Burosumab: Monoclonal antibody that renders FGF23 largely unable to cause phosphate-wasting. Marketed as Crysvita by Ultragenyx Pharmaceutical in North America (other locations may have a different pharmaceutical company involved).
Calcitriol: active vitamin D, may be prescribed for patients who are not being treated by burosumab. This is not the same as over-the-counter vitamin D.
Enthesopathy: calcification of soft tissue (ligaments and tendons), which leads to pain and reduced range of motion in joints.
FGF23: Fibroblast Growth Factor 23, a hormone that regulates phosphorus levels. In excessive amounts, it causes the kidneys to waste phosphorus.
Hypophosphatemia: low levels of phosphorus in the blood
PHEX: the section of the X chromosome where the XLH mutation occurs, known as PHEX, or Phosphate Regulating Endopeptidase Homolog X-Linked.
Phosphorus: mineral necessary for strong bones. It is also part of adenosine triphosphate, which is the fuel for muscle function. May be prescribed for treatment of patients who are not being treated by burosumab.
Rickets: soft bones during childhood.
X-Linked: refers to the location of a genetic mutation on the X chromosome.
XLH: abbreviation for X-Linked Hypophosphatemia, a phosphate-wasting disorder caused by overproduction of a hormone known as FGF23.