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PAH results from abnormal changes in the walls of the pulmonary arteries that cause the arteries to narrow, making it harder for blood to flow through them. It is not clear what triggers the changes in the arteries that lead to PAH, but once the process begins, it tends to progress over time.

Types of PAH

What are some of the types of pulmonary arterial hypertension (PAH)?

  • IPAH—PAH for which no specific cause or risk factor can be identified is referred to as idiopathic PAH
  • FPAH—PAH that tends to run in families and is caused by changes in certain genes is called familial PAH (also known as heritable PAH)
  • APAH—PAH associated with another disease or condition that a person already has is called associated PAH

What are the diseases and conditions associated with PAH?

  • Connective tissue disease (sometimes known as collagen vascular disease), which occurs when the body's immune system mistakenly attacks its own tissues and cells (systemic sclerosis [scleroderma], lupus, and rheumatoid arthritis are examples)
  • Congenital heart disease (a birth defect in the heart)
  • Chronic liver disease, such as cirrhosis (scarring of the liver)
  • Human immunodeficiency virus (HIV) infection
  • Exposure to certain drugs and toxins, such as cocaine, amphetamines (for example, "speed" or methamphetamine), and some diet drugs

The list shows only some common associations. PAH can also be associated with other, more unusual conditions.