Health Library

Absence seizures are a type of epilepsy that most often occur in children. Read on for details about this condition.

Achalasia is a disease that makes it hard to eat and drink normally. It affects your esophagus, which is the swallowing tube that connects the back of your throat to your stomach.

Achalasia is a rare disease that makes it hard to swallow food and liquids. In achalasia, there is a problem with the tube that carries food from the mouth to the stomach (esophagus).

Achilles tendon injuries affect the Achilles tendon, a fibrous band of tissue that links the muscles in your calf to your heel. The strength and flexibility of this tendon are important for jumping, running, and walking.

Achondroplasia is a group of rare genetic (inherited) bone disorders. Achondroplasia is the most common type of what was once called dwarfism, in which the child's arms and legs are short in proportion to body length.

Acne affects teens and adults of all ages. It happens when oil secreted by sebaceous glands clogs the hair follicle. Bacteria infect the clogged follicle and cause pimples.

Acne is a disorder of the hair follicles and sebaceous glands. Hair follicles are the areas around the base or root of each hair. Sebaceous glands are the tiny glands that release oil (sebum) into the hair follicles. The sebum moistens the skin and hair. The sebum and hair get to the skin surface through tiny holes called pores.

Detailed information on different methods for acne scar removal. These include dermabrasion, chemical peels, collagen injections, laser resurfacing, punch grafts, and autologous fat transfer.

Acoustic neuroma is a rare noncancer tumor. It affects hearing and balance when the tumor presses on the nerves in the inner ear.

If you have hemophagocytic lymphohistiocytosis, your immune system does not work normally. Certain white blood cells - histiocytes and lymphocytes - attack your other blood cells. These abnormal blood cells accumulate in your spleen and liver, causing these organs to enlarge.

Hypothyroidism is when the thyroid gland doesn't make enough thyroid hormone. The condition is more common in adults. But it’s the most common thyroid disorder in children. Not enough thyroid hormone leads to signs, such as slow growth, lack of activity, and poor performance in school.

Acromegaly is abnormal growth that occurs when an adult's pituitary gland makes too much growth hormone. The abnormal growth starts in your hands and feet, as soft tissue begins to swell. This rare disease affects mostly middle-aged people.

Detailed information on actinic keratosis, including causes and treatment.

Acupuncture is the practice of putting thin needles into the skin at certain parts of the body. It's done to ease symptoms linked to many diseases. Read on to learn more.

Acute bacterial rhinosinusitis (ABRS) is an infection of both your nasal cavity and sinuses. It's caused by bacteria. Here's what you need to know about this condition.

There are several different types of bronchitis. But the most common are acute and chronic. Acute bronchitis may also be called a chest cold.

Bronchitis is an inflammation of the large breathing tubes (bronchi) in the lungs. Short-term (acute) bronchitis means that the symptoms often develop quickly and don't last long.

AFLP is a rare, but serious, liver problem in pregnancy. With AFLP the liver cells have too much fat, which can damage the liver.

AFM is a rare condition that affects the nervous system.

Acute liver failure is when your liver suddenly starts to not work. This often happens right after an overdose of medicine or poisoning.

A helpful look at the symptoms of acute lymphocytic leukemia.

Detailed information on acute myelogenous leukemia, including symptoms, diagnosis, and treatment.

Pancreatitis is inflammation of the pancreas. It can be caused by gallstones, alcohol consumption, and certain medicines, among other causes.

Detailed information on acute respiratory disorders in children

A traumatic injury to the spine can cause a bruise, a partial tear, or a complete tear in the spinal cord. Read on for details about causes, symptoms, treatment, prevention, and management.

Car accidents, falls, and other injuries are a common cause of acute spinal cord injury.

Acute spinal cord injury (SCI) is when the spinal cord is damaged from an accident or other situation. An SCI may be a bruise (contusion), a partial tear, or a complete tear (transection) in the spinal cord.

When you think of addiction, you might think about drugs or alcohol. But there are other kinds of addictions, and all of them involve your health and well-being.

