Answers to questions about pseudogout.
Q What's the difference between pseudogout and gout?
A Gout occurs when uric acid crystals are deposited into your joints, causing pain. Uric acid is formed when you metabolize substances known as purines, found in your body's tissues and a number of foods.
Like gout, pseudogout is characterized by crystal-like deposits that settle in the joints and cause pain and warmth/redness, but these deposits are composed of a different substance: calcium pyrophosphate dihydrate (CPPD). For this reason, pseudogout is also known as CPPD disease.
Exactly why CPPD crystals form in the joints is unclear. People who've suffered an injury to a joint, have an underactive thyroid (hypothyroidism), overactive parathyroid gland (hyperparathyroidism), too much iron in their body, or low magnesium are at increased risk of pseudogout. Pseudogout also is more common among older adults. Whereas gout typically affects the joint of the big toe first, pseudogout commonly occurs in the knees and wrists, but it also can affect the fingers, toes, ankles, hips, elbows, and shoulders.
The drug allopurinol can treat the cause of gout (high uric acid levels), but no such medication is available to reduce CPPD. Pseudogout attacks usually are treated with anti-inflammatory medications, including colchicine and nonsteroidal anti-inflammatory drugs.
Richard S. Lang,
M.D., M.PH., EA.C.P.