SPP1 and periodontal disorder: Our histological analysis revealed altered tooth attachment in the Hyp mice, consistent with previous observations in mice9 and humans.6 This deficiency of the periodontium may explain the higher susceptibility to periodontal disease of adult patients with XLH.6,39 Here, both FGF23-mAb doses partially rescued the Hyp PDL attachment, with improved acellular cementum continuity associated with the restoration of BSP and OPN markers expression, leading to PDL fibers insertion to connect the alveolar bone and the tooth root.