In addition, chronically high levels of PTH have been associated with fibrous dysplasia in humans, a disorder where normal bone and bone marrow are replaced by fibrous tissue.32,33 Interestingly, immunohistochemical analysis revealed that this human phenotype resembles the fibroblast-loaded bone phenotype observed in Vdr−/− mice on normal diet and VdrΔAF2 mice on both normal and rescue diets. This evidence concerns the gene PTH and fibrous dysplasia.