All Diseases

Antibiotic-associated diarrhea describes frequent, watery bowel movements (diarrhea) that occur in response to medications used to treat bacterial infections (antibiotics).

Most often, antibiotic-associated diarrhea is mild and clears up shortly after you stop taking the antibiotic. But in some cases, antibiotic-associated diarrhea leads to colitis, an inflammation of your colon, or a more serious form of colitis called pseudomembranous colitis. Both can cause abdominal pain, fever and bloody diarrhea.

Mild antibiotic-associated diarrhea may not require treatment. More serious antibiotic-associated diarrhea may require stopping or switching antibiotic medications.

Antiphospholipid syndrome occurs when your immune system mistakenly attacks some of the normal proteins in your blood. Antiphospholipid syndrome can cause blood clots to form within your arteries or veins. It can also cause pregnancy complications, such as miscarriage and stillbirth.

Antiphospholipid syndrome may cause blood clots to form in your leg veins, a condition known as deep vein thrombosis (DVT). Antiphospholipid syndrome may also cause blood clots to form in organs such as your kidneys or lungs. Damage depends on the extent and location of the clot. For instance, a clot in your brain can cause stroke.

There's no cure for antiphospholipid syndrome, but medications can be effective in reducing your risk of blood clots.

Antisocial personality disorder is a type of chronic mental condition in which a person's ways of thinking, perceiving situations and relating to others are dysfunctional — and destructive. People with antisocial personality disorder typically have no regard for right and wrong and often disregard the rights, wishes and feelings of others.

Those with antisocial personality disorder tend to antagonize, manipulate or treat others either harshly or with callous indifference. They may often violate the law, landing in frequent trouble, yet they show no guilt or remorse. They may lie, behave violently or impulsively, and have problems with drug and alcohol use. These characteristics typically make people with antisocial personality disorder unable to fulfill responsibilities related to family, work or school.

Experiencing occasional anxiety is a normal part of life. However, people with anxiety disorders frequently have intense, excessive and persistent worry and fear about everyday situations. Often, anxiety disorders involve repeated episodes of sudden feelings of intense anxiety and fear or terror that reach a peak within minutes (panic attacks).

These feelings of anxiety and panic interfere with daily activities, are difficult to control, are out of proportion to the actual danger and can last a long time. Symptoms may start during childhood or the teen years and continue into adulthood.

Examples of anxiety disorders include social anxiety disorder (social phobia), specific phobias and separation anxiety disorder. A person can have more than one anxiety disorder.

Sometimes anxiety results from a medical condition that needs treatment. Whatever form of anxiety you have, treatment can help.

An aortic dissection is a serious condition in which the inner layer of the aorta, the large blood vessel branching off the heart, tears. Blood surges through the tear, causing the inner and middle layers of the aorta to separate (dissect). If the blood-filled channel ruptures through the outside aortic wall, aortic dissection is often fatal.

Aortic dissection is relatively uncommon. The condition most frequently occurs in men in their 60s and 70s. Symptoms of aortic dissection may mimic those of other diseases, often leading to delays in diagnosis. However, when an aortic dissection is detected early and treated promptly, the chance of survival greatly improves.

Aortic valve regurgitation — or aortic regurgitation — is a condition that occurs when your heart's aortic valve doesn't close tightly. Aortic valve regurgitation allows some of the blood that was just pumped out of your heart's main pumping chamber (left ventricle) to leak back into it.

The leakage may prevent your heart from efficiently pumping blood to the rest of your body. As a result, you may feel fatigued and short of breath.

Aortic valve regurgitation can develop suddenly or over decades. Once aortic valve regurgitation becomes severe, surgery is often required to repair or replace the aortic valve.

Aortic valve stenosis — or aortic stenosis — occurs when the heart's aortic valve narrows. This narrowing prevents the valve from opening fully, which obstructs blood flow from your heart into your aorta and onward to the rest of your body.

When the aortic valve is obstructed, your heart needs to work harder to pump blood to your body. Eventually, this extra work limits the amount of blood it can pump and may weaken your heart muscle.

If you have severe aortic valve stenosis, you'll usually need surgery to replace the valve. Left untreated, aortic valve stenosis can lead to serious heart problems.

Aphasia is a condition that robs you of the ability to communicate. Aphasia can affect your ability to express and understand language, both verbal and written.

Aphasia typically occurs suddenly after a stroke or a head injury. But it can also come on gradually from a slowly growing brain tumor or a degenerative disease. The amount of disability depends on the location and the severity of the brain damage.

Once the underlying cause has been treated, the primary treatment for aphasia is speech therapy that focuses on relearning and practicing language skills and using alternative or supplementary communication methods. Family members often participate in the therapy process and function as communication partners of the person with aphasia.

Aplastic anemia is a condition that occurs when your body stops producing enough new blood cells. Aplastic anemia leaves you feeling fatigued and with a higher risk of infections and uncontrolled bleeding.

A rare and serious condition, aplastic anemia can develop at any age. Aplastic anemia may occur suddenly, or it can occur slowly and get worse over a long period of time. Treatment for aplastic anemia may include medications, blood transfusions or a stem cell transplant.

Appendicitis is an inflammation of the appendix, a finger-shaped pouch that projects from your colon on the lower right side of your abdomen. The appendix doesn't seem to have a specific purpose.

Appendicitis causes pain in your lower right abdomen. However, in most people, pain begins around the navel and then moves. As inflammation worsens, appendicitis pain typically increases and eventually becomes severe.

Although anyone can develop appendicitis, most often it occurs in people between the ages of 10 and 30. Standard treatment is surgical removal of the appendix.