Pseudogout results from the abnormal formation of calcium pyrophosphate (CPP) crystals in the cartilage (cushioning material between the bones), which is later followed by the release of crystals into the joint fluid. When CPP crystals are released into the joint, they can cause a sudden attack of arthritis, similar to gout.
The cause of abnormal deposits of CPP crystals in cartilage is unknown. They may form due to abnormal cells in the cartilage, or they may be produced as the result of another disease that damages cartilage. CPP crystals may be released from cartilage during a sudden illness, joint injury, or surgery. The abnormal formation of CPP crystals also may be a hereditary trait.
Like gout, pseudogout occurs more frequently in people over age 60. People who have a thyroid condition, kidney failure, or disorders that affect calcium, phosphate, or iron metabolism are at increased risk for pseudogout.