In-depth

Acromegaly

Acromegaly is an uncommon hormonal disorder caused by the overproduction of growth hormone. It typically causes signs such as enlarged hands and feet.

Acute kidney failure

Acute kidney failure is the sudden loss of your kidneys' ability to filter waste from your bloodstream. Correcting the underlying cause increases the likelihood of recovery.

Acute lymphocytic leukemia

Acute lymphocytic leukemia is a type of leukemia that affects immature white blood cells. It's the most common cancer in children and adolescents.

Acute myelogenous leukemia (AML)

Acute myelogenous leukemia (AML), a form of cancer that affects the blood cells, is the most common type of leukemia.

Acute sinusitis

Acute sinusitis occurs when your sinus cavities become inflamed. Antibiotics, decongestants and corticosteroids may relieve pain and congestion and prevent development of chronic sinusitis.

Amyloidosis

Anaphylaxis

Anaphylaxis is the most serious type of allergic reaction. It often occurs rapidly after exposure to an allergen and may be life-threatening.

Anemia

Angina

Anorexia nervosa

Anthrax

Anxiety

Aortic valve regurgitation

Aortic valve stenosis

Aplastic anemia

Aplastic anemia occurs when your bone marrow stops producing enough new blood cells. It's a serious problem, but treatments are available.

ARDS

Arteriovenous fistula

Ascariasis

Aspergillosis

Atrial septal defect

Atrioventricular canal defect

Atrioventricular canal defect is a congenital heart defect involving a hole in the center of the heart and abnormal valves between the heart's chambers.

Autoimmune hepatitis

Autoimmune hepatitis — Early detection, medications can help.

Bipolar disorder

Blastocystis hominis infection

A microscopic parasite causes Blastocystis hominis infection. Experts disagree as to whether this infection causes diarrhea and other associated signs and symptoms.

Bradycardia

Bronchitis

Bronchitis often develops after a cold. Learn how to prevent this potentially serious lung infection.

Brucellosis

Brucellosis is an infectious disease that spreads from animals to people, mainly via unpasteurized dairy products. Travelers should take special care to avoid infection.

Brugada syndrome

Cancer

Cardiomyopathy

Castleman disease

Celiac disease

Celiac disease is an immune reaction to gluten, a protein found in certain foods. As a result, the body is unable to absorb some important nutrients.

Chagas disease

Chemo brain

Chemo brain causes thinking and memory problems in cancer survivors. Find out how to cope.

Cholera

Cholera causes severe diarrhea and can kill in a matter of hours, yet can be easily treated with oral or intravenous fluids.

Chronic fatigue syndrome

Chronic kidney disease

Chronic kidney disease, often caused by diabetes or high blood pressure, is the gradual loss of kidney function. Early detection and treatment can help.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia is a cancer of the blood and bone marrow. Unlike other cancers, this form of leukemia doesn't always initially require treatment.

Chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a rare type of blood cancer. New treatments may be improving the prognosis for many people with CML.

Chronic sinusitis

Chronic sinusitis involves long-term inflammation or infection of the sinus cavities. Medications can help, and in rare cases surgery can treat this painful condition.

Churg-Strauss syndrome

Churg-Strauss syndrome is a rare disorder marked by blood vessel inflammation that affects organs throughout the body. Asthma is the most common sign.

Cirrhosis

Colon cancer

Colon cancer and rectal cancer combined are the second-leading cause of cancer-related deaths in the United States. Regular screening tests can help reduce your risk.

Common cold

You've got a cold, or you're trying to prevent getting one. Here are some timely tips.

Concussion

Concussions can be serious injuries that need sufficient time to heal.

Crohn's disease

Cushing syndrome

Cushing syndrome is caused by an excess of the hormone cortisol, originating from your adrenal glands or from corticosteroid medications you're taking for another illness.

Cyclospora infection

Cyclothymia

Cyclothymia may be a mild form of bipolar disorder, but your fluctuating moods can have serious consequences. Learn about treatment options.

Depression

Take control of your mood and health. Explore the many depression treatment options and learn coping skills.

Dermatomyositis

Diabetes

Diabetes affects how your body uses blood sugar. Too much blood sugar over long periods can cause serious health problems, but treatments are available.

Diabetic coma

Diabetic ketoacidosis

Diabetic ketoacidosis is a serious diabetes complication. Learn the warning signs — and know when to seek emergency care.

Dilated cardiomyopathy

Dumping syndrome

Dysthymia

Dysthymia is a mild but long-term form of depression that can greatly reduce your quality of life. Learn about dysthymia symptoms and treatment options.

Ebstein's anomaly

Ebstein's anomaly is a rare heart defect. Some people may not have any symptoms, but others may need treatment, including surgery.

Encephalitis

Encephalitis is inflammation of the brain usually caused by a viral infection. Severe cases can cause brain damage, even death.

Endocarditis

Endometriosis

Endometriosis is a common and often painful disorder in which tissue that normally lines the inside of your uterus grows outside your uterus.

Enlarged liver

You can get an enlarged liver from a number of medical problems or personal habits. Treatment depends on what's causing the enlargement.

