question: Pulmonary Hypertension (Causes): Pulmonary hypertension (PH) begins with inflammation and changes in the cells that line your pulmonary arteries. Other factors also can affect the pulmonary arteries and cause PH. For example, the condition may develop if: The walls of the arteries tighten. The walls of the arteries are stiff at birth or become stiff from an overgrowth of cells. Blood clots form in the arteries. These changes make it hard for your heart to push blood through your pulmonary arteries and into your lungs. Thus, the pressure in the arteries rises, causing PH. Many factors can contribute to the process that leads to the different types of PH. Group 1 pulmonary arterial hypertension (PAH) may have no known cause, or the condition may be inherited. ("Inherited" means the condition is passed from parents to children through genes.) Some diseases and conditions also can cause group 1 PAH. Examples include HIV infection, congenital heart disease, and sickle cell disease. Also, the use of street drugs (such as cocaine) and certain diet medicines can lead to PAH. Many diseases and conditions can cause groups 2 through 5 PH (often called secondary PH), including: Mitral valve disease Lung diseases, such as COPD (chronic obstructive pulmonary disease) Sleep apnea Sarcoidosis For more information about the types of PH and the diseases, conditions, and factors that can cause them, go to "Types of Pulmonary Hypertension."