Animated Medical Graphics


Cell Gout is a disorder that results when a person's body does not correctly handle a substance known as uric acid. Uric acid is produced from the chemical breakdown of nucleoproteins such as DNA (the substance that holds the genetic code). This chemical process is natural and normal and takes place in everyone. The nucleoproteins that are broken down come from food and from the human body itself. Although all the foods that we eat contain the DNA of whichever plants or animals they come from, our bodies cannot use this foreign genetic material. Therefore, our bodily systems digest and break down the DNA into simpler molecules, one of which is called purine. Purine also results from the natural death and breakdown of our own cells, a process that occurs throughout our lives. A picture of an average cell is shown on the right; DNA is mostly found in the nucleus and RNA is found in the nucleus and cytoplasm. The purine thus derived is either recycled into new DNA and RNA or is further broken down into uric acid by the liver and intestine.

Ordinarily, uric acid circulates in the bloodstream and is excreted by the kidneys into the urine (actually, uric acid goes through a more complex series of steps, but this simplified account will suffice for understanding what happens in gout). Gout occurs when uric acid is deposited in the tissues instead of remaining in circulation or being excreted. This may happen if there is a genetic prediliction for either underexcreting (or occasionally overproducing) uric acid leading to an increase in the blood level of uric acid, a state known as hyperuricemia. Some factors favoring hyperuricemia include renal failure, obesity, atherosclerosis, diabetes, foods like meat and legumes (peas and beans), and alcohol. Gout occurs almost exclusively in men, usually starting when they are 40 to 50 years of age.

Gout in great toe Uric acid crystals

Uric acid in gout is deposited as crystals usually in and around joints, starting in one joint and then spreading to other joints. One of the most commonly affected joints is in the great toe (see left, where the bones and joints inside the toe have been exposed). The uric acid deposits are called tophi and have the appearance and consistency of dried, white toothpaste. In the animation on the left the crystals are seen to gradually cover the joint between the second and third bones. An acute attack of gout occurs when the tophi induce an inflammatory response which results in pain, swelling, and redness. A laboratory test useful in diagnosing gout is examination of joint fluid by polarized microscopy (see right): uric acid crystals appear as bright yellow needle-like structures when aligned parallel to the polarized filter's axis.

Note: The material provided in this web page is educational in nature and not medical advice. It is meant neither for self-diagnosis nor as a treatment recommendation. If you are concerned about any condition you think you may have, CONSULT YOUR DOCTOR.