Observational study comprising prospective follow up as well as retrospective chart review in order to evaluate the longitudinal course of the disease in XLH patients with a specific focus on functional impairment, physical performance and complications associated with the disease or respective treatment.

This is an observational / non-interventional study in order to assess the longitudinal course of XLH including disease related burden of disease and functional impairment. This is accomplished by both prospective follow up of affected patients as well as retrospective chart review. Evaluation conducted as per clincal routine and specifically evaluated as part of this study will include

• baseline documententation / demographic (as obtained from medical records)
• general data on XLH-disease specific medical history
• physical examination results
• functional assessments
• technical assessments
• quality of life / questionnaires
• laboratory evaluations

Inclusion Criteria:

• Male or female, aged ≥ 18 years, inclusive, at the time of enrollment

• Diagnosis of X-linked Hypophosphatemia confirmed by

  • documented PHEX mutation in either the patient, or in a directly related family member
  • positive family history of XLH and symptoms of the disease or
  • Phosphaturia + elevated serum levels of c-term FGF23 or iFGF23 and symptoms of the disease

• Written informed consent

Exclusion Criteria:

- Suspected of confirmed diagnosis of another phosphate wasting disorder

Adult patients with X-linked Hypophosphatemia

Individual participant data cannot be shared in order to warrant patients privacy.