Histopathological characterization of melorheostosis

Melorheostotic bone was examined histopathologically. In the severely affec ted areas, an abundance of osteoid and increased angiogenesis was observed. Increased osteoid without mineralization indicated the overproduction of b one matrix. Bone resorption also appeared to increase because osteoclasts w ere numerous in melorheostotic bone, thus suggesting a high rate of bone tu rnover. In addition, transforming growth factor-beta was immunolocalized in the periosteal fibroblasts, mesenchymal cells surrounding vessels, endothe lial cells, and osteoblasts, while basic fibroblast growth factor was found in endothelial cells and mast cells near vessels. These cytokines may have some association with the exuberant bone matrix production and angiogenesi s in melorheostosis.