This is an international, multicentre, prospective, non-interventional, observational Registry of patients with X-Linked hypophosphatemia (XLH). The objectives of this XLH Registry is to collect natural history data of XLH to characterise the treatment, progression and long-term outcomes of XLH in both adult and paediatric patients.

This XLH Registry will invite & include patients with XLH, of all ages & gender, irrespective of whether they are on, or not on, a treatment regimen for their XLH.

However, patients who are concurrently participating in an interventional clinical trial, including Investigator-Initiated Studies, are excluded from the XLH Registry, as per the Exclusion Criteria as set in the Protocol. These patients participating in an interventional clinical trial, when their involvement in the trial has ended, will be approached and invited to be included in the XLH Registry.

A subset of the XLH Registry data will be used to fulfil a Post-Authorisation Safety Study (PASS) as requested by the European Medicines Agency’s (EMA’s) Committee for Medical Products for Human Use (CHMP). Study centres which agree to participate in the PASS will be asked to solicit adverse events on enrolled patients. Not all centres are expected to participate in the PASS. Furthermore, as part of burosumab’s Risk Management Plan (RMP), the majority of the safety concerns are being investigated in a Category 3 Post-Authorisation Safety Study (PASS), which uses the XLH Registry. The data source to conduct the PASS is the data collected in the XLH Registry.

All eligible patients at the participating clinics will be asked to participate in the XLH Registry: