Gout is one of the most painful forms of arthritis. It usually develops when there are chronically high levels of uric acid in the blood. Uric acid is the waste product formed from the breakdown of purines. Purines are substances found in all of the body's tissues as well as in many foods, such as organ meats and seafood.

The uric acid can form into sharp, needle-like crystals that accumulate in the body’s connective tissues, particularly in the joint space between the bones. These deposits of uric acid crystals (called monosodium urate crystals or MSU) produce swelling, redness, heat, pain and stiffness in the joints. The joints are the most commonly affected part of the body, but crystals can also form beneath the skin (called tophi) and in the kidneys (kidney stones) or other parts of the urinary system.

Uric acid normally dissolves in the blood and passes through the kidneys before being eliminated in the urine. People with gout either produce excessive levels of uric acid or their kidneys have a problem eliminating it. This condition is called hyperuricemia and occurs when uric acid reaches or exceeds 7 milligrams/deciliter in the blood. Not all people with hyperuricemia develop gout, and some patients who do develop gout have normal blood levels of uric acid. The reason for this is not thoroughly understood.

Elevated levels of uric acid also increase the risk of fatal heart disease, according to long-term research using data from the National Health and Nutrition Examination Survey (NHANES).

Gout can be primary or secondary. Primary gout occurs on its own and is due to the body’s overproduction of purines in the liver or an inherent inability to eliminate purines in the urine. Primary gout is uncommon.

Secondary gout, which is much more common, is due to an underlying medical condition or the therapy to treat a medical condition. For instance, diuretics (medications used to treat high blood pressure and other conditions) help flush water from the body. These medications can retain uric acid, thus causing levels of uric acid to rise.

Gout is sometimes confused with another form of arthritis called pseudogout because it produces similar symptoms of inflammation and swelling. However, in the latter condition, deposits are made up of calcium phosphate crystals rather than uric acid.

Up to 3 million Americans have gout, according to the American College of Rheumatology. Gout is rare in children and young adults. It is more prevalent in men than women.

Gout is highly treatable. If left untreated, however, it can erode the joints and bones and cause disfigurement. In addition, patients with gout have an increased risk for developing kidney stones because uric acid crystals can also collect in the urinary tract and kidneys, which can impair kidney function.

If gout is properly diagnosed and treated early, most patients experience relief from their symptoms. Patients are advised to seek medical treatment with a rheumatologist because these physicians specialize in the management of gout and other forms of arthritis.