Pulmonary hypertension (PH) is a rare but life-threatening lung disease that occurs when the pulmonary arteries become narrowed and stiff. The pulmonary arteries are the vessels that move blood from the heart to the lungs, and when they are obstructed, the heart needs to work harder to pump the blood. The disease can cause an enlargement and weakening of the heart, and ultimately right heart failure or other fatal consequences.
The most common symptoms of pulmonary hypertension include shortness of breath (dyspnea), fatigue, dizziness or fainting spells (syncope), pressure or pain in the chest, swelling (edema) in the ankles, legs or abdomen (ascites), bluish color of the lips and skin (cyanosis) and irregular heart beat. The disease is difficult to diagnose because its symptoms are easily mistaken by other lung or heart disease, but also because its causes are not fully disclosed and are different depending on the subtype of disease.
While PH symptoms are well documented, it is often unclear to patients what actually causes the disease. This article answers the question, “what causes pulmonary hypertension?”
Pulmonary Arterial Hypertension Causes
Pulmonary arterial hypertension (PAH) is the first subtype of PH according to the World Health Organization (WHO) definition. This type of pulmonary hypertension is a result of a defect in the smaller branches of pulmonary arteries. These alterations that occur in patients with PAH are usually the most serious: since the main problem in PH occurs in the pulmonary arteries, the condition can be treated at its roots, while it may not be the case in other subtypes of PH.
Causes For Idiopathic Pulmonary Hypertension
“Idiopathic” is a medical term that indicates that the reason for the disease is not known. Idiopathic pulmonary hypertension is also included in the first group of the disease and, as the name indicates, physicians diagnose it when they cannot define the underlying causes of the disease through exams and tests. The condition is particularly rare, with a prevalence of only two new patients in every million people reported annually. Unlike other diseases, the underlying causes cannot be treated, which makes the process more difficult.
Inherited Pulmonary Hypertension Causes
Cases where there is more than one pulmonary hypertension patient in the same family are also included in the first WHO group. When this is the case, physicians conduct a genetic test to search for a mutation that is inherited from parents to children. Researchers believe that the disease is related to one of the six genes BMPR-II, ALK1, ENG, SMAD9, CAV1 and KCNK3, and it is estimated that 10 percent of idiopathic pulmonary hypertension patients have a history of PH in the family.
Pulmonary Hypertension Caused By Other Conditions
There are other conditions that cause pulmonary hypertension and are included in the first WHO group to classify the subtypes of PH. Connective tissue diseases that affect the body’s structure or composition of the tissue like scleroderma, congenital heart problems, high blood pressure in liver (portal hypertension), HIV, determined medications or drugs, thyroid gland disorder, sickle cell disease, glycogen storage disorders, as well as rare blood conditions like pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis can also cause the disease. Figuring out which primary condition is causing pulmonary hypertension as secondary disorder is the first step to treating this form of the disease.
Causes of Persistent Pulmonary Hypertension of the Newborn
Persistent pulmonary hypertension of the newborn (PPHN) is a disease that affects about two in every thousand newborn babies or young children. The disease can be caused by severe pulmonary hypoplasia, which means underdevelopment of the lungs, hypoglycaemia, which is an abnormally low level of glucose in the blood, the severe disease caused by infections called sepsis, meconium aspiration syndrome, a condition that occurs when the baby breathes in a mixture of amniotic fluid and their first feces (meconium), or genetic mutations.
Pulmonary Hypertension Caused By Left Heart Disease
Left heart disease is a common cause of pulmonary hypertension, and it comprises the second group of the WHO definition. The left side of the heart is the one that pumps blood from the heart to all the other parts of the body but the lungs. While the blood flows through the heart and pulmonary arteries, anything that affects the left side of the heart can also affect the right side of the heart, which is the side that pumps blood to the lungs. About 60% of patients who suffer from a severe left ventricle dysfunction, such as mitral valve disease or long-term high blood pressure, also suffer from or end up developing pulmonary hypertension.
Reasons For Lung Disease-Related Pulmonary Hypertension
The third group of pulmonary hypertension causes is lung diseases or hypoxia, which is the name for a shortage of oxygen in the body. The most common diseases that cause pulmonary hypertension are chronic obstructive pulmonary disease (COPD), interstitial lung disease , and sleep-disordered breathing, a group of disorders that affect the breathing during the sleep like obstructive sleep apnoea (OSA). To treat pulmonary hypertension in these patients, it is necessary to treat the primary disease first.
Blood Clots That Cause Pulmonary Hypertension
Blood clots are the natural way that the body stops internal bleeding when there is a cut or injury, but when it occurs for no apparent reason it can be harmful and cause narrowing or a blockage in the pulmonary arteries. When a blood clot blocks the arteries, the patient can develop pulmonary embolism or pulmonary hypertension, which is the fourth WHO pulmonary hypertension group. Once again, the disease can be reversed with proper treatment to address the blood clots.
Other Causes Related To Pulmonary Hypertension
The fifth and last group of pulmonary hypertension causes defined by the WHO includes all of the other, less common, reasons for the disease. It includes sarcoidosis, which is a condition that results in inflammation of different organs like the lungs and lymph nodes, histiocytosis X, a rare disorder that causes scarring, granulomas and air-filled cysts mostly in the lungs, as well as compression of the blood vessels in the lungs, which can occur for numerous reasons like tumors.
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