A light and ultrastructural study of rice bodies recovered from a case of date thorn-induced extra-articular synovitis.

Rice bodies are most commonly found in inflammatory joints of patients with rheumatoid arthritis and have traditionally been considered to be a nonspecific response to inflammatory synovial disease. In the present study 18 rice bodies were found in the tibialis tendon sheath of a nine-year-old Omani boy subsequent to a date thorn injury. The rice bodies consisted of three major components: fibrin, collagen, and fibroblasts. In contrast to the findings of other authors there were no type A, B, or C synoviocytes, cartilage, or vascularisation of the rice body. At this extra-articulate site it would appear that rice bodies are composed chiefly of fibrin and that the fibrosis of the rice body occurs as a result of the entrapment of fibroblasts, which subsequently produce collagen. These findings shed doubt on the synovial origin of rice bodies and suggest that rice bodies may have multiple origins, depending on their location. This is the first ultrastructural study of rice bodies associated with a date thorn injury.