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Basic Calcium Phosphate Crystal Deposition Disease and Calcium Oxalate Crystal Deposition Disease

By Lawrence M. Ryan, MD, Professor of Medicine, Medical College of Wisconsin

Basic calcium phosphate and calcium oxalate are chemical compounds that occur naturally in the body. These compounds can form crystals that cause joint symptoms similar to those of gout (including podagra), pseudogout, or sometimes other joint disorders. Basic calcium phosphate crystals and calcium oxalate crystals can also form in tendons and connective tissues.

Basic calcium phosphate crystals can destroy joints and cause severe inflammation in and around the joint. For example, they can cause Milwaukee shoulder syndrome, causing severe destruction affecting the shoulder joint, a disorder that affects mostly older women.

Calcium oxalate crystals rarely accumulate and form deposits. They occur most often in people who are being treated with dialysis (an artificial process for removing waste products and excess fluids from the body) because levels of waste products in the blood are too high.


  • X-rays

  • Microscopic examination of joint fluid

To check for these crystals, doctors take x-rays. The crystals are sometimes visible on x-rays. Basic calcium phosphate crystals, calcium oxalate crystals, and calcium pyrophosphate crystals may look the same on x-rays, but almost all such crystals that are visible on x-rays are calcium pyrophosphate crystals.

Doctors may also need to use a needle to withdraw joint fluid (joint aspiration) and test it for these crystals. Calcium oxalate crystals are visible under a microscope with polarized light, but basic calcium phosphate crystals, which are much smaller, can be seen only with a special type of microscope (a transmission electron microscope).


  • Nonsteroidal anti-inflammatory drugs

  • Colchicine taken by mouth

  • A corticosteroid injection

These disorders are usually treated similarly to gout, with nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine taken by mouth, or a corticosteroid injection into the joint (see Table: Drugs Used to Treat Gout). There is no way to completely rid the body of these crystals.