This pathologic change could be caused by both the intrinsic osteoblast defect owing to a loss of DMP1 and an indirect role of hypophosphatemia on Dmp1 null osteoblasts because restoration of Pi by injections of Fgf23Ab greatly improves osteoclast numbers and bone remodeling (Fig. 6E). The gene discussed is DMP1; the disease is hypophosphatemia.