by Nicole Evans M.D.

Created on: September 10, 2008   Last Updated: March 24, 2010

Up to 50% of people over 85 years old are affected by pseudogout, which can occur in men and women of any ethnicity. Pseudogout is the deposition of calcium pyrophosphate dehydrate (CPPD) crystals in joint spaces. This differs from regular gout which is the deposition of monosodium urate crystals in joint spaces. Pseudogout may also be referred to as pyrophosphate arthropathy.

Causes of Pseudogout:

The exact cause of pseudogout is unknown, but it is thought that changes related to age make the synovial fluid environment inside joints more hospitable to CPPD crystal growth. The deposition of CPPD crystals in the joint spaces can then cause an acute inflammatory reaction.

Signs, Symptoms and Diagnosis of Pseudogout:

Similar to gout, the affected joints are painful, red and swollen. Pseudogout usually involves multiple joints. However, it may initially present in a single joint.  The symptoms and diagnosis of pseudogout differs from gout in the following ways:

-Large joints are affected in pseudogout, such as knees, wrists, hip and shoulder. This is in contrast to gout which tends to occur in small joints, especially the toes.
-Radiographs show calcification in the articular cartilage of joints affected by pseudogout. This is called chondrocalcinosis. The calcification of cartilage does not occur in joints affected by gout.
-The CPPD crystals in aspirated joint fluid are rhomboid in pseudogout, where as gouty crystals are needle or spindle-shaped.
- In pseudogout, aspirated joint fluid displays positive birefringence of crystals under polarized light vs. gouty crystals that have negative birefringence under polarized light.

Treatment of Pseudogout:

NSAIDs such as Indomethacin are used in both gout and pseudogout to alleviate the pain and inflammation. NSAIDs in low doses are also used chronically to help prevent a flare of pseudogout. Another treatment option in pseudogout includes the aspiration of the synovial fluid in affected joints. This usually shortens the duration of the attacks. Additionally, corticosteroids may also be injected directly in the joint to relieve acute inflammation.

Occasionally, high doses of colchicine may be used. Colchicine is a medication commonly used in gout that works by inhibiting the migration of specific white blood cells, called granulocytes.  These granulocytes are responsible for initiating the inflammation in the joints.

The other medications that are highly effective in gout, such as allopurinol, sulfinpyrazone and probenicid, are completely ineffective in pseudogout. These medications inhibit the formation of urate crystals rather than the CPPD crystals of pseudogout. There is currently no therapy available that can actually remove the CPPD crystals.  However, research into the surgical removal of calcifications in joints is underway.

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