Meet Cheryl and learn how she stays positive while managing her XLH.

At age two, Cheryl’s parents noticed that her legs were bowed. Throughout her life, she had seven surgeries in an attempt to straighten them. In the beginning, a physician told her parents that x-linked hypophosphatemia (XLH) was a childhood disease that would correct itself, but that is not accurate. This experience taught Cheryl that finding the right healthcare team is crucial. As an adult, she keeps active, and she’s found that having a positive attitude makes all the difference. Cheryl can’t control her symptoms, but she can control her attitude, and she’s not letting XLH stop her!

X-linked Hypophosphatemia (XLH)

What is it?

X-linked hypophosphatemia (XLH) is a rare, progressive, and lifelong disorder caused by low levels of phosphate in the bloodstream.

What causes it?

People with XLH produce too much of a protein called fibroblast growth factor 23 (FGF23). Too much FGF23 causes the kidneys to waste phosphate into the urine and results in chronically low levels of phosphate in the bloodstream, is also known as hypophosphatemia. Phosphate is essential for building bones and teeth.

What are some of the common symptoms?

  • Bone and joint pain
  • Bowed legs and/or knock-knees
  • Delayed growth
  • Irregular head shape
  • Muscle weakness
  • Osteomalacia
  • Short stature
  • Tooth abscesses

How many people have it?

XLH is a rare disorder, occurring in anywhere from 1 in 20,000 to 1 in 25,000, people.1

Common names for XLH

  • X-Linked Hypophosphatemic Rickets
  • Familial Hypophosphatemia
  • Familial Hypophosphatemic Rickets
  • Vitamin D-Resistant Rickets (VDRR)
  • Genetic Rickets

1Beck-Nielsen SS, Brock-Jacobsen B, Gram J, Brixen K, Jensen TK. Incidence and prevalence of nutritional and hereditary rickets in southern Denmark. Eur J Endocrinol. 2009; 160(3):491-497.

Ultragenyx Opportunities to Participate

Research plays a critical part in advancing science and treatments. Volunteers who participate in this research are essential. Future therapies would not be possible without them. Participating in clinical trials, interviews, observational studies, and disease monitoring programs help to drive research, treatment development, and disease education. It is also a way to advocate for yourself and your community. To learn more about Ultragenyx research, email [email protected].

The BEYONDXLH disease monitoring program (DMP) collects and tracks health information from children and adults with XLH.

BEYONDXLH is a non-interventional, prospective, observational DMP conducted through a mobile/web-based application. The program is designed to encourage patients, their doctors, and researchers to learn more about the disorder across a broad group of patients. Information collected from this diverse population will help patients and clinicians better understand the impact of the disease, improve treatment management, and inform future research. For more info, visit

The in-clinic BEYONDXLH DMP is a global multicenter study of people with XLH. The study evaluates how XLH progresses over time, how it affects people in different aspects of their lives, and how the therapy affects XLH symptoms. The DMP can help patients, healthcare providers, regulators, and researchers understand how XLH progresses with or without treatment. For more info, visit

Note: The disease monitoring program does not include any experimental treatments or procedures and is not a clinical trial.

*These organizations are an incomplete listing of rare disease support organizations and are not controlled by, endorsed by, or affiliated with Ultragenyx Pharmaceutical Inc. The list is meant for informational purposes only and is not intended to replace your healthcare professional’s medical advice. Ask your doctor or nurse any questions you may have about your disease or treatment plan. If you would like to have your group added to the list, please contact [email protected].