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

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.

*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 patientadvocacy@ultragenyx.com.