Uric acid is a substance that results from the breakdown of purines, which are part of all human tissue and are found in many foods. Normally, uric acid is dissolved in the blood and passed through the kidneys into the urine, where it is eliminated. If the body increases its production of uric acid or if the kidneys do not eliminate enough uric acid from the body, levels of it build up in the blood (a condition called hyperuricemia). Hyperuricemia also may result when a person eats too many high-purine foods, such as liver, dried beans and peas, anchovies, and gravies. Hyperuricemia is not a disease and by itself is not dangerous. However, if excess uric acid crystals form as a result of hyperuricemia, gout can develop. The excess crystals build up in the joint spaces, causing inflammation. Deposits of uric acid, called tophi (singular: tophus), can appear as lumps under the skin around the joints and at the rim of the ear. In addition, uric acid crystals can collect in the kidneys and cause kidney stones.

For many people, gout initially affects the joints in the big toe. Sometime during the course of the disease, gout will affect the big toe in about 75 percent of patients. It also can affect the instep, ankles, heels, knees, wrists, fingers, and elbows. The disease can progress through four stages:

• Asymptomatic (without symptoms) hyperuricemia--In this stage, a person has elevated levels of uric acid in the blood but no other symptoms. A person in this stage does not usually require treatment.
• Acute gout, or acute gouty arthritis--In this stage, hyperuricemia has caused the deposit of uric acid crystals in joint spaces. This leads to a sudden onset of intense pain and swelling in the joints, which also may be warm and very tender. An acute attack commonly occurs at night and can be triggered by stressful events, alcohol or drugs, or the presence of another illness. Early attacks usually subside within 3 to 10 days, even without treatment, and the next attack may not occur for months or even years. Over time, however, attacks can last longer and occur more frequently.
• Interval or intercritical gout--This is the period between acute attacks. In this stage, a person does not have any symptoms and has normal joint function.
• Chronic tophaceous gout--This is the most disabling stage of gout and usually develops over a long period, such as 10 years. In this stage, the disease has caused permanent damage to the affected joints and sometimes to the kidneys. With proper treatment, most people with gout do not progress to this advanced stage.

What Causes Gout?

A number of risk factors are related to the development of hyperuricemia and gout:

• Genetics may play a role in determining a person's risk, since up to 18 percent of people with gout have a family history of the disease.
• Gender and age are related to the risk of developing gout; it is more common in men than in women and more common in adults than in children.
• Being overweight increases the risk of developing hyperuricemia and gout because there is more tissue available for turnover or breakdown, which leads to excess uric acid production.
• Drinking too much alcohol can lead to hyperuricemia because it interferes with the removal of uric acid from the body.
• Eating too many foods rich in purines can cause or aggravate gout in some people.
• An enzyme defect that interferes with the way the body breaks down purines causes gout in a small number of people, many of whom have a family history of gout.
• Exposure to lead in the environment can cause gout.

Some people who take certain medicines or have certain conditions are at risk for having high levels of uric acid in their body fluids. For example, the following types of medicines can lead to hyperuricemia because they reduce the body's ability to remove uric acid:

• Diuretics, which are taken to eliminate excess fluid from the body in conditions like hypertension, edema, and heart disease, and which decrease the amount of uric acid passed in the urine;
• Salicylates, or anti-inflammatory medicines made from salicylic acid, such as aspirin;
• The vitamin niacin, also called nicotinic acid;
• Cyclosporine, a medicine used to suppress the body's immune system (the system that protects the body from infection and disease) and control the body's rejection of transplanted organs; and
• Levodopa, a medicine used to support communication along nerve pathways in the treatment of Parkinson's disease.

Who Is Likely To Develop Gout?

Gout occurs in approximately 840 out of every 100,000 people. It is rare in children and young adults. Adult men, particularly those between the ages of 40 and 50, are more likely to develop gout than women, who rarely develop the disorder before menopause. People who have had an organ transplant are more susceptible to gout.

Where Can People Find More Information About Gout?

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
National Institutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
Phone: 301-495-4484 or 877-22-NIAMS (226-4267) (free of charge)
TTY: 301-565-2966
Fax: 301-718-6366
E-mail: NIAMSInfo@mail.nih.gov
www.niams.nih.gov

NIAMS provides information about various forms of arthritis and rheumatic diseases and bone, muscle, joint, and skin diseases. It distributes patient and professional education materials and also refers people to other sources of information. Additional information and updates can be found on the NIAMS Web site.

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the National Institutes of Health (NIH), is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases, the training of basic and clinical scientists to carry out this research, and the dissemination of information on research progress in these diseases. The National Institute of Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse is a public service sponsored by the NIAMS that provides health information and information sources. Additional information can be found on the NIAMS Web site at www.niams.nih.gov.

This booklet is not copyrighted. Readers are encouraged to duplicate and distribute as many copies as needed.

Additional copies of this booklet are available from

National Institute of Arthritis and Musculoskeletal
and Skin Diseases
NIAMS/National Institutes of Health (NIH)
1 AMS Circle
Bethesda, MD 20892-3675

NIH Publication No. 02-5027

http://www.niams.nih.gov/hi/topics/gout/gout.htm