Your milk is best, but it's not always complete with the nutritional needs of very small premature babies or some very sick newborns.

Addison disease is when the adrenal glands don't make enough of 2 steroid hormones. The hormones are cortisol and aldosterone. Cortisol controls the body's metabolism, blocks inflammatory reactions, and affects the immune system. Aldosterone manages sodium and potassium levels. Addison disease is fairly rare and may first appear at any age.

Adenoviruses are a group of viruses that cause a variety of infections. These include the common cold, conjunctivitis, and croup.

Food intolerance means that after surgery you may have problems eating foods that you once ate or that are part of your new diet. This can make it hard to stick to your new diet and keep the pounds off.

An adjustment disorder is an unhealthy emotional or behavioral reaction to a stressful event or change in a person's life. The response happens within 3 months of the stressful event.

Detailed information on adolescence, ages 13 to 18 years

Detailed information on adolescent growth and development

Detailed information on adolescent health problems and injuries, including acne, asthma, breast conditions, breast self-examination, diabetes, eye care, eye safety, gynecological conditions, menstrual conditions, gynecologic problems, pap test, vaginitis, vulvitis, menstrual disorders, amenorrhea, dysmenorrhea, premenstrual syndrome (PMS), high blood pressure, infectious mononucleosis, obesity, oral health, orthodontics, braces, wisdom teeth extraction, periodontal disease, orthopedic problems, osgood schlatter disease, scoliosis, slipped capital femoral epiphysis, sexually transmitted diseases, safer sex guidelines, sports safety, sports injuries, sprains, strains, tennis elbow, mouthguards, heat related illness, heat cramps, heat exhaustion, and heat stroke

Detailed information on adolescent mental health disorders, including schizophrenia, mood disorders, major depression, dysthymia, manic depression (bipolar disorder), teen suicide, anxiety disorders, generalized anxiety disorder, obsessive-compulsive disorder, phobia, post-traumatic stress disorder, behavior disorders, attention-deficit/hyperactivity disorder, conduct disorder, oppositional defiant disorder, eating disorders, anorexia nervosa, bulimia nervosa, substance abuse/chemical dependence, and adjustment disorders

Detailed information on adolescent problems of the teeth and mouth

Adrenal insufficiency is a disorder that occurs when the adrenal glands don't make enough of the hormone cortisol. This hormone controls blood pressure and affects how your immune system works.

Afferent loop syndrome is a complication of certain types of stomach surgery.

African sleeping sickness (African trypanosomiasis) is a disease caused by a parasite. It is passed on by the bite of the infected tsetse fly.

Details about when to call your child's healthcare provider after a burn.

Detailed information on postoperative discomforts and potential complications, including shock, hemorrhage, wound infection, deep vein thrombosis, pulmonary complications, urinary retention, and reaction to anesthesia.

Detailed information on health considerations after returning home from traveling abroad

A helpful look at age-appropriate hearing milestones for babies and toddlers.

Age-related hearing loss (presbycusis) is the slow loss of hearing in both ears. It’s a common problem linked to aging.

Age-related macular degeneration (AMD) is a disease that affects a person’s central vision. It's the most common cause of severe eyesight loss among people age 50 and older.

People who have AIDS are much more likely to get certain types of cancer than people without the disease.

AIDS-related lymphoma is a type of cancer called non-Hodgkin lymphoma. It grows in some people with AIDS. AIDS is a disease that weakens the immune system. AIDS raises the risk for long-term (chronic) disease, such as cancer.

Detailed information on air pollution and air pollution prevention

Detailed information on healthy considerations for air travel, including ways to prevent motion sickness and jet lag

Infants and children under age 4 are particularly at risk for choking on food or small objects because their upper airways are smaller, and they tend to explore things with their mouths.

Choking hazards in the home: round, firm foods, such as grapes and popcorn, and small nonfood items, such as coins, balloons, and marbles.

