Pulmonary hypertension can be hereditary, but most cases are not. Among people diagnosed with pulmonary arterial hypertension (PAH), the form most closely linked to genetics, familial cases account for roughly 1 in every 15 diagnoses. The rest are classified as idiopathic, meaning no family history is apparent. That said, the line between “hereditary” and “idiopathic” is blurrier than it seems: about 15% of people initially labeled as having no genetic cause turn out to carry an inherited gene mutation when tested.
The Main Gene Behind Heritable PAH
The gene most commonly responsible is called BMPR2. It provides instructions for a protein that helps regulate cell growth in the blood vessels of the lungs. When this gene is altered, the small arteries in the lungs can narrow and stiffen over time, forcing the right side of the heart to work much harder than it should. BMPR2 mutations are found in the majority of families with a clear hereditary pattern of PAH.
Inheriting a BMPR2 mutation does not mean you will develop the disease. Only about 20% to 30% of people who carry the mutation ever go on to have symptoms. This is known as reduced penetrance, and it’s one of the reasons pulmonary hypertension can skip generations or appear to strike “out of nowhere” in a family. Something beyond the gene itself, whether hormonal factors, infections, other genetic influences, or environmental triggers, appears to be needed to tip a carrier into active disease.
Other Genes That Play a Role
BMPR2 is the biggest player, but it’s not the only one. The gene for a protein called BMP9 is the second most common culprit, found in roughly 7% of heritable cases. Several other genes have been identified in smaller numbers of families, including those involved in potassium channel function, cell signaling, and blood vessel development. Two of these genes, ACVRL1 and ENG, are also linked to a condition called hereditary hemorrhagic telangiectasia, which causes abnormal blood vessel formation throughout the body. People with that condition sometimes develop PAH as well.
TBX4 and Childhood-Onset Disease
One gene that has gained attention more recently is TBX4. It plays a key role in lung development before birth and is especially relevant in children. Mutations in TBX4 can cause a complex pattern that includes pulmonary hypertension appearing shortly after birth, sometimes improving temporarily, then returning during infancy or early childhood. These children often have other features too, including skeletal abnormalities and, in some cases, developmental differences. About 63% of affected children in one study showed this two-phase pattern of symptoms at birth followed by a period of apparent improvement and then a return of high lung pressures.
How the Inheritance Works
Most heritable PAH follows an autosomal dominant pattern. That means only one copy of the altered gene, inherited from one parent, is enough to create risk. Each child of a carrier has a 50% chance of inheriting the mutation. But because penetrance is low, many carriers live full lives without symptoms. A parent can pass the gene to multiple children, and none of them may develop the disease, or only one might.
There is one notable exception to this dominant pattern. A related condition called pulmonary veno-occlusive disease, which affects the smallest veins in the lungs rather than the arteries, follows a recessive inheritance pattern. This means a person needs to inherit a defective copy of the EIF2AK4 gene from both parents to develop the disease. In one population-based study, about 29% of patients with this condition carried these recessive mutations.
Why “Idiopathic” Cases May Actually Be Genetic
The distinction between heritable and idiopathic PAH is partly a matter of testing. Historically, if no one else in your family had the condition, it was labeled idiopathic. But genetic testing has revealed that a significant portion of these seemingly spontaneous cases are caused by the same mutations found in families with obvious hereditary patterns. Roughly 15% of people diagnosed with idiopathic PAH actually carry a BMPR2 mutation, with some studies putting that figure as high as 40%. Because idiopathic PAH is far more common in absolute numbers than familial PAH, these “hidden” genetic cases actually represent the largest group of people with heritable disease.
This matters for family planning and screening. If you’re diagnosed with PAH and no one in your family has had it, you could still be carrying a gene mutation your children might inherit.
Genetic Testing and Screening for Relatives
Current guidelines recommend genetic counseling for relatives of PAH patients in whom a disease-causing gene has been identified. For families with a known BMPR2 mutation, a non-invasive annual monitoring approach has been shown to be practical for healthy carriers. This typically includes an echocardiogram (an ultrasound of the heart), exercise testing, lung function tests, and a blood marker that reflects strain on the heart. The goal is to catch rising lung pressures early, before symptoms appear, because earlier treatment tends to lead to better outcomes.
Screening protocols are well established for BMPR2 carriers but less clear for some of the rarer genes. For TBX4 carriers, for example, there are currently no formal screening recommendations, even though the gene clearly causes disease. This is an area where clinical practice is still catching up to the genetic discoveries.
What This Means in Practical Terms
If you’ve been diagnosed with PAH, genetic testing can clarify whether your case has a hereditary component, even if no one else in your family is affected. If a mutation is found, your first-degree relatives (parents, siblings, children) can be tested to see if they carry the same variant. A positive result doesn’t mean they’ll get sick. It means they should be monitored so that if lung pressures start to rise, treatment can begin at the earliest possible stage.
If you’re a family member of someone with PAH and you’re wondering about your own risk, the most important thing to know is that carrying a mutation is not a diagnosis. The majority of carriers, 70% to 80% in the case of BMPR2, never develop the condition. Regular screening, not worry, is the appropriate response to a positive genetic test.