Merck Manual

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


N. Lawrence Edwards

, MD, Department of Medicine, University of Florida College of Medicine

Last full review/revision May 2018| Content last modified May 2018
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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 crystal deposition disease

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).

Calcium oxalate crystal deposition disease

Calcium oxalate crystals rarely accumulate and form deposits. They occur most often in people with chronic kidney disease 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. 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).


  • Nonsteroidal anti-inflammatory drugs

  • Colchicine taken by mouth

  • A corticosteroid injection into the joint

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.

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