All Diseases

Ataxia describes a lack of muscle control during voluntary movements, such as walking or picking up objects. A sign of an underlying condition, ataxia can affect movement, speech, eye movement and swallowing.

Persistent ataxia usually results from damage to your cerebellum — the part of your brain that controls muscle coordination. Many conditions can cause ataxia, including alcohol abuse, stroke, tumor, cerebral palsy and multiple sclerosis. An inherited defective gene also can cause ataxia.

Treatment for ataxia depends on the cause. Adaptive devices, such as walkers or canes, might help you maintain your independence. Physical therapy, occupational therapy and speech therapy also might help.

Atelectasis (at-uh-LEK-tuh-sis) — a complete or partial collapse of a lung or lobe of a lung — develops when the tiny air sacs (alveoli) within the lung become deflated. It is one of the most common breathing (respiratory) complications after surgery. Atelectasis is also a possible complication of other respiratory problems, including cystic fibrosis, inhaled foreign objects, lung tumors, fluid in the lung, severe asthma and chest injuries.

The amount of lung tissue involved in atelectasis is variable, depending on the cause. Signs and symptoms of atelectasis also vary. Atelectasis can be serious because it reduces the amount of oxygen available to your body. Treatment depends on the cause and severity of the collapse.

Athlete's foot (tinea pedis) is a fungal infection that usually begins between the toes. It occurs most commonly in people whose feet have become very sweaty while confined within tight-fitting shoes.

Signs and symptoms of athlete's foot include a scaly rash that usually causes itching, stinging and burning. Athlete's foot is contagious and can be spread via contaminated floors, towels or clothing.

Athlete's foot is closely related to other fungal infections such as ringworm and jock itch. It can be treated with over-the-counter antifungal medications, but the infection often recurs. Prescription medications also are available.

Atopic dermatitis (eczema) is a condition that makes your skin red and itchy. It's common in children but can occur at any age. Atopic dermatitis is long lasting (chronic) and tends to flare periodically and then subside. It may be accompanied by asthma or hay fever.

No cure has been found for atopic dermatitis. But treatments and self-care measures can relieve itching and prevent new outbreaks. For example, it helps to avoid harsh soaps and other irritants, apply medicated creams or ointments, and moisturize your skin.

See your doctor if your atopic dermatitis symptoms distract you from your daily routines or prevent you from sleeping.

Atrial fibrillation is an irregular and often rapid heart rate that commonly causes poor blood flow to the body.

During atrial fibrillation, the heart's two upper chambers (the atria) beat chaotically and irregularly — out of coordination with the two lower chambers (the ventricles) of the heart. Atrial fibrillation symptoms often include heart palpitations, shortness of breath and weakness.

Episodes of atrial fibrillation can come and go, or you may develop atrial fibrillation that doesn't go away and may require treatment. Although atrial fibrillation itself usually isn't life-threatening, it is a serious medical condition that sometimes requires emergency treatment. It can lead to complications. Atrial fibrillation may lead to blood clots forming in the heart that may circulate to other organs and lead to blocked blood flow (ischemia).

Treatments for atrial fibrillation may include medications and other interventions to try to alter the heart's electrical system.

An atrial septal defect (ASD) is a hole in the wall between the two upper chambers of your heart (atria). The condition is present from birth (congenital). Small atrial septal defects may close on their own during infancy or early childhood.

Large and long-standing atrial septal defects can damage your heart and lungs. Small defects may never cause a problem and may be found incidentally. An adult who has had an undetected atrial septal defect for decades may have a shortened life span from heart failure or high blood pressure that affects the arteries in the lungs (pulmonary hypertension). Surgery may be necessary to repair atrial septal defects to prevent complications.

Atrioventricular canal defect is a combination of several abnormalities in the heart present at birth (congenital abnormalities). This defect, which is sometimes called endocardial cushion defect or atrioventricular septal defect, occurs when there's a hole between the chambers of the heart and problems with the valves that regulate blood flow in the heart.

Atrioventricular canal defect allows extra blood to circulate to the lungs. Ensuing problems overwork the heart and cause it to enlarge.

Atrioventricular canal defect is often associated with Down syndrome. If left untreated, atrioventricular canal defect may cause heart failure and high blood pressure in the lungs. To fix this defect, doctors often recommend surgery during the first year of life to close the hole and reconstruct the valves.

Attention-deficit/hyperactivity disorder (ADHD) is a chronic condition that affects millions of children and often persists into adulthood. ADHD includes a combination of problems, such as difficulty sustaining attention, hyperactivity and impulsive behavior.

Children with ADHD also may struggle with low self-esteem, troubled relationships and poor performance in school. Symptoms sometimes lessen with age. However, some people never completely outgrow their ADHD symptoms. But they can learn strategies to be successful.

While treatment won't cure ADHD, it can help a great deal with symptoms. Treatment typically involves medications and behavioral interventions. Early diagnosis and treatment can make a big difference in outcome.

Any type of depression can make you feel sad and keep you from enjoying life. However, if you have atypical depression, certain key signs and symptoms tend to occur. These include increased hunger, weight gain, sleeping a lot, feeling that your arms and legs are heavy, and difficulty maintaining relationships.

Atypical depression often starts in the teenage years and is more common in women than in men. Despite the name, atypical depression isn't uncommon or unusual. Similar to other forms of depression, treatment for atypical depression includes medications, psychological counseling (psychotherapy) and lifestyle changes.

Atypical hyperplasia is a precancerous condition that affects cells in the breast. Atypical hyperplasia describes an accumulation of abnormal cells in the breast.

Atypical hyperplasia isn't cancer, but it can be a forerunner to the development of breast cancer. Over the course of your lifetime, if the atypical hyperplasia cells keep dividing and become more abnormal, this can transition into noninvasive breast cancer (carcinoma in situ) or invasive breast cancer.

If you've been diagnosed with atypical hyperplasia, you have an increased risk of developing breast cancer in the future. For this reason, doctors often recommend intensive breast cancer screening and medications to reduce breast cancer risk.