of prescribed or illicit drugs. In many cases, the cause of PH is unknown — or as doctors say, idiopathic. Types of PH are categorized by cause.

Risk Factors for Pulmonary Hypertension

Although researchers have established that both hereditary and environmental factors influence a person’s risk of developing PH, no one is certain why some people get PH and others don’t. Most scientists believe PH is most likely caused by a combination of inherited and environmental factors.

In general, the risk of PH rises with age. However, even children can develop PH. Women are 2.5 times more likely to develop PAH than men, especially during their childbearing years.

Hereditary Factors

In some people, PH — specifically PAH — is directly caused by genetic variants inherited from one’s parents. In these cases, genes cause an overgrowth of cells in the pulmonary arteries that narrows the arteries and causes hypertension. For this reason, having family members with PH raises your risk of developing PH. In other people, PAH may be directly caused by a random genetic mutation that their parents do not have.

For others with PH, genes inherited from parents may not cause PH directly, but a wide range of genetic variants may predispose you to develop the condition when exposed to environmental factors. Most researchers believe that many genes influence the risk of developing PH and the severity of their PH.

Some people are born with congenital heart defects that increase their risk of developing PH later on.

Environmental Factors

Living at high altitudes can cause some people to develop PH because of chronic hypoxia (low oxygen). Oxygen levels fall as elevation increases. Different elevations may be problematic for different people.

In those who are predisposed to develop PH, the risk for developing PH may be higher during pregnancy.

PH caused by another condition, a medical treatment, or exposure to a drug or toxin is called associated PH.

Drugs and toxins that can cause associated PH include:

• Aminorex
• Dasatinib
• Illegal stimulants
• Interferons
• Mazindol
• Phentermine

Diseases that can cause associated PH include:

• Blood clots lodged in the pulmonary arteries
• Chronic hemolytic anemia
• Chronic kidney failure
• Chronic obstructive pulmonary disease
• Chronic hypertension (high blood pressure)
• Congenital (present at birth) heart defects
• Coronary artery disease
• Fibrosing mediastinitis
• Gaucher’s disease
• Glycogen storage disease
• HIV infection
• Interstitial lung disease
• Leukemia
• Liver disease
• Lupus
• Mitral valve disease
• Polycythemia vera
• Sarcoidosis
• Schistosomiasis
• Scleroderma
• Sickle cell disease
• Sleep apnea (especially when combined with obesity)
• Thrombocythemia
• Thyroid disease
• Tumors that compress the pulmonary arteries

PH can also be a late side effect of splenectomy (surgical removal of the spleen) or radiation therapy or chemotherapy for cancer.

Condition Guide

• Pulmonary Hypertension — An Overview
• Classes of Pulmonary Hypertension
• Pulmonary Hypertension — The Path to Diagnosis
• Symptoms of Pulmonary Hypertension
• Treatments for Pulmonary Hypertension
• Types of Pulmonary Hypertension