Because most accidental child strangulations, chokings, and suffocations happen in the home, it's important to carefully childproof your residence.

Alagille syndrome is an inherited condition in which bile builds up in the liver because there are too few bile ducts to drain the bile. This results in liver damage.

Drinking alcohol while pregnant is a leading cause of birth defects in a baby. In addition, the risk for miscarriage and stillbirth increases with alcohol consumption. Read on to learn more.

Alcohol can lower blood sugar levels to the point of hypoglycemia. Keep careful track of your blood sugar levels when drinking alcohol, because certain diabetes medicines also lower blood glucose levels.

Alcohol-induced liver disease is caused by heavy use of alcohol. The liver's job is to break down alcohol. If you drink more than it can process, it can become badly damaged.

Alcoholic hepatitis is liver inflammation and damage caused by drinking too much alcohol over time.

Detailed information on allergy, including symptoms, diagnosis, and treatment

Asthma is a chronic, inflammatory lung disease with recurrent breathing problems.

Detailed information on allergic reactions to insect bites and stings.

Household pets, such as cats and dogs, are the most common sources of animal allergens. Here's what you need to know about symptoms and treatments.

Idiopathic environmental intolerance (IEI) is a set of symptoms caused by contact with some kinds of substances. Read on to learn more about causes, symptoms, triggers, and treatment.

Dust mites are microscopic organisms that can live throughout homes and businesses. Read on to learn more.

Pollen is the most common cause of hay fever. Read on for more information--and helpful tips for reducing the effects of hay fever during pollen season.

Detailed information on allergy triggers and symptom control

Allergic rhinitis can happen on a seasonal basis or year-round. There is often a family history of allergic rhinitis, eczema, asthma, or food allergy. Read on to learn details about treating and managing this condition.

Detailed information on allergies in children, including information on allergic rhinitis and food allergies

Most allergic reactions are a result of an immune system that responds to a "false alarm."

Allergies are problems of the immune system. Most allergic reactions happen when the immune system reacts to a “false alarm.” Normally, the human body defends itself against harmful things, such as viruses or bacteria. But sometimes the defenses violently attack mostly mild things, such as dust, mold, or pollen.

Detailed information on allergy, including symptoms, diagnosis, and treatment

Allergies are problems of the immune system. Normally the immune system attacks harmful things such as viruses or bacteria. But sometimes it overreacts and responds to things that are normally harmless. These may include dust, mold, pollen, or food.

Thalassemia is an inherited blood disorder. It is passed down from one or both parents through their genes. Learn about the4 types of alpha thalassemia, symptoms, treatment options, and more.

Alpha thalassemia is an inherited blood disorder. This means it is passed down through the parent’s genes. It causes anemia in affected children. Learn more about symptoms, diagnosis, and treatment.

Alpha-fetoprotein screening is a blood test that measures the level of AFP in the mother's blood. Abnormal levels may indicate certain problems with the fetus.

Alzheimer disease is a disease that affects the brain and nervous system. It is a type of dementia that happens when nerve cells in the brain die.

Amenorrhea means you haven't had your period for more than 3 cycles. It can be caused by a variety of things including overexercising, being overweight, or due to an ovulation problem.

Amenorrhea is when a girl's menstrual bleeding (period) doesn't occur.

Detailed information about causes, symptoms, diagnosis, and treatment of ampullary cancer.

Amyotrophic lateral sclerosis is a fatal neurological disorder that causes progressive degeneration of nerve cells in the spinal cord and brain. It is often referred to as Lou Gehrig disease.

An anal fissure is a small, painful tear in the lining of the anus. Anal fissures may hurt and bleed during or after a bowel movement, but about 90% heal without surgery.

An anal fistula is an abnormal opening in the skin near the anus. It leads to the inside of the anal canal in the colon.

Taking one or a mix of painkiller medicines daily over a long time may cause chronic kidney problems. This is called analgesic nephropathy. Painkillers that combine two or more medicines (such as, aspirin and acetaminophen together) with caffeine or codeine are the most likely to harm the kidneys.

