Gout is a painful condition that occurs when the bodily waste product uric acid is deposited as needle-like crystals in the joints and/or soft tissues. In the joints, these uric acid crystals cause inflammatory arthritis, which in turn leads to intermittent swelling, redness, heat, pain, and stiffness in the joints.
In many people, gout initially affects the joints of the big toe. But many other joints and areas around the joints can be affected in addition to or instead of the big toe. These include the insteps, ankles, heels, knees, wrists, fingers, and elbows. Chalky deposits of uric acid, also known as tophi, can appear as lumps under the skin that surrounds the joints and covers the rim of the ear. Uric acid crystals can also collect in the kidneys and cause kidney stones.
What Is Uric Acid?
Uric acid is a substance that results from the breakdown of purines. A normal part of all human tissue, purines 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 there is an increase in the 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 it is not dangerous. However, if excess uric acid crystals form as a result of hyperuricemia, gout can develop. The crystals form and accumulate in the joint, causing inflammation.
When It’s Not Gout, It May Be Pseudogout
Gout is sometimes confused with other forms of arthritis because the symptoms—acute and episodic attacks of joint warmth, pain, swelling, and stiffness—can be similar. One form of arthritis often confused with gout is called pseudogout or calcium pyrophosphate deposition (CPPD). The pain, swelling, and redness of pseudogout can also come on suddenly and may be severe, closely resembling the symptoms of gout. However, the crystals that irritate the joint are calcium phosphate crystals, not uric acid. Therefore, pseudogout is treated somewhat differently and is not reviewed in this publication.
Who Is Likely to Develop Gout?
Scientists estimate that 6 million adults age 20 and older report having had gout at some time in their lives.1 It is rare in children and young adults. 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.
Corticosteroids. Powerful anti-inflammatory hormones made naturally in the body or man-made for use as medicine. Injections of corticosteroid drugs are sometimes used to treat inflammation in the shoulder, knee, and other joints.
Diuretics. A type of medication that promotes the formation and output of urine. Diuretics are prescribed to treat the accumulation of excess fluid in bodily tissues that can result from diseases of the kidneys, liver, lungs, or heart. They may also be used to treat high blood pressure or glaucoma, a condition in which pressure builds up inside the eye.
Hemolytic anemia. A form of anemia (deficiency of red blood cells) caused by the destruction of the cells rather than the body’s inability to produce them in adequate numbers.
Hyperuricemia. The presence of elevated levels of uric acid in the blood.
Hypothyroidism. A condition in which the thyroid gland (the gland that makes and stores hormones that regulate heart rate, blood pressure, body temperature, and the rate at which food is converted to energy) is underactive. Without treatment, this condition can result in fatigue, weight gain, other serious medical problems, and even death.
NSAIDs. A class of medications, available over the counter or with a prescription, that ease pain and inflammation.
Podagra. Gout in the big toe.
Pseudogout. A condition often mistaken for gout that results from the deposit of calcium phosphate crystals (not uric acid crystals as in gout) in the joints and other tissues. This condition is also called chondrocalcinosis.
Psoriasis. An autoimmune disease characterized by a red scaly rash that is often located over the surfaces of the elbows, knees, and scalp, and around or in the ears, navel, genitals, or buttocks. Approximately 10 to 15 percent of people with psoriasis develop an associated arthritis referred to as psoriatic arthritis.
Purines. Found in the DNA and RNA within the nuclei of cells, purines are part of all human tissue and are found in many foods, especially those high in protein.
Synovial fluid. The slippery fluid produced by the synovium (joint lining) to lubricate the joints.
Tophi. Nodular masses of uric acid crystals that sometimes form in the soft tissue of people with chronic gout. Although tophi are most common around the fingers, elbows, and big toe, they can occur in virtually any part of the body. (The singular is tophus.)
Uric acid. A substance that results from the breakdown of purines, which are part of all human tissue and are found in many foods.
1According to the National Arthritis Data Workgroup, this estimate is based on self-reports, which may produce an overestimation of prevalence, as cited in Helmick CG, Felson DT, Lawrence RC, Gabriel S, Hirsch R, Kwoh CK, et al.; National Arthritis Data Workgroup. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part 1. Arthritis and Rheumatism 2008;1:15-25.
Reference: National Institute of Arthritis and Musculoskeletal and Skin Diseases
Last updated September 15, 2016
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