Pulmonary arterial hypertension (PAH) is a rare, serious condition that affects the blood vessels in the lungs and can lead to serious complications if it isn’t treated. There are four main types of PAH, also called subtypes, based on what causes the condition. While these types often share similar symptoms, there are important differences that can affect diagnosis, treatment, and outlook.

PAH is a type of pulmonary hypertension (PH), which means hypertension (high blood pressure) in the arteries of the lungs. In PAH, the small blood vessels in the lungs become narrowed, stiff, or damaged, making it harder for blood to flow through them. As blood flow slows, pressure builds up in the lung arteries, forcing the heart to work harder.

Over time, the right side of the heart (which pumps blood into the lungs) has to strain to keep up. This extra effort can cause the right side of the heart muscle to weaken. People living with PAH have a higher risk of right heart failure, a condition in which the heart can’t pump enough blood to meet the body’s needs. Right-sided heart failure can be life-threatening and requires ongoing medical care.

Below, we’ll break down the four types of PAH and the symptoms that may help tell them apart.

General Symptoms of PAH

Many symptoms of PAH are shared across all four types. Common symptoms may include:

• Fatigue (extreme tiredness that doesn’t improve with rest)
• Dyspnea (shortness of breath), especially during physical activity
• Dizziness or syncope (fainting), which can happen when the heart can’t pump enough blood to the body — often during exercise — leading to reduced blood flow to the brain
• Edema (swelling) in the legs, feet, abdomen, or other areas caused by fluid buildup related to right-sided heart weakness
• Heart palpitations (a fast or pounding heartbeat)
• Chest pain or pressure
• Cough or hoarseness
• Cyanosis (bluish lips or fingers), a sign of low oxygen levels

Because these symptoms can be subtle at first or look like signs of other conditions, getting a PAH diagnosis may take time. Other health conditions that can cause similar symptoms include:

• Chronic obstructive pulmonary disease (COPD), including emphysema
• Pulmonary fibrosis (scarring of the lungs)
• Left-sided heart disease

Although there’s currently no cure for PAH, regular monitoring and adjusting treatment as needed can help manage symptoms and improve quality of life. In more advanced cases, a doctor may recommend a lung transplant after careful evaluation.

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

1. Heritable Pulmonary Arterial Hypertension

Heritable pulmonary arterial hypertension (HPAH) is a form of PAH that is caused by a disease-causing genetic mutation and may run in families. People with HPAH have an inherited or spontaneous (new) genetic change that increases their risk of developing PAH. When multiple family members are affected, it’s sometimes called familial pulmonary arterial hypertension.

PAH is considered heritable when it is linked to a gene mutation known to cause PAH, even if there is no known family history of the disease. In some cases, the mutation is inherited from a parent. In others, it occurs for the first time in the person diagnosed.

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

Researchers don’t yet fully understand why some people with PAH-related gene mutations develop symptoms while others do not. Studies have found that around 75 percent of people with HPAH had a mutation in the BMPR2 gene, which helps control how blood vessel cells grow and repair themselves.

Other uncommon genetic mutations can be found in people with HPAH. A rare mutation of the TBX4 gene is more often associated with children. Children with a TBX4 mutation may also have differences in bone and muscle development, lung development, or heart structure (congenital heart disease), as well as developmental delays.

Symptoms of HPAH include shortness of breath, fatigue, chest pain, rapid or irregular heartbeat, dizziness or fainting, and swelling. HPAH can start at a younger age and may cause more severe symptoms.

Heritable PAH can start at a younger age and may cause more severe symptoms.

Treatment response often varies by person and specific genetic cause. People with HPAH are more likely to have a lower cardiac index (a measurement of blood flow) and higher blood pressure in their lungs.

2. Idiopathic Pulmonary Arterial Hypertension

Idiopathic PAH (IPAH) refers to PAH with no known cause. As with other forms of PAH, symptoms of iPAH include shortness of breath with exercise, fatigue, dizziness or fainting, and swelling of the legs and feet.

“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 diseases (affect tissues that support organs and other parts of the body)
• Liver disease with portal hypertension
• Congenital heart disease
• Human immunodeficiency virus (HIV)
• Schistosomiasis (infection caused by a parasite)

Research has shown that about 74 percent of APAH cases linked to connective tissue disorders occur in people with scleroderma (systemic sclerosis) — a rare set of diseases defined by hardening or tightening of the skin. However, APAH can occur in other connective tissue diseases, including systemic lupus erythematosus (the most common form of lupus) and mixed connective tissue disease.

About 74 percent of the cases of associated PAH due to connective tissue disorders occur in people with scleroderma.

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. The World Health Organization (WHO) classifies toxin- and drug-induced PAH as DPAH.

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 previously diagnosed with congestive heart failure and was always told it would go away. Don’t worry.”

Drug-induced PAH has been linked to:

• Anorexigens (drugs that suppress appetite) like aminorex fumarate, benfluorex, dexfenfluramine, fenfluramine
• Dasatinib, a tyrosine kinase inhibitor (TKI)
• Recreational stimulants, including methamphetamines
• Some prescription drugs (as a rare but serious side effect), such as amphetamines, antivirals, diazoxide, immunosuppressants, interferon alpha/beta, other TKIs like bosutinib and ponatinib
• Toxic oil syndrome from contaminated rapeseed oil

Health experts don’t fully understand how drugs and toxins may induce PAH. However, they believe that people who develop PAH from drug or toxin exposure may have genetic risk factors.

Symptoms of DPAH are the same as other PAH symptoms. But the course of the disease can be less predictable and may depend on eliminating the drug or toxin that may have caused PAH.

Symptoms from DPAH are the same as other PAH symptoms. But the course of the disease can be less predictable and may depend on eliminating the drug or toxin that may have caused PAH. Although the four types of PAH share many of the same symptoms, the underlying cause can affect diagnosis, treatment, and outlook. With DPAH, symptoms may improve if the triggering drug or toxin is stopped. Other types may run in families or be linked to another health condition. If you’re not sure which type you have, ask your doctor.

People who develop PAH from drug or toxin exposure may also have genetic risk factors for the condition.

Join the Conversation

On myPHteam, people share their experiences with pulmonary hypertension, get advice, and find support from others who understand.

What type of PAH do you have, and what are your symptoms? Let others know in the comments below.