Anaphylaxis is a severe and sometimes life-threatening reaction to an allergen. An allergen is something that your child is allergic to. Anaphylaxis is a medical emergency. Your child can have a reaction within seconds or as long as an hour after contact.

Anaplasmosis is an illness caused by bacteria that’s spread by ticks. The bacteria are called Anaplasma phagocytophilum. The illness causes fever, muscle aches, and other symptoms.

One risk of gastric bypass surgery is that the anastomosis, the new connection created in your intestines during the bypass surgery, will leak. Leaking of digestive juices and partially digested food through an anastomosis is one of the most serious complications after bypass surgery.

After gastric bypass surgery for weight loss, the new connection between the stomach pouch and the small intestine may narrow. This is called an anastomotic stenosis. It’s also known as a stricture.

Detailed information on several of the different divisions of anatomical pathology, including biopsy, surgical pathology, cytology, and autopsy

Children's teeth begin developing in the fetus. Good nutrition from the mother during pregnancy is important in the development of the teeth.

Detailed information and illustrations about the 2 coronary arteries, which supply blood to the heart muscle.

Detailed anatomical description of the heart's electrical system, including simple definitions and a labeled, full-color illustration

Detailed anatomical description of the heart valves, including simple definitions and a labeled, full-color illustration.

The heart is a pump made of muscle tissue. Its pumping action is controlled by electrical impulses.

Detailed anatomical description of the urinary system, including simple definitions and labeled, full-color illustrations.

The main parts of the ear are the outer ear, the eardrum (tympanic membrane), the middle ear, and the inner ear.

A helpful guide to the nose, the sinuses, and the throat.

The brain can be divided into 3 main parts: the cerebrum, the brainstem, and the cerebellum.

Joints are the areas where 2 or more bones meet. Most joints are mobile, allowing the bones to move.

Detailed anatomical information on the newborn skull.

The female pelvic area contains a number of organs and structures: the endometrium, uterus, ovaries, cervix, vagina, and vulva.

The brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respiration, and every process that regulates your body.

A closer look at the structure of the breast.

The elbow is a hinge joint between the humerus bone in the upper arm and the radius and ulnar bones in the lower arm.

The endocrine system includes not only the pancreas—the organ involved in the development of diabetes—but also the pituitary, thyroid, and other glands.

Detailed information on the endocrine system, its anatomy and function, including a full-color, labeled illustration.

The structures of the eye include the cornea, iris, pupil, macula, retina, and the optic nerve.

Your feet are susceptible to many stresses. Foot pain and problems can cause pain, inflammation, or injury.

Each of your hands has three types of bones: phalanges in your fingers; metacarpals in your mid-hand, and carpals in your wrist.

The knee is a vulnerable joint that bears a lot of stress from everyday activities, such as lifting and from high-impact activities, such as jogging.

The pelvis is a basin-shaped structure that supports the spinal column and protects the abdominal organs.

Details about the size, location, and function of the prostate gland, including a diagram.

A detailed look at the respiratory system and how it works.

A detailed anatomical description of the respiratory system, including simple definitions and labeled, full-color illustrations.

The shoulder is a complex joint with several layers, including bones, ligaments, tendons, and muscles.

The skin is the body's largest organ. It serves as a protective shield against heat, light, injury, and infection.

Made up of bundles of nerves, the spinal cord carries signals from your body to your brain, and vice versa.

Your backbone, also called the vertebral column, is made up of 33 vertebrae separated by spongy disks.

Definitions of terms related to the anatomy of a fetus in utero.

Chemotherapy can damage your body’s ability to make red blood cells, so body tissues don't get enough oxygen. This is a condition called anemia. People who have anemia may feel very weak or tired, dizzy, faint, or short of breath, or may feel that their hearts are beating very fast.

Anemia is a common problem in children. A child who has anemia doesn't have enough red blood cells or hemoglobin. Read on to learn more about causes, symptoms, diagnosis, and treatment.

