Pseudogout (CPPD)

What is pseudogout?

Pseudogout is a form of arthritis triggered by deposits of calcium crystals (calcium pyrophosphate dihydrate) in the joints. It is also called calcium pyrophosphate deposition disease (CPPD). This disease can cause short-term or long-term swelling in joints, most often the knee, wrist, shoulder, ankle, or elbow.

As the name suggests, this condition can appear similar to gout, which is caused by another type of crystal — uric acid crystals — and commonly causes sudden pain and swelling in a single joint, usually in the foot. Pseudogout also can resemble osteoarthritis or rheumatoid arthritis.

Pseudogout is most common in the elderly. It affects about 3% of people in their 60s and as many as half of people in their 90s. Many people who get pseudogout already have joint damage from other conditions, or they may have age-related degenerative joint disease. One theory is that an injury to cartilage allows calcium crystals to be released into the joint space, and these crystals cause inflammation.

In some cases, other medical conditions can make people more likely to develop pseudogout. These include:

• a genetic disorder of iron overload (hemochromatosis)
• high blood levels of calcium (hypercalcemia)
• too little magnesium (hypomagnesemia) in the blood.

Pseudogout also can be triggered by joint injury, such as joint surgery or a sprain, or the stress of a medical illness. Frequently, however, nothing can be identified that might have triggered the disease. Although age-related joint degeneration, prior joint damage or trauma, and these other medical conditions increase the likelihood of an attack of pseudogout, the reason some people develop this condition while others do not is often unknown.

Symptoms of pseudogout

The most common symptoms are pain, swelling, and stiffness around a single joint, especially the knee or wrist. Occasionally, more than one joint is affected at the same time. A low-grade fever may occur during the flare.

Diagnosing pseudogout

Diagnosing pseudogout can be tricky because it can resemble gout, an infection, or other causes of joint inflammation. Also, pseudogout is commonly associated with other joint problems.

X-rays may reveal calcium deposits along the affected joints, although x-rays of many healthy elderly people often show such deposits even when the person has no symptoms of pseudogout. Your doctor may recommend that joint fluid be removed from an inflamed joint. The sample will be tested for the presence of calcium pyrophosphate crystals. The sample may also need to be tested for an infection or other cause of joint inflammation.

Your doctor may want to request tests for conditions that can trigger pseudogout. These may include tests of iron, calcium, magnesium and thyroid function.

Expected duration of pseudogout

Attacks of pseudogout can last for days or weeks. If the condition is not diagnosed and treated, it can cause the joint to degenerate (break down).

Preventing pseudogout

Treatment of a condition that increases the risk of pseudogout (such as hemochromatosis) may prevent development of the disease or repeated attacks. However, when there is no known cause or trigger, there is no way to prevent the development of pseudogout. For people with frequent attacks, taking a nonsteroidal anti-inflammatory drug (NSAID) or colchicine daily may prevent future attacks.

Treating pseudogout

Fluid can be removed from the joint to ease the pressure. In this procedure, called joint aspiration, a needle is inserted into the joint after the area is numbed, to withdraw fluid. Treatment usually also includes NSAIDs or injections of a medication called a glucocorticoid to keep the swelling down. These two treatments usually eliminate symptoms within hours to a few days.

You may also need to take oral corticosteroids for a short time. Your doctor may prescribe a medicine called colchicine or an NSAID to prevent attacks. For people with frequent attacks or chronic joint inflammation due to pseudogout despite treatments mentioned, other medications to reduce inflammation may be recommended such as hydroxychloroquine or methotrexate. If other treatments aren't effective, newer medications such as anakinra or tocilizumab may be recommended.

Occasionally, people with recurrent or chronic pseudogout may develop degenerative joint disease. In this case, surgery (such as joint replacement) may become the only effective treatment.

When to call a professional

If you experience significant joint pain, especially if the joint is swollen, contact your doctor.

Prognosis

With treatment, the outlook for pseudogout is usually good. Joint pain and swelling usually go away promptly. It's common for attacks to return, but usually they can be controlled with repeated treatment.

Additional info

American College of Rheumatology
http://www.rheumatology.org

Arthritis Foundation
http://www.arthritis.org

National Institute of Arthritis and Musculoskeletal and Skin Diseases
http://www.niams.nih.gov