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), calcium pyrophosphate arthritis (previously called 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.
Milwaukee shoulder syndrome, which is a destructive disorder that mostly affects the shoulders and often the knees in older women, is one example.
Acute pseudopodagra is another joint disorder caused by basic calcium phosphate crystals and can mimic gout. It affects the joints of the big toe and occurs in young women (less often young men).
To check for these crystals, doctors take x-rays. Basic calcium crystals are sometimes visible on x-rays around the joints, and not usually in the joint cartilage.
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, usually can be seen only with a special stain or a special type of microscope (a transmission electron microscope).
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.