Pulmonary hypertension is a rare lung disorder in which the arteries that carry blood from the heart to the lungs become narrowed, making it difficult for blood to flow through the vessels. As a result, the blood pressure in these arteries -- called pulmonary arteries -- rises far above normal levels. This abnormally high pressure strains the right ventricle of the heart, causing it to expand in size. Overworked and enlarged, the right ventricle gradually becomes weaker and loses its ability to pump enough blood to the lungs. This could lead to the development of right heart failure.
When pulmonary hypertension occurs in the absence of a known cause, it is referred to as idiopathic pulmonary arterial hypertension (IPAH). This term should not be construed to mean that because it has a single name it is a single disease. There are likely many unknown causes of IPAH. IPAH is extremely rare, occurring in about two persons per million.
Secondary pulmonary hypertension means the cause is known. A common cause of secondary PH are the breathing disorders emphysema and bronchitis. Other less frequent causes are the inflammatory or collagen vascular diseases such as scleroderma, CREST syndrome or systemic lupus erythematosus (SLE), the list goes on.
Pulmonary hypertension occurs in individuals of all ages, races, and ethnic backgrounds although it is much more common in young adults and is approximately twice as common in women as in men.
Merle - OHPA