Ernst von Romberg, a German physician, first described pulmonary arterial hypertension (PAH) in 1891. While conducting an autopsy, he noticed a thickening of the pulmonary artery, but there was no evidence of heart or lung disease that might have caused the condition. The term primary pulmonary hypertension or pulmonary arterial hypertension was coined decades later, in the 1950s by David Drysdale.

PAH is a rare subtype of pulmonary hypertension. The primary character of PAH is the constriction of the pulmonary arteries. It causes blood circulation inefficient and makes the lungs and heart work harder. Pulmonary arterial hypertension symptoms largely include shortness of breath, fatigue, tiredness, dizziness, fainting, cyanosis, swelling in legs, ankles, and feet, heart palpitations, chest pain, and arrhythmia.

Some risk factors for pulmonary arterial hypertension are mentioned below:

1. Family history
About 20% of patients with PAH have a close relative who suffers from the disease. Research has linked PAH to mutation of the BMPR2 gene. This gene regulates the number of cells in tissues, and mutations can cause irregular development of the pulmonary arteries. In most cases, they branch out and decrease in width. Smaller blood vessels raise blood pressure, leading to PAH.

2. Other heart and lung diseases
Dysfunction of the heart valves causes heart valve disorders, and congenital heart diseases are congenital disabilities. Both of these cause bad circulation. And when the left side of the heart is affected, it can trigger pulmonary arterial hypertension. With lung diseases like chronic obstructive pulmonary disease or sarcoidosis too, there is impairment of oxygenation of the blood.

3. Cirrhosis
Cirrhosis is the scarring of the liver. It manifests in the later stages of chronic kidney disease. Exposure to toxins like alcohol or viral infections can cause cirrhosis, and 60% of those with PAH have some kind of liver dysfunction. The exact mechanism of the relationship is not known, but researchers have identified a significant correlation.

4. Use of certain narcotics
Smoking is a well-known risk factor for cardiovascular and lung diseases. Also, the use of certain substances like cocaine and amphetamines damages the circulatory system. There is also a very strong link between exposure to tobacco, PAH, and chronic obstructive pulmonary disease. Certain diet pills can cause an increase in serotonin levels. It encourages the growth of pulmonary arteries and forces them to grow thinner, and that triggers PAH. Most diet pills related to PAH are not available in the market, but recreational drugs are illegally available.

5. Connective tissue disorders (CTD)
Connective tissue disorders include ailments related to skin, fat, muscles, joints, tendons, bones, cartilage, blood, and blood vessels. These can cause a range of complications, including pulmonary hypertension. 30% of patients with PAH also have associated connective tissue disorder.

6. Cancer
Lung cancer patients almost invariably develop some kind of respiratory distress. More than half of lung cancer patients suffer from one of the five types of pulmonary hypertension. When tumors press on the pulmonary arteries, PAH can also develop.

Sometimes occupational exposure to small particles like sawdust can also trigger pulmonary arterial hypertension. The PAH diagnosis uses electrocardiograms to test electrical activity in the heart. Pulmonary function tests check lung function, imaging studies visualize the heart, lungs, and blood vessels, and walking tests check activity tolerance.