[Osteoarthritis with rice bodies rich in calcium microcrystals. 4 cases with ultrastructural study].

Rice bodies are often found in inflammatory joint fluid specimens, especially from rheumatoid arthritis patients, but have rarely been reported in osteoarthritis. We found rice bodies in knee joint fluid specimens from four of 88 patients with osteoarthritis. There were three males and one female. Age ranged from 61 to 86 years. Three patients had slowly progressive knee osteoarthritis and one had rapidly destructive disease. Abundant, recurrent effusions occurred in all four patients despite one to five local corticosteroid injections per patient and radiation synovectomy in two patients. The joint fluid specimens contained 120 to 320 cells/mm3 and large numbers of rice bodies that stained with alizarin red S. Transmission electron microscopy studies showed that the rice bodies were composed of fibrin and contained numerous intra- and extra-cellular calcium crystals composed of apatite alone in two cases and of a combination of apatite and calcium pyrophosphate dihydrate in the two others. Collagen fibers and fragments of bone and cartilage were present in a few rice bodies. Phagocytic cells, type C synoviocytes, chondrocytes and a few inflammatory cells were also seen. These rice bodies composed mainly of fibrin and apatite may have played a role in the pathogenesis of the recurrent joint effusions in our patients.