All Diseases

Acute respiratory distress syndrome (ARDS) occurs when fluid builds up in the tiny, elastic air sacs (alveoli) in your lungs. More fluid in your lungs means less oxygen can reach your bloodstream. This deprives your organs of the oxygen they need to function.

ARDS typically occurs in people who are already critically ill or who have significant injuries. Severe shortness of breath — the main symptom of ARDS — usually develops within a few hours to a few days after the original disease or trauma.

Many people who develop ARDS don't survive. The risk of death increases with age and severity of illness. Of the people who do survive ARDS, some recover completely while others experience lasting damage to their lungs.

Arteriosclerosis occurs when the blood vessels that carry oxygen and nutrients from your heart to the rest of your body (arteries) become thick and stiff — sometimes restricting blood flow to your organs and tissues. Healthy arteries are flexible and elastic, but over time, the walls in your arteries can harden, a condition commonly called hardening of the arteries.

Atherosclerosis is a specific type of arteriosclerosis, but the terms are sometimes used interchangeably. Atherosclerosis refers to the buildup of fats, cholesterol and other substances in and on your artery walls (plaques), which can restrict blood flow.

These plaques can burst, triggering a blood clot. Although atherosclerosis is often considered a heart problem, it can affect arteries anywhere in your body. Atherosclerosis usually is preventable and is treatable.

An arteriovenous (AV) fistula is an abnormal connection between an artery and a vein. Normally, blood flows from your arteries to your capillaries to your veins. Nutrients and oxygen in your blood travel from your capillaries to tissues in your body.

With an arteriovenous fistula, blood flows directly from an artery into a vein, bypassing some capillaries. When this happens, tissues below the bypassed capillaries receive less blood supply.

Arteriovenous fistulas usually occur in the legs, but can develop anywhere in the body. Arteriovenous fistulas are often surgically created for use in dialysis in people with severe kidney disease.

A large untreated arteriovenous fistula can lead to serious complications. If you've had an arteriovenous fistula created for dialysis, your doctors will monitor you for complications.

Arthritis is inflammation of one or more of your joints. The main symptoms of arthritis are joint pain and stiffness, which typically worsen with age. The most common types of arthritis are osteoarthritis and rheumatoid arthritis.

Osteoarthritis causes cartilage — the hard, slippery tissue that covers the ends of bones where they form a joint — to break down. Rheumatoid arthritis is an autoimmune disorder that first targets the lining of joints (synovium).

Uric acid crystals, infections or underlying disease, such as psoriasis or lupus, can cause other types of arthritis.

Treatments vary depending on the type of arthritis. The main goals of arthritis treatments are to reduce symptoms and improve quality of life.

Asbestosis (as-bes-TOE-sis) is a chronic lung disease caused by inhaling asbestos fibers. Prolonged exposure to these fibers can cause lung tissue scarring and shortness of breath. Asbestosis symptoms can range from mild to severe, and usually don't appear until many years after continued exposure.

Asbestos is a natural mineral product that's resistant to heat and corrosion. It was used extensively in the past in products such as insulation, cement and some floor tiles.

Most people with asbestosis acquired it on the job before the federal government began regulating the use of asbestos and asbestos products in the 1970s. Today, its handling is strictly regulated. Acquiring asbestosis is extremely unlikely if you follow your employer's safety procedures. Treatment focuses on relieving your symptoms.

Ascariasis (as-kuh-RIE-uh-sis) is a type of roundworm infection. These worms are parasites that use your body as a host to mature from larvae or eggs to adult worms and reproduce. Adult worms can be more than a foot (30 centimeters) long.

Ascariasis is one of the most common human worm infections worldwide, although it's uncommon in the United States. Because most people have such mild cases of ascariasis, they have no symptoms. But when your body is infested with hundreds of worms, serious symptoms and complications can occur.

Ascariasis occurs most often in young children and is most prevalent in tropical and subtropical regions of the world — especially in areas where sanitation and hygiene are poor. In the United States, ascariasis is most likely to occur in rural areas of the Southeast.

Aspergillosis is an infection caused by a type of mold. The illnesses resulting from aspergillosis infection usually affect the respiratory system, but their signs and severity vary greatly. The mold that triggers the illnesses, aspergillus, is everywhere, indoors and outdoors. Most strains of this mold are harmless, but a few can cause serious illnesses when people with weakened immune systems, underlying lung disease or asthma inhale their spores.

In some people, the spores trigger an allergic reaction. Other people develop mild to serious lung infections. The most serious form of aspergillosis — invasive aspergillosis — occurs when the infection spreads to blood vessels and beyond.

Depending on the type of aspergillosis, treatment may involve observation, antifungal medications or, in rare cases, surgery.

Asthma is a condition in which your airways narrow and swell and produce extra mucus. This can make breathing difficult and trigger coughing, wheezing and shortness of breath.

For some people, asthma is a minor nuisance. For others, it can be a major problem that interferes with daily activities and may lead to a life-threatening asthma attack.

Asthma can't be cured, but its symptoms can be controlled. Because asthma often changes over time, it's important that you work with your doctor to track your signs and symptoms and adjust treatment as needed.

During an asthma attack, also called an asthma exacerbation, your airways become swollen and inflamed. The muscles around the airways contract, causing your breathing (bronchial) tubes to narrow.

During an asthma attack, you may cough, wheeze and have trouble breathing. An asthma attack may be minor, with symptoms that get better with prompt home treatment, or it may be more serious. A severe asthma attack that doesn't improve with home treatment can become a life-threatening emergency.

The key to stopping an asthma attack is recognizing and treating an asthma flare-up early. Follow the treatment plan you worked out with your doctor ahead of time. This plan should include what to do when your asthma starts getting worse, and how to deal with an asthma attack in progress.

Astigmatism (uh-STIG-muh-tiz-um) is a common, mild and generally easily treatable imperfection in the curvature of your eye. The condition can cause blurred vision.

Astigmatism occurs when the front surface of your eye (cornea) or the lens, inside your eye, has a slightly different surface curvature in one direction from the other. Instead of being even and smooth in all directions, the surface may have some areas that are flatter or steeper.

Astigmatism blurs your vision at all distances. Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it's not pronounced enough to require corrective action. When it is, your treatment options include corrective lenses and surgery.