Gout - Introduction

Highlights	Complications	Medications
Introduction	Risk Factors	Lifestyle Changes
Causes	Diagnosis	Resources
Symptoms	Treatment	References

Introduction

Gout is an arthritic condition that causes inflammation of the joints. It mostly affects men over 40 and is usually associated with chronic hyperuricemia, a long-lasting abnormally high concentration of uric acid in the blood.

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The ProcessesLeading toHyperuricemia and Gout

Metabolism of Purines. The process leading to hyperuricemia and gout begins with the metabolism of purines, nitrogen-containing compounds that are important for energy. Purines can be divided into two types:

Endogenous purines are manufactured within human cells.
Exogenous purines are obtained from foods.

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All mammals except humans possess an enzyme called uricase that breaks purines down so they can be dissolved and eliminated easily from the body. In humans, however, purine breaks down into uric acid, which is not as easily eliminated and can build up in body tissues.

Uric Acid and Hyperuricemia. The path leading to high concentrations of uric acid and gout is the following:

Uric acid is produced from purines in the liver. It then enters the bloodstream. Most uric acid then eventually passes through the kidneys and is excreted in the urine. The rest is disposed of in the intestines, where it is processed and broken down by bacteria.
Normally these processes keep the concentration of uric acid in the blood plasma (the liquid part of the blood) at a healthy level, which is below 6.8 mg/dL.
Under certain circumstances, however, the body produces too much uric acid or excretes too little. In either case, concentrations of uric acid increase in the blood. This condition is known as hyperuricemia.
If concentrations of uric acid reach 7 mg/dL and above, the blood becomes supersaturated. Needlelike crystals of a salt called monosodium urate (MSU) form.
In time, as MSU crystals accumulate in the joints, they cause inflammation and pain, the characteristic symptoms of gout.

Gout and Other Conditions Associated with Hyperuricemia

High levels of uric acid are associated not only with gout, but also with a number of other conditions. They can occur independently, but may also develop one after the other if gout is untreated.

Acute Gouty Arthritis. Acute gouty arthritis is the stage at which the first symptoms of gout appear. It most often occurs in men.

Chronic Tophaceous Gout and Tophi. After several years, persistent gout can develop into a conditioncalled chronic tophaceous gout. This long-term condition often produces tophi, which are solid deposits of MSU crystals that form in the joints, cartilage, bones, and elsewhere in the body. In some cases, tophi break through the skin and appear as white or yellowish-white, chalky nodules that have been described as looking like crab eyes.