Gout and pseudogout: different disorders

ON CALL

April 27, 1993|By Dr. Simeon Margolis | Dr. Simeon Margolis,Contributing Writer

Last week I developed a painful swollen knee and went to my doctor, who did some tests and said I had pseudogout. What is the difference between gout and pseudogout?

In both pseudogout and gout, the accumulation of crystals within a joint produces an acute inflammation and arthritis. The two disorders, however, differ in a number of important ways. The crystals in gout are composed of sodium urate and are associated with elevated levels of uric acid in the blood. In seudogout the crystals are made up of calcium pyrophosphate, and blood uric acid levels are usually normal. Pseudogout is often first suspected when X-rays demonstrate calcification in cartilage (chondrocalcinosis) of the affected joint.

Pseudogout brings attacks of acute arthritis, generally involving large joints like the knees and wrists, which occur most often in people over the age of 60. The disorder affects only joints, whereas gout may be complicated by uric acid kidney stones and chronic kidney failure. Pseudogout is frequently associated with some underlying metabolic abnormality such as diabetes mellitus, hypothyroidism, hyperparathyroidism, excessive tissue deposits of iron (hemochromatosis) or copper (Wilson's disease), and even true gout.

No known medication can prevent pseudogout. By contrast, attacks of arthritis in gout may be prevented by lowering the blood levels of uric acid.

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.

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