Pulmonary arterial hypertension (PAH) is a rare disease that affects the lungs and can lead to serious complications. There are four types of PAH, and while their symptoms have some key similarities, some important differences distinguish each type.

PAH is a type of pulmonary hypertension (PH) that occurs due to constriction (narrowing) and damage in small blood vessels in the lungs. Decreased blood flow causes hypertension (high blood pressure) in the lungs. In people with PAH, the heart muscle has to work harder to pump blood into the lungs, which weakens the right side of the heart. People with PAH have an increased risk of right heart failure, which can be life-threatening.

General Symptoms of PAH

Common symptoms shared among all types of PAH include:

• Fatigue
• Dyspnea (shortness of breath)
• Syncope (dizziness or fainting) due to hypoxia (low blood oxygen levels)
• Edema (swelling in legs, feet, abdomen, and other parts of the body)
• Palpitation (racing or pounding heartbeat)
• Chest pain
• Cough or hoarseness
• Blue lips or fingers

An accurate diagnosis for PAH may be delayed because symptoms can resemble those of other lung diseases, including:

• Chronic obstructive pulmonary disease (COPD), such as emphysema
• Pulmonary fibrosis
• Disease in the left side of the heart

Although there is no cure for PAH, monitoring disease progression and adjusting treatment as needed can help ease symptoms and improve quality of life. In severe cases of PAH, a doctor may advise a lung transplant.

Knowing more about specific types of PAH can help you better understand your condition and ensure you’re receiving appropriate health care. Although many symptoms are generally the same among all types of PAH, some subtle differences distinguish each type.

1. Heritable Pulmonary Arterial Hypertension

People with heritable PAH (hPAH) have a family history of the disease and a genetic risk of developing PAH. Sometimes the condition is called familial pulmonary arterial hypertension. A person’s PAH is considered heritable if they have at least one close family member with PAH and a mutation in one of the genes associated with hPAH.

“I realize now that my PAH was inherited from my mom, who died 33 years ago. Plus my oldest sister passed at 82 and also had PAH,” a myPHteam member wrote.

Medical researchers don’t understand the exact cause of hPAH, although studies have found that around 75 percent of people with hPAH had a mutation in the bone morphogenetic protein receptor type 2 (BMPR2) gene.

Other uncommon genetic mutations can also be found in people with hPAH. A rare mutation of the T-box transcription factor 4 (TBX4) gene is associated primarily with children, who may also have abnormalities in musculoskeletal development and function, developmental lung disease and other developmental delays, and congenital heart disease.

Symptoms of hPAH include shortness of breath, fatigue, chest pain, rapid or irregular heartbeat, dizziness or fainting, and swelling. The condition can be less responsive to medication and harder to treat than other forms of PAH. People with hPAH are more likely to have a lower cardiac index (a measurement of blood flow) and higher hypertension in their lungs.

2. Idiopathic Pulmonary Arterial Hypertension

Idiopathic PAH (iPAH) is PAH with no known cause. As with other forms of PAH, the most common symptom of iPAH is shortness of breath due to physical exertion. Other common symptoms of PAH can occur as well, including fatigue, dizziness or fainting, irregular heartbeat, angina (chest pain due to reduced blood flow from the heart), and swelling of the legs.

“I have idiopathic pulmonary arterial hypertension. Just basically they have done all the testing and can’t figure out what's causing it. I have a lot of the symptoms and have days where I just sleep all day,” said a myPHteam member.

3. Associated Pulmonary Arterial Hypertension

Associated PAH (aPAH) can occur as a complication of another health condition, such as:

• Connective tissue disease (affects tissues that support organs and other parts of the body)
• Liver disease
• Human immunodeficiency virus (HIV)

According to results published in the journal Experimental Biology and Medicine, approximately 74 percent of aPAH cases linked to connective tissue disorders occur in people with scleroderma (systemic sclerosis) — a rare group of diseases characterized by hardening or tightening of the skin. However, aPAH can occur in other connective tissue diseases, including systemic lupus erythematosus and mixed connective tissue disease.

One myPHteam member shared their experience: “My own diagnosis of pulmonary arterial hypertension is associated with scleroderma, an autoimmune disease. So it didn’t happen all by itself, so to speak. I see my specialists regularly and follow their guidance. I live a relatively normal life knowing what my limitations are.”

Some symptoms of aPAH, such as fatigue and shortness of breath, may appear as symptoms of connective tissue disorders and other conditions linked to aPAH. This overlap can delay diagnosis of PAH in cases associated with another disease. People with systemic sclerosis are also prone to PH secondary to left heart disease, which can also produce symptoms that resemble PAH.

Researchers have investigated links between autoimmunity and aPAH. These connections suggest that immune system dysfunction may play a role in developing aPAH, particularly in cases associated with connective tissue disease.

4. Pulmonary Arterial Hypertension From Drug or Toxin Exposure

Certain drugs and toxins can induce PAH in some people. Sometimes toxin- and drug-induced PAH is known as dPAH. It may also be referred to as associated pulmonary arterial hypertension because it is caused by another health condition.

One myPHteam member described their dPAH: “For several years I’ve needed help doing everything — lifting, bending, squatting, just anything. It’s embarrassing, but I mean, my mom helps me with stuff. Everything gets me lightheaded and dizzy almost to the point of passing out. If I overexert, it’s been pretty bad. I was diagnosed previously with congestive heart failure and was always told it’ll go away. Don’t worry.”

Drug-induced PAH has been linked to:

• Anorexigens, which are drugs that suppress appetite, like aminorex fumarate
• Recreational stimulants, including methamphetamines
• Some prescription drugs, but this is a rare but serious side effect

Although researchers don’t fully understand how drugs and toxins may induce PAH, they believe that people who develop PAH from drug or toxin exposure may have genetic vulnerabilities.

Symptoms from dPAH are identical to general symptoms of PAH. However, the course of the disease can be less predictable and may depend on eliminating the drug or toxin that may have caused PAH.

Talk With Others Who Understand

On myPHteam, the social network for people with pulmonary hypertension and their loved ones, more than 49,000 members come together to ask questions, give advice, and share their stories with others who understand life with pulmonary hypertension.

What type of PAH do you have, and what are your symptoms? Share your advice in the comments below, or start a conversation by posting on your Activities page.