context: Pulmonary arterial hypertension, or PAH, is a type of high blood pressure that affects the arteries in your lungs and the right side of your heart. It's a very serious condition that can change your day-to-day life. When you get the right diagnosis, though, you can get the care you need to ease your symptoms. Your heart pumps blood through your arteries, sending oxygen to all parts of your body. In a single heartbeat, the left side of your heart sends the blood out to your body, and blood returns to the right side from your body. The right side then pumps it through the pulmonary artery to the lungs, where it swaps carbon dioxide for oxygen. The oxygen-filled blood goes back to the left side of the heart, and the process starts again with the next heartbeat. It's a short distance from your heart to your lungs. So normally, the right side doesn't have to pump very hard. But with PAH, blood doesn't move easily through the arteries in your lungs. Your heart works much harder to force it through. Over time, the heart muscle gets weak. It can become enlarged and stop working properly. When your blood doesn't flow well, your body doesn't get enough oxygen. Many people have PAH for a long time before they realize something is wrong. The symptoms are subtle at first. You may just feel tired or out of shape. And your doctor may mistake your condition for something more common. The early symptoms are: Shortness of breath during normal physical activity Fatigue Chest pains A racing heartbeat As the disease gets worse, you may also have: Lightheadedness Fainting Swelling in your legs, hands, or belly Dry cough, sometimes with blood Blue lips or fingers Many people who get PAH are women between the ages of 30 and 60. But it can happen to people of all ages, races, and sexes. Some things make you more likely to get the disease: A family history of the condition Other diseases of the heart and lungs Obesity If you've used some street drugs, like cocaine, or diet medicines Living at high altitudes Most people get PAH when another illness has damaged their heart or lungs. The most common problems that raise your pulmonary blood pressure are: Heart problems: Conditions like mitral valve disease or long-term high blood pressure damage the left side of the heart to the point that it doesn't work well. That makes blood back up in the blood vessels of the lungs. Lung diseases: When there's a problem in your lungs, your body tries to protect its oxygen supply. It keeps the blood away from damaged areas and forces it into healthy areas. It can happen if you have sleep apnea, chronic obstructive pulmonary disease ( COPD), and diseases that scar the lungs, like emphysema. Blood clots Other diseases, including some blood disorders, thyroid disease and other metabolic disorders, and immune system disorders that affect many different parts of the body, like sarcoidosis and vasculitis. In rare cases, the problem is with the arteries themselves. They become narrow and stiff, leaving little room for blood to pass through. Causes of this type of PAH include: A defect in a gene An illness that affects many parts of your body, like lupus, sickle cell disease, or scleroderma A heart defect that you were born with that changes the normal way blood flows through it Some drugs and toxins, especially diet drugs like fenfluramine (the "fen" part of fen-phen) and street drugs like cocaine or methamphetamines that tighten blood vessels Infection with HIV or a parasite called schistosoma Sometimes, doctors can't tell what causes PAH. Talk to your doctor if you're having trouble with shortness of breath, fatigue, dizziness, or swelling in your legs and ankles. They can do some tests to find out what's going on. It's important to get the right diagnosis so you can get the right treatment. The sooner you treat PAH, the easier it is to control.