Which crystals cause pseudogout?

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joint disease A 65-year-old man with advanced rheumatoid arthritis.

Pseudogout is caused by the deposition of rhomboid-shaped calcium pyrophosphate crystals, a condition known as calcium pyrophosphate deposition (CPPD) disease.1

While the symptoms of pseudogout closely resemble those of gout, the two conditions are distinct in their underlying pathology. Gout is caused by the accumulation of needle-shaped monosodium urate crystals, whereas pseudogout involves the buildup of calcium pyrophosphate in the joint space. The presence of these crystals triggers joint inflammation, pain, and destruction.1

Factors that may lead to the excess levels of pyrophosphate associated with pseudogout include cellular injury—often resulting from trauma, surgery, or severe illness—as well as a deficiency in the enzyme alkaline phosphatase. Additionally, other medical conditions such as hyperparathyroidism, hypothyroidism, hemochromatosis, and Wilson disease are associated with the development of synovial CPPD.1