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While we do not know the cause of pulmonary hypertension, i.e., why the cells and tissues behave abnormally, we can almost always determine the type of pulmonary hypertension for any given patient. This is very important for choosing therapy and predicting outcome. The most common types of pulmonary hypertension include:
1. Idiopathic (aka "primary" or "unexplained") pulmonary hypertension. This is usually the diagnosis when there is pulmonary hypertension without explanation, or conditions known to be associated with pulmonary hypertension. Idiopathic pulmonary hypertension occasionally runs in families ("familial" pulmonary hypertension), and in these (and a few others) it sometimes turns out that the BMPR2 gene is involved.
2. Certain congenital abnormalities of the heart, especially those which increase pressure and flow within the lungs, can cause pulmonary hypertension.
3. Patients with lung disease usually have normal pulmonary artery pressure, but occasionally can have pulmonary hypertension. In pediatrics, such lung disease is often related to prematurity. Certain congenital malformations which affect the lungs (such as congenital diaphragmatic hernia) can be associated with pulmonary hypertension.
4. Pulmonary hypertension can occasionally occur with diseases that primarily affect other organs. Collagen vascular disease (e.g., scleroderma), certain forms of liver disease, hereditary hemorrhagic telangiectasia, AIDS/HIV, and sickle cell disease are examples of such diseases that can be complicated by pulmonary hypertension.
5. Pulmonary hypertension can be caused by abnormal function of the left ventricle, or abnormal function of the valves on the left side of the heart. This is because these abnormalities can increase pressure in the left side of the heart, increasing the pressure needed to push blood into the left ventricle.
6. Pulmonary hypertension can be caused by chronic thromboembolic disease (where many small blood clots from outside the lungs travel to the lungs and are lodged there. This is rarely seen in children, but is an important cause of pulmonary hypertension in adults.
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