X-linked Hypophosphatemia Disease Monitoring Program

The XLH-DMP is a global, prospective, multicenter, longitudinal, long-term outcomes program
for subjects on or off any treatment designed to characterize XLH disease presentation and
progression, assess long-term safety and effectiveness of burosumab, as well as prospectively
investigate longitudinal change over time across biomarker(s), clinical assessments, and
patient/caregiver-reported outcome measures in a representative population. The XLH-DMP will
collect demographic, biochemical, physiologic, disease severity, and progression data in
patients taking burosumab and those not taking burosumab. In this DMP, patients will only
have access to burosumab through authorized prescribed use. The Sponsor will not provide any
treatments as part of the DMP.

Inclusion Criteria:

- Willing and able to provide informed consent or, in the case of patients under the age
of 18 years (or 16 years, depending on the region), provide assent (if required) and
informed consent by a legally authorized representative after the nature of the study
has been explained, and prior to any research-related procedures.

- Clinical diagnosis of XLH based on family history, OR confirmed PHEX mutation, OR
biochemical profile consistent with XLH.

- Willing and able to comply with the study visit schedule and study procedures.

Exclusion Criteria:

- Concurrent enrollment in an Ultragenyx-sponsored clinical trial is NOT permitted.

- Serious medical or psychiatric comorbidity.

- Less than five years of life expectancy.