Pulmonary arterial hypertension (PAH) is a type of high blood pressure that affects the pulmonary arteries and capillaries. Pulmonary arteries are the blood vessels that take blood from the right ventricles to the lungs. As the pressure in the pulmonary arteries and the smaller capillaries builds up, the heart must work harder to pump blood. It weakens the heart over time and can even lead to heart failure.

The symptoms of PAH may not be noticeable initially, but as the condition worsens, they become pronounced. Some of them include difficulty breathing; fatigue; dizziness; swelling in the legs; arms, and abdomen; a bluish tinge on the lips; chest pain; a rapid pulse; and heart palpitations. There is no cure for PAH yet, but there is a range of treatments to lessen symptoms and lower the risk of complications. PAH develops when the pulmonary arteries and capillaries connecting the heart and lungs become constricted or damaged. A range of related conditions can trigger it, but the exact cause is unknown. Some of the possible causes of PAH are as follows:

1. Genetics

Studies say that close to 20 percent of PAH cases are inherited. Genetic mutations in the BMPR2 gene are responsible for increasing one’s likelihood of developing PAH. This gene is responsible for regulating a number of cells in specific tissues. Mutations can cause unregulated development of pulmonary arteries, making them smaller and increasing blood pressure.

2. Lung diseases

Problems with the lungs can cause the body to try to protect its oxygen supply. That is, the body diverts oxygen away from the damaged lungs to other areas that are healthy. PAH is linked to lung problems, such as chronic obstructive pulmonary disease (COPD) and emphysema.

3. Congenital heart disease (CHD)

CHD is caused by damage or disease in the heart’s major blood vessels. The disease is genetic, but it may also be caused due to plaque build-up in the vessels. It causes the coronary arteries to narrow, thus increasing blood pressure.

4. Cirrhosis

Cirrhosis or chronic liver disease is the term used to describe liver scarring and damage. Cirrhosis has many causes, but hepatitis and alcoholism top the list. The relationship between cirrhosis and PAH is complicated and can take place through a variety of mechanisms. Some examples include pulmonary venous hypertension, vascular constriction of the pulmonary arterial bed, or a hyperdynamic state.

5. Connective tissue disease (CTD)

Connective tissue disease (CTD) is the term used to describe a range of disorders affecting the skin, fat, muscles, joints, tendons, ligaments, bones, cartilage, and even blood vessels. Some examples include rheumatoid arthritis, scleroderma, Marfan syndrome, and lupus. CTD comes with a broad range of complications, starting from kidney failure to pulmonary complications. PAH is also a common complication of connective tissue disorders.

6. Toxins and drugs

PAH is characterized by progressive deterioration of the pulmonary arteries. Certain drugs and toxins are associated with the condition. Appetite suppressants, such as aminorex and benfluorex are particularly bad. It is the reason they were removed from distribution in the market. The damage done by them is related to elevated serotonin levels that encourage the growth of pulmonary artery muscles, which leads to the branching and thinning of the arteries. Amphetamine and mazindol are also linked to an increased risk for PAH.