OBJECTIVE: X-linked hypophosphatemia (XLH) is a rare genetic disease that disturbs bone and teeth mineralization. It also affects craniofacial growth and patients with XLH often require orthodontic treatment. The aim of this study was to describe changes in the dental health of XLH children during orthodontic treatment compared with those in matched controls undergoing similar orthodontic procedures.
METHODS: For this retrospective case-control study, we included all individuals less than 16 years old diagnosed with XLH, orthodontically treated in our centre from 2016 to 2022 and pair-matched them to patients with no chronic or genetic conditions. Clinical and radiological parameters concerning their malocclusion, craniofacial discrepancy and the characteristics and iatrogenic effects of their orthodontic treatment were analysed.
RESULTS: Fifteen XLH patients (mean age: 11.3 ± 2.1), pair-matched to 15 control patients were included. Orthodontic treatment was successfully conducted in XLH patients with slightly shorter duration and similar iatrogenic effects as in the control group, except for the occurrence of dental abscess during and after orthodontic tooth movement. XLH patients did not show more relapse than the controls.
CONCLUSIONS: Despite the presence of oral manifestations of XLH such as spontaneous abscesses, XLH patients can undergo orthodontic treatment with no obvious additional iatrogenic effects.

Hypophosphatemic rickets (HR) is a genetic disorder with various types of inheritance. It results mainly from defects in factors that control mineral ion homeostasis such as 1,25(OH)2D (Calcitriol) and FGF23 (Fibroblast Growth Factor 23). The existing bibliography regarding orthodontic treatment in patients with hypophosphatemic rickets is extremely limited. The aim of this case report is to describe the orthodontic treatment of a 9-year old Caucasian female patient suffering from HR. The patient presented a healthy late mixed dentition and periodontium. She suffered from a mild Class III maxillary skeletal pattern. There was a bilateral posterior crossbite, short lingual frenulum, a right maxillary mesioposition with a Class II subdivision on this side and a moderate space deficiency in the dental arches. The disorder was controlled by medication. In specific, patient was taking 1.5mL of phosphate four times per day, 0.3mL of calcitriol twice per day and 50,000 IU of Vitamin D3 on a weekly basis. Given the Class III skeletal pattern, the medical condition and the absence of relevant bibliography, it was decided to perform maxillary expansion, facemask traction and orthodontic treatment with fixed appliances. By the end of treatment, Class I canine and molar relationships were achieved, overjet and overbite were corrected and space deficiency was addressed in both arches. PAR index was 27 at the beginning of treatment and became 2 by the end of treatment (92.5% correction). The aesthetic component of IOTN was 4 and changed to 1, while the dental component used to be 5i and became 2g. With regards to retention, upper and lower fixed retainers from canine to canine and upper and lower vacuum formed appliances were used. In conclusion, a patient with controlled HR was orthodontically treated in a successful way. Orthodontic therapy was performed in a minimally invasive manner. Thus, HR does not constitute a contraindication for orthodontic treatment, when the disorder is kept under control.