Anemia is when your blood has too few red blood cells. Having too few red blood cells makes it harder for your blood to carry oxygen or iron. This can affect how cells work in nerves and muscles. During pregnancy, your baby also needs your blood.

Anemia is a common blood disorder. It occurs when you have fewer red blood cells than normal, or not enough hemoglobin in your blood. Here's what you need to know about this condition.

Detailed information on the different types of anemia, including aplastic anemia, anemia of folate deficiency, glucose-6-phosphate dehydrogenase deficiency, hemolytic anemia, iron deficiency anemia, megaloblastic anemia, and sickle cell disease

Anencephaly is a birth defect that affects the brain and skull bones. With this condition, the brain isn't fully formed. It often lacks part or all of the cerebrum.

An aneurysm is a bulging, weak area in the wall of a blood vessel. An aneurysm may occur in any blood vessel, but most often develops in an artery rather than a vein.

Anger management helps you deal with your child or grandchild in a kind and constructive way. It also sets a good example of how to handle challenging situations and work out conflicts.

Angina pectoris--or simply angina--is chest pain or discomfort that keeps coming back. It happens when some part of your heart does not get enough blood and oxygen. Read on for details.

Sometimes called antiangiogenic therapy, this treatment may prevent the growth of cancer by blocking the formation of new blood vessels.

Detailed information on animal bites and rabies, including symptoms, diagnosis, treatment, and prevention

Aniridia is a serious and rare eye disorder in which the iris is partly or completely gone.

A joint dislocation is when there is an abnormal separation between the bones of a joint. When this happens in your ankle joint, it's known as an ankle dislocation. It is a severe injury.

Tongue-tie (ankyloglossia) is a problem with the tongue that is present from birth. It causes speech and eating problems in some children.

Ankylosing spondylitis (AS) is a type of arthritis that affects the spine. Read on to learn details about this condition, including symptoms, diagnosis, and treatment.

The term annular pancreas means that a ring of excess pancreatic tissue encases the first part of your small intestine. Your pancreas can still function, but the excess tissue can cause a number of symptoms. Read on to learn more.

An anomalous coronary artery (ACA) is a heart defect. This is something your baby is born with (congenital). In ACA, the blood vessels that supply blood to your child’s heart muscle aren’t normal.

An anorectal abscess is a collection of pus under the skin in the area of the anus and rectum.

Anorectal malformations are birth defects, or problems that happen as an unborn baby is developing during pregnancy. With this defect, the anus and rectum don’t develop properly. They are the lower part of the digestive tract.

Anorexia nervosa (or simply anorexia) is an eating disorder that causes people to obsess about their weight and food. People who suffer with this behavior problem have a distorted body image. They see themselves as overweight even when their weight is dangerously low.

Anorexia nervosa is an eating disorder. It is a form of self-starvation. Children and teens with this health problem have a distorted body image. They think they weigh too much.

Detailed information on anterior pituitary disorders, including hypopituitarism

This diet involves choosing a healthy variety of foods. It focuses on foods that may help reduce chronic (long-lasting) inflammation, such as fruits, vegetables, and whole grains.

Antibiotics are medicines used to kill bacteria. Over time, certain groups of these germs may adapt to these medicines. They may change in such a way that antibiotics can't kill them. This is called antibiotic resistance.

Detailed information on the use of antibiotics and children

Anticipatory grief is similar to the normal process of mourning, but it happens before the actual death.

Antiphospholipid syndrome is an autoimmune disease. This happens when your immune system fights against normal cells. In this condition, your body makes antibodies that attack a kind of fat in cells. This makes your blood clot too easily.

Detailed information on the most common types of anxiety disorders, including panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, generalized anxiety disorder, and phobias

Detailed information on the most common types of anxiety disorders, including panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, generalized anxiety disorder, and phobias

Problems such as high blood pressure can weaken an area of the aorta over time. This can cause a tear in the lining of that area.

