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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• What is hydroxyapatite?
• What are hydroxyapatite crystals?
• Is hydroxyapatite crystal disease the same as gout or pseudogout?
• How are hydroxyapatite crystals identified?
• How is hydroxyapatite crystal disease treated?
• Hydroxyapatite Crystal Disease At A Glance
• Hydroxyapatite Index

Hydroxyapatite molecules can group together (crystallize) to form microscopic clumps, called hydroxyapatite crystals.

Tiny crystals of hydroxyapatite sometimes form in or around joints and can cause inflammation of joints and tissues around the joints, such as tendons and ligaments. They have been described particularly as a cause of rotator cuff inflammation of the shoulder.

The inflammation caused by hydroxyapatite crystals has been referred to as hydroxyapatite crystal disease.

No. These conditions are similar in that they are all caused by the inflammation that results from the body's reaction to crystals. However, hydroxyapatite crystals are distinctly different from the crystals of pseudogout or gout. While hydroxyapatite crystals can sometimes also be found in the company of the calcium pyrophosphate crystals characteristic of pseudogout, these are quite different types of crystals.

Sometimes, hydroxyapatite crystals can be seen clumped in the fluid of a joint that has developed arthritis. The crystals are usually so small as to be invisible under a regular microscope and thus require a special (electron) microscope for identification.

The treatment of the inflammation caused by hydroxyapatite crystals includes rest, cold application, and medications to reduce inflammation. Cortisone-related medications injected into inflamed tissues can also sometimes help decrease inflammation and thereby relieve pain.

• Hydroxyapatite is an essential mineral of normal bone.
• Crystals of hydroxyapatite deposited in and about the joints cause inflammation.
• Inflammation and pain are part of hydroxyapatite crystal disease.
• This disease is distinct and different from gout and pseudogout.
• Treatment includes measures to reduce inflammation and pain.