Explore · Understand · Check the source
Patient-friendly health topic summaries from the US National Library of Medicine.
The retina is a layer of tissue in the back of your eye that senses light and sends images to your brain. It provides the sharp, central vision needed for reading, driving, and seeing fine detail. A retinal detachment lifts or pulls…
Pulmonary hypertension, sometimes called PH, is a serious condition that affects the blood vessels in the lungs. It develops when the blood pressure in your lungs is higher than normal. Your heart pumps blood to your lungs so they can…
An arrhythmia is a problem with the rate or rhythm of your heartbeat. Your heart beats too quickly, too slowly, or with an irregular pattern. Changes in the electrical signals that control your heartbeat cause arrhythmias. • When your…
Hidradenitis suppurativa (HS) is a chronic skin disease. Another name for it is acne inversa. It causes painful, boil-like lumps that form under the skin. It often affects areas where the skin rubs together, such as your armpits and…
Cushing's syndrome is a hormonal disorder. The cause is long-term exposure to too much cortisol, a hormone that your adrenal gland makes. Sometimes, taking synthetic hormone medicine to treat an inflammatory disease leads to…
A peptic ulcer is a sore in the lining of your stomach or your duodenum, the first part of your small intestine. A burning stomach pain is the most common symptom. The pain: • Starts between meals or during the night • Briefly stops…
Scleroderma means "hard skin." It's the name of an autoimmune disease that causes inflammation and thickening in the skin and other areas of the body. This inflammation causes you to have areas of tight, hard skin. Scleroderma may…
You have two kidneys, each about the size of your fist. They are near the middle of your back, just below the rib cage. Inside each kidney there are about a million tiny structures called nephrons. They filter your blood. They remove…
A stroke happens when there is a loss of blood flow to part of the brain. Your brain cells cannot get the oxygen and nutrients they need from blood, and they start to die within a few minutes. This can cause lasting brain damage,…
The pancreas is a gland behind your stomach and in front of your spine. It produces the juices that help break down food and the hormones that help control blood sugar levels. Pancreatic cancer usually begins in the cells that produce…
Macular degeneration, or age-related macular degeneration (AMD), is a leading cause of vision loss in Americans 60 and older. It is a disease that destroys your sharp, central vision. You need central vision to see objects clearly and…
Sleep apnea is a common disorder that causes your breathing to stop or get very shallow. Breathing pauses can last from a few seconds to minutes. They may occur 30 times or more an hour. The most common type is obstructive sleep…
Cardiomyopathy is the name for diseases of the heart muscle. These diseases enlarge your heart muscle or make it thicker and more rigid than normal. In rare cases, scar tissue replaces the muscle tissue. Some people live long, healthy…
You lose up to 100 hairs from your scalp every day. That's normal, and in most people, those hairs grow back. But many men -- and some women -- lose hair as they grow older. You can also lose your hair if you have certain diseases,…
Polycystic ovary syndrome (PCOS), also known as polyendocrine metabolic ovary syndrome (PMOS), is the name of a hormonal disorder. PCOS affects the ovaries, as well as many other parts of the body. If you have PCOS, you usually have…
The pancreas is a large gland behind the stomach and close to the first part of the small intestine. It secretes digestive juices into the small intestine through a tube called the pancreatic duct. The pancreas also releases the…
Vasculitis is an inflammation of the blood vessels. It happens when the body's immune system attacks the blood vessel by mistake. It can happen because of an infection, a medicine, or another disease. The cause is often unknown.…
Interstitial cystitis (IC) is a condition that causes discomfort or pain in the bladder and a need to urinate frequently and urgently. It is far more common in women than in men. The symptoms vary from person to person. Some people…
Amyotrophic lateral sclerosis (ALS) is a nervous system disease that attacks nerve cells called neurons in your brain and spinal cord. These neurons transmit messages from your brain and spinal cord to your voluntary muscles - the…
Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells which will develop into white blood cells, red blood cells, and platelets. Each type…
Diabetes is a disease in which your blood glucose, or blood sugar, levels are too high. Glucose comes from foods you eat. The cells of your body need glucose for energy. A hormone called insulin helps the glucose get into your cells.…
When you breathe in, the air travels down through your trachea (windpipe). It then goes through two tubes to your lungs. These tubes are your bronchi. Bronchial disorders can make it hard for you to breathe. The most common problem…
Heart valve disease happens when one or more of your heart valves don't work well. Your heart has four valves: the tricuspid, pulmonary, mitral, and aortic valves. The valves have flaps that open and close. The flaps make sure that…
Pemphigus is an autoimmune disorder. If you have it, your immune system attacks healthy cells in your skin and mouth, causing blisters and sores. No one knows the cause. Pemphigus does not spread from person to person. It does not…
Each reference identifies its source, coverage and retrieval date. Full text is shown only where reuse is permitted; some entries are terminology or bibliographic records. Sources and coverage.