Pseudogout is a joint disease that can cause attacks of arthritis. Like gout, the condition involves the formation of crystals in the joints. But in pseudogout, the crystals are formed from a salt instead of uric acid.

Pseudogout is caused by the collection of salt called calcium pyrophosphate dihydrate (CPPD). The build up of this salt forms crystals in the joints. This leads to attacks of joint swelling and pain in the knees, wrists, ankles, and other joints.

Among older adults, pseudogout is a common cause of sudden (acute) arthritis in one joint.

Pseudogout mainly affects the elderly. However, it can sometimes affect younger patients who have conditions such as acromegaly, ochronosis, thyroid disease, hemochromatosis, Wilson disease, and parathyroid disease, which are known to increase risk.

Pseudogout can initially be misdiagnosed as gouty arthritis (gout), rheumatoid arthritis, or osteoarthritis because the symptoms are similar.

• Attacks of joint pain and fluid accumulation in the joint, leading to joint swelling
• No symptoms between attacks
• Chronic (long-term) arthritis

• An examination of joint fluid would show white blood cells and calcium pyrophosphate crystals.
• Joint x-rays may show joint damage, calcification of cartilage, and calcium deposits in joint spaces.

Careful workup, with analysis of crystals found in joints, should ultimately lead to the correct diagnosis. Fortunately, because most conditions involving joint pain are treated by the same medicines (such as steroids and nonsteroidal anti-inflammatory drugs), early misdiagnosis does not necessarily result in inappropriate treatment.