Enlarged spleen

An enlarged spleen is usually a sign of an underlying problem. Treatment varies, depending on what's causing the enlargement.

Esophageal cancer

Reduce your risk of esophageal cancer by eating more fruits and vegetables.

Fibromyalgia

Fatigue and widespread pain are common with fibromyalgia, a condition affecting mainly women. Treatment often focuses on managing symptoms with medication and self-care.

Gaucher's disease

Generalized anxiety disorder

Giardiasis

Giardia infection is a common waterborne illness. Learn the symptoms and reduce your risk.

Glomerulonephritis

Glomerulonephritis affects your kidneys' filtering function. Complications include high blood pressure, protein in the urine (proteinuria) and kidney failure.

Grand mal seizure

Graves' disease

Hairy cell leukemia

Hangovers

Hashimoto's disease

Hashimoto's disease (chronic lymphocytic thyroiditis) causes thyroid gland inflammation and often an underactive thyroid (hypothyroidism). Treatment may involve thyroid hormone replacement medication.

Heart arrhythmias

Heart attack

Heart disease

Heart disease, usually thought of as blockages in the arteries that can cause a heart attack, can describe any medical condition affecting your heart.

Heart failure

Heat exhaustion

Hemochromatosis

Hemochromatosis causes your body to store large amounts of iron, which can cause life-threatening complications. The simple treatment is to regularly remove blood.

Hemolytic uremic syndrome (HUS)

Hemolytic uremic syndrome is an uncommon condition that can cause life-threatening kidney failure, especially for children and older adults.

Hemophilia

Hepatitis A

Hepatitis B

Hepatitis C

Hiatal hernia

Hirschsprung's disease

Hirschsprung's disease, a disease of the colon, is present at birth and can cause serious problems passing stool.

HIV/AIDS

More than 39 million people are living with HIV — the virus that causes AIDS. Millions more are likely to become infected in the next decade.

Hodgkin's lymphoma

Huntington's disease

Hypercalcemia

Hyperglycemia in diabetes

Hyperparathyroidism

Hyperthyroidism

Hyperthyroidism occurs when your thyroid gland produces too much of the hormone thyroxine — speeding up your metabolism and sometimes leading to serious complications.

Hyponatremia

Hypoparathyroidism

Hypopituitarism

In hypopituitarism, your pituitary gland produces too little — or none — of one or more hormones. Disruption of any number of routine body functions can result.

Hypothermia

Hypothyroidism

Although low levels of thyroid hormones (hypothyroidism) can leave you feeling tired and depressed, medications can help you live a normal life.

Inflammatory bowel disease (IBD)

Influenza (flu)

Insomnia

Sleepless nights? Insomnia includes difficulty going to sleep, staying asleep or going back to sleep after you awaken. Insomnia may be temporary or chronic.

Iron deficiency anemia

Iron deficiency anemia may leave you feeling sapped of energy. This condition is especially common in women. Iron supplements usually help.

Jet lag disorder

Flying across multiple time zones disrupts your natural body rhythms, leading to sleep problems and other symptoms. Learn how to put jet lag to rest.

Kidney cancer

Lead poisoning

Legionnaires' disease

Legionnaires' disease, a severe form of pneumonia, is caused by bacteria that can live in water in air conditioning systems, showers and spas.

Leukemia

Liver cancer

The risk of liver cancer may be reduced by protecting yourself from serious liver diseases such as cirrhosis and hepatitis B and C.

Long QT syndrome

Long QT syndrome is an electrical disturbance that can cause sudden, rapid heart rates. It can be genetic or a side effect of medication.

Low blood pressure (hypotension)

Low blood pressure (hypotension) can be a sign of good health or of a life-threatening condition. Find out more about hypotension's causes and treatment options.

Lupus

Lyme disease

Lyme disease is a tick-borne illness. Left untreated, it can lead to serious and lingering complications — including arthritis.

Male hypogonadism

Membranous nephropathy

Menorrhagia

Mental illness

Mitral valve prolapse

Mitral valve prolapse occurs when the valve separating two of your heart's chambers malfunctions. The disorder usually isn't serious and often doesn't require surgical treatment.

Mitral valve stenosis

Mixed connective tissue disease

Mononucleosis

Mononucleosis — also called kissing disease because it can be spread by kissing — causes fatigue, fever and swollen lymph glands.

Multiple myeloma

Multiple sclerosis

Mumps

Mumps is a viral illness marked by swollen cheeks. Vaccination is important in preventing mumps.

Myelodysplastic syndromes

Myelofibrosis

In myelofibrosis, healthy bone marrow is replaced with scar tissue, leading to severe anemia and fatigue.

Myocarditis

Myocarditis is a disease in which the heart muscle becomes inflamed and swollen, often as the result of an infection.

Nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is associated with obesity and diabetes. Lifestyle changes may prevent it from becoming serious.

Non-Hodgkin's lymphoma

Parvovirus infection

Pectus excavatum

Pelvic inflammatory disease (PID)

Pericarditis

Peritonitis

Plague

Plague is a disease carried by rats and other rodents. The risk of developing plague is low, and most cases occur in Africa.