Aortic stenosis means that your child has a heart valve that is too narrow or is blocked.  The aortic valve is 1 of 4 heart valves that keep blood flowing through the heart. The valves make sure blood flows in only one direction. The aortic valve keeps blood flowing from the left ventricle to the aorta.

Aortic valve regurgitation is when a person's aortic valve leaks. The aortic valve is 1 of the heart's 4 valves. These valves help the blood flow through the heart and out to the body. Normally, the aortic valve stops blood from flowing back into the left ventricle. With aortic valve regurgitation, some blood leaks back through the valve as the heart relaxes.

Aphasia is a language disorder caused by damage in a specific area of the brain that controls language expression and comprehension. Aphasia leaves a person unable to communicate effectively with others.

Aplastic anemia occurs when your bone marrow doesn’t make enough red and white blood cells, and platelets.

Aplastic anemia is a serious condition in which the bone marrow doesn’t make enough new blood cells. Read on for details about causes, symptoms, diagnosis, and treatment.

Apnea is a term that means breathing has stopped for more than 20 seconds. It can happen in full-term babies, but it is more common in premature babies. The more premature the baby, the greater the chances that apnea will occur.

Appendicitis is a medical emergency that happens when your appendix becomes sore, swollen, and diseased.

Appendicitis is a painful swelling and infection of the appendix.  It is a medical emergency. The appendix can burst or rupture. This is serious and can lead to more infection. If not treated, it can be fatal.

Treatment for cancer, as well as the cancer itself, can affect your sense of taste or smell. You may find that many foods seem to have less taste. Other foods, especially meat or other high-protein foods, may taste bitter or metallic. Read on to learn what you can do about it.

An arrhythmia is an abnormal heart rhythm that can cause problems with the contractions of your heart chambers.

An arrhythmia is an abnormal rhythm of the heart. In an arrhythmia, abnormal electrical signals through the heart muscle may cause the heart to beat too fast (tachycardia), too slow (bradycardia), or irregularly. Read on to learn more.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease of the heart muscle. In this disease, fatty fibrous tissue replaces normal heart muscle. This interrupts normal electrical signals in the heart and may cause irregular and potentially life-threatening heart rhythms. The heart also becomes weaker over time leading to heart failure.

Art, dance, music—all are examples of mind-body therapy. Although these therapies do not cure cancer, they provide an outlet for emotions and can improve mental and physical well-being.

Detailed information on art therapy, dance/movement therapy, and music therapy.

Arteriovenous malformations (AVMs) happen when a group of blood vessels in your body forms incorrectly. Here's what you need to know.

Arthritis and other rheumatic diseases are common conditions that cause pain, swelling, and limited movement. They affect joints and connective tissues around the body. Millions of people in the U.S. have some form of arthritis.

Diagnosing arthritis and other rheumatic diseases is often difficult, as many symptoms are similar among the different diseases.

Orthopedic surgeons use arthroscopy to diagnose and treat joint problems. An arthroscope is a small, tube shaped instrument that is used to look inside a joint.

Ascites is a condition that occurs when fluid collects in spaces in your belly. It can be painful and keep you from moving around comfortably. Ascites can set the stage for an infection in your belly. Fluid may also move into your chest and surround your lungs. This makes it hard to breathe.

Aspiration is when something enters your airway or lungs by accident. It may be food, liquid, or some other material. This can cause serious health problems, such as pneumonia. Aspiration can happen when you have trouble swallowing normally. This is called dysphagia.

Aspiration is when something enters the airway or lungs by accident. It may be food, liquid, or some other material. This can cause serious health problems, such as pneumonia.

Each newborn baby is carefully checked at birth for signs of problems or complications.

Assisted living (AL) is a setting for older adults or in some centers, adults of any age who are living with disability.

Assistive equipment is any kind of tool or device that can help simplify caregiving or make the environment safer for an ill, disabled, or elderly person.

Asthma is a chronic lung disease. The airways become sensitive to triggers (allergens and irritants). Here's what you need to know.

Exercise is a common trigger for many people with asthma. This is called exercise-induced bronchoconstriction or EIB. But living with EIB doesn't mean you need to give up exercise.

With correct asthma management and good prenatal care, most women with asthma can have healthy pregnancies.

Asthma is a long-term (chronic) lung disease that causes your child's airways to become sensitive to certain things (triggers).

Detailed information on asthma, including triggers of an asthma attack, symptoms, diagnosis, management, and treatment

Your child's asthma may be triggered by a number of things: pollen, molds, certain foods, strong odors, or even exercise.

A peak flow meter for asthma is like a thermometer for a fever - it helps you keep track of what's going on inside your lungs by measuring airflow out of the lungs.

Astrocytoma is the most common type of brain tumor in children. It is usually low grade, which means slow-growing.

Ataxia means without coordination. People with ataxia lose muscle control in their arms and legs, which may lead to a lack of balance, coordination, and trouble walking. Ataxia may affect the fingers, hands, arms, legs, body, speech, and even eye movements.

A-T is a rare childhood disease that affects the nervous system and other body systems.

Atherosclerosis is a type of thickening or hardening of the arteries caused by a buildup of plaque in the inner lining of an artery. It can increase your risk of heart attack, stroke, and other circulatory conditions.

Atopic dermatitis is a chronic skin disorder. It is also called eczema. It often affects infants and may last until adulthood. It causes itchy, scaly patches on the skin.

Atopic dermatitis is a long-term (chronic) skin condition. It causes dry, itchy skin. It’s a very common condition in babies and children. It often first appears between ages 3 and 6 months.

Atrial fibrillation, or AFib, is a kind of abnormal heart rhythm or arrhythmia. AFib increases the risk for blood clots. These clots can then travel to the brain, causing a stroke. This is why AFib significantly increases the risk for stroke.

Atrial fibrillation increases the risk for stroke. So stroke prevention is an important part of treatment for atrial fibrillation.

Atrial flutter is an abnormal heart rhythm that causes the atria to beat more quickly than they should.

The atrial septum is the wall between the two upper chambers of the heart (right and left atria). An atrial septal defect (ASD) is an abnormal hole in this wall. ASD is a heart problem that is present at birth (congenital). Read on for details about symptoms, diagnosis, and treatment.

An atrioventricular (AV) canal defect is a congenital heart defect. This means that your child is born with it. These defects may range from partial to complete. These conditions cause oxygen-rich (red) blood and oxygen-poor (blue) blood to mix. This sends extra blood to the child's lungs.

Attention-deficit/hyperactivity disorder (ADHD) is a brain-based, or neurodevelopmental, disorder. It is often first diagnosed in childhood.

Audiologists measure and evaluate a person's ability to hear sounds. They specialize in treating people with hearing disorders.

Audiologists address hearing and balance problems in people of all ages. They also help with the fitting and management of hearing aids.

Autism spectrum disorder is a problem that affects a child's nervous system and growth and development. It often shows up during a child's first 3 years of life.

Detailed information on autoimmune diseases and pregnancy

Autoimmune hepatitis is when your body’s infection-fighting system (immune system) attacks your liver cells. This causes redness and swelling (inflammation) and liver damage.

An AED is a small, portable, battery-powered machine with a computer in it. The machine detects heart activity. It can give an electric shock to someone if needed.

Detailed information on autopsy, including who does the procedure and how an autopsy is done.

A mutation is a change in a gene that prevents it from working correctly. We inherit mutations from our parents in specific ways, one of which is called autosomal dominant inheritance.

Detailed information on autosomal recessive genes.

Overview of autosomal recessive inheritance, including cystic fibrosis, sickle cell anemia, and Tay Sachs disease.

Avascular necrosis develops when blood supply to a bone is cut off. This causes the bone to die and can cause pain and joint problems.

Ayurveda is a holistic system of medicine based on the idea that imbalance leads to disease.