A histologic and immunohistochemical study of calcium pyrophosphate dihydrate crystal deposition disease.

The articular cartilage, synovial membrane, and meniscus from ten patients who had calcium pyrophosphate dihydrate (CPPD) crystal deposition disease showed strong immunoreactivity for dermatan sulfate proteoglycan, Type I collagen, and S-100 protein in hypertrophic chondrocytes around the crystals, their pericellular matrix, and deposits of the crystals. Electron microscopy revealed that small crystals were formed around the hypertrophic chondrocytes, especially in the degenerated matrix containing electron-dense granular materials and cellular debris. Chondrocytes of this kind were never observed in the articular tissue from ten patients who had osteoarthrosis. These hypertrophic chondrocytes with several unique immunohistochemical characteristics may initiate the formation of CPPD crystals.