Pneumonia

Pneumonitis

Pneumonitis is a general term for lung inflammation. It can cause difficulty breathing, often accompanied by a cough.

Polio

One of the most feared diseases of the 20th century, polio has been eradicated from the developed world but remains a threat in less developed nations.

Polycythemia vera

Polycythemia vera is a rare blood disorder in which a person's bone marrow makes too many blood cells.

Polymyalgia rheumatica

Polymyalgia rheumatica is an inflammatory disorder that causes pain and stiffness in the neck, shoulders, upper arms, hips and thighs.

Polymyositis

Post-concussion syndrome

Postpartum depression

Postpartum depression can interfere with your ability to care for your baby and handle other daily tasks. Prompt treatment can help.

Post-polio syndrome

Prediabetes

Premenstrual syndrome (PMS)

Primary biliary cirrhosis

Primary sclerosing cholangitis

Pulmonary atresia

Pulmonary atresia is a heart defect that you're born with. Fortunately, treatment soon after birth and ongoing throughout childhood and adulthood greatly improve your prognosis.

Pulmonary edema

Pulmonary fibrosis

Pulmonary fibrosis results from scar tissue that forms in your lungs. This affects your ability to breathe and obtain enough oxygen.

Pulmonary hypertension

High blood pressure affecting only the arteries in your lungs is known as pulmonary hypertension. Discover the symptoms, risk factors and treatment for this condition.

Pulmonary valve stenosis

Q fever

Rheumatic fever

Rheumatic fever, an inflammatory disease triggered by untreated or poorly treated strep throat, can cause permanent heart damage.

Rheumatoid arthritis

Rocky Mountain spotted fever

Roseola

Sarcoidosis

Sarcoidosis starts in your lungs but can cause inflammation in any part of your body. It can last a lifetime, or disappear in a few years.

Sheehan's syndrome

Sheehan's syndrome is a rare pituitary gland disorder that occurs in women usually as a result of severe blood loss during childbirth.

Shingles

Sick sinus syndrome

Sinus headaches

Sjogren's syndrome

Small vessel disease

If you have symptoms of heart disease, but your doctor doesn't see any blocked major arteries, small vessel disease may be the cause.

Smallpox

Somatic symptom disorder

Stomach cancer

Reduce your risk of stomach cancer by eating more fruits and vegetables.

Strep throat

Strep throat is a bacterial throat infection. It typically causes a very sore throat and is treated with antibiotics.

Sudden cardiac arrest

Sudden cardiac arrest is a medical emergency. Rapid treatment improves your chances of survival.

Sunburn: Soothing solutions

Swine flu (H1N1 flu)

Swine flu — Comprehensive overview covers swine flu symptoms, tests, treatment and prevention.

Takayasu's arteritis

Takayasu's arteritis is an uncommon form of vasculitis that affects the large arteries.

Teen depression

All teens feel down from time to time. But if negative feelings persist or start to interfere with daily life, it might be depression.

Thalassemia

Thalassemia is an inherited blood disorder, characterized by less hemoglobin and fewer red blood cells than normal. When necessary, treatment includes blood transfusions.

Toxic hepatitis

Toxic hepatitis is liver damage that occurs when your liver isn't able to break down certain toxins — including common pain relievers such as Tylenol.

Toxoplasmosis

Toxoplasmosis is an infection caused by a parasite. It doesn't make most people ill, but infants and people with HIV/AIDS are at risk of complications.

Trench mouth

Although trench mouth is much less common than in years past, some people still get this painful gum infection. Brushing and flossing are keys to prevention.

Tricuspid atresia

A heart with tricuspid atresia doesn't have a tricuspid valve. This heart defect prevents blood flow from the right atrium to the right ventricle.

Tuberculosis

Type 1 diabetes

Type 1 diabetes in children

Type 1 diabetes is a lifelong — sometimes frightening — condition, but it doesn't need to slow your child down. Learn more about managing type 1 diabetes.

Type 2 diabetes

Type 2 diabetes in children

Typhoid fever

Although rare in industrialized nations, typhoid fever is a serious threat in many parts of the world. Learn how to stay safe when you travel.

Ulcerative colitis

Valley fever

Vasculitis

Viral hemorrhagic fevers

Ebola and Marburg viruses and yellow fever belong to a group of potentially deadly illnesses called viral hemorrhagic fevers. Find out about risk.

Vitamin deficiency anemia

Lacking certain vitamins can lead to vitamin deficiency anemia. Find out which vitamins are linked to this condition.

Von Willebrand disease

Von Willebrand disease is an inherited bleeding condition caused by a deficit in or impairment of a protein essential for blood clotting.

Wegener's granulomatosis

Wegener's granulomatosis is an uncommon disease that causes blood vessel inflammation that can damage lungs, kidneys and other organs. Untreated, it can be fatal.

West Nile virus

West Nile virus infection usually resolves on its own, but occasionally it can be serious.

Whiplash

Whipple's disease

Whipple's disease is a rare bacterial infection that affects primarily the gastrointestinal system, and can be treated successfully with antibiotics.

Whooping cough

Wilson's disease

Feb. 27, 2013