EXTENDED REPORT

Calcium apatite crystals in synovial fluid rice bodies

J Li-Yu¹, G M Clayburne², M S Sieck², S E Walker³, B H Athreya⁴, R J DeHoratius⁵, H R Schumacher, Jr²

¹ Section of Rheumatology and Clinical Immunology, Santo Tomas University Hospital, España, Manila, Philippines
² Division of Rheumatology, VA Medical Center and Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
³ Division of Rheumatology, Harry Truman Memorial Veterans Affairs Hospital, Colombia, Missouri, USA
⁴ Pediatric Rheumatology, DuPont Hospital for Children, Wilmington, Delaware, USA
⁵ Division of Rheumatology, Jefferson Medical College, Philadelphia, Pennsylvania, USA

Correspondence to:
Correspondence to:
Dr H R Schumacher Jr, Rheumatology 151K, VA Medical Center, University and Woodland Ave, Philadelphia, PA 19104, USA;
schumacr{at}mail.med.upenn.edu

Background: Rice bodies can occur in the joints in many rheumatic conditions, but they are most common in rheumatoid arthritis. They are generally believed to occur rarely in patients with osteoarthritis, but one study reported rice bodies with apatite crystals.

Objective: To report on a series of joint fluids with rice bodies containing apatite clumps and examine their clinical pictures.

Methods: All synovial fluid analysis reports for 10 years were reviewed for rice bodies and eight patients were reported on. A series of patients with a variety of diseases with synovial fluid rice bodies found to contain calcific material is described. All were examined by compensated polarised light and alizarin red stain, and four were examined by electron microscopy.

Results: The eight patients all had alizarin red S chunks embedded throughout the rice body. Transmission electron microscopy disclosed the presence of a matrix of collagen, fibrin, and amorphous materials containing typical apatite crystals. Clinical diagnoses, radiographic findings, and leucocyte counts varied, but six of the eight patients had had previous repeated corticosteroid injections into the joints.

Conclusion: Aggregates of apatites may be more common than previously recognised in rice bodies as they are not routinely sought. Whether they are a result of joint damage or depot steroid injections and whether that might contribute to further joint injury now needs to be investigated.

Keywords: calcium apatite; synovial fluid; rice bodies

Abbreviations: CPPD, calcium pyrophosphate dihydrate; OA, osteoarthritis; RA, rheumatoid arthritis; SF, synovial fluid

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This article has been cited by other articles:

• Sommer, O. J., Kladosek, A., Weiler, V., Czembirek, H., Boeck, M., Stiskal, M. (2005). Rheumatoid Arthritis: A Practical Guide to State-of-the-Art Imaging, Image Interpretation, and Clinical Implications. RadioGraphics 25: 381-398 [Abstract] [Full Text]  
• Mohr, W (2003). On the origin of rice bodies with apatite crystals. Ann Rheum Dis 62: 910-911 